Preparation process of high-strength 3D printing concrete material with adjustable rheology

Abstract

The present invention discloses a preparation process of a high-strength 3D printing concrete material with adjustable rheology, comprising the following steps: (1) heating and melting stearic acid solid into a liquid state, then adding magnesium phosphate cement powder and inorganic filler, mixing and stirring evenly, and grinding the obtained solidified product after cooling to obtain a precursor powder. (2) spraying anhydrous ethanol solution in which a silane coupling agent is dissolved on the precursor powder, mixing and drying evenly to obtain a rheology regulator powder. (3) using cement-based cementitious material, the rheology regulator, fine aggregate, cellulose nanocrystals, and a water reducer as raw materials, mixing the above raw materials, adding water and stirring evenly to obtain a 3D printing concrete material. The process of the present invention can not only quickly change the rheology of the concrete slurry before and after extrusion, but also enhance the interfacial bonding force between the stacked layers and improve the structural stability of the printed product.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing concrete materials, and in particular to a preparation process of a high-strength 3D printing concrete material with adjustable rheology. Background Art

[0002] The traditional construction industry is characterized by high energy consumption and high carbon emissions. The development of innovative construction technologies and green cement-based materials is an effective way to promote energy conservation and reduce carbon emissions. 3D printing methods (also known as additive manufacturing) provide significant environmental benefits and have the potential for widespread application in the construction industry. The promotion and application of 3D printing technology in the construction industry depends on the research and development of high-performance cement-based composite materials. On the one hand, concrete 3D printing technology requires that the printing slurry has good fluidity before extrusion to ensure pumpability, extrudability and continuity, that is, a lower dynamic yield stress (stress required to maintain flow) is required to ensure normal pumping and extrusion. On the other hand, 3D printed concrete materials require a higher static yield stress (stress required to start flow) to maintain the dimensional stability (stackability) of each layer after printing under the weight of itself and the upper layer material.

[0003] However, concrete 3D printing technology requires that the concrete paste has good fluidity before extrusion and excellent stacking properties after extrusion, which is a contradictory relationship. In addition, since 3D printing technology converts three-dimensional structure slices into two-dimensional structures, the result of this dimensionality reduction printing is that the poor matching between the printing material and the model will seriously affect the stacking performance of the printed paste, thereby generating weak surfaces between the printing layers, causing the printed products to have anisotropy of mechanical properties, affecting the structural stability and dimensional accuracy of the printed products. Therefore, solving the above problems is the key to ensuring the practical application of concrete 3D printing technology. Summary of the invention

[0004] The present invention discloses a preparation process of a high-strength 3D printing concrete material with adjustable rheology, which can not only quickly change the rheology of the concrete slurry before and after extrusion, but also enhance the interface bonding force between stacked layers and improve the structural stability of the printed product. To achieve the above purpose, the present invention discloses the following technical solutions.

[0005] A preparation process of a high-strength 3D printing concrete material with adjustable rheology comprises the following steps:

[0006] (1) Heat and melt stearic acid solid into a liquid state, then add magnesium phosphate cement powder and inorganic filler and mix them evenly. After cooling, grind the obtained solidified product to obtain a precursor powder.

[0007] (2) Spraying anhydrous ethanol solution containing a silane coupling agent on the precursor powder, mixing the mixture evenly, and drying the mixture to obtain a rheology modifier powder.

[0008] (3) Using cement-based cementitious material, the rheology regulator, fine aggregate, cellulose nanocrystals, and a water reducing agent as raw materials, the raw materials are mixed and then water is added and stirred evenly to obtain a 3D printing concrete material.

[0009] Furthermore, in step (1), the heating temperature is 75-110°C. The temperature is maintained until the stearic acid solid (i.e., octadecanoic acid, CH3(CH2) 16 COOH) are all melted into liquid state.

[0010] Furthermore, in step (1), the ratio of the stearic acid solid, the magnesium phosphate cement powder, and the inorganic filler is 2.5-3.5 parts by weight: 7-10 parts by weight: 1-2 parts by weight.

[0011] Furthermore, in step (1), the inorganic filler includes at least one of glass powder, silicon dioxide powder, steel slag powder, calcium carbonate powder, etc. Optionally, the fineness of the inorganic filler is 100-150 mesh. Preferably, the glass powder is made of waste glass, which helps to reduce costs and recycle waste resources.

[0012] Furthermore, in step (1), the particle size of the precursor powder may be between 0.3 and 0.5 mm.

[0013] Furthermore, in step (2), the mass fraction of the silane coupling agent in the anhydrous ethanol solution is 1-1.5%. Optionally, the silane coupling agent includes any one of KH550 (γ-aminopropyl triethoxysilane), KH560 (γ-glycidyloxypropyl trimethoxysilane), KH570 (γ-methacryloxypropyl trimethoxysilane), etc.

[0014] Furthermore, in step (2), the ratio of the precursor powder to the anhydrous ethanol solution in which the silane coupling agent is dissolved is 1 g: 0.2-0.3 ml.

[0015] Furthermore, in step (2), the drying temperature is lower than the melting point of stearic acid. Optionally, the drying temperature is 40-45°C, the drying time is 15-25 minutes, and stirring is performed continuously during the drying process to accelerate the volatilization of the solvent ethanol.

[0016] Furthermore, in step (3), the proportions of the raw materials are: 340-380 parts by weight of cement-based cementitious material, 60-75 parts by weight of rheology modifier, and 1400-1530 parts by weight of fine aggregate. The amount of the cellulose nanocrystals is 0.5-2% of the mass of the cement-based cementitious material, and the amount of the water reducing agent is 1.5-2.5% of the mass of the cement-based cementitious material. The cellulose nanocrystals help to increase the structural density of the concrete structure and generate additional mechanical bonding between the layers of the printed product through the interlocking of the fibers and the fine aggregate.

[0017] Furthermore, in step (3), the amount of water added is based on a water-cement ratio of 0.55 to 0.60. The "cement" refers to cement-based cementitious material.

[0018] Furthermore, in step (3), the raw material further comprises 7 to 10 parts by weight of chopped fibers. Optionally, the length of the chopped fibers is 1 to 5 mm. The chopped fibers include at least one of polyvinyl alcohol fibers, polypropylene fibers, polyacrylonitrile fibers, glass fibers, etc. The addition of chopped fibers helps to enhance the compressive and flexural strength of the 3D printed concrete structure.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: As mentioned above, concrete 3D printing technology requires that the concrete slurry has good fluidity before extrusion, and has good stacking properties after extrusion. To this end, the present invention adds the rheology regulator prepared by the present invention to the concrete slurry, and the rheology regulator is formed by magnesium phosphate cement powder and inorganic filler bonded and fixed together by stearic acid, and the surface of the rheology regulator has been hydrophobically modified by a silane coupling agent. When the above-mentioned rheology regulator is added to the concrete slurry in the early stage, the surface silane coupling agent prevents the absorption and consumption of the mixing water from reducing the fluidity of the concrete slurry under the hydrophobic protection of the surface silane coupling agent, thereby ensuring the good pumpability, extrudability and continuity of the concrete slurry. After the concrete slurry is extruded, with the hydration of the cementitious material in the concrete slurry, the hydration product calcium hydroxide produced by it reacts with the stearic acid in the rheology regulator to produce an acid-base neutralization reaction, thereby starting the rheology regulator to play a role. On the one hand, the acid-base neutralization reaction can quickly destroy the surface structure of the rheology regulator, so that the external mixing water enters the rheology regulator and contacts the magnesium phosphate cement. After the magnesium phosphate cement meets water, it can complete the hydration reaction in a short time to achieve hardening, so that the rheology regulator is transformed into a high-strength hardened body mainly formed by the hydration product of magnesium phosphate cement. In this process, the mixing water in the concrete slurry can be quickly consumed, reducing the fluidity of the concrete slurry. On the second hand, the hardened body also plays a role in skeleton support, which can quickly improve the static yield stress of the concrete slurry, so that the printed concrete structure has better stacking / structural stability, reduce structural deformation, and improve the dimensional accuracy of the printed concrete structure. On the third hand, the hydration product formed after the magnesium phosphate cement is hydrated has a strong gelling and bonding ability. On the one hand, it can make the hardened body and the matrix well combined, and improve the mechanical strength of the concrete structure. On the other hand, the printed concrete material layers can be better combined by the good bonding effect brought by the hardened body at the interface, increase the bonding force between the printed layers, overcome the problem of weak surfaces between the printed layers, and help improve the overall mechanical properties of the concrete structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention and do not constitute an improper limitation of the present invention. The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein:

[0021] Figure 1 This is a rheological test diagram of the 3D printing concrete material prepared in the following Example 1. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with specific embodiments. It should be understood that these embodiments and materials are for demonstration purposes only and are not all embodiments. All other embodiments obtained by ordinary technicians in this field based on these embodiments without creative work are within the scope of protection of the present invention. The technical solution of the present invention is further described according to the accompanying drawings and specific embodiments of the specification.

[0023] Example 1

[0024] A preparation process of a high-strength 3D printing concrete material with adjustable rheology comprises the following steps:

[0025] (1) Heat the stearic acid solid to 80°C and keep it warm until it is completely melted into a liquid state, then add magnesium phosphate cement powder and glass powder, mix and stir evenly, wherein: the ratio of the stearic acid, magnesium phosphate cement powder and glass powder is 3.0 parts by weight: 8.5 parts by weight: 1.5 parts by weight, and the fineness of the glass powder is 150 mesh. Keep heating during the stirring process to keep the stearic acid in good fluidity. Stop heating after stirring evenly, and grind the obtained solidified product mechanically after cooling, and then sieve out the particles with a particle size distribution between 0.3 and 0.5 mm to obtain the precursor powder for standby use.

[0026] (2) Dissolve the silane coupling agent KH550 in anhydrous ethanol to form a surface modification liquid with a mass fraction of 1.5%, and then spray the surface modification liquid on the precursor powder at a ratio of 1g:0.25ml, and then heat to 45°C and dry for 20 minutes, and stir continuously during the drying process. After completion, the rheology modifier powder is obtained and set aside.

[0027] (3) Take the following components: 360 parts by weight of 42.5 ordinary Portland cement, 70 parts by weight of the rheology modifier prepared in this embodiment, 1450 parts by weight of fine aggregate, 3.6 parts by weight of cellulose nanocrystals, and 7.6 parts by weight of water reducer. Among them: the fine aggregate is medium sand with a particle size distribution between 0.35 and 0.5 mm. The diameter of the cellulose nanocrystals is distributed between 4 and 10 nm, and the length is distributed between 100 and 300 nm. Add the above raw materials to a mixer and mix them evenly, then add water according to a water-cement ratio of 0.58 and stir evenly to obtain 3D printing concrete material.

[0028] Performance test: The rheological properties of the 3D printed concrete material prepared in this embodiment before and after printing were tested according to the "Method for Determination of Fluidity of Cement Mortar" (GB / T 2419-2005). The rheological properties before printing were tested after the 3D printed concrete material was prepared (e.g. Figure 1As shown in the figure, the rheological properties after printing were tested after the 3D printed concrete material was left to stand for 5 minutes. In addition, the 28d interlayer bonding strength of the concrete structure obtained after printing was tested according to the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T17671-1999). The test results are shown below.

[0029] Performance Indicators Rheology before printing Rheology after printing Interlayer bonding strength Example 1 178mm 159mm 6.72MPa

[0030] Example 2

[0031] A preparation process of a high-strength 3D printing concrete material with adjustable rheology comprises the following steps:

[0032] (1) Heat the stearic acid solid to 75°C and keep it warm until it is completely melted into a liquid state, then add magnesium phosphate cement powder and silicon dioxide powder, mix and stir evenly, wherein: the ratio of the stearic acid, magnesium phosphate cement powder and silicon dioxide powder is 3.5 parts by weight: 10 parts by weight: 2 parts by weight, and the fineness of the silicon dioxide powder is 100 mesh. Keep heating during the stirring process to keep the stearic acid in good fluidity. Stop heating after stirring evenly, and grind the obtained solidified product mechanically after cooling, and then sieve out the particles with a particle size distribution between 0.3 and 0.5 mm to obtain the precursor powder for standby use.

[0033] (2) Dissolve the silane coupling agent KH570 in anhydrous ethanol to form a surface modification liquid with a mass fraction of 1.2%, and then spray the surface modification liquid on the precursor powder at a ratio of 1g:0.3ml, and then heat to 45°C and dry for 15 minutes, and stir continuously during the drying process. After completion, the rheology modifier powder is obtained and set aside.

[0034] (3) Take the following components: 330 parts by weight of 42.5 ordinary Portland cement, 60 parts by weight of the rheology modifier prepared in this embodiment, 1400 parts by weight of fine aggregate, 1.7 parts by weight of cellulose nanocrystals, 5.1 parts by weight of water reducer, and 7 parts by weight of chopped polyvinyl alcohol fibers. Among them: the fine aggregate is medium sand with a particle size distribution between 0.35 and 0.5 mm. The diameter of the cellulose nanocrystals is distributed between 4 and 10 nm, and the length is distributed between 100 and 300 nm. The length of the polyvinyl alcohol fiber is 5 mm. Add the above raw materials into a mixer and mix them evenly, then add water according to a water-cement ratio of 0.55 and stir evenly to obtain a 3D printing concrete material.

[0035] Performance test: The rheological properties of the 3D printed concrete material prepared in this embodiment before and after printing were tested according to the "Method for Determining the Fluidity of Cement Mortar" (GB / T 2419-2005). Among them, the rheological properties before printing were tested immediately after the 3D printed concrete material was prepared. The rheological properties after printing were tested after the 3D printed concrete material was left to stand for 5 minutes after printing. In addition, the 28d interlayer bonding strength of the concrete structure obtained after printing was tested according to the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-1999). The test results are shown below.

[0036] Performance Indicators Rheology before printing Rheology after printing Interlayer bonding strength Example 2 184mm 161mm 6.04MPa

[0037] Example 3

[0038] A preparation process of a high-strength 3D printing concrete material with adjustable rheology comprises the following steps:

[0039] (1) Heat the stearic acid solid to 110°C and keep it warm until it is completely melted into a liquid state, then add magnesium phosphate cement powder and steel slag powder and mix them and stir them evenly, wherein: the ratio of the stearic acid, magnesium phosphate cement powder and steel slag powder is 2.5 parts by weight: 7 parts by weight: 1 part by weight, and the fineness of the steel slag powder is 120 mesh. Keep heating during the stirring process to ensure that the stearic acid maintains good fluidity. Stop heating after stirring evenly, and after cooling, mechanically grind the obtained solidified product, and then sieve out particles with a particle size distribution between 0.3 and 0.5 mm to obtain the precursor powder for standby use.

[0040] (2) Dissolve the silane coupling agent KH560 in anhydrous ethanol to form a surface modification liquid with a mass fraction of 1.2%, and then spray the surface modification liquid on the precursor powder at a ratio of 1g:0.2ml, and then heat to 40°C and dry for 25 minutes, and stir continuously during the drying process. After completion, the rheology modifier powder is obtained and set aside.

[0041] (3) Take the following components: 380 parts by weight of 42.5 ordinary Portland cement, 75 parts by weight of the rheology modifier prepared in this embodiment, 1530 parts by weight of fine aggregate, 7.6 parts by weight of cellulose nanocrystals, 9.5 parts by weight of water reducer, and 10 parts by weight of chopped polypropylene fibers. Among them: the fine aggregate is medium sand with a particle size distribution between 0.35 and 0.5 mm. The diameter of the cellulose nanocrystals is distributed between 4 and 10 nm, and the length is distributed between 100 and 300 nm. The length of the polypropylene fiber is 1 mm. Add the above raw materials into a mixer and mix them evenly, then add water according to a water-cement ratio of 0.60 and stir evenly to obtain a 3D printing concrete material.

[0042] Performance test: The rheological properties of the 3D printed concrete material prepared in this embodiment before and after printing were tested according to the "Method for Determining the Fluidity of Cement Mortar" (GB / T 2419-2005). Among them, the rheological properties before printing were tested immediately after the 3D printed concrete material was prepared. The rheological properties after printing were tested after the 3D printed concrete material was left to stand for 5 minutes after printing. In addition, the 28d interlayer bonding strength of the concrete structure obtained after printing was tested according to the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-1999). The test results are shown below.

[0043] Performance Indicators Rheology before printing Rheology after printing Interlayer bonding strength Example 3 176mm 155mm 6.37MPa

[0044] Example 4

[0045] A preparation process of a high-strength 3D printing concrete material with adjustable rheology comprises the following steps:

[0046] Take the following components: 360 parts by weight of 42.5 ordinary Portland cement, 1450 parts by weight of fine aggregate, 3.6 parts by weight of cellulose nanocrystals, and 7.6 parts by weight of water reducer. Wherein: the fine aggregate is medium sand with a particle size distribution between 0.35 and 0.5 mm. The diameter of the cellulose nanocrystals is distributed between 4 and 10 nm, and the length is distributed between 100 and 300 nm. Add the above raw materials to a mixer and mix them evenly, then add water according to a water-cement ratio of 0.58 and stir evenly to obtain 3D printing concrete material.

[0047] Performance test: The rheological properties of the 3D printed concrete material prepared in this embodiment before and after printing were tested according to the "Method for Determining the Fluidity of Cement Mortar" (GB / T 2419-2005). Among them, the rheological properties before printing were tested immediately after the 3D printed concrete material was prepared. The rheological properties after printing were tested after the 3D printed concrete material was left to stand for 5 minutes after printing. In addition, the 28d interlayer bonding strength of the concrete structure obtained after printing was tested according to the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-1999). The test results are shown below.

[0048] Performance Indicators Rheology before printing Rheology after printing Interlayer bonding strength Example 4 181mm 174mm 3.58MPa

[0049] Example 5

[0050] A preparation process of a high-strength 3D printing concrete material with adjustable rheology comprises the following steps:

[0051] (1) Heat the stearic acid solid to 80°C and keep it warm until it is completely melted into a liquid state, then add magnesium phosphate cement powder and glass powder and mix them and stir them evenly, wherein the ratio of the stearic acid, magnesium phosphate cement powder and glass powder is 3.0 parts by weight: 8.5 parts by weight: 1.5 parts by weight, and the fineness of the glass powder is 150 mesh. Keep heating during the stirring process to ensure that the stearic acid maintains good fluidity. Stop heating after stirring evenly, and grind the obtained solidified product mechanically after cooling, and then sieve out particles with a particle size distribution between 0.3 and 0.5 mm to obtain a rheology modifier powder for standby use.

[0052] (2) Spray the precursor powder with anhydrous ethanol at a ratio of 1 g: 0.25 ml, and then heat to 45°C and dry for 20 minutes, stirring continuously during the drying process. After completion, the rheology regulator powder is obtained and set aside.

[0053] (3) Take the following components: 360 parts by weight of 42.5 ordinary Portland cement, 70 parts by weight of the rheology modifier prepared in this embodiment, 1450 parts by weight of fine aggregate, 3.6 parts by weight of cellulose nanocrystals, and 7.6 parts by weight of water reducer. Among them: the fine aggregate is medium sand with a particle size distribution between 0.35 and 0.5 mm. The diameter of the cellulose nanocrystals is distributed between 4 and 10 nm, and the length is distributed between 100 and 300 nm. Add the above raw materials to a mixer and mix them evenly, then add water according to a water-cement ratio of 0.58 and stir evenly to obtain 3D printing concrete material.

[0054] Performance test: The rheological properties of the 3D printed concrete material prepared in this embodiment before and after printing were tested according to the "Method for Determining the Fluidity of Cement Mortar" (GB / T 2419-2005). Among them, the rheological properties before printing were tested immediately after the 3D printed concrete material was prepared. The rheological properties after printing were tested after the 3D printed concrete material was left to stand for 5 minutes after printing. In addition, the 28d interlayer bonding strength of the concrete structure obtained after printing was tested according to the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-1999). The test results are shown below.

[0055] Performance Indicators Rheology before printing Rheology after printing Interlayer bonding strength Example 5 164mm 152mm 4.11MPa

[0056] Example 6

[0057] A preparation process of a high-strength 3D printing concrete material with adjustable rheology comprises the following steps:

[0058] (1) Heat the stearic acid solid to 75°C and keep it warm until it is completely melted into a liquid state, then add phosphorus silicon dioxide powder and mix and stir evenly, wherein: the ratio of the stearic acid to the silicon dioxide powder is 3.5 parts by weight: 2 parts by weight, and the fineness of the silicon dioxide powder is 100 mesh. Keep heating during the stirring process to ensure that the stearic acid maintains good fluidity. Stop heating after stirring evenly, and grind the obtained solidified product mechanically after cooling, and then sieve out particles with a particle size distribution between 0.3 and 0.5 mm to obtain the precursor powder for standby use.

[0059] (2) Dissolve the silane coupling agent KH570 in anhydrous ethanol to form a surface modification liquid with a mass fraction of 1.2%, and then spray the surface modification liquid on the precursor powder at a ratio of 1g:0.3ml, and then heat to 45°C and dry for 15 minutes, and stir continuously during the drying process. After completion, the rheology modifier powder is obtained and set aside.

[0060] (3) Take the following components: 330 parts by weight of 42.5 ordinary Portland cement, 60 parts by weight of the rheology modifier prepared in this embodiment, 1400 parts by weight of fine aggregate, 1.7 parts by weight of cellulose nanocrystals, 5.1 parts by weight of water reducer, and 7 parts by weight of chopped polyvinyl alcohol fibers. Among them: the fine aggregate is medium sand with a particle size distribution between 0.35 and 0.5 mm. The diameter of the cellulose nanocrystals is distributed between 4 and 10 nm, and the length is distributed between 100 and 300 nm. The length of the polyvinyl alcohol fiber is 5 mm. Add the above raw materials into a mixer and mix them evenly, then add water according to a water-cement ratio of 0.55 and stir evenly to obtain a 3D printing concrete material.

[0061] Performance test: The rheological properties of the 3D printed concrete material prepared in this embodiment before and after printing were tested according to the "Method for Determining the Fluidity of Cement Mortar" (GB / T 2419-2005). Among them, the rheological properties before printing were tested immediately after the 3D printed concrete material was prepared. The rheological properties after printing were tested after the 3D printed concrete material was left to stand for 5 minutes after printing. In addition, the 28d interlayer bonding strength of the concrete structure obtained after printing was tested according to the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-1999). The test results are shown below.

[0062] Performance Indicators Rheology before printing Rheology after printing Interlayer bonding strength Example 6 185mm 177mm 3.93MPa

[0063] Example 7

[0064] A preparation process of a high-strength 3D printing concrete material with adjustable rheology comprises the following steps:

[0065] (1) Heat the paraffin solid to 110°C and keep it warm until it is completely melted into a liquid state, then add magnesium phosphate cement powder and steel slag powder and mix them and stir them evenly, wherein the ratio of the paraffin, magnesium phosphate cement powder and steel slag powder is 2.5 parts by weight: 7 parts by weight: 1 part by weight, and the fineness of the steel slag powder is 120 mesh. Keep heating during the stirring process to ensure that the paraffin maintains good fluidity. Stop heating after stirring evenly, and grind the obtained solidified product mechanically after cooling, and then sieve out particles with a particle size distribution between 0.3 and 0.5 mm to obtain the precursor powder for standby use.

[0066] (2) Dissolve the silane coupling agent KH560 in anhydrous ethanol to form a surface modification liquid with a mass fraction of 1.2%, and then spray the surface modification liquid on the precursor powder at a ratio of 1g:0.2ml, and then heat to 40°C and dry for 25 minutes, and stir continuously during the drying process. After completion, the rheology modifier powder is obtained and set aside.

[0067] (3) Take the following components: 380 parts by weight of 42.5 ordinary Portland cement, 75 parts by weight of the rheology modifier prepared in this embodiment, 1530 parts by weight of fine aggregate, 7.6 parts by weight of cellulose nanocrystals, 9.5 parts by weight of water reducer, and 10 parts by weight of chopped polypropylene fibers. Among them: the fine aggregate is medium sand with a particle size distribution between 0.35 and 0.5 mm. The diameter of the cellulose nanocrystals is distributed between 4 and 10 nm, and the length is distributed between 100 and 300 nm. The length of the polypropylene fiber is 1 mm. Add the above raw materials into a mixer and mix them evenly, then add water according to a water-cement ratio of 0.60 and stir evenly to obtain a 3D printing concrete material.

[0068] Performance test: The rheological properties of the 3D printed concrete material prepared in this embodiment before and after printing were tested according to the "Method for Determining the Fluidity of Cement Mortar" (GB / T 2419-2005). Among them, the rheological properties before printing were tested immediately after the 3D printed concrete material was prepared. The rheological properties after printing were tested after the 3D printed concrete material was left to stand for 5 minutes after printing. In addition, the 28d interlayer bonding strength of the concrete structure obtained after printing was tested according to the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-1999). The test results are shown below.

[0069] Performance Indicators Rheology before printing Rheology after printing Interlayer bonding strength Example 7 188mm 182mm 3.17MPa

[0070] Example 8

[0071] A preparation process of a high-strength 3D printing concrete material with adjustable rheology comprises the following steps:

[0072] (1) Heat the stearic acid solid to 75°C and keep it warm until it is completely melted into a liquid state, then add the magnesium phosphate cement powder and mix and stir evenly, wherein the ratio of the stearic acid to the magnesium phosphate cement powder is 3.5 parts by weight: 10 parts by weight. Keep heating during the stirring process to ensure that the stearic acid maintains good fluidity. After stirring evenly, stop heating, and after cooling, mechanically grind the obtained solidified product, and then sieve out the particles with a particle size distribution between 0.3 and 0.5 mm to obtain the precursor powder for standby use.

[0073] (2) Dissolve the silane coupling agent KH570 in anhydrous ethanol to form a surface modification liquid with a mass fraction of 1.2%, and then spray the surface modification liquid on the precursor powder at a ratio of 1g:0.3ml, and then heat to 45°C and dry for 15 minutes, and stir continuously during the drying process. After completion, the rheology modifier powder is obtained and set aside.

[0074] (3) Take the following components: 330 parts by weight of 42.5 ordinary Portland cement, 60 parts by weight of the rheology modifier prepared in this embodiment, 1400 parts by weight of fine aggregate, 1.7 parts by weight of cellulose nanocrystals, 5.1 parts by weight of water reducer, and 7 parts by weight of chopped polyvinyl alcohol fibers. Among them: the fine aggregate is medium sand with a particle size distribution between 0.35 and 0.5 mm. The diameter of the cellulose nanocrystals is distributed between 4 and 10 nm, and the length is distributed between 100 and 300 nm. The length of the polyvinyl alcohol fiber is 5 mm. Add the above raw materials into a mixer and mix them evenly, then add water according to a water-cement ratio of 0.55 and stir evenly to obtain a 3D printing concrete material.

[0075] Performance test: The rheological properties of the 3D printed concrete material prepared in this embodiment before and after printing were tested according to the "Method for Determining the Fluidity of Cement Mortar" (GB / T 2419-2005). Among them, the rheological properties before printing were tested immediately after the 3D printed concrete material was prepared. The rheological properties after printing were tested after the 3D printed concrete material was left to stand for 5 minutes after printing. In addition, the 28d interlayer bonding strength of the concrete structure obtained after printing was tested according to the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-1999). The test results are shown below.

[0076] Performance Indicators Rheology before printing Rheology after printing Interlayer bonding strength Example 8 183mm 164mm 5.48MPa

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation process of high-strength 3D printing concrete material with adjustable rheology, characterized in that: The steps include: (1) heating and melting stearic acid solid into a liquid state, then adding magnesium phosphate cement powder and inorganic filler and mixing and stirring evenly, and grinding the obtained solidified product after cooling to obtain a precursor powder; (2) spraying anhydrous ethanol solution containing a silane coupling agent on the precursor powder, mixing and drying the mixture to obtain a rheology modifier powder; (3) Using cement-based cementitious material, the rheology regulator, fine aggregate, cellulose nanocrystals, and a water reducing agent as raw materials, mixing the above raw materials, adding water, and stirring evenly to obtain the 3D printing concrete material; In step (1), the ratio of the stearic acid solid, magnesium phosphate cement powder and inorganic filler is 2.5-3.5 parts by weight: 7-10 parts by weight: 1-2 parts by weight; In step (3), the proportions of the raw materials are: 340-380 parts by weight of cement-based cementitious material, 60-75 parts by weight of rheology modifier, and 1400-1530 parts by weight of fine aggregate; the amount of the cellulose nanocrystals is 0.5-2% of the mass of the cement-based cementitious material, and the amount of the water reducing agent is 1.5-2.5% of the mass of the cement-based cementitious material; In step (2), the ratio of the precursor powder to the anhydrous ethanol solution containing the silane coupling agent is 1 g: 0.2-0.3 ml; the mass fraction of the silane coupling agent in the anhydrous ethanol solution is 1-1.5%, and the silane coupling agent includes any one of KH550, KH560, and KH570.

2. The preparation process of the high-strength 3D printing concrete material with adjustable rheology according to claim 1, characterized in that: In step (1), the heating temperature is 75-110°C.

3. The preparation process of the high-strength 3D printing concrete material with adjustable rheology according to claim 1, characterized in that: In step (1), the inorganic filler includes at least one of glass powder, silicon dioxide powder, steel slag powder and calcium carbonate powder.

4. The preparation process of the high-strength 3D printing concrete material with adjustable rheology according to claim 3, characterized in that: The glass powder is made of waste glass.

5. The preparation process of the high-strength 3D printing concrete material with adjustable rheology according to claim 1, characterized in that: In step (1), the fineness of the inorganic filler is 100-150 mesh.

6. The preparation process of the high-strength 3D printing concrete material with adjustable rheology according to claim 1, characterized in that: In step (1), the particle size of the precursor powder is between 0.3 and 0.5 mm.

7. The preparation process of the high-strength 3D printing concrete material with adjustable rheology according to claim 1, characterized in that: In step (2), the drying temperature is lower than the melting point of stearic acid.

8. The preparation process of the high-strength 3D printing concrete material with adjustable rheology according to claim 1, characterized in that: The drying temperature is 40-45° C., the drying time is 15-25 min, and stirring is performed continuously during the drying process.

9. The preparation process of the high-strength 3D printing concrete material with adjustable rheology according to claim 1, characterized in that: In step (3), the water-cement ratio is 0.55-0.

60.

10. The preparation process of the high-strength 3D printing concrete material with adjustable rheology according to any one of claims 1 to 9, characterized in that: In step (3), the raw material also includes 7 to 10 parts by weight of chopped fibers.

11. The preparation process of the high-strength 3D printing concrete material with adjustable rheology according to claim 10, characterized in that: The length of the chopped fibers is 1 to 5 mm.

12. The preparation process of the high-strength 3D printing concrete material with adjustable rheology according to claim 10, characterized in that: The chopped fibers include at least one of polyvinyl alcohol fibers, polypropylene fibers, polyacrylonitrile fibers, and glass fibers.

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