CN111348868A

CN111348868A - Fly ash-based polymer 3D printing material and preparation method thereof

Info

Publication number: CN111348868A
Application number: CN202010130011.7A
Authority: CN
Inventors: 郭晓潞; 杨君奕
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2020-02-28
Filing date: 2020-02-28
Publication date: 2020-06-30

Abstract

The invention relates to a fly ash based polymer 3D printing material and a preparation method thereof, wherein the fly ash based polymer 3D printing material comprises the following raw materials: base material, quartz sand, toughening agent, thickening agent, dispersible emulsion powder and composite excitant; wherein the base material comprises the following components in percentage by weight: 80-90% of fly ash, 5-10% of mineral powder and 5-10% of silica fume; the compound excitant is prepared from water glass and NaOH. According to the invention, the geopolymer 3D printing material is prepared from the fly ash, the mineral powder and the silica fume, so that on one hand, the resource utilization way of solid waste is expanded, the reduction, the resource utilization and the high-value resource utilization of the solid waste are realized, the pollution problem of the occupied site of waste stacking is solved, and a new way is created for protecting the ecological environment; on the other hand, the fly ash-based polymer material is innovatively combined with the 3D printing technology to establish a geopolymer system for 3D printing buildings, and the strategy of national intelligent high-end manufacturing and civil engineering sustainable development is met.

Description

Fly ash-based polymer 3D printing material and preparation method thereof

Technical Field

The invention belongs to the technical field of resource utilization of building materials and solid wastes, and particularly relates to a fly ash-based polymer 3D printing material and a preparation method thereof.

Background

In less than 200 years, the Portland cement is widely applied and becomes an indispensable material foundation in modern human civilization construction. However, it is possible to use a single-layer,portland cement is a cementing material with high energy consumption and high resource consumption. In addition, a large amount of harmful gas such as NO is emitted during the cement production process_X、SO₂And dust and the like. Therefore, the development of a novel cementing material with low energy consumption and high benefit, which can replace or be superior to portland cement, is an inherent demand of social development, and the geopolymer is a novel environment-friendly inorganic cementing material.

Fly ash is a solid waste produced in thermal power plants, metallurgy, chemical industry and other industries. The abundant coal resources in China still dominate thermal power generation in the power generation industry. The electric coal accounts for more than 50% of the coal consumption in China, and the utilization form of the coal resource can be maintained for a long time. A large amount of fly ash is generated in the coal burning process and accounts for 15-40% of the mass of the raw coal. Fly ash has become one of the most industrial wastes in our country which accumulate the storage amount and occupy the cultivated land.

The ore powder is a by-product in the blast furnace ironmaking process. In the iron-making process, iron oxide is reduced into metallic iron at high temperature, impurities in iron ore such as silicon dioxide, aluminum oxide and the like react with lime and the like to generate a melt with silicate and aluminosilicate as main components, and the melt is quenched to form loose and porous granular substances, namely blast furnace mineral powder, which is called mineral powder for short.

The silicon ash, also called as micro silicon powder or condensed silicon ash, is a large amount of SiO with strong volatility produced in the ore-smelting electric furnace when ferroalloy is used for smelting ferrosilicon and industrial silicon (metallic silicon)₂And Si gas, which is a byproduct in large-scale industrial smelting and is formed by quick oxidation, condensation and precipitation with air after the gas is discharged.

Informatization and digitization are the inevitable trends in the development of various industries, and the world is facing the wave of the third historical industrial revolution. The 3D printing technology is evaluated as the most marked production tool in the third industrial revolution. The building 3D printing technology is a novel building technology which organically combines 3D printing and building construction. Compared with the traditional building technology, the building 3D printing technology has the advantages that the speed is high, a template is not needed, a large number of building workers are not needed, the labor cost can be saved, and the building efficiency is improved. At present, the 3D printing technology for buildings is mainly in the research and development stage, and it is now possible to print some building components and some buildings with simple structure and shape by using cement-based materials. However, the research on domestic polymer 3D printing materials is less, and the research on fly ash-based polymer 3D printing materials is almost blank.

Disclosure of Invention

The invention aims to provide a fly ash-based polymer 3D printing material and a preparation method thereof, aiming at the problem of limitation of resource utilization of solid wastes in the prior art.

The invention aims to widen the utilization way of solid waste resources, and provides a novel geopolymer material suitable for 3D printing, which is prepared by taking fly ash, mineral powder and silica fume as main raw materials, water glass and sodium hydroxide as a composite excitant, quartz sand as an aggregate, PVA (polyvinyl alcohol) fiber as a toughening material and hydroxypropyl cellulose ether and dispersible latex powder as additives.

The purpose of the invention is realized by the following technical scheme:

a fly ash-based polymer 3D printing material comprises the following raw materials: base material, quartz sand, toughening agent, thickening agent, dispersible emulsion powder and composite excitant; wherein the base material comprises the following components in percentage by weight: 80-90% of fly ash, 5-10% of mineral powder and 5-10% of silica fume; the compound excitant is prepared from water glass and NaOH.

Preferably, the modulus M of the composite exciting agent is 1.4-1.6, wherein M represents SiO₂Mole number of (3) and Na₂The ratio of the number of moles of O.

Preferably, the addition amount of the compound excitant water glass and NaOH is calculated according to the formula (1):

in the formula (1), G₁Is the mass of water glass, and N is Na₂Mass ratio of O to water glass, M₁The initial modulus of the water glass; m₂The preparation modulus of the composite excitant is shown; p is the purity of NaOH; g₂Is the doping mass of NaOH. NaOH is added into water glass firstly, and then is mixed with other materials, so that the composite excitant can be mixed more fully.

The addition amount of the composite excitant is the Na introduced₂The content of O is 5-8% of the total mass of the base material.

Preferably, the fly ash is power plant fly ash or II-grade ash, and the specific surface area of the fly ash is 300-400 m²/kg；

The mineral powder is residue after mineral separation or smelting, and the specific surface area of the mineral powder is 400-500 m²/kg；

The silicon ash is a byproduct of iron and steel alloy during smelting ferrosilicon and industrial silicon, and the specific surface area is 15000-30000 m²/kg。

Preferably, the grain composition of the quartz sand is 40-80 meshes, and the addition amount is 1.5 times of the mass of the base material.

Preferably, the toughening agent is polypropylene glycol fiber, the elastic modulus is 40-45 Gpa, and the ultimate elongation is 6-10%. The addition amount accounts for 0.1-0.3% of the total volume of the base material, the polyvinyl alcohol fiber is also called PVA fiber, the PVA fiber with different lengths can be obtained by preparing a polyvinyl alcohol raw material into a tow by adopting advanced technical means such as wet spinning, dry spinning and the like, and cutting the tow, for example, Kuraray-II RECS-15 type polyvinyl alcohol fiber produced by Kuraray company of Japan can be adopted.

Preferably, the thickening agent is hydroxypropyl methyl cellulose ether, the viscosity specification is 20 ten thousand, and the surface density is about 0.5g/cm³The addition amount accounts for 2.5% +/-0.1% of the mass of the base material. The hydroxypropyl cellulose ether is a non-ionic polymer, and hydroxyl on a molecular chain of the hydroxypropyl cellulose ether and oxygen atoms on ether bonds can be associated with water molecules to form hydrogen bonds, so that free water is changed into bound water, and a good water retention effect and a thickening effect are achieved.

Preferably, the bulk density of the dispersible latex powder is 460-560 kg/m³The particle size is 0.5-8 um, the addition amount accounts for 0.2-0.3 percent of the mass of the base material, and the base material can beThe dispersed emulsion powder is water-soluble redispersible powder, is a powder adhesive prepared by spray drying ethylene/vinyl acetate copolymer and the like, can be quickly redispersed into emulsion after contacting with water, and has the performances of high bonding capability, water resistance, constructability, heat insulation property and the like.

Preferably, the water-solid ratio adopted by the geopolymer 3D printing material is 0.28-0.32, wherein: the water in the water-solid ratio comprises the water content and the external water content of the sodium water glass solution; the solids in the water-to-solid ratio refers to the mass of the base material.

A preparation method of a fly ash based polymer 3D printing material comprises the following steps: mixing mineral powder, silica fume and fly ash, adding quartz sand, a thickening agent, dispersible latex powder and a toughening agent, fully mixing, adding a composite exciting agent, controlling the water-solid ratio to be 0.28-0.32, mixing, performing 3D printing, and performing geopolymer reaction, condensation and hardening to obtain the geopolymer 3D printing body.

The invention creatively combines the fly ash-based polymer material with the 3D printing technology to establish a geopolymer system for 3D printing buildings. Meanwhile, the resource recycling means of various solid waste materials is widened, the burden of the environment is reduced, the cost is reduced, the resource consumption is reduced, and the requirements of energy conservation and emission reduction are met.

Compared with the prior art, the invention has the following beneficial effects and advantages:

3D printing belongs to template-free and rib-free construction, so that the toughness of a printing body is improved to be of great importance. According to the invention, the PVA fiber is used for toughening the geopolymer 3D printing material, so that the novel toughened geopolymer 3D printing material is prepared.

When the matrix is pulled, the matrix can transmit stress to the PVA fiber, and then the stress is transmitted back to the matrix which is not cracked through the fiber, so that the effect of dispersing stress is achieved, and the compressive strength and the tensile strength of the geopolymer 3D printing material can be effectively improved. On the basis, mineral powder and silica fume are doped, after a certain amount of fly ash is replaced by the mineral powder, the mineral powder is filled in gaps among fly ash particles, free water wrapped among the fly ash particles is released, so that the free water in the geopolymer is increased, a certain lubricating effect is achieved among the fly ash particles, and the rheological property of the geopolymer is increased; after the silica fume is doped, the apparent viscosity of the geopolymer is increased, because the specific surface area of the silica fume is larger, the water demand is higher, and the cohesiveness of the geopolymer can be improved after the silica fume is doped into the geopolymer mortar, so that the thixotropy and the yield stress of the geopolymer 3D printing mortar are effectively improved, and the performance of the geopolymer 3D printing material in the construction process is effectively improved.

The invention maximally connects the traditional cement material, effectively utilizes the 3D printing construction technology, and meets the national strategy of intelligent high-end manufacturing and civil engineering sustainable development; meanwhile, industrial wastes such as fly ash and mineral powder are utilized, so that the resource recycling way is widened, a new way is provided for the utilization of the wastes, the burden of the environment is reduced, the cost is reduced, the resource consumption is reduced, and the requirements of energy conservation and emission reduction are met.

Drawings

FIG. 1 shows thixotropy of examples and comparative examples;

FIG. 2 shows the rheology of the examples and comparative examples;

FIG. 3 is a 3D printing object diagram of geopolymer.

Detailed Description

The present invention will be described in further detail with reference to examples.

The percentages used in the examples of the present invention are mass percentages.

The main raw materials in the experiment of the embodiment of the invention are as follows: the fly ash is obtained from a certain power plant, II-grade ash and has the specific surface area of 350m²In terms of/kg. The mineral powder is residue of a certain refinery, and the specific surface area is about 400-500 m²In terms of/kg. The siliceous dust is a by-product produced by a certain ferrosilicon smelting plant, and the specific surface area is about 15000-30000 m²/kg。

The quartz sand used in the test was one having a particle size distribution of 40 to 80 mesh.

The thickening agent used in the test is hydroxypropyl cellulose ether with the viscosity of 20 ten thousand produced by Shanghai minister and initiator chemical technology Co.

The dispersible latex powder used in the test is 5044N type dispersible latex powder produced by Wake of Germany.

The sodium hydroxide used in the test was NaOH with a purity of 96% by weight; the water glass has a solid content of 43.74% and contains 13.75% of Na₂O, 29.99% SiO₂And 56.26 wt% water.

The toughening agent adopts Kuraray-II RECS-15 type polyvinyl alcohol (PVA) fiber produced by Kuraray company of Japan.

Example 1

The percentage of the raw materials used is as follows: blending amount of fly ash: 80 percent; mixing amount of mineral powder: 10 percent; the doping amount of the silica fume: 10 percent; (the sum of the mass of the mineral powder, the silica fume and the fly ash is 100%).

The fiber mixing amount is as follows: 0.1% (volume mixing amount);

modulus of the composite excitant: 1.5; the mixing amount of the composite excitant (external mixing): 6 percent;

water-solid ratio: 0.30;

bone-to-glue ratio: 1.5;

mixing 10% by mass of mineral powder, 10% by mass of silica fume and 80% by mass of fly ash; adding PVA fiber accounting for 0.1 percent of the total volume of the mineral powder, the silica fume and the fly ash; adding a thickening agent accounting for 2.5 percent of the total mass of the mineral powder, the silica fume and the fly ash; adding dispersible emulsion powder accounting for 0.25 percent of the total mass of the mineral powder, the silica fume and the fly ash; adding 40-80 mesh quartz sand with bone glue ratio of 1.5; adding composite excitant (Na is introduced) accounting for 6 percent of the total mass of the mineral powder, the silica fume and the fly ash₂O content); the water-solid ratio of the system is 0.30, wherein the water comprises two parts of water content and external water content in the water glass solution, namely the water-solid ratio of the system is controlled to be 0.30, and the insufficient water content except the water content in the water glass solution is complemented by the external water content; mixing;

and 3D printing is adopted, and the geopolymer 3D printing material is obtained through geopolymer reaction, coagulation and hardening. FIG. 3 is a 3D printing object diagram of geopolymer.

The compounding ratio of example 1 is shown in table 2. Specifically, the compound activator is prepared by mixing water glass and sodium hydroxide, and controlling the mixtureThe modulus M is 1.5, the water glass having a solids content of 43.74%, in fact, Na₂The content of O is 21.24%, SiO₂In an amount of 27.46%, H₂The O content was 51.50%, the purity of sodium hydroxide was 96%, and the amount of sodium hydroxide added was 16.76g, as shown in Table 1.

TABLE 1 sodium silicate modulus before and after adjustment of the content of the main component

TABLE 2 compounding ratio of example 1

Example 2

The compounding ratio of example 2 is shown in table 3.

TABLE 3 compounding ratio of example 2

Example 3

The compounding ratio of example 3 is shown in Table 4.

TABLE 4 compounding ratio of example 3

Example 4

The compounding ratio of example 4 is shown in Table 5.

TABLE 5 compounding ratio of example 4

Example 5

The compounding ratio of example 5 is shown in Table 6.

TABLE 6 compounding ratio of example 5

Comparative example 1

The compounding ratio of comparative example 1 is shown in table 7.

TABLE 7 compounding ratio of comparative example 1

Comparative example 2

The compounding ratio of comparative example 2 is shown in Table 8.

TABLE 8 compounding ratio of comparative example 2

The mechanical property of a printed body is generally represented by indexes such as compressive strength, tensile strength and the like in the current industry; the constructable performance of the printing body is characterized by indexes such as thixotropy, rheological property and the like.

The basic properties of the geopolymer 3D printing materials prepared in examples 1-5 and comparative examples 1-2 are shown in Table 9. 3D printing belongs to template-free and rib-free construction, so that the toughness of a printing body is improved to be of great importance. As can be seen from table 9, the compressive strength and the ultimate tensile strength (the ultimate tensile strength is the strength at break of the test block) of the geopolymer 3D printing material of each example are significantly improved compared with the comparative example.

TABLE 9 Performance data for examples and comparative examples

Thixotropy and rheological property indexes directly influence the constructability of the 3D printing mortar, so that the 3D printing material needs to have good thixotropy and rheological property. Fluids whose viscosity decreases with increasing shear time are called thixotropic fluids. Its curve form is represented as: the "up curve" no longer overlaps the "down curve" in the flow diagram, but rather a closed "shuttle" thixotropic ring is formed between the two curves. The size of the area of this thixotropic ring determines the measure of thixotropic performance, with larger thixotropic rings giving better thixotropy, and the fitted graph of fig. 1 was processed by origin for polygonal area, with the results shown in table 10.

TABLE 10 thixotropic Ring area for examples and comparative examples

	Example 1	Example 2	Example 3	Example 4	Example 5	Comparative example 1	Comparative example 2
								Area of graph fit	3006.12	3544.15	5077.03	4854.68	2384.41	2282.11	1551.26

As can be seen from table 10, the geopolymer 3D printing material has good thixotropy, and also has a certain thixotropy after being incorporated into PVA fibers. The rheology of the geopolymer 3D printing material conforms to the Bingham fluid model (FIG. 2) and has a certain yield stress (shear rate of 0 s)^-1Shear stress of the time), the yield stress of the geopolymer 3D printed material after the addition of the fibers is higher than that of the non-doped fibers.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. The fly ash-based polymer 3D printing material is characterized by comprising the following raw materials: base material, quartz sand, toughening agent, thickening agent, dispersible emulsion powder and composite excitant;

wherein the base material comprises the following components in percentage by weight: 80-90% of fly ash, 5-10% of mineral powder and 5-10% of silica fume; the compound excitant is prepared from water glass and NaOH.

2. The fly ash-based 3D polymer printing material as claimed in claim 1, wherein the modulus M of the composite activator is 1.4-1.6, wherein M represents SiO₂Mole number of (3) and Na₂The ratio of the number of moles of O.

3. The fly ash based 3D printing material as claimed in claim 2, wherein the addition amount of the composite activator water glass and NaOH is calculated according to formula (1):

in the formula (1), G₁Is the mass of water glass, and N is Na₂Mass ratio of O to water glass, M₁The initial modulus of the water glass; m₂The preparation modulus of the composite excitant is shown; p is the purity of NaOH; g₂The doping quality of NaOH;

4. The fly ash based 3D printing material as claimed in claim 1, wherein the fly ash is power plant fly ash, class II ash, and has a specific surface area of 300-400 m²/kg；

5. The fly ash based 3D printing material as claimed in claim 1, wherein the quartz sand has a particle size distribution of 40-80 mesh and is added in an amount of 1.5 times the mass of the base material.

6. The fly ash based 3D printing material as claimed in claim 1, wherein the toughening agent is a polypropylene alcohol fiber, the elastic modulus is 40-45 Gpa, and the ultimate elongation is 6 wt% -10%. The adding amount accounts for 0.1 to 0.3 percent of the total volume of the base material.

7. The fly ash based 3D printing material as claimed in claim 1, wherein the thickening agent is hydroxypropyl methyl cellulose ether, the viscosity specification is 20 ten thousand, and the surface density is highThe degree is about 0.5g/cm³The addition amount accounts for 2.5% +/-0.1% of the mass of the base material.

8. The fly ash-based polymer 3D printing material as claimed in claim 1, wherein the bulk density of the dispersible latex powder is 460-560 kg/m³The particle size is 0.5-8 um, and the addition amount accounts for 0.2-0.3% of the mass of the base material.

9. The fly ash based geopolymer 3D printing material according to any one of claims 1-8, wherein the geopolymer 3D printing material adopts a water-solid ratio of 0.28-0.32, wherein: the water in the water-solid ratio comprises the water content and the external water content of the sodium water glass solution; the solids in the water-to-solid ratio refers to the mass of the base material.

10. The method for preparing the fly ash based polymer 3D printing material as claimed in claim 1, comprising the following steps: mixing mineral powder, silica fume and fly ash, adding quartz sand, a thickening agent, dispersible latex powder and a toughening agent, fully mixing, adding a composite exciting agent, controlling the water-solid ratio to be 0.28-0.32, mixing, performing 3D printing, and performing geopolymer reaction, condensation and hardening to obtain the geopolymer 3D printing body.