Fiber-reinforced cement-based printing material for 3D printing and preparation method thereof

Abstract

The invention relates to a fiber reinforced cement-based printing material for 3D printing, which is characterized by comprising the following raw materials in parts by weight: 570 to 660 parts of composite cement, 570 to 660 parts of active slag, 390 to 480 parts of high-quality fine aggregate, 15 to 25 parts of anhydrite powder, 10 to 30 parts of chopped fiber, 390 to 520 parts of water and 1 to 5 parts of thickening agent, the composite cement comprises Portland cement and sulphoaluminate cement; the weight ratio of the Portland cement to the sulphoaluminate cement is (0.95: 0.05)-(0.6: 0.4); the particle size of the active slag is less than or equal to 400 meshes; the content of calcium sulfate in the anhydrite powder is greater than 90wt%; the chopped fibers comprise at least one of organic polymer fibers and mineral fibers; the length of the chopped fiber is 3-10 mm, and the diameter of the chopped fiber is 15-35 microns; the problems that in the prior art, a 3D printing material is large in cement usage amount and high in cost, and the toughness of the printing material after hardening is low are solved, and the requirement of the printing material for constructability can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing, and in particular to a fiber reinforced cement-based printing material for 3D printing and a preparation method thereof. Background Art

[0002] With the development of 3D printing technology, architectural 3D printing technology has received more and more attention from industry scholars and government agencies. At present, the printing materials used for architectural 3D printing are usually concrete mortar with a high cement content, which uses a large amount of cement and has a high cost. In addition, the toughness of the printing material after hardening is relatively low, and it is easy to crack under the influence of drying shrinkage and local stress concentration, affecting the overall safety of concrete architectural 3D printed components. The existing technology usually adopts the method of directly adding reinforcing fibers to the printing material or adding an automatic mixing device to the printing equipment to automatically and continuously add fine steel wires or continuous long fibers during the printing process to reinforce the printing material.

[0003] Among them, the method of adding thin steel wires or continuous long fibers during the printing process does not address the problem of insufficient toughness of the printing material itself. The printed concrete structure may suffer sudden brittle failure when subjected to external loads, affecting the safety of concrete building 3D printed components.

[0004] Although adding reinforcing fibers to the printing material to form a fiber-reinforced printing material can directly increase the toughness and other properties of the printing material after hardening, the buildability indicators (including fluidity, plasticity and hardening time) of the obtained fiber-reinforced printing material are usually poor, which makes it easy to cause equipment blockage, poor interlayer bonding or structural deformation, instability and other problems during printing. Strict and refined operation and processing are required, which seriously affects the construction speed and maintenance cost. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof, which solves the problems of large cement usage, high cost and low toughness of the printing material after hardening in the prior art 3D printing materials, and can meet the requirements of the printing material for constructibility.

[0007] (II) Technical solution

[0008] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0009] In a first aspect, the present invention provides a fiber-reinforced cement-based printing material for 3D printing. The raw materials of the fiber-reinforced cement-based printing material include, by weight: 570-660 parts of composite cement, 570-660 parts of active slag, 390-480 parts of high-quality fine aggregate, 15-25 parts of anhydrite powder, 10-30 parts of chopped fibers, 390-520 parts of water, and 1-5 parts of thickener;

[0010] The composite cement comprises silicate cement and sulphoaluminate cement; the weight ratio of silicate cement to sulphoaluminate cement is 0.95:0.05-0.6:0.4; the particle size of the active slag is less than or equal to 400 mesh; the calcium sulfate content in the anhydrite powder is greater than 90wt%; the chopped fibers comprise at least one of organic polymer fibers and mineral fibers; the length of the chopped fibers is 3-10mm and the diameter is 15-35μm.

[0011] According to a preferred embodiment of the present invention, the raw materials of the fiber-reinforced cement-based printing material include, by weight: 600-630 parts of composite cement, 600-630 parts of active slag, 420-450 parts of high-quality fine aggregate, 18-20 parts of anhydrite powder, 10-20 parts of chopped fibers, 420-480 parts of water, and 1-2 parts of thickener;

[0012] The composite cement comprises silicate cement and sulphoaluminate cement, wherein the weight ratio of silicate cement to sulphoaluminate cement is 0.9:0.1-0.65:0.35; the particle size of the active slag is less than or equal to 500 meshes; the calcium sulfate content in the anhydrite powder is greater than 94wt% and the water content does not exceed 2wt%; the chopped fibers are organic polymer fibers; the length of the chopped fibers is 4-8mm and the diameter is 21-28μm.

[0013] According to a preferred embodiment of the present invention, the silicate cement is at least one of PO52.5 cement, PO62.5 cement, P.II.52.5 cement or P.II.62.5 cement; the sulphoaluminate cement is fast-setting and fast-hardening sulphoaluminate cement; the strength grade of the fast-setting and fast-hardening sulphoaluminate cement is 42.5, 52.5, 62.5 or 72.5.

[0014] According to a preferred embodiment of the present invention, the activity grade of the active slag is S95 or S105; the anhydrite in the anhydrite powder is at least one of first-grade anhydrite and special-grade anhydrite, and the particle size of the anhydrite powder is less than 200 meshes.

[0015] According to a preferred embodiment of the present invention, the high-quality fine aggregate includes at least one of quartz sand, river sand, aeolian sand, selected machine-made sand and desalted sea sand; the particle size range of the high-quality fine aggregate is 50-250 μm, and the average particle size is 90-110 μm; the mud content of the high-quality fine aggregate does not exceed 1wt%, and the chloride ion content does not exceed 0.02wt%.

[0016] According to a preferred embodiment of the present invention, the organic polymer fiber includes at least one of polyethylene fiber, aramid fiber and polyvinyl alcohol fiber; the length of the short-cut fiber is 5-8 mm; and the average diameter of the short-cut fiber is 24-25 μm.

[0017] According to a preferred embodiment of the present invention, the thickener includes at least one of hydroxypropyl methylcellulose, methylcellulose, hydroxyethyl methylcellulose ether and wood cellulose; and the viscosity of the thickener is 80000-120000 Pa·s.

[0018] According to a preferred embodiment of the present invention, the raw materials of the fiber reinforced cement-based printing material also include a coagulant.

[0019] In a second aspect, the present invention provides a method for preparing a fiber reinforced cement-based printing material as described in any one of the first aspects, comprising the following steps:

[0020] S1: Mix and stir composite cement, active slag, high-quality fine aggregate and anhydrite powder to obtain a uniformly mixed dry material;

[0021] S2: mixing and stirring water and thickener to obtain a uniformly stirred wet material;

[0022] S3: mixing and stirring the wet material with the dry material to obtain a concrete paste;

[0023] S4: Adding chopped fibers to the concrete slurry and continuously stirring to obtain a fiber-reinforced cement-based printing material for 3D printing.

[0024] According to a preferred embodiment of the present invention, in step S1, the uniformly mixed dry material also includes a coagulant.

[0025] (III) Beneficial effects

[0026] The beneficial effects of the present invention are as follows: a fiber-reinforced cement-based printing material for 3D printing of the present invention comprises composite cement, active slag, high-quality fine aggregate, anhydrite powder, chopped fibers, thickeners and other materials. Compared with the prior art, the fiber-reinforced cement-based printing material of the present invention enhances the performance of the fiber-reinforced cement-based printing material by adding chopped fibers, so that it can have higher toughness and higher bearing capacity after hardening, and is not prone to brittle failure; the present invention also adopts an optimized combination of composite cement + chopped fibers + anhydrite powder, which adjusts the fluidity and hardening time performance of the fiber-reinforced cement-based printing material of the present invention by optimizing the proportion of composite cement, anhydrite powder and active slag , so that it can still maintain good fluidity, moderate hardening time and high plasticity after adding chopped fibers, its overall constructability is high, the instability during construction is low, the construction speed can be increased, and the maintenance cost can be reduced; and, compared with the prior art, the present invention also uses a large amount of active slag to replace cement, thereby reducing the amount of cement added in the formula and reducing the use cost of the fiber-reinforced cement-based printing material of the present invention; at the same time, the addition of a large amount of active slag can further improve the density and fluidity of the fiber-reinforced cement-based printing material of the present invention, making it more plastic, and preventing the first extruded material from being squeezed and deformed by the later extruded material during printing, resulting in structural deformation, instability and other problems.

[0027] In addition, the present invention also provides a method for preparing a fiber-reinforced cement-based printing material for 3D printing. Compared with the prior art, the material design of the present invention is based on the material design of the present invention, and the preparation method does not involve specially designed incorporation equipment, printing equipment or other additional enhanced integrated processes. The process is simpler and the construction cost is lower. DETAILED DESCRIPTION

[0028] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation methods.

[0029] The present invention provides a fiber-reinforced cement-based printing material for 3D printing. The raw materials of the fiber-reinforced cement-based printing material include, by weight: 570-660 parts of composite cement, 570-660 parts of active slag, 390-480 parts of high-quality fine aggregate, 15-25 parts of anhydrite powder, 10-30 parts of chopped fibers, 390-520 parts of water, and 1-5 parts of thickener;

[0030] The composite cement comprises silicate cement and sulphoaluminate cement; the weight ratio of silicate cement to sulphoaluminate cement is 0.95:0.05-0.6:0.4; the particle size of the active slag is less than or equal to 400 mesh; the calcium sulfate content in the anhydrite powder is greater than 90wt%; the chopped fibers comprise at least one of organic polymer fibers and mineral fibers; the length of the chopped fibers is 3-10mm and the diameter is 15-35μm.

[0031] According to a preferred embodiment of the present invention, the raw materials of the fiber-reinforced cement-based printing material include, by weight: 600-630 parts of composite cement, 600-630 parts of active slag, 420-450 parts of high-quality fine aggregate, 18-20 parts of anhydrite powder, 10-20 parts of chopped fibers, 420-480 parts of water, and 1-2 parts of thickener;

[0032] The composite cement comprises silicate cement and sulphoaluminate cement, wherein the weight ratio of silicate cement to sulphoaluminate cement is 0.9:0.1-0.65:0.35; the particle size of the active slag is less than or equal to 500 meshes; the calcium sulfate content in the anhydrite powder is greater than 94wt% and the water content does not exceed 2wt%; the chopped fibers are organic polymer fibers; the length of the chopped fibers is 4-8mm and the diameter is 21-28μm.

[0033] More preferably, the weight ratio between Portland cement and sulphoaluminate cement is: 0.7:0.3-0.65:0.35.

[0034] More preferably, the calcium sulfate content in the anhydrite powder is greater than 95wt%, and the water content does not exceed 1wt%. Too high water content in anhydrite will lead to a decrease in its performance.

[0035] Among them, the ratio between silicate cement and sulphoaluminate cement in the composite cement is a key factor in controlling the properties of fiber-reinforced cement-based printing materials such as buildability and long-term strength; sulphoaluminate cement has a faster hardening speed. After being compounded with silicate cement to form cement, it can make the fiber-reinforced cement-based printing material of the present invention (hereinafter referred to as printing material) have a faster early strength growth rate, but due to the large-scale use of sulphoaluminate cement, the hardening speed of the printing material may be too fast, the fluidity decreases, the long-term strength after hardening is low, and the stability is poor, so its ratio cannot be too high; in the present invention, a higher ratio of sulphoaluminate cement and silicate cement is used for compounding, and it is optimized and adjusted by adding materials such as hard gypsum powder, chopped fibers and active slag, so that the printing material of the present invention can have a suitable hardening time while also being able to obtain higher long-term strength and stability, and can simultaneously meet the requirements of 3D printing for early hardening speed and late hardening strength.

[0036] Preferably, the silicate cement is at least one of PO52.5R cement, PO62.5 cement, P.II.52.5R cement or P.II.62.5 cement; the sulphoaluminate cement is fast-setting and fast-hardening sulphoaluminate cement; and the strength grade of the fast-setting and fast-hardening sulphoaluminate cement is 42.5, 52.5, 62.5 or 72.5.

[0037] Among them, silicate cement and fast-setting and fast-hardening sulphoaluminate cement are not limited to the above types. Other types of cement materials can also be selected according to actual conditions. For example, when the printing equipment is good and fast construction is required, in order to obtain faster hardening speed, PO62.5R cement, P.Ⅱ.62.5R cement or other fast-setting and fast-hardening sulphoaluminate cements with faster strength development can be used, but their costs may increase to a certain extent.

[0038] More preferably, the silicate cement is PO52.5 cement or P.II.52.5 cement; the strength grade of the fast-setting and fast-hardening sulphoaluminate cement is 52.5 or 62.5.

[0039] Preferably, the activity grade of the active slag is S95 or S105.

[0040] The printing material of the present invention also uses a large amount of active slag, which can replace part of the cement, reduce the amount of cement used in the formula, and reduce the raw material cost of the printing material of the present invention; at the same time, the active slag can also be filled into the gaps between the cement particles to improve the density of the printing material, thereby making the printing material of the present invention have a higher early strength, and prevent the first extruded material from being deformed by the extrusion of the later extruded material during printing, resulting in structural deformation, instability and other problems; the active slag also has good lubricity, which can improve the fluidity and plasticity of the printing material of the present invention, making it easier to pump and extrude, and can maintain uniform distribution during the printing process to prevent uneven interlayer bonding; in addition, the addition of a large amount of active slag can also improve the later strength and durability of the printing material of the present invention after hardening, compensate for the adverse factors generated after the addition of sulphoaluminate cement, and improve the structural safety of the printed components. Among them, the active slag with an activity level of S95 or S105 has a larger specific surface area and a smaller particle size, which can further improve the early strength, fluidity and plasticity of the printing material of the present invention, so that the components printed by the printing material of the present invention have higher strength and durability.

[0041] More preferably, the activity grade of the active slag is S95, which has lower cost and higher practicality.

[0042] Preferably, the high-quality fine aggregate includes at least one of quartz sand, river sand, aeolian sand, selected machine-made sand and desalted sea sand; the particle size range of the high-quality fine aggregate is 50-250 μm, and the average particle size is 90-110 μm; the mud content of the high-quality fine aggregate does not exceed 1wt%, and the chloride ion content does not exceed 0.02wt%.

[0043] The fine aggregate with relatively high quality, less impurities and distinct particles is used to avoid the impurities therein causing unstable effects on the performance of the printing material of the present invention, prevent the occurrence of uneven dispersion, decreased fluidity and plasticity, etc., and improve the overall stability of the printing material of the present invention.

[0044] More preferably, the high-quality fine aggregate is quartz sand; the average particle size of the high-quality fine aggregate is 100 μm.

[0045] Preferably, the organic polymer fiber includes at least one of polyethylene fiber, aramid fiber and polyvinyl alcohol fiber; the length of the short-cut fiber is 5-8 mm; and the average diameter of the short-cut fiber is 24-25 μm.

[0046] Preferably, the density of the mineral fiber is less than 3.2 g / cm3 and the tensile strength is greater than 1000 MPa.

[0047] Preferably, the mineral fiber includes at least one of basalt fiber, glass fiber and sepiolite fiber.

[0048] More preferably, the chopped fibers are polyethylene fibers, aramid fibers or basalt fibers; the length of the chopped fibers is 6 mm and the diameter is 24 μm.

[0049] Short-cut fibers are added to the printing material of the present invention. After the printing material hardens, the short-cut fibers will cross-link with each other, thereby improving the toughness of the printing material of the present invention after hardening, so that the components printed by using the printing material of the present invention have good tensile strength and are not prone to sudden brittle failure; and, since the short-cut fibers use organic polymer fibers or mineral fibers of specific sizes, they have relatively low density, light weight, relatively good dispersibility and fluidity, and can be evenly dispersed in the printing material of the present invention, avoiding fiber deposition, uneven dispersion and clogging of the printing equipment; at the same time, since the short-cut fibers also have a certain water retention capacity, they can also be combined with the composite cement used in the present invention to adjust the hardening time of the printing material of the present invention.

[0050] The use of mineral fibers can improve the fluidity and plasticity of the printing material of the present invention while further adjusting and improving the smoothness of the surface of the component printed using the printing material of the present invention.

[0051] Preferably, the anhydrite in the anhydrite powder is at least one of first-grade anhydrite and special-grade anhydrite, and the particle size of the anhydrite powder is less than 200 meshes.

[0052] The printing material of the present invention is further added with anhydrite powder, and the performance of the printing material of the present invention is further adjusted by the anhydrite powder; wherein, the anhydrite has good granularity, dispersibility and certain dispersibility, which helps the various components in the printing material of the present invention to be evenly dispersed, further ensures its overall fluidity, and prevents the occurrence of blockage or local hardening caused by uneven dispersion; and the addition of an appropriate amount of anhydrite can not only accelerate the hydration speed of the cement in the printing material of the present invention and improve its early strength, but also delay its initial setting time to a certain extent, prevent it from hardening prematurely, and provide a certain time redundancy for actual construction; in addition, the anhydrite can also expand during the cement hydration process and produce stable compounds such as calcium sulfonate, fill the tiny gaps in the printing material, compensate for the volume shrinkage of the printing material during the drying process, reduce the generation of microcracks, promote the uniform hydration of the printing material, and improve the density and compressive strength of the printing material of the present invention after hardening; in addition, the anhydrite component can also improve the surface flatness of the printing material of the present invention after hardening, and its surface is more flat and beautiful, which is conducive to subsequent processing.

[0053] More preferably, the anhydrite powder is first-grade anhydrite, which has higher purity, lower water content, lower cost and higher cost performance.

[0054] Preferably, the thickener includes at least one of hydroxypropyl methylcellulose, methylcellulose, hydroxyethyl methylcellulose ether and wood cellulose.

[0055] Preferably, the viscosity of the thickener is 80000-120000 Pa·s. The thickener can be used to further flexibly adjust the material properties such as the fluidity of the printing material of the present invention, thereby reducing the interference caused by unstable factors at the construction site.

[0056] More preferably, the thickener is hydroxypropyl methylcellulose; the viscosity of the thickener is 105000-95000 Pa·s.

[0057] Preferably, the raw materials of the printing material of the present invention further include 0.3-4 parts of a coagulant by weight; the coagulant includes at least one of lithium carbonate, lithium hydroxide, sodium metasilicate and sodium sulfate. The use of a coagulant can further shorten the initial setting time of the printing material of the present invention and improve its early strength, and is suitable for situations requiring emergency treatment and emergency printing. The use of a coagulant will increase costs, and it does not need to be added in normal construction, and is only an optional solution.

[0058] The present invention also provides a method for preparing a fiber-reinforced cement-based printing material for 3D printing, comprising the following steps:

[0059] S1: Mix and stir composite cement, active slag, high-quality fine aggregate and anhydrite powder to obtain a uniformly mixed dry material;

[0060] S2: mixing and stirring water and thickener to obtain a uniformly stirred wet material;

[0061] S3: mixing and stirring the wet material with the dry material to obtain a concrete paste;

[0062] S4: Add chopped fibers to the concrete slurry and continue stirring to obtain a fiber-reinforced cement-based printing material for 3D printing.

[0063] Preferably, in step S1, the stirring speed is 50-70 rpm; and the stirring time is 30 s-60 s (seconds).

[0064] Preferably, in step S2, the stirring speed is 300-500 rpm; and the stirring time is 30s-60s.

[0065] Preferably, in step S3, the stirring speed is 200-300 rpm; and the stirring time is 2 min-3 min (minutes).

[0066] Preferably, in step S4, the stirring speed is 200-300 rpm; and the stirring time is 3 min-6 min.

[0067] Preferably, in step S1, composite cement, active slag, high-quality fine aggregate, accelerator and anhydrite powder are mixed and stirred to obtain a uniformly mixed dry material.

[0068] Preferably, in step S4, the chopped fibers are divided into multiple portions and gradually added into the concrete slurry to further prevent the chopped fibers from agglomerating or being unevenly dispersed during stirring, which may lead to blockage of the print head and reduced printing effect during printing.

[0069] More preferably, the chopped fibers are divided into three portions, and one portion is added every 30 seconds.

[0070] In order to better understand the above technical scheme, exemplary embodiments of the present invention will be described in more detail below. Although some exemplary embodiments of the present invention are shown below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a clearer and more thorough understanding of the present invention, and to be able to fully convey the scope of the present invention to those skilled in the art.

[0071] Example 1

[0072] The present embodiment provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof. The raw materials of the fiber-reinforced cement-based printing material include, by weight, 610 parts of composite cement (the weight ratio between silicate cement and sulphoaluminate cement is 0.8:0.2), 630 parts of active slag, 440 parts of quartz sand, 18 parts of anhydrite powder, 10 parts of polyethylene fiber, 420 parts of water, and 1 part of hydroxypropyl methylcellulose.

[0073] Among them, the silicate cement is PO52.5R cement; the strength grade of the fast-setting and fast-hardening sulphoaluminate cement is 52.5; the activity grade of the active slag is S95; the anhydrite powder is first-grade anhydrite powder; the length of the chopped fiber is 6 mm and the diameter is 24 μm.

[0074] The preparation method of fiber reinforced cement-based printing material comprises the following steps:

[0075] S1: Mix and stir composite cement, active slag, high-quality fine aggregate and anhydrite powder to obtain a uniformly mixed dry material;

[0076] S2: mixing and stirring water and hydroxypropyl methylcellulose to obtain a uniformly stirred wet material;

[0077] S3: mixing and stirring the wet material with the dry material to obtain a concrete paste;

[0078] S4: Add polyethylene fibers to the concrete slurry and continue stirring to obtain a fiber-reinforced cement-based printing material for 3D printing.

[0079] Preferably, in step S1, the stirring speed is 60 rpm and the stirring time is 1 min.

[0080] Preferably, in step S2, the stirring speed is 400 rpm and the stirring time is 1 min.

[0081] Preferably, in step S3, the stirring speed is 220 rpm and the stirring time is 3 min.

[0082] Preferably, in step S4, the stirring speed is 220 rpm and the stirring time is 5 min.

[0083] After testing, the obtained fiber-reinforced cement-based printing material has an expansion of 183mm, an initial setting time of 47min, a 2h (hour) compressive strength of 11.4MPa, a 1d (day) compressive strength of 38.4MPa, a 28d compressive strength of 82.5MPa, a 28d ultimate tensile strength of 5.36MPa, and a 28d tensile strain of 4.77%.

[0084] Example 2

[0085] The present embodiment provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof. The raw materials of the fiber-reinforced cement-based printing material include, by weight, 630 parts of composite cement (the weight ratio between silicate cement and sulphoaluminate cement is 0.73:0.27), 610 parts of active slag, 450 parts of quartz sand, 20 parts of anhydrite powder, 20 parts of polyethylene fiber, 470 parts of water, and 1 part of hydroxypropyl methylcellulose.

[0086] Among them, the silicate cement is PO52.5R cement; the strength grade of the fast-setting and fast-hardening sulphoaluminate cement is 52.5; the activity grade of the active slag is S95; the anhydrite powder is first-grade anhydrite powder; the length of the chopped fiber is 6 mm and the diameter is 24 μm.

[0087] The preparation method of fiber reinforced cement-based printing material comprises the following steps:

[0088] S1: Mix and stir composite cement, active slag, high-quality fine aggregate and anhydrite powder to obtain a uniformly mixed dry material;

[0089] S2: mixing and stirring water and hydroxypropyl methylcellulose to obtain a uniformly stirred wet material;

[0090] S3: mixing and stirring the wet material with the dry material to obtain a concrete paste;

[0091] S4: Add polyethylene fibers to the concrete slurry and continue stirring to obtain a fiber-reinforced cement-based printing material for 3D printing.

[0092] Preferably, in step S1, the stirring speed is 50 rpm and the stirring time is 60 s.

[0093] Preferably, in step S2, the stirring speed is 450 rpm; and the stirring time is 45 s.

[0094] Preferably, in step S3, the stirring speed is 250 rpm and the stirring time is 3 min.

[0095] Preferably, in step S4, the stirring speed is 220 rpm and the stirring time is 5 min.

[0096] After testing, the obtained fiber-reinforced cement-based printing material has an expansion of 185mm, an initial setting time of 44min, a 2h compressive strength of 12.4MPa, a 1d compressive strength of 39.6MPa, a 28d compressive strength of 84.7MPa, a 28d ultimate tensile strength of 6.15MPa, and a 28d tensile strain of 5.87%.

[0097] Example 3

[0098] The present embodiment provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof. The difference from Example 2 is that, in parts by weight, the raw materials include: 630 parts of composite cement (the weight ratio between silicate cement and sulphoaluminate cement is 0.7:0.3), 610 parts of active slag, 440 parts of quartz sand, 20 parts of anhydrite powder, 20 parts of polyethylene fiber, 450 parts of water, and 1 part of hydroxypropyl methylcellulose.

[0099] After testing, the obtained fiber-reinforced cement-based printing material has an expansion of 181mm, an initial setting time of 41min, a 2h compressive strength of 12.7MPa, a 1d compressive strength of 39.8MPa, a 28d compressive strength of 84.3MPa, a 28d ultimate tensile strength of 6.09MPa, and a 28d tensile strain of 5.81%.

[0100] Example 4

[0101] The present embodiment provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof. The difference from Example 2 is that, in parts by weight, the raw materials include: 630 parts of composite cement (the weight ratio between silicate cement and sulphoaluminate cement is 0.65:0.35), 610 parts of active slag, 450 parts of quartz sand, 23 parts of anhydrite powder, 15 parts of polyethylene fiber, 470 parts of water, and 1 part of hydroxypropyl methylcellulose.

[0102] After testing, the obtained fiber-reinforced cement-based printing material has an expansion of 179mm, an initial setting time of 39min, a 2h compressive strength of 13.9MPa, a 1d compressive strength of 42.5MPa, a 28d compressive strength of 83.9MPa, a 28d ultimate tensile strength of 5.78MPa, and a 28d tensile strain of 5.35%.

[0103] Example 5

[0104] This embodiment provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof. The difference from Embodiment 2 is that, by weight, the raw materials include: 660 parts of composite cement (the weight ratio between silicate cement and sulphoaluminate cement is 0.6:0.4), 570 parts of active slag, 150 parts of river sand, 240 parts of aeolian sand, 25 parts of anhydrite powder, 30 parts of polyvinyl alcohol fiber, 520 parts of water, and 4 parts of hydroxypropyl methylcellulose. The silicate cement is P.II.52.5R cement.

[0105] After testing, the obtained fiber-reinforced cement-based printing material has an expansion of 182mm, an initial setting time of 33min, a 2h compressive strength of 15.4MPa, a 1d compressive strength of 43.2MPa, a 28d compressive strength of 78.2MPa, a 28d ultimate tensile strength of 6.17MPa, and a 28d tensile strain of 5.88%.

[0106] Example 6

[0107] The present embodiment provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof. The difference from Example 2 is that, in parts by weight, the raw materials include: 570 parts of composite cement (the weight ratio between silicate cement and sulphoaluminate cement is 0.95:0.05), 660 parts of active slag, 200 parts of river sand, 190 parts of aeolian sand, 15 parts of anhydrite powder, 10 parts of aramid fiber, 5 parts of polyethylene fiber, 440 parts of water, 1 part of hydroxypropyl methylcellulose and 1 part of methylcellulose.

[0108] The silicate cement includes PO52.5R cement and PO62.5 cement, and the weight ratio between PO52.5R cement and PO62.5 cement is 1:1. The length of the aramid fiber and the polyethylene fiber is 5 mm and the diameter is 25 μm.

[0109] After testing, the obtained fiber-reinforced cement-based printing material has an expansion of 188mm, an initial setting time of 55min, a 2h compressive strength of 10.5MPa, a 1d compressive strength of 34.2MPa, a 28d compressive strength of 85.8MPa, a 28d ultimate tensile strength of 6.23MPa, and a 28d tensile strain of 5.96%.

[0110] Example 7

[0111] This embodiment provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof. The difference from Example 4 is that the silicate cement used is P.Ⅱ.62.5 cement, and the strength grade of fast-setting and fast-hardening sulphoaluminate cement is 62.5.

[0112] After testing, the obtained fiber-reinforced cement-based printing material has an expansion of 183mm, an initial setting time of 39min, a 2h compressive strength of 15.6MPa, a 1d compressive strength of 49.2MPa, a 28d compressive strength of 87.8MPa, a 28d ultimate tensile strength of 6.13MPa, and a 28d tensile strain of 5.79%.

[0113] Example 8

[0114] This embodiment provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof. The difference from Embodiment 1 is that the chopped fibers are basalt fibers.

[0115] After testing, the obtained fiber-reinforced cement-based printing material has an expansion of 185mm, an initial setting time of 48min, a 2h compressive strength of 11.2MPa, a 1d compressive strength of 37.7MPa, a 28d compressive strength of 83.7MPa, a 28d ultimate tensile strength of 5.21MPa, and a 28d tensile strain of 4.65%.

[0116] Example 9

[0117] This embodiment provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof. The difference from Embodiment 1 is that, by weight, the raw materials further include 3 parts of lithium carbonate; in the preparation method, step S1 is: mixing and stirring composite cement, active slag, high-quality fine aggregate, accelerator and anhydrite powder to obtain a uniformly mixed dry material.

[0118] After testing, the obtained fiber-reinforced cement-based printing material has an expansion of 182mm, an initial setting time of 40min, a 2h compressive strength of 14.1MPa, a 1d compressive strength of 39.6MPa, and a 28d compressive strength of 81.8MPa.

[0119] Comparative Example 1

[0120] This comparative example provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof. The difference from Example 2 is that the grade of the active slag is S75.

[0121] After testing, the obtained fiber-reinforced cement-based printing material has an expansion of 190mm, an initial setting time of 60min, a 2h compressive strength of 7.9MPa, a 1d compressive strength of 27MPa, a 28d compressive strength of 66.8MPa, a 28d ultimate tensile strength of 4.85MPa, and a 28d tensile strain of 4.74%.

[0122] Comparative Example 2

[0123] This comparative example provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof, which is different from Example 2 in that 630 parts of PO52.5R cement are used instead of composite cement.

[0124] After testing, the expansion of the obtained fiber-reinforced cement-based printing material was 195mm, the initial setting time was 100min, and the 1d compressive strength was 29.8MPa.

[0125] Comparative Example 3

[0126] This comparative example provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof. The difference from Example 2 is that, in parts by weight, the raw materials of the fiber-reinforced cement-based printing material include: 630 parts of composite cement (the weight ratio between silicate cement and sulphoaluminate cement is 0.73:0.27), 610 parts of fly ash, 450 parts of quartz sand, 20 parts of anhydrite powder, 20 parts of polyethylene fiber, 470 parts of water, and 1 part of hydroxypropyl methylcellulose.

[0127] After testing, the expansion of the obtained fiber-reinforced cement-based printing material was 230mm, and the printing equipment collapsed during printing.

[0128] Comparative Example 4

[0129] This comparative example provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof, which differs from Example 2 in that chopped fibers are not used.

[0130] After testing, the obtained fiber-reinforced cement-based printing material has an expansion of 210 mm, an initial setting time of 43 min, a 28-day ultimate tensile strength of 4.52 MPa, and a 28-day tensile strain of 3.24%.

[0131] Comparative Example 5

[0132] This comparative example provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof. The difference from Example 2 is that the polyethylene fiber has a length of 20 mm and a diameter of 50 μm.

[0133] After testing, the obtained fiber-reinforced cement-based printing material frequently clogs during pipeline transportation and is not suitable for 3D printing.

[0134] Comparative Example 6

[0135] This comparative example provides a fiber-reinforced cement-based printing material for 3D printing and a preparation method thereof. The difference from Example 1 is that the preparation method comprises the following steps:

[0136] S1: Mix and stir high-quality fine aggregate, composite cement, active slag, anhydrite powder and chopped fibers to obtain a uniformly mixed dry material;

[0137] S2: mixing and stirring water and hydroxypropyl methylcellulose to obtain a uniformly stirred wet material;

[0138] S3: Mix and stir the wet material with the dry material to obtain a concrete slurry, and obtain a fiber-reinforced cement-based printing material for 3D printing.

[0139] Preferably, in step S1, the stirring speed is 100 rpm and the stirring time is 3 min.

[0140] Preferably, in step S2, the stirring speed is 40 rpm and the stirring time is 1 min.

[0141] Preferably, in step S3, the stirring speed is 220 rpm; and the stirring time is 2 min.

[0142] After testing, it was found that the fiber-reinforced cement-based printing material obtained by this process contained a large number of fiber agglomerates and cracked frequently during hardening, making it unsuitable for 3D printing.

[0143] According to the data of Examples 2-4 and Comparative Example 2, it can be found that the change in the proportion of composite cement can significantly change the expansion degree, initial setting time and early strength development rate of the printed material of the present invention. Since Comparative Example 2 does not use sulphoaluminate cement, its performance is greatly reduced, and the constructability and early strength development rate are low.

[0144] According to the data of Example 2 and Comparative Example 2, it can be found that the printing material of Comparative Example 2 has excessive expansion and low plasticity due to the replacement of active slag with other admixtures. It is easy to collapse during printing and cannot meet the requirements of 3D printing materials for constructability.

[0145] According to the data of Example 2, Example 6 and Comparative Examples 4-5, it can be found that since Comparative Example 4 does not add chopped fibers, its fluidity is too high, and the toughness of the printed material after hardening is also significantly lower, which cannot meet the toughness requirements; Comparative Example 5 uses longer and thicker fibers, so its dispersion effect is poor and the pumping capacity is low, which cannot meet the 3D printing requirements.

[0146] Compared with the preparation method of Example 1, the preparation method of Comparative Example 6 changes the order of feeding and blends the chopped fibers with the dry material in advance, resulting in uneven dispersion of the chopped fibers, more agglomeration, and easy cracking.

[0147] In summary, the fiber-reinforced cement-based printing material for 3D printing and the preparation method thereof of the present invention can solve the problems of large cement usage, high cost and low toughness of the printing material after hardening in the prior art 3D printing materials, and can meet the requirements of the printing material for constructability.

[0148] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fiber-reinforced cement-based printing material for 3D printing, characterized in that: The raw materials of the fiber-reinforced cement-based printing material include, by weight: 570-660 parts of composite cement, 570-660 parts of active slag, 390-480 parts of high-quality fine aggregate, 15-25 parts of anhydrite powder, 10-30 parts of chopped fibers, 390-520 parts of water, and 1-5 parts of thickener; The composite cement comprises silicate cement and sulphoaluminate cement; the weight ratio of the silicate cement to the sulphoaluminate cement is 0.95:0.05-0.6:0.4; the particle size of the active slag is less than or equal to 400 mesh; the calcium sulfate content in the anhydrite powder is greater than 90wt%; the chopped fibers comprise at least one of organic polymer fibers and mineral fibers; the length of the chopped fibers is 3-10mm and the diameter is 15-35μm.

2. The fiber-reinforced cement-based printing material according to claim 1, characterized in that: The raw materials of the fiber-reinforced cement-based printing material include, by weight: 600-630 parts of composite cement, 600-630 parts of active slag, 420-450 parts of high-quality fine aggregate, 18-20 parts of anhydrite powder, 10-20 parts of chopped fibers, 420-480 parts of water, and 1-2 parts of thickener; The composite cement comprises silicate cement and sulphoaluminate cement, wherein the weight ratio of the silicate cement to the sulphoaluminate cement is 0.9:0.1-0.65:0.35; the particle size of the active slag is less than or equal to 500 meshes; the calcium sulfate content in the anhydrite powder is greater than 94wt%, and the water content does not exceed 2wt%; the chopped fibers are organic polymer fibers; the length of the chopped fibers is 4-8mm, and the diameter is 21-28μm.

3. The fiber-reinforced cement-based printing material according to claim 2, characterized in that: The silicate cement is at least one of PO52.5 cement, PO62.5 cement, P.II.52.5 cement and P.II.62.5 cement; the sulphoaluminate cement is fast-setting and fast-hardening sulphoaluminate cement; the strength grade of the fast-setting and fast-hardening sulphoaluminate cement is 42.5, 52.5, 62.5 or 72.

5.

4. The fiber-reinforced cement-based printing material according to claim 2, characterized in that: The activity grade of the active slag is S95 or S105; the anhydrite in the anhydrite powder is at least one of first-grade anhydrite and special-grade anhydrite, and the particle size of the anhydrite powder is less than 200 meshes.

5. The fiber-reinforced cement-based printing material according to claim 2, characterized in that: The high-quality fine aggregate includes at least one of quartz sand, river sand, aeolian sand, selected machine-made sand and desalted sea sand; the particle size range of the high-quality fine aggregate is 50-250 μm, and the average particle size is 90-110 μm; the mud content of the high-quality fine aggregate does not exceed 1wt%, and the chloride ion content does not exceed 0.02wt%.

6. The fiber-reinforced cement-based printing material according to claim 2, characterized in that: The organic polymer fiber includes at least one of polyethylene fiber, aramid fiber and polyvinyl alcohol fiber; the length of the chopped fiber is 5-8 mm; and the average diameter of the chopped fiber is 24-25 μm.

7. The fiber reinforced cement-based printing material according to claim 2, characterized in that: The thickener comprises at least one of hydroxypropyl methylcellulose, methylcellulose, hydroxyethyl methylcellulose ether and wood cellulose; and the viscosity of the thickener is 80000-120000 Pa·s.

8. The fiber-reinforced cement-based printing material according to claim 2, characterized in that: The raw materials of the fiber reinforced cement-based printing material also include a coagulant.

9. A method for preparing a fiber-reinforced cement-based printing material for 3D printing according to any one of claims 1 to 8, characterized in that: The steps include: S1: Mix and stir composite cement, active slag, high-quality fine aggregate and anhydrite powder to obtain a uniformly mixed dry material; S2: mixing and stirring water and thickener to obtain a uniformly stirred wet material; S3: mixing and stirring the wet material and the dry material to obtain a concrete slurry; S4: Adding chopped fibers to the concrete slurry and continuously stirring to obtain a fiber-reinforced cement-based printing material for 3D printing.

10. The fiber-reinforced cement-based printing material according to claim 9, characterized in that: In step S1, the uniformly mixed dry material also includes a coagulant.