Cement-based 3d printing light-weight building ink and method for preparing the same

Abstract

A cement-based 3D printing light building ink comprises cement, sand, polysilicon waste and flexible glue powder, wherein the cement is 30-42 parts by weight, the sand is 53-65.5 parts by weight, the polysilicon waste is 3-5 parts by weight, and the flexible glue powder is 1.5-2 parts by weight.A preparation method of the cement-based 3D printing light building ink comprises the following steps: mixing cement, sand, polysilicon waste, lignin fiber, thickening agent and flexible glue powder, stirring uniformly to obtain a mixture; dissolving water reducing agent in water; adding two-thirds of the water reducing agent solution into the mixture to stir once; and then adding the remaining water reducing agent solution to stir twice.The cement-based 3D printing light building ink and the preparation method thereof apply polysilicon waste to the 3D printing light building ink, and the hardened printing body has high strength, high interlayer adhesion and low drying shrinkage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of 3D printing building ink materials, and particularly relates to a cement-based 3D printing light building ink and a preparation method thereof. BACKGROUND

[0002] 3D printing technology appeared in the 1990s, is a kind of rapid prototyping technology based on digital model files, using powdered metal or plastic and other materials that can be bonded, and constructing objects through layer-by-layer printing; usually realized by a digital technology material printer. The technology overcomes the limitations of traditional production methods for a long time, and can shorten the product development cycle and reduce production costs without mechanical processing or molds, directly generating parts according to computer graphics data.

[0003] In the construction industry, the raw material used for 3D printing is a kind of special building mortar with functionality. It has the basic performance of ordinary building mortar, and needs to abandon the dependence on formwork when traditional mortar is used to construct structures. Since the special mortar used for 3D printing has the basic properties of traditional mortar, it can absorb a large amount of solid waste like ordinary mortar, highlighting its "green" characteristics. In addition, the lightweight of the special mortar can reduce the load of the building weight on the base. However, the existing 3D printing special building mortar has a high cost.

[0004] Under the current situation of increasingly strict environmental governance, industrial waste such as fly ash, slag and steel slag has attracted special attention due to its large amount of emissions, and its comprehensive utilization rate has been continuously improved (the comprehensive utilization rate of slag has reached 100%). However, some non-mainstream industrial waste has relatively low production, and its comprehensive utilization research is less, and its emission has caused serious burden to the environment. For example, the production process of polysilicon enterprises will produce a large amount of wastewater, and the wastewater will mix with other metal elements such as Al, Fe and Ca during the treatment process, which has been difficult to recover as raw materials for polysilicon. It has been found through research that the silicon powder particles remaining in the wastewater are between nanoscale and submicron scale, and have similar particle size to white carbon black (nanoscale silicon dioxide). Nanoscale silicon dioxide has strong volcanic ash activity, crystal nucleus effect and micro-aggregate filling effect, which can significantly improve the performance of the printing ink, make the ink more compact, increase the toughness, and increase the early strength. The elemental silicon in the polysilicon waste is oxidized to form silicon dioxide, which has the same effect as white carbon black when mixed into the ink. During the treatment process of the wastewater, flocculants and Fenton reagents are used, which will bring part of the oxidizing agent, which can locally oxidize elemental silicon. The oxidizing agent hydrogen peroxide will release gas, which will make the mortar expand and have the characteristics of lightweight. SUMMARY

[0005] The present application aims to overcome the defects of the prior art and provide a cement-based 3D printing light building ink and a preparation method thereof.

[0006] To achieve the above object, the application adopts the following technical scheme:

[0007] A cement-based 3D printing light building ink, comprising cement, sand, polysilicon waste and flexible glue powder, wherein the weight fraction of the cement is 30-42 parts, the weight fraction of the sand is 53-65.5 parts, the weight fraction of the polysilicon waste is 3-5 parts, and the weight fraction of the flexible glue powder is 1.5-2 parts.

[0008] Preferably, the cement is a mixture of portland cement and sulphoaluminate cement, and the mass ratio of the portland cement to the sulphoaluminate cement is 2:1-7:3.

[0009] Preferably, the polysilicon waste is a semi-dry powder obtained by flocculation and oxidation of a cutting cleaning solution in a polysilicon production process, and the water content is 20-25%.

[0010] Preferably, the flexible glue powder is VAE redispersible emulsion powder, which is a copolymer of ethylene and vinyl acetate, and polyvinyl alcohol is used as a protective colloid thereof.

[0011] Preferably, the sand is natural river sand, machine-made sand or quartz sand with a fineness of 40-70 mesh and a water content of less than 0.5%, wherein the clay content of the natural river sand is less than 1%, the crushing value index of the machine-made sand is less than 20%, and the stone powder content is less than 1%.

[0012] Preferably, the cement-based 3D printing light building ink further comprises an admixture and an auxiliary agent, the admixture comprises a water reducing agent, a lignin fiber and a thickening agent, and the auxiliary agent is water, wherein, based on 100 parts of the cement-based 3D printing light building ink, the weight fraction of the water reducing agent is 0.05-0.15 parts, the weight fraction of the lignin fiber is 0.05-0.15 parts, the weight fraction of the thickening agent is 0.05-0.15 parts, and the weight fraction of the water is 12-16 parts.

[0013] Preferably, the water reducing agent is a polycarboxylic acid water reducing agent powder, and the water reducing rate is 35%.

[0014] Preferably, the lignin fiber has a length of 250-500 μm.

[0015] Preferably, the thickening agent is hydroxyethyl methyl cellulose, and the viscosity is 40,000.

[0016] A preparation method of a cement-based 3D printing light building ink, comprising the following steps:

[0017] Step a: mixing cement, sand, polysilicon waste, lignin fiber, thickening agent and flexible glue powder, and stirring uniformly to obtain a mixture;

[0018] Step b: dissolve the water reducing agent in water first; then add two-thirds of the water reducing agent solution into the mixture obtained in step a for the first stirring, and stir until uniform; then add the remaining one-third of the water reducing agent solution for the second stirring, until the mixture is in a uniform and stable state, to obtain the cement-based 3D printing light building ink.

[0019] Preferably, the stirrer used in the stirring of steps a and b is a special vertical shaft planetary stirrer, and the stirring speed is 25-30 rpm; in step a, the stirring time is 3-5 minutes; in step b, the stirring time of the first stirring is 2-3 minutes, and the stirring time of the second stirring is 3-5 minutes.

[0020] The cement-based 3D printing light building ink and the preparation method thereof of the present application utilize industrial solid waste, solve the problem of difficult recovery of a large amount of wastewater containing Al, Fe and Ca in the production process of a polysilicon enterprise, apply the polysilicon waste to the 3D printing light building ink, replace the high-priced white carbon black with the polysilicon waste, reduce the production cost, and the polysilicon waste contains a flocculating agent and a Fenton reagent, which release gas, so that the printing light building ink has the characteristics of light weight, plasticity and easy construction, the moderately expanded mortar reduces the self-weight of the material, and the application space of the 3D printing light building ink is widened. The cement-based 3D printing light building ink meets the performance requirements of the conveying and extrusion accumulation process suitable for printing, has excellent extrusion, accumulation and thixotropy, and the printed body after hardening has high strength, interlayer adhesion and low drying shrinkage, has strong adaptability, is more suitable for construction in a high-temperature environment in summer, the material is light in weight, and the self-weight of the building is reduced. DETAILED DESCRIPTION

[0021] The following further describes the specific embodiments of the cement-based 3D printing light building ink and the preparation method thereof of the present application. The cement-based 3D printing light building ink and the preparation method thereof of the present application are not limited to the description of the following examples.

[0022] The cement-based lightweight building ink for 3D printing of the present invention comprises cement, sand, polysilicon waste, and flexible adhesive powder, wherein the cement comprises 30-42 parts by weight, the sand comprises 53-65.5 parts by weight, the polysilicon waste comprises 3-5 parts by weight, and the flexible adhesive powder comprises 1.5-2 parts by weight. The cement-based lightweight building ink for 3D printing of the present invention meets the performance requirements of suitable printing conveying and extrusion deposition processes, exhibiting excellent extrudability, buildability, and thixotropy. Simultaneously, the hardened printed body possesses high strength, interlayer adhesion, and low drying shrinkage, demonstrating strong adaptability and making it more suitable for construction in high-temperature summer environments. The material is lightweight, reducing the building's self-weight. Furthermore, by utilizing industrial solid waste, the problem of difficult recycling of large amounts of wastewater containing Al, Fe, and Ca during the production process of polysilicon enterprises can be solved. Polysilicon waste can be applied to lightweight building inks for 3D printing. Polysilicon waste replaces expensive silica, reducing production costs. Moreover, polysilicon waste contains flocculants and Fenton reagents, which release gases, giving the lightweight building inks lightweight, malleable, and easy-to-apply properties. The moderately expanding mortar reduces the material's weight, broadening the application scope of lightweight building inks for 3D printing.

[0023] Preferably, the cement is a mixture of silicate cement and sulfoaluminate cement, wherein the mass ratio of silicate cement to sulfoaluminate cement is 2:1 to 7:3. The use of a composite of P.O42.5 ordinary silicate cement and sulfoaluminate cement aims to regulate the setting time of the printing ink and improve its early strength. The ratio of ordinary silicate cement to sulfoaluminate cement can be adjusted appropriately according to construction needs. The suitable open working time for construction is controlled at 40 to 60 minutes, and the ink flowability is 160 to 200 mm.

[0024] Preferably, the polysilicon waste is a semi-dry powder material obtained by flocculation and oxidation of the cutting cleaning fluid in the polysilicon production process, with a water content of 20-25%, that is, polysilicon waste material after the cutting cleaning fluid has been treated with flocculant and Fenton reagent.

[0025] Preferably, the flexible adhesive powder is a VAE redispersible latex powder, which is a copolymer of ethylene and vinyl acetate, with polyvinyl alcohol (PVA) as its protective colloid. The flexible adhesive powder can improve the printing time of cement-based 3D printing lightweight building inks, increase bond strength, reduce elastic modulus, and enhance water-repellent properties, thus exhibiting better durability and weather resistance than other building materials.

[0026] Preferably, the sand is natural river sand, manufactured sand, or quartz sand with a fineness of 40-70 mesh and a moisture content of less than 0.5%, wherein the mud content of the natural river sand is less than 1%, the crushing value of the manufactured sand is less than 20%, and the stone powder content is less than 1%.

[0027] Furthermore, the cement-based 3D printing lightweight building ink of the present invention also includes admixtures and additives. The admixtures include water-reducing agents, lignin fibers, and thickeners. The additive is water. Based on 100 parts of cement-based 3D printing lightweight building ink, the weight parts of the water-reducing agent are 0.05 to 0.15 parts, the weight parts of the lignin fibers are 0.05 to 0.15 parts, the weight parts of the thickener are 0.05 to 0.15 parts, and the weight parts of the water are 12 to 16 parts.

[0028] Preferably, the water-reducing agent is a polycarboxylate water-reducing agent powder with a water reduction rate of 35%.

[0029] Preferably, the lignin fiber length is 250–500 μm. The lignin fiber is used as a water-retaining agent, and also has certain anti-cracking and mortar plasticity-improving effects, reducing plastic shrinkage and maintaining ink stability during printing.

[0030] Preferably, the thickener is hydroxyethyl methyl cellulose (HEMC) with a viscosity of 40,000. Because the structure of 3D printed bodies is thin and moisture dissipates quickly after molding, HEMC is chosen as the thickener. HEMC has more hydrophilic groups than other thickeners such as HPMC, resulting in better water retention, especially better thermal stability. Its high-temperature water retention loss is less than that of general thickeners, making it more suitable for construction in high-temperature summer environments.

[0031] The method for preparing cement-based 3D printing lightweight building ink of the present invention includes the following steps:

[0032] Step a: Mix cement, sand, polysilicon waste, lignin fiber, thickener, and flexible adhesive powder, and stir evenly to obtain a mixture;

[0033] Step b: Dissolve the water-reducing agent in water first; then add two-thirds of the water-reducing agent aqueous solution to the mixture obtained in step a and stir once until uniform; then add the remaining one-third of the water-reducing agent aqueous solution and stir a second time until the mixture is uniform and stable, thus obtaining cement-based 3D printing lightweight building ink.

[0034] Preferably, the mixer used for stirring in steps a and b is a dedicated vertical shaft planetary mixer with a stirring speed of 25-30 rpm; in step a, the stirring time is 3-5 minutes; in step b, the stirring time for the first stirring is 2-3 minutes, and the stirring time for the second stirring is 3-5 minutes. Through two stirrings, the water-reducing agent aqueous solution is thoroughly and evenly mixed with the mixture, better utilizing the water-reducing agent's effect and thus improving the stability of the cement-based 3D printing lightweight building ink. The components of the cement-based 3D printing lightweight building ink can adopt the preferred proportions of the cement-based 3D printing lightweight building ink of this invention.

[0035] The following examples, from Examples 1 to 4, provide a more detailed description of the cement-based 3D printing lightweight building ink and its preparation method in this invention.

[0036] Example 1

[0037] This embodiment of the cement-based 3D printing lightweight building ink comprises 21 parts of silicate cement with a strength grade of 42.5, 9 parts of sulfoaluminate cement with a strength grade of 42.5, 65.5 parts of natural river sand, 3 parts of polysilicon waste, 1.5 parts of VAE redispersible latex powder, admixtures, and auxiliary agents. Based on 100 parts of the cement-based 3D printing lightweight building ink, the admixtures in this embodiment include 0.05 parts of a water-reducing agent with a water reduction rate of 35%, 0.05 parts of lignin fiber, and 0.08 parts of HEMC with a viscosity of 40,000; the auxiliary agent in this embodiment is 12 parts of water. The polysilicon waste is a semi-dry powder obtained by flocculation and oxidation of the cutting cleaning fluid from the polysilicon production process, with a moisture content of 20%; the lignin fiber has a length of 250–500 μm; the natural river sand has a fineness of 40–70 mesh, a moisture content of less than 0.5%, and a mud content of less than 1%.

[0038] The method for preparing cement-based 3D printing lightweight building ink in this embodiment includes the following steps:

[0039] Step a: Mix 21 parts silicate cement, 9 parts sulfoaluminate cement, 65.5 parts natural river sand, 3 parts polysilicon waste, 0.05 parts lignin fiber, 0.05 parts HEMC, and 1.5 parts VAE redispersible latex powder, stir evenly for 3 minutes to obtain the mixture;

[0040] Step b: Dissolve 0.05 parts of water-reducing agent in 12 parts of water; then add two-thirds of the water-reducing agent aqueous solution to the mixture obtained in step a and stir for 2 minutes until uniform; then add the remaining one-third of the water-reducing agent aqueous solution and stir for 3 minutes until the mixture is uniform and stable, thus obtaining cement-based 3D printing lightweight building ink.

[0041] The mixer used in steps a and b is a dedicated vertical shaft planetary mixer with a mixing speed of 30 rpm.

[0042] The cement-based lightweight building ink for 3D printing prepared in this embodiment has a flowability of 180 mm, and its open working time meets the requirements for printing construction. Later tests showed that its 28-day compressive strength was 37.5 MPa, its 28-day bond strength was 1.4 MPa, and its 28-day impermeability pressure was 1.9 MPa.

[0043] Example 2

[0044] This embodiment of the cement-based 3D printing lightweight building ink comprises 25 parts of silicate cement with a strength grade of 42.5, 11 parts of sulfoaluminate cement with a strength grade of 42.5, 58.3 parts of manufactured sand, 4 parts of polysilicon waste, 1.7 parts of VAE redispersible latex powder, admixtures, and auxiliary agents. Based on 100 parts of the cement-based 3D printing lightweight building ink, the admixtures in this embodiment include 0.07 parts of a water-reducing agent with a water reduction rate of 35%, 0.05 parts of lignin fiber, and 0.08 parts of HEMC with a viscosity of 40,000; the auxiliary agent in this embodiment is 13 parts of water. The polysilicon waste is a semi-dry powder obtained by flocculation and oxidation of the cutting cleaning fluid from the polysilicon production process, with a moisture content of 25%; the lignin fiber has a length of 250–500 μm; the manufactured sand has a fineness of 40–70 mesh, a moisture content of less than 0.5%, a crushing value of less than 20%, and a stone powder content of less than 1%.

[0045] The method for preparing cement-based 3D printing lightweight building ink in this embodiment includes the following steps:

[0046] Step a: Mix 25 parts silicate cement, 11 parts sulfoaluminate cement, 58.3 parts manufactured sand, 4 parts polysilicon waste, 0.05 parts lignin fiber, 0.08 parts HEMC, and 1.7 parts VAE redispersible latex powder, stir evenly for 5 minutes to obtain the mixture;

[0047] Step b: Dissolve 0.07 parts of water-reducing agent in 13 parts of water; then add two-thirds of the water-reducing agent aqueous solution to the mixture obtained in step a and stir for 3 minutes until uniform; then add the remaining one-third of the water-reducing agent aqueous solution and stir for 5 minutes until the mixture is uniform and stable, thus obtaining cement-based 3D printing lightweight building ink.

[0048] The mixer used in steps a and b is a dedicated vertical shaft planetary mixer with a mixing speed of 30 rpm.

[0049] The cement-based lightweight building ink for 3D printing prepared in this embodiment has a flowability of 185 mm, and its open working time meets the requirements for printing construction. Later tests showed that its 28-day compressive strength was 46.5 MPa, its 28-day bond strength was 1.5 MPa, and its 28-day impermeability pressure was 2.1 MPa.

[0050] Example 3

[0051] This embodiment of the cement-based 3D printing lightweight building ink comprises 28 parts of silicate cement with a strength grade of 42.5, 12 parts of sulfoaluminate cement with a strength grade of 42.5, 53 parts of quartz sand, 5 parts of polysilicon waste, 2 parts of VAE redispersible latex powder, admixtures, and auxiliary agents. Based on 100 parts of the cement-based 3D printing lightweight building ink, the admixtures in this embodiment include 0.07 parts of a water-reducing agent with a water reduction rate of 35%, 0.12 parts of lignin fiber, and 0.10 parts of HEMC with a viscosity of 40,000; the auxiliary agent in this embodiment is 15 parts of water. The polysilicon waste is a semi-dry powder obtained by flocculation and oxidation of the cutting cleaning fluid from the polysilicon production process, with a moisture content of 24%; the lignin fiber has a length of 250–500 μm; and the quartz sand has a fineness of 40–70 mesh and a moisture content of less than 0.5%.

[0052] The method for preparing cement-based 3D printing lightweight building ink in this embodiment includes the following steps:

[0053] Step a: Mix 28 parts silicate cement, 12 parts sulfoaluminate cement, 53 parts quartz sand, 5 parts polysilicon waste, 0.12 parts lignin fiber, 0.10 parts HEMC, and 2 parts VAE redispersible latex powder, stir evenly for 4 minutes to obtain the mixture.

[0054] Step b: Dissolve 0.07 parts of water-reducing agent in 15 parts of water; then add two-thirds of the water-reducing agent aqueous solution to the mixture obtained in step a and stir for 2 minutes until uniform; then add the remaining one-third of the water-reducing agent aqueous solution and stir for 5 minutes until the mixture is uniform and stable, thus obtaining cement-based 3D printing lightweight building ink.

[0055] The mixer used in steps a and b is a dedicated vertical shaft planetary mixer with a mixing speed of 30 rpm.

[0056] The cement-based lightweight building ink for 3D printing prepared in this embodiment has a flowability of 185 mm, and its open working time meets the requirements for printing construction. Later tests showed that its 28-day compressive strength was 57.2 MPa, its 28-day bond strength was 1.6 MPa, and its 28-day impermeability pressure was 2.3 MPa.

[0057] Example 4

[0058] This embodiment of the cement-based 3D printing lightweight building ink comprises 28 parts of silicate cement with a strength grade of 42.5, 14 parts of sulfoaluminate cement with a strength grade of 42.5, 53 parts of quartz sand, 3 parts of polysilicon waste, 2 parts of VAE redispersible latex powder, admixtures, and auxiliary agents. Based on 100 parts of the cement-based 3D printing lightweight building ink, the admixtures in this embodiment include 0.15 parts of a water-reducing agent with a water reduction rate of 35%, 0.15 parts of lignin fiber, and 0.15 parts of HEMC with a viscosity of 40,000; the auxiliary agent in this embodiment is 16 parts of water. The polysilicon waste is a semi-dry powder obtained by flocculation and oxidation of the cutting cleaning fluid from the polysilicon production process, with a moisture content of 24%; the lignin fiber has a length of 250–500 μm; and the quartz sand has a fineness of 40–70 mesh and a moisture content of less than 0.5%.

[0059] The method for preparing cement-based 3D printing lightweight building ink in this embodiment includes the following steps:

[0060] Step a: Mix 28 parts silicate cement, 14 parts sulfoaluminate cement, 53 parts quartz sand, 3 parts polysilicon waste, 0.15 parts lignin fiber, 0.15 parts HEMC, and 2 parts VAE redispersible latex powder, stir evenly for 4 minutes to obtain the mixture.

[0061] Step b: Dissolve 0.15 parts of water-reducing agent in 16 parts of water; then add two-thirds of the water-reducing agent aqueous solution to the mixture obtained in step a and stir for 3 minutes until uniform; then add the remaining one-third of the water-reducing agent aqueous solution and stir for 5 minutes until the mixture is uniform and stable, thus obtaining cement-based 3D printing lightweight building ink.

[0062] The mixer used in steps a and b is a dedicated vertical shaft planetary mixer with a mixing speed of 25 rpm.

[0063] The cement-based lightweight building ink for 3D printing prepared in this embodiment has a flowability of 183 mm, and its open working time meets the requirements for printing construction. Later tests showed that its 28-day compressive strength was 56.2 MPa, its 28-day bond strength was 1.5 MPa, and its 28-day impermeability pressure was 2.0 MPa.

[0064] The compressive strength, bond strength, and impermeability pressure of Examples 1 and 2 are significantly lower. The compressive strength mainly depends on the content of silicate cement and sulfoaluminate cement; Examples 1 and 2 have lower silicate cement and sulfoaluminate cement content than Example 3. Bond strength and impermeability pressure, besides being related to the content of the two types of cement, mainly depend on the content of VAE redispersible latex powder; Examples 1 and 2 have lower VAE redispersible latex powder content than Example 3. Although the content of the two types of cement and VAE redispersible latex powder in Example 4 is the same as or higher than in Example 3, the sulfoaluminate cement content is slightly higher. This shortens the open working time of the printed lightweight building ink, requiring an increase in water and thickener to adjust the open working time. The increase in thickener and water will reduce compressive strength, bond strength, and impermeability pressure. In conclusion, Example 3 is the optimal example.

[0065] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A cement-based lightweight architectural ink for 3D printing, characterized in that: The material includes cement, sand, polysilicon waste, and flexible adhesive powder. The cement comprises 30-42 parts by weight, the sand comprises 53-65.5 parts by weight, the polysilicon waste comprises 3-5 parts by weight, and the flexible adhesive powder comprises 1.5-2 parts by weight. The polysilicon waste is a semi-dry powder obtained by flocculating and oxidizing the cutting cleaning fluid used in the polysilicon production process with flocculants and Fenton's reagent. It has a moisture content of 20-25% and releases gas to reduce the material's weight.

2. The cement-based 3D printing lightweight building ink according to claim 1, characterized in that: The cement is a mixture of silicate cement and sulfoaluminate cement, wherein the mass ratio of silicate cement to sulfoaluminate cement is 2:1 to 7:

3.

3. The cement-based 3D printing lightweight building ink according to claim 1, characterized in that: The flexible adhesive powder is VAE redispersible latex powder, which is a copolymer of ethylene and vinyl acetate, with polyvinyl alcohol as its protective colloid.

4. The cement-based 3D printing lightweight building ink according to claim 1, characterized in that: The sand is natural river sand, manufactured sand, or quartz sand with a fineness of 40-70 mesh and a moisture content of less than 0.5%. The mud content of the natural river sand is less than 1%, the crushing value of the manufactured sand is less than 20%, and the stone powder content is less than 1%.

5. The cement-based 3D printing lightweight building ink according to claim 1, characterized in that: It also includes admixtures and additives. The admixtures include water-reducing agents, lignin fibers, and thickeners. The additive is water. Based on 100 parts of cement-based 3D printing lightweight building ink, the weight parts of the water-reducing agent are 0.05 to 0.15 parts, the weight parts of the lignin fibers are 0.05 to 0.15 parts, the weight parts of the thickener are 0.05 to 0.15 parts, and the weight parts of the water are 12 to 16 parts.

6. The cement-based 3D printing lightweight building ink according to claim 5, characterized in that: The water-reducing agent is a polycarboxylate water-reducing agent powder with a water reduction rate of 35%.

7. The cement-based 3D printing lightweight building ink according to claim 5, characterized in that: The lignin fibers have a length of 250–500 μm.

8. The cement-based 3D printing lightweight building ink according to claim 5, characterized in that: The thickener is hydroxyethyl methyl cellulose with a viscosity of 40,000.

9. A method for preparing a cement-based lightweight building ink for 3D printing, characterized in that: The method for preparing the cement-based 3D printing lightweight building ink according to any one of claims 1-8 comprises the following steps: Step a: Mix cement, sand, polysilicon waste, lignin fiber, thickener, and flexible adhesive powder, and stir evenly to obtain a mixture; Step b: Dissolve the water-reducing agent in water first; then add two-thirds of the water-reducing agent aqueous solution to the mixture obtained in step a and stir once until uniform; then add the remaining one-third of the water-reducing agent aqueous solution and stir a second time to obtain cement-based 3D printing lightweight building ink.

10. The method for preparing cement-based 3D printing lightweight building ink according to claim 9, characterized in that: The mixer used for mixing in steps a and b is a dedicated vertical shaft planetary mixer with a mixing speed of 25-30 rpm. In step a, the mixing time is 3-5 minutes. In step b, the mixing time for the first mixing is 2-3 minutes, and the mixing time for the second mixing is 3-5 minutes.