Clay-based 3D printing special mortar and preparation method thereof

Abstract

The application provides a clay-based 3D printing special mortar, which comprises the following components in parts by weight: clay, 30-40 parts; sand, 32-50 parts; PP fiber, 0.12-0.15 parts; water glass alkali residue, 4-6 parts; calcium oxide, 3-5 parts; fly ash, 1.5-2 parts; water, 11-15 parts; water reducing agent, 0.02-0.03 parts. A preparation method of the clay-based 3D printing special mortar comprises the following steps: S1: pre-mixing clay, sand, fly ash and calcium oxide; S2: adding water and water glass alkali residue and stirring; S3: continuously adding PP fiber and stirring again to obtain the clay-based 3D printing special mortar. The clay-based 3D printing special mortar of the application improves the early strength of the clay-based special mortar based on the excitation effect of sodium silicate in geopolymer.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of 3D printing materials, in particular to a clay-based 3D printing special mortar and a preparation method thereof. BACKGROUND

[0002] 3D printing technology, also known as additive manufacturing technology, has attracted more and more attention from domestic and foreign experts and scholars due to its characteristics such as no need for any mold or machining, direct production of parts according to computer graphics data, and suitability for various complex structures. With continuous research and development, 3D printing technology has been gradually applied to traditional manufacturing, medical industry, cultural heritage protection, civil engineering, aerospace and many other fields.

[0003] 3D printing special mortar is mainly divided into cement-based, gypsum-based and clay-based according to its hardening mechanism and raw material composition. Compared with cement mortar, the flexibility of its hardening mechanism makes it have strong absorption capacity for industrial solid waste which is difficult to apply in cement-based materials.

[0004] Water glass alkali slag is a precipitate produced after the solid phase is dissolved in the production process of water glass. The precipitate is mainly composed of crystalline silicon dioxide and sodium silicate hydrate, as well as part of calcium silicate and calcium hydroxide. This industrial waste slag has good grindability and is suitable for preparation into powder. However, sodium silicate hydrate can accelerate the setting and hardening of silicate cement, greatly shorten the setting time of cement, and reduce the 28d strength of cement, so it is difficult to be directly used as an admixture in concrete or as a mixed material in cement production. Moreover, sodium silicate hydrate contains a large amount of sodium oxide, so this industrial waste slag is also not suitable for preparing raw materials from siliceous materials into the kiln for calcination. So far, the comprehensive utilization rate of this industrial waste slag is still close to zero.

[0005] In the clay-based 3D printing special mortar, part of the clay raw material loses water, and a certain amount of metakaolin (kaolin is a kind of clay, which forms metakaolin after calcination and dehydration) is associated in the clay. Sodium silicate has a good excitation effect on metakaolin and other geopolymer materials. SUMMARY

[0006] The present application aims to overcome the defects of the prior art and provide a clay-based 3D printing special mortar and a preparation method thereof. Based on the excitation effect of sodium silicate in geopolymer, an effective treatment method is provided for water glass alkali slag. The moderate excitation of sodium silicate improves the early strength of the clay-based special mortar to a certain extent.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0008] A clay-based 3D printing special mortar, characterized by comprising, in terms of weight fraction,

[0009]

[0010] Preferably, the clay is red clay.

[0011] Preferably, the sand is one of quartz sand or river sand, and the fineness is 50-100 mesh.

[0012] Preferably, the length of the PP fiber is 6-12 mm.

[0013] Preferably, the water glass alkali residue is a precipitate produced after solid phase dissolution in the water glass production process, and the precipitate includes crystalline silicon dioxide and sodium silicate hydrate.

[0014] Preferably, the fly ash is a fly ash produced by a power plant, and the loss on ignition is 2.76%.

[0015] Preferably, the water reducing agent is a cationic polycarboxylic acid powder water reducing agent, and the water reducing rate is 25%.

[0016] The clay-based 3D printing special mortar of the present application uses clay (containing a certain amount of metakaolin, which has super plasticity) as one of the main raw materials, uses the super plasticity of the clay to make the mortar have good extrudability and formability, and the clay-based 3D printing special mortar has higher extrudability and 3D printing capacity than other 3D printing materials, higher early strength, and the 3-day strength can reach about 30 MPa. Moreover, the industrial waste residue, i.e., water glass alkali residue, is used as an activator for geopolymer reaction, solving the problem of extremely low utilization rate of water glass alkali residue, realizing comprehensive utilization of resources, eliminating the problem of pollution of the natural environment by alkali residue, and having ecological and economic benefits, and the prepared 3D printing mortar has high compressive strength and excellent printing construction performance.

[0017] The present application also provides a preparation method of the clay-based 3D printing special mortar.

[0018] S1: pre-mixing clay, sand, fly ash and calcium oxide to obtain a mixture;

[0019] S2: adding water and water glass alkali residue to the mixture obtained in S1, stirring, and causing geopolymer reaction, and the reaction formula is as follows:

[0020] Na2SiO3+CaO+H2O=CaSiO3+2NaOH;

[0021] S3: continuously adding PP fiber, and stirring to obtain the clay-based 3D printing special mortar.

[0022] Preferably, the clay is pretreated by high-temperature calcination before S1, and the particle fineness of the clay used in S1 is 800-2000 mesh.

[0023] Preferably, the water glass alkali residue is pretreated by grinding before S2, and the water glass alkali residue used in S2 is ground to a specific surface area of 400-450 m2 / kg.

[0024] The preparation method of the clay-based 3D printing special mortar of the present application adopts a step-by-step mixing manner, the various dry powders are mixed fully in S1, which can reduce the mixing difficulty of subsequent S2 and S3, water and water glass are added in S2 to generate geopolymer reaction, and stirring is performed to fully chemically react, PP fibers are added in the last S3, so as to not affect the mixing and reaction of S1 and S2, and avoid the problems of agglomeration, difficulty in dispersion, etc. in the stirring process of S1 and S2. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the XRD pattern of the water glass alkali residue of the present application. DETAILED DESCRIPTION

[0026] The following examples given in combination with the accompanying drawings further illustrate the specific embodiments of the clay-based 3D printing special mortar of the present application and the preparation method thereof. The clay-based 3D printing special mortar of the present application and the preparation method thereof are not limited to the description of the following examples.

[0027] The clay-based 3D printing special mortar of the present application comprises, by weight fraction

[0028]

[0029]

[0030] The clay-based 3D printing special mortar of the present application uses clay (containing a certain amount of metakaolin, which has super plasticity) as one of the main raw materials, uses the super plasticity of clay to make the mortar have good extrudability and formability, and the clay-based 3D printing special mortar has higher extrudability and 3D printing capacity than other 3D printing materials, higher early strength, and 3-day strength of about 30 MPa. Moreover, the industrial waste residue-sodium silicate alkali residue is used as an activator of geopolymer reaction, solving the problem of very low utilization rate of sodium silicate alkali residue-industrial waste residue, realizing comprehensive utilization of resources, eliminating the problem of pollution of natural environment by alkali residue, and having ecological and economic benefits, and the prepared 3D printing mortar has high compressive strength and excellent printing construction performance. In addition, the clay-based material has a porous structure on the surface, has good air permeability, and has a certain effect of adjusting indoor humidity; when iron oxide exists in the clay-based material, due to different deposition environments, it will form rich and fascinating colors. Without any artificial color adjustment, any modern paint will lose its luster in front of the natural clay-based material.

[0031] Preferably, the clay is red clay, which is a residual, slope or residual-slope high-plasticity clay formed by weathering of carbonate rocks (such as limestone, dolomite, argillaceous mudstone) under subtropical warm and humid climate conditions. The clay has a clay content of more than 50%, has very good plasticity index, low compressibility and high strength, and therefore is selected as the main binding component of the printing material, and the prepared mortar has good plastic forming ability and strong support, which is very beneficial to the printing forming of various special-shaped structures.

[0032] Preferably, the sand is one of quartz sand or river sand, and the fineness is 50-100 mesh.

[0033] Preferably, the length of the PP fiber (polypropylene fiber) is 6-12 mm. The fiber can improve the anti-cracking ability of the mortar.

[0034] Preferably, the sodium silicate alkali residue is a precipitate produced after solid-phase dissolution in the production process of sodium silicate, and the XRD pattern of the precipitate is as shown in Figure 1 The activation of sodium silicate can promote the occurrence of geopolymer reaction and has the effect of fast setting and early strength, and can make the strength rise to tens of megapascals within a few hours, which is very beneficial to rapid printing engineering and makes the printed structure have good self-supporting ability. In addition, calcium oxide improves the alkaline environment of the clay-based 3D printing special mortar, and the sodium silicate alkali residue is used in combination with calcium oxide (molar ratio within a certain range) to make the mortar have very high early strength.

[0035] Preferably, the fly ash is the fly ash produced by power plants, and the loss on ignition is 2.76%. The fly ash used in the present application is the fly ash produced by Jianqi Power Plant. The fly ash improves the workability of the clay-based 3D printing special mortar, and reduces the mortar mixing time. Preferably, the water reducing agent is a cationic polycarboxylic acid powder water reducing agent, and the water reducing rate is 25%. The water reducing agent improves the workability of the clay-based 3D printing special mortar, increases the mortar density, and improves the mortar strength.

[0036] The preparation method of the clay-based 3D printing special mortar of the present application comprises the following steps:

[0037] S1: Pre-mixing clay, sand, fly ash, calcium oxide and water reducing agent to obtain a mixture;

[0038] S2: Adding water and water glass alkali residue to the mixture obtained in S1 and stirring for 3-5 minutes to cause a geopolymer reaction, and the reaction formula is as follows:

[0039] Na2SiO3+CaO+H2O=CaSiO3+2NaOH;

[0040] S3: Continuously adding PP fibers and stirring for 1 minute to obtain a plastic paste-shaped clay-based 3D printing special mortar suitable for printing.

[0041] In the preparation method of the clay-based 3D printing special mortar of the present application, the various dry powders are mixed in S1, which can reduce the mixing difficulty in subsequent S2 and S3. In S2, water and water glass are added to cause a geopolymer reaction, and stirring is performed to fully react chemically. In the final S3, PP fibers are added, so as not to affect the mixing and reaction in S1 and S2, and to avoid problems such as agglomeration, difficulty in dispersion, etc. in the stirring process of S1 and S2.

[0042] In the preparation method of the clay-based 3D printing special mortar of the present application, the various dry powders are mixed in S1, which can reduce the mixing difficulty in subsequent S2 and S3. In S2, water and water glass are added to cause a geopolymer reaction, and stirring is performed to fully react chemically. In the final S3, PP fibers are added, so as not to affect the mixing and reaction in S1 and S2, and to avoid problems such as agglomeration, difficulty in dispersion, etc. in the stirring process of S1 and S2.

[0043] Preferably, the clay is subjected to high-temperature calcination pretreatment before S1. The clay used in S1 is subjected to high-temperature calcination to remove organic matter. The particle fineness of the calcined clay is 800-2000 mesh.

[0044] Preferably, the water glass alkali residue is subjected to grinding pretreatment before S2. The water glass alkali residue used in S2 is ground to a specific surface area of 400-450 m2 / kg. Grinding the water glass alkali residue for pretreatment facilitates full chemical reaction and improves the utilization rate.

[0045] The water glass alkali residue is ground to a specific surface area of 400-450 m2 / kg, and the proportions of the water glass alkali residue, metakaolin (calcined clay) and fly ash are adjusted according to the proportioning principle of geopolymer, so that the molar ratio of each oxide meets the theoretical value of PSS type geopolymer (the molar ratio of SiO2 / Al2O3 is 4±1). The proportions of metakaolin (calcined clay) and fly ash, the proportion of water glass alkali residue and calcium oxide, and the water-cement ratio are adjusted within a certain range, so as to increase the amount of water glass alkali residue as much as possible under the premise of ensuring the mechanical properties of geopolymer.

[0046] According to the preparation method of the present application, verification tests are carried out by using different batching schemes in Examples 1-4, and good printability and thixotropy of the sand slurry can be obtained.

[0047] The weight fractions of the components in Examples 1-4 are as follows:

[0048] Example 1 Example 2 Example 3 Example 4 Clay 30 35 40 39.82 Sand 50 42.06 37.06 32 Fly ash 1.5 1.8 1.8 2 Calcium oxide 3 3 4 5 Sodium silicate alkali residue 4.36 5 4 6 Water reducing agent 0.02 0.02 0.02 0.03 Water 11 13 13 15 PP fiber 0.12 0.12 0.12 0.15

[0049] The performance test results of the hardened sand slurry are as follows:

[0050] Example 1 Example 2 Example 3 Example 4 3-day compressive strength (MPa) 30.1 27.9 22.5 28.6 28-day compressive strength (MPa) 48.2 45.7 41.0 44.9

[0051] It should be noted that in the description of the present application, the terms "upper", "lower", "left", "right", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly used in use, and are only for the convenience of description, and cannot be understood as indicating that the device or element referred to must have a particular orientation, therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" and the like are only used for differentiation in description, and cannot be understood as indicating relative importance.

[0052] The above is a further detailed description of the present application in combination with specific preferred embodiments, and cannot be considered as limiting the specific implementation of the present application to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, a number of simple deductions or substitutions can be made without departing from the concept of the present application, and all of them should be considered as falling within the protection scope of the present application.

Claims

1. A clay-based 3D printing specialty mortar, characterized in that: The clay is red clay.

2. Clay-based 3D printing special mortar according to claim 1, characterized in that: The sand is one of quartz sand or river sand, and the fineness is 50-100 mesh.

3. The clay-based 3D printing special mortar according to claim 1, characterized in that: The length of the PP fiber is 6-12 mm.

4. The clay-based 3D printing special mortar according to claim 1, characterized in that: The water glass alkali residue is the precipitate produced after the solid phase dissolution in the production process of water glass, and the precipitate includes crystalline silicon dioxide and sodium silicate hydrate.

5. The clay-based 3D printing special mortar according to claim 1, characterized in that: The fly ash is the fly ash produced by power plants, and the loss on ignition is 2.76%.

6. The clay-based 3D printing special mortar according to claim 1, characterized in that: The water reducing agent is a cationic polycarboxylic acid powder water reducing agent, and the water reducing rate is 25%.

7. The clay-based 3D printing special mortar according to claim 1, characterized in that: The method comprises the following steps:

8. A method of preparing a clay-based 3D printing special mortar according to any one of claims 1-7, characterized by: S1: pre-mixing clay, sand, fly ash, calcium oxide and water reducing agent to obtain a mixture; S2: adding water and water glass alkali residue to the mixture obtained in S1, stirring, and carrying out geopolymer reaction, and the reaction formula is as follows: Na2SiO3+CaO+H2O=CaSiO3+2NaOH; S3: continuously adding PP fiber, and stirring to obtain clay-based 3D printing special mortar. The clay is subjected to high-temperature calcination pretreatment before S1, and the particle fineness of the clay used in S1 is 800-2000 mesh.

9. A process for the preparation of clay-based 3D printing special mortar according to claim 8, characterized by: The water glass alkali residue is subjected to grinding pretreatment before S2, and the water glass alkali residue used in S2 is ground to a specific surface area of 400-450 m2 / kg.

10. A process for the preparation of clay-based 3D printing special mortar according to claim 8, characterized by: ​

Images