Powder 3d printing high toughness fast hardening sulphoaluminate cement based material

Abstract

The application discloses a kind of powder 3D printing high-toughness fast-hardening sulphoaluminate cement-based materials, surface modification is carried out to fast-hardening sulphoaluminate cement using nano-oxide, for powder 3D printing fast-hardening sulphoaluminate cement material, using water solution post-treatment maintenance, after printing forming, immerse saturated calcium chloride aqueous solution, make unhydrated sulphoaluminate cement further reaction hardening, immerse in water glass solution again, make the calcium chloride in the inside of printing model pore and the sodium silicate in water glass solution react to generate calcium silicate, fill the inside of printing model pore, simultaneously, the hydration sulphoaluminate calcium crystal and ettringite are tightly bonded, form dense mesh structure, improve the density and mechanical properties of material.

Description

Technical Field

[0001] This invention relates to the field of novel inorganic materials technology, specifically to a powder 3D printing high-toughness, fast-hardening sulfoaluminate cement-based material. Background Technology

[0002] In recent years, 3D printing technology has gradually emerged and has been widely applied in many fields such as construction engineering, industrial manufacturing, aerospace, and biomedicine. Unlike traditional construction processes, 3D printing technology first slices a digital 3D model into multiple layers of 2D planar graphics, and then constructs a three-dimensional model by sequentially printing and stacking these layers. 3D printing technology has enormous development potential in the construction field, and its application in civil engineering is of great significance, representing a major advancement in the direction of green and intelligent buildings.

[0003] Powder 3D printing, as an emerging additive manufacturing technology, boasts advantages such as fast forming speed, high printing accuracy, low material cost, moldless construction, and flexible and intelligent operation. This technology involves spraying a binder onto specific locations of a flattened powder material, causing the powder to bond and harden, stacking layers to ultimately print the target model. Currently, gypsum powder material systems based on powder 3D printing technology have been developed, for example, Chinese patents CN104230289A and CN104744000A. However, models made using this material exhibit low strength, severely limiting its application. In contrast, Chinese patent CN112759298A discloses a 3D printing material made from cement powder with higher compressive strength; however, specimens formed using magnesium phosphate cement exhibit significant brittleness and poor durability, making it unsuitable for use in construction engineering.

[0004] Based on the above problems, this invention creatively uses powder 3D printing to print high-toughness, fast-hardening sulfoaluminate cement-based materials, which can improve the brittleness and durability of cement-based powder 3D printing materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide a powder 3D printing high-toughness, fast-hardening sulfoaluminate cement-based material, which can realize powder 3D printing of sulfoaluminate cement, improve the brittleness problem of magnesium phosphate cement material, and enhance the mechanical properties and durability of the printed material.

[0006] The present invention solves the aforementioned technical problem by adopting the following technical solution:

[0007] A powder 3D printing high-toughness, fast-hardening sulfoaluminate cement-based material, wherein the composition and content of the cement-based material, by weight, are as follows:

[0008] Powder composition: 2-2.5 parts rapid-hardening sulfoaluminate cement, 0.3-0.6 parts quartz sand, 0.3-0.6 parts metakaolin, 0.15-0.3 parts anhydrite, 0.15-0.3 parts accelerator, 0.15-0.3 parts water-reducing agent, 0.1-0.15 parts redispersible latex powder, 0.1-0.15 parts polyvinyl alcohol (PVA) powder, 0.05-0.1 parts carbon nanotubes, 0.01-0.03 parts nano-oxides;

[0009] Binder components: 0.01-0.03 parts 1,2-propylene glycol, 0.01-0.03 parts glycerin, 0.01-0.03 parts Surfynol 465 surfactant, 0.4-0.5 parts water;

[0010] The preparation process of the powder 3D printing rapid hardening sulfoaluminate cement-based material is as follows:

[0011] 1) Surface modification pretreatment of sulfoaluminate cement: Rapid hardening sulfoaluminate cement and nano-oxides are put into a planetary ball mill and ground until there is no agglomeration between cement particles and good fluidity, so as to obtain the modified sulfoaluminate cement.

[0012] 2) Mixing powder materials: Put the modified rapid hardening sulfoaluminate cement, quartz sand, metakaolin, anhydrite, accelerator, water-reducing agent and PVA powder into a mixer and mix for no less than 5 minutes. Then add redispersible latex powder and multi-walled carbon nanotubes, continue to mix evenly, and put it into a silo for later use.

[0013] 3) Mixing the binder: Dissolve the Surfynol 465 surfactant, 1,2-propylene glycol and glycerin in water, and ultrasonically vibrate to obtain a homogeneous binder, which is then placed in the ink cartridge for later use;

[0014] 4) Powder printing: Set the printer parameters, the printing layer thickness is 0.1-0.3mm, the roller speed is 300-500r / min, then lay a layer of powder material, spray the binder on the flat powder surface, the binder reacts with the powder material to bond and harden, and continuously repeat the process of laying powder and spraying binder to obtain the printed specimen;

[0015] 5) Powder removal: Let the printed specimen stand for 10 minutes, remove it from the powder bed and remove excess powder, soak it in a saturated calcium chloride solution for no less than 1 hour, and then soak it in a water glass solution for 3 hours to obtain a powder 3D printing fast-hardening sulfoaluminate cement-based material that meets the requirements of brittleness and durability.

[0016] The rapid-hardening sulfoaluminate cement has a particle size of less than 150 μm; the maximum particle size of the quartz sand does not exceed 150 μm; the maximum particle size of the metakaolin does not exceed 100 μm, and the density is 2.54–2.6 g / cm³.3 The coagulant is mainly prepared from lithium carbonate, with a maximum particle size not exceeding 100 μm; the water-reducing agent is mainly prepared from calcium lignosulfonate, with a maximum particle size not exceeding 100 μm; the redispersible latex powder is polyvinyl acetate redispersible latex powder with a purity greater than 98% and a maximum particle size not exceeding 100 μm; the PVA powder is high-polymer polyvinyl alcohol with a molecular weight of 150,000 to 250,000 and a particle size less than 100 μm; the carbon nanotubes are multi-walled carbon nanotubes with an outer diameter between 30 and 50 nm.

[0017] The particle size range of the nano-oxide is 30-50 nm.

[0018] The nano-oxide is at least one of nano-SiO2, nano-titanium dioxide, nano-iron oxide, nano-alumina, and nano-zirconium dioxide.

[0019] In step 1), good flowability is defined as follows: the flowability of the powder is tested by the funnel method. 50g of the ground powder is placed in a standard funnel with a diameter of 2.5mm, and the time for all the powder to flow out is measured. If the time for the powder to flow out completely is within 3s and the continuous flow of the powder can be observed, then the powder has good flowability.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1) This invention uses nano-oxides to surface-modify rapid-hardening sulfoaluminate cement. The modified sulfoaluminate cement particles are closer to spherical in shape. The nano-oxide film adheres to the surface of the cement particles, reducing cement moisture and particle-to-particle contact, thereby effectively improving the fluidity and spreading performance of rapid-hardening sulfoaluminate cement, solving the problem of difficult smooth spreading of sulfoaluminate cement, and without changing the chemical properties of the cement itself. For powder 3D printing of rapid-hardening sulfoaluminate cement material, an aqueous solution post-treatment curing method is used. After printing, the cement is soaked in a saturated calcium chloride aqueous solution to further react and harden the unhydrated sulfoaluminate cement. It is then soaked again in a water glass solution, allowing the calcium chloride that has penetrated into the pores of the printed model to react with the sodium silicate in the water glass solution to form calcium silicate, which fills the pores inside the printed model. At the same time, the hydrated calcium sulfoaluminate crystals and ettringite are tightly bonded together to form a dense network structure, improving the density and mechanical properties of the material.

[0022] 2) In this invention, appropriate amounts of PVA powder, accelerator, anhydrite, and metakaolin were added to the powder composition to ensure that the fast-hardening sulfoaluminate cement-based powder material has good fluidity and spreadability, and can control printing accuracy. It can also harden rapidly after reacting with the binder. By adjusting the materials in the powder composition, the printing performance of the material and the mechanical and durability properties of the molded specimens were optimized. The high-toughness and fast-hardening sulfoaluminate cement material with the required mechanical and durability properties was successfully obtained, which broadened the application scope of powder 3D printing technology in the field of civil engineering.

[0023] 3) The powder material of this invention simultaneously incorporates redispersible latex powder and PVA powder. The redispersible latex powder, upon contact with the binder, forms a highly tough and adhesive film, tightly binding the components of the powder material and improving the strength and flexural toughness of the molded specimen. The addition of multi-walled carbon nanotubes, which overlap with the internal hydration products, prevents crack propagation in the cement matrix at the microscale. Furthermore, the nano-SiO2 on the surface of the modified rapid-hardening sulfoaluminate cement reacts with the cement material to produce a pozzolanic effect, generating hydrated calcium silicate. Unreacted nano-SiO2 particles fill the pores between cement particles, enhancing the overall density of the structure at the microscale. This improves the cracking load, ultimate load, and ultimate strain under flexural load of the printed specimen, providing more possibilities for the application of powder 3D printing technology in building structural engineering.

[0024] 4) In this invention, the particle size distribution of each material in the powder composition is optimized to ensure that the powder bed has high density, the powder material can react and harden quickly with the binder, the interlayer bonding performance is good, and the molded specimen has high printing accuracy. Detailed Implementation

[0025] The present invention will be further explained below with reference to the embodiments, but these are not intended to limit the scope of protection of this application.

[0026] This invention relates to a powder 3D printing high-toughness, fast-hardening sulfoaluminate cement-based material. The composition and content of this cement-based material, by weight, are as follows:

[0027] Powder composition: 2-2.5 parts rapid-hardening sulfoaluminate cement, 0.3-0.6 parts quartz sand, 0.3-0.6 parts metakaolin, 0.15-0.3 parts anhydrite, 0.15-0.3 parts accelerator, 0.15-0.3 parts water-reducing agent, 0.1-0.15 parts redispersible latex powder, 0.1-0.15 parts polyvinyl alcohol (PVA) powder, 0.05-0.1 parts carbon nanotubes, 0.01-0.03 parts nano-oxides;

[0028] Binder components: 0.01-0.03 parts 1,2-propylene glycol, 0.01-0.03 parts glycerin, 0.01-0.03 parts Surfynol 465 surfactant, 0.4-0.5 parts water;

[0029] Among them, rapid-hardening sulfoaluminate cement is calcined at 1300–1350℃ and has a particle size of less than 150 μm; quartz sand has a maximum particle size of no more than 150 μm; metakaolin has a maximum particle size of no more than 100 μm and a density of 2.54–2.6 g / cm³. 3 Anhydrite, with a maximum particle size not exceeding 100 μm; coagulant, mainly prepared from lithium carbonate, with a maximum particle size not exceeding 100 μm; water-reducing agent, mainly prepared from calcium lignosulfonate, with a maximum particle size not exceeding 100 μm; polyvinyl alcohol (PVA) powder, with a molecular weight of 150,000 to 250,000 and a particle size less than 100 μm; redispersible latex powder, with a particle size less than 100 μm; multi-walled carbon nanotubes, with an outer diameter between 30 and 50 nm; nano-oxides, with a maximum particle size not exceeding 50 nm.

[0030] The nano-oxides described in this invention include nano-SiO2, nano-titanium dioxide, nano-iron oxide, nano-alumina, and nano-zirconium dioxide, with a maximum particle size not exceeding 50 nm. These nano-oxides can improve the spreading performance of rapid-hardening sulfoaluminate cement powder. Because sulfoaluminate cement has an uneven particle size distribution, completely irregular particle morphology, and strong hygroscopicity, it is prone to agglomeration when exposed to air, resulting in poor powder flowability and difficulty in spreading smoothly on the powder bed surface. Preferably, nano-SiO2 is used as the nano-oxide. Simultaneous grinding of nano-SiO2 and rapid-hardening sulfoaluminate cement makes the cement particles more spherical and coats the surface with a thin layer of nano-SiO2, reducing moisture absorption and particle contact, thus improving the agglomeration of the cement powder. However, the particle size of nano-SiO2 should not be too small and the dosage should not be too large. Smaller nano-SiO2 particles adsorb and agglomerate with each other, making it difficult to disperse evenly in cement powder. High dosage of nano-SiO2 will also reduce the amount of calcium sulfoaluminate hydrate crystals and ettringite, resulting in a decrease in the strength of the final printed model.

[0031] In this invention, Surfynol 465 surfactant, 1,2-propylene glycol and glycerin are binder regulating components. These components are used in the preparation of the binder to regulate the surface tension and viscosity of the liquid, so that the binder can flow smoothly in the pipeline and be ejected from the print head in a better droplet shape.

[0032] In this invention, the preferred PVA powder is high-polymer polyvinyl alcohol, which reduces the lateral penetration of the binder in the powder and improves the longitudinal penetration effect of the binder, thus helping to improve printing accuracy.

[0033] In this invention, the process of modifying rapid-hardening sulfoaluminate cement uses the funnel method to test powder flowability. Specifically, a Hall effect flowmeter with a 2.5 mm pore size is used. 50 g of the ground powder is placed in the funnel, and the time it takes for it to completely drain is measured. If the complete draining time is within 3 seconds, and continuous powder flow can be observed, it indicates that the powder has good flowability. The flowability test determines the particle size range of the nano-oxides and the powder-to-water ratio.

[0034] Example 1

[0035] This embodiment describes the preparation of a powder 3D printing high-toughness, fast-hardening sulfoaluminate cement-based material. The specific process is as follows:

[0036] Step 1: First, the surface modification pretreatment of sulfoaluminate cement is carried out. 2.5 parts of rapid hardening sulfoaluminate cement and 0.02 parts of nano SiO2 are put into a planetary ball mill and ground for 10 minutes. At this time, there is no agglomeration between cement particles and they have good fluidity.

[0037] Step 2: Put the modified rapid-hardening sulfoaluminate cement, 0.4 parts quartz sand, 0.4 parts metakaolin, 0.2 parts anhydrite, 0.2 parts accelerator, 0.2 parts water-reducing agent and 0.1 parts PVA powder into a mixer and mix for no less than 5 minutes. Then add 0.15 parts redispersible latex powder and 0.1 parts multi-walled carbon nanotubes, and continue mixing for about 3 minutes. Put the mixture into a silo for later use.

[0038] Step 3: Place 0.025 parts of Surfynol 465 surfactant, 0.02 parts of 1,2-propylene glycol, 0.025 parts of glycerin and 0.5 parts of water into an ultrasonic vibrator and ultrasonically vibrate at a frequency of 50 Hz for 3 minutes to prepare an adhesive. Place the adhesive into an ink cartridge for later use.

[0039] Step 4: Design a 3D model based on the printing target, export it as an STL format, and input it into the printing software for slicing.

[0040] Step 5: Set the powder spreading module, printing module, and forming module of the powder 3D printing equipment to operating status. Adjust the Z-axis height so that the distance between the powder bed surface and the nozzle is 7mm. Move the nozzle to the printing origin position, set the nozzle negative pressure and inkjet voltage to ensure that the binder can be smoothly ejected through the nozzle and sprayed onto the powder bed surface in a good droplet shape. Pre-spread the powder material until the powder bed surface is sufficiently flat.

[0041] Step 6: Set printer parameters: print layer thickness is 0.1mm, roller speed is 500r / min, powder spreader moving speed is 450mm / s, vibrator vibration speed is 50mm / s, and print head moving speed is 300mm / s.

[0042] Step 7: Begin printing the first layer. First, lay down a layer of powder material, then spray adhesive onto the flat powder surface. The adhesive reacts with the powder material, bonding and hardening. Continue printing the second layer, and repeat the above process until all printing is complete.

[0043] Step 8: After printing, let the printed specimen stand for 10 minutes, remove it from the powder bed and remove excess powder, soak it in a saturated calcium chloride solution for 1 hour to fully hydrate the rapid-hardening sulfoaluminate cement, and then soak it again in a water glass solution for 3 hours to achieve secondary hydration, finally obtaining a powder 3D printed rapid-hardening sulfoaluminate cement-based material that meets the requirements of brittleness and durability.

[0044] In this embodiment, multiple printed specimens were prepared according to the above method, and their average 7-day compressive strength and average flexural strength reached 35.8 MPa and 14.5 MPa, respectively. The sulfoaluminate cement-based powder material has good printing performance, and its early strength, setting time, powder spreading performance, and printing accuracy all meet the requirements of powder 3D printing process.

[0045] Comparative Examples 1-3 differ from Example 1 only in the content of nano-SiO2. The preparation and printing processes of other component materials remain unchanged. The specific proportions and experimental results are shown in Table 1.

[0046] Table 1. Specific experimental phenomena of Comparative Examples 1-3

[0047]

[0048] Comparative Example 4: The amount of quartz sand, metakaolin, and anhydrite added to the powder composition was changed, while the rest of the components were exactly the same as in Example 1. The amount of quartz sand, metakaolin, and anhydrite added in this comparative example was 0.25 parts, 0.3 parts, and 0.15 parts.

[0049] In this comparative example, the amount of quartz sand was adjusted to be lower than the range described in the technical solution of this invention. It was found that the spreading performance of the powder material deteriorated significantly, resulting in a reduction in the accuracy and mechanical properties of the printed specimen.

[0050] Comparative Example 5: The amounts of quartz sand, metakaolin, and anhydrite in the powder composition were changed, while the rest of the components were exactly the same as in Example 1. The amounts of quartz sand, metakaolin, and anhydrite in this comparative example were 0.6 parts, 0.65 parts, and 0.35 parts.

[0051] In this comparative example, 0.65 parts of metakaolin and 0.35 parts of anhydrite were added, which is higher than the range described in this invention. The excessive addition of metakaolin and anhydrite resulted in poor flowability of the powder material. Although this phenomenon was improved after increasing the amount of quartz sand, the powder material still could not be spread evenly and smoothly, resulting in defects inside the printed specimen and lower mechanical properties of the printed specimen.

[0052] Comparative Example 6 differs from Example 1 only in that it is not soaked in solution after printing, but is placed in the air for curing. The preparation process of other component materials and the printing process remain unchanged.

[0053] The printed specimens in this comparative example were not post-processed, and the sulfoaluminate cement inside the molded specimens was not fully hydrated and hardened. The content of hydrated calcium sulfoaluminate crystals and ettringite generated inside the specimens was the lowest, so the mechanical properties were the lowest, and their crack resistance and durability were far inferior to those of the molded specimens in Example 1.

[0054] Table 2 Mechanical properties of Example 1 and Comparative Examples 1-6

[0055]

[0056] The mechanical property test results of each group of printed specimens are shown in Table 1, which displays the 3D compressive strength and flexural strength of specimens in different printing directions. The X direction represents the powder spreader movement direction, the Y direction represents the printing nozzle movement direction, and the Z direction represents the powder material stacking direction. The mechanical properties of the specimens exhibit anisotropy. Due to the molding process of powder 3D printing, there are interlayer weaknesses within the molded specimens. Therefore, the flexural strength in the Z direction is significantly lower than in the other two directions, and the flexural strength in the Z direction is not of reference value. It can be observed that the powder 3D printed rapid-hardening sulfoaluminate cement-based material prepared according to Example 1 exhibits the best printing performance and mechanical properties.

[0057] The experimental results clearly show that, within the scope of this application, the powder 3D printed high-toughness, rapid-hardening sulfoaluminate cement-based material of this invention, compared with traditional construction methods and cement-based 3D printing technologies, has advantages such as high strength and toughness, high printing precision, moldless construction, flexible and intelligent operation, and strong stability, thus expanding the application range of powder 3D printed cement-based materials. The embodiments described in this invention are easy to understand, and those skilled in the art can normally prepare and use the powder 3D printed rapid-hardening sulfoaluminate cement-based material, facilitating implementation and enabling its widespread use in the field of new materials technology.

[0058] The 7-day compressive strength of the printed specimens of this invention is above 30 MPa in all three printing directions, preferably 32-27 MPa, and the 7-day flexural strength is above 13 MPa in two printing directions, indicating a significant improvement in mechanical properties. In this embodiment, a three-point bending test revealed that the displacement-load curve of the printed specimen exhibits a non-linear trend and increases slowly. After reaching the ultimate load, the carbon nanotubes inside the specimen prevent energy concentration, and multiple cracks slowly grow during the failure process until the specimen completely fractures, demonstrating good flexural strength and toughness.

[0059] Where this invention is not described herein, it applies to the prior art. Therefore, any improvements and modifications made by those skilled in the art based on the disclosure of this invention without departing from the scope of this invention should be within the protection scope of this invention.

Claims

1. A powder 3D printing high-toughness, fast-hardening sulfoaluminate cement-based material, characterized in that, The composition and content of this cement-based material, by weight, are as follows: Powder composition: 2~2.5 parts rapid-hardening sulfoaluminate cement, 0.3~0.6 parts quartz sand, 0.3~0.6 parts metakaolin, 0.15~0.3 parts anhydrite, 0.15~0.3 parts accelerator, 0.15~0.3 parts water-reducing agent, 0.1~0.15 parts redispersible latex powder, 0.1~0.15 parts PVA powder, 0.05~0.1 parts carbon nanotubes, 0.01~0.03 parts nano oxides; Binder components: 0.01~0.03 parts 1,2-propylene glycol, 0.01~0.03 parts glycerin, 0.01~0.03 parts Surfynol 465 surfactant, 0.4~0.5 parts water; The particle size of the rapid-hardening sulfoaluminate cement is less than 150 μm; The maximum particle size of quartz sand does not exceed 150 μm; the maximum particle size of metakaolin does not exceed 100 μm, and the density is 2.54~2.6 g / cm³. 3 The coagulant is mainly prepared from lithium carbonate, with a maximum particle size not exceeding 100 μm; the water-reducing agent is mainly prepared from calcium lignosulfonate, with a maximum particle size not exceeding 100 μm; the redispersible latex powder is polyvinyl acetate redispersible latex powder with a purity greater than 98% and a maximum particle size not exceeding 100 μm; the PVA powder is high-polymer polyvinyl alcohol with a molecular weight of 150,000 to 250,000 and a particle size less than 100 μm; the carbon nanotubes are multi-walled carbon nanotubes with an outer diameter between 30 and 50 nm. The particle size range of the nano-oxides is 30-50 nm; The preparation process of the powder 3D printing high-toughness, fast-hardening sulfoaluminate cement-based material is as follows: 1) Surface modification pretreatment of sulfoaluminate cement: Rapid-hardening sulfoaluminate cement and nano-oxides are ground together in a planetary ball mill until there is no agglomeration between cement particles and good flowability, thus obtaining modified rapid-hardening sulfoaluminate cement; the good flowability is determined by testing the powder flowability using the funnel method. 50g of the ground powder is placed in a standard funnel with a 2.5mm aperture, and the time for all the powder to flow out is measured. If the powder flows out completely within 3 seconds and continuous flow of the powder can be observed, then the powder has good flowability. 2) Mixing powder materials: Put the modified rapid hardening sulfoaluminate cement, quartz sand, metakaolin, anhydrite, accelerator, water-reducing agent and PVA powder into a mixer and mix for no less than 5 minutes. Then add redispersible latex powder and carbon nanotubes, continue to mix evenly, and put it into the silo for later use. 3) Mixing the binder: Dissolve the Surfynol 465 surfactant, 1,2-propylene glycol and glycerin in water, and ultrasonically vibrate to obtain a homogeneous binder, which is then placed in the ink cartridge for later use; 4) Powder printing: Set the printer parameters, the printing layer thickness is 0.1-0.3 mm, the roller speed is 300~500 r / min, then lay a layer of powder material, spray the binder on the flat powder surface, the binder reacts with the powder material to bond and harden, and continuously repeat the process of laying powder and spraying binder to obtain the printed specimen; 5) Powder removal: Let the printed specimen stand for 10 minutes, remove it from the powder bed and remove excess powder, soak it in a saturated calcium chloride solution for no less than 1 hour, and then soak it in a water glass solution for 3 hours to obtain a powder 3D printing high toughness fast hardening sulfoaluminate cement-based material that meets the requirements of brittleness and durability.

2. The powder 3D printing high-toughness, fast-hardening sulfoaluminate cement-based material according to claim 1, characterized in that, The nano-oxide is at least one of nano-SiO2, nano-titanium dioxide, nano-iron oxide, nano-alumina, and nano-zirconium dioxide.

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