Novel 3D printing material based on blending of recycled micro powder and recycled fine aggregate and preparation method of novel 3D printing material

Abstract

The invention discloses a novel 3D printing material based on recycled micro powder and recycled fine aggregate blending and a preparation method thereof, and belongs to the technical field of industrial solid waste resource utilization and building materials. The material is prepared from the following main raw materials in parts by weight: 32-48 parts of fine sand, 18-24 parts of cement, 6-22 parts of recycled fine aggregate and 3-9 parts of recycled micro powder. The material has good rheological properties, printability and anisotropic mechanical properties. A soybean urease solution is used for repairing internal interlayer gaps and is added when dry materials are stirred, soybean urease catalyzes urea hydrolysis, and calcium carbonate precipitates are rapidly generated to block the interlayer gaps. The method is suitable for the field of building 3D printing, and solid waste recycling and collaborative development of low-carbon building materials are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial solid waste resource utilization and building materials, and particularly relates to a new 3D printing material based on mixing of regenerated micro powder and regenerated fine aggregate and a preparation method thereof. BACKGROUND

[0002] With the acceleration of urbanization, a large amount of construction waste is generated every year, and the treatment of construction waste is also a noteworthy problem. The traditional recycling process of waste concrete is divided into three stages, which are mainly output as regenerated coarse aggregate, regenerated fine aggregate and regenerated micro powder. The components of regenerated micro powder and regenerated fine aggregate mainly include hardened cement stone, unhydrated cement and gravel aggregate powder, etc. The surface is rough and porous, the pore size distribution is uneven and the components are relatively complex, and it has certain potential activity. As the core technology of industrial 4.0, the development of 3D printing has attracted more and more attention. Among them, the problems such as the structure of the interlayer space in the 3D printing technology need to be solved. SUMMARY

[0003] The purpose of the present application is to provide a new 3D printing material based on mixing of regenerated micro powder and regenerated fine aggregate, to strengthen mineralization by microorganisms, to enhance the strength of regenerated fine aggregate and to activate regenerated micro powder, while reducing production cost and carbon emission. In addition, the preparation method of the 3D printing material is also provided.

[0004] The technical scheme of the present application is a new 3D printing material based on mixing of regenerated micro powder and regenerated fine aggregate, which comprises, by weight fraction, fine sand: 32-48 parts, cement: 18-24 parts, regenerated fine aggregate: 6-22 parts, regenerated micro powder: 3-9 parts, water reducing agent: 3 parts, thickening agent: 5 parts; wherein the regenerated fine aggregate is modified regenerated fine aggregate induced by Bacillus mineralization, and the regenerated micro powder is activated regenerated micro powder induced by Bacillus mineralization.

[0005] Preferably, it further comprises soybean urease: 0.36-0.48 parts, urea solution: 0.45-0.6 parts, calcium chloride solution: 0.27-0.36 parts; wherein the concentration of urea solution and calcium chloride solution is 0.5M.

[0006] Preferably, it further comprises soybean urease: 0.42 parts, urea solution: 0.55 parts, calcium chloride solution: 0.32 parts.

[0007] Preferably, the water reducing agent is sodium gluconate, and the thickening agent is hydroxypropyl methyl cellulose.

[0008] Preferably, the fine sand is river sand with a particle size of 0.15-2.36 mm, and the type of cement is 42.5 ordinary portland cement.

[0009] Preferably, the recycled fine aggregate is modified recycled fine aggregate induced mineralization by Bacillus bacteria solution with OD600 of 1-2, and the recycled micro powder is activated recycled micro powder induced mineralization by Bacillus bacteria solution with OD600 of 0.8-1.2

[0010] In another aspect, the application provides a preparation method of the novel 3D printing material, which comprises the following steps: uniformly mixing cement, modified recycled fine aggregate, activated recycled micro powder and thickening agent to obtain dry mixture; dissolving water reducing agent in water to obtain a liquid; mixing the liquid with the dry mixture to obtain the novel 3D printing material.

[0011] Preferably, the preparation method of the novel 3D printing material comprises the following steps: uniformly mixing cement, modified recycled fine aggregate, activated recycled micro powder and thickening agent to obtain dry mixture; mixing soybean urease solution, urea solution and calcium chloride solution to obtain mixed solution a; dissolving water reducing agent in water to obtain mixed solution b; mixing the mixed solution a and the mixed solution b to obtain mixed solution c; mixing the mixed solution c with the dry mixture to obtain the novel 3D printing material.

[0012] Preferably, the preparation method of the modified recycled fine aggregate comprises the following steps: crushing industrial waste concrete blocks, screening recycled fine aggregate with a particle size of 0.15mm-2.36mm, placing the recycled fine aggregate soaked with Bacillus bacteria solution into a carbonization box for carbonization, and taking out and drying to obtain the modified recycled fine aggregate.

[0013] Preferably, the preparation method of the activated recycled micro powder comprises the following steps: screening recycled micro powder with a particle size of less than 75μm, soaking the recycled micro powder in Bacillus bacteria solution, and placing the recycled micro powder into a carbonization box for carbonization to obtain the activated recycled micro powder.

[0014] Preferably, the preparation method of the soybean urease comprises the following steps: soaking soybean powder in water, stirring and mixing, centrifuging, and collecting the supernatant; adding ammonium sulfate to the supernatant to collect the precipitate, which is the soybean urease.

[0015] Preferably, in the preparation method of the soybean urease, the mass ratio of the soybean powder to water is 1:(5-8).

[0016] Principle: The recycled fine aggregate of the application has pores and cracks generated by crushing, resulting in a high porosity of the recycled aggregate. In the carbonization process, CO2 mainly reacts with Ca(OH)2 and C-S-H in the attached mortar on the surface of the recycled aggregate. First, CO2 penetrates into the attached mortar on the recycled aggregate through pores or cracks and is dissolved in pore water to generate carbonic acid. Ca 2+ and Ca 2+ in the solution added by human beings 2-Further reaction generates CaCO3 and silica gel. Finally, calcite, vanadium stone, aragonite and other forms are precipitated in the pores and cracks of the recycled aggregate, which helps to improve the performance of the recycled aggregate. In addition, the carbonic anhydrase in the microorganism can improve the solubility of carbon dioxide in water.

[0017] In order to solve the "bottleneck" problem of low activity and low utilization of recycled fine powder, the microbial induced mineralization calcium precipitation reaction in the carbonization process of recycled fine powder is higher in alkaline environment, CO2 is more easily dissolved in the fine powder slurry and forms carbonate precipitate with calcium and magnesium ions in the slurry. The surface and pores of the recycled fine powder after carbonization treatment are filled and covered by calcite type CaCO3, the porosity is reduced, and the particle size distribution is improved. At the same time, because the size of the newly formed biogenic precipitated calcium carbonate crystal is small, the specific surface area is large, so it can be used as a nucleating material to induce the formation of C-S-H gel, and then accelerate the hydration and improve the mortar or concrete strength.

[0018] The interlayer voids in the interior of the 3D printed building have the characteristics of wide distribution and deep degree. In order to solve this difficulty and improve the anisotropic mechanical properties of the building, considering the large-scale use of real engineering and economic factors, soybean urease solution is used. Soybean urease catalyzes the hydrolysis of urea into ammonia and carbonate ions, and carbonate ions combine with calcium ions to form calcium carbonate precipitate. It is suitable for inducing calcium carbonate precipitation in anoxic environment such as deep voids of concrete, and improving the overall performance of the building.

[0019] Advantages: Compared with the prior art, the present application has the following obvious advantages: (1) the present application realizes the utilization of industrial solid waste, and the cost is reduced by 40%-50% compared with traditional cement-based materials; (2) the present application has good mechanical properties of 3D printed test pieces; (3) the present application can efficiently repair deep interlayer voids of 3D printed test pieces, and greatly improve the overall performance. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Preparation flow chart of novel 3D printing material;

[0021] Figure 2 Flow chart of deep interlayer void repair method of novel 3D printing material;

[0022] Figure 3 Comparison chart of compressive strength of 3D printed test pieces under different formulations; DETAILED DESCRIPTION

[0023] The recycled fine aggregate and recycled fine powder used in the embodiments of the present application are obtained by crushing and ball milling of waste concrete from a construction site in Zhenjiang, Jiangsu, and the main component is silicon dioxide (SiO2). The water reducing agent in the embodiments is sodium gluconate, and the thickening agent is hydroxypropyl methyl cellulose.

[0024] Embodiment 1

[0025] The embodiment of the application provides a novel 3D printing material, which comprises, in parts by weight, fine sand 43 parts, cement 24 parts, recycled fine aggregate 11 parts, recycled micro powder 3 parts, water 11 parts, water reducing agent 3 parts and thickening agent 5 parts.

[0026] The embodiment of the application provides a preparation method of the novel 3D printing material, which comprises the following steps:

[0027] (1) The purchased construction waste concrete is placed in a crusher, and is classified through a 2.36 mm aperture vibrating screen, so that recycled fine aggregate with a particle size of 0.15 mm to 2.36 mm is screened out, and the recycled fine aggregate is obtained.

[0028] (2) The purchased construction waste concrete is placed in a ball mill, and the powder obtained by ball milling is screened to a particle size of <75 mu m through a vibrating shaker, and the recycled micro powder is obtained.

[0029] (3) 10 g of bacillus powder is mixed with 300 ml of water and fully stirred, 10 ml of supernatant is taken after standing for 20 min, and is injected into an LB culture medium, and is placed in a shaking box for 24 h, so that modified bacteria liquid is obtained, OD600 is 1.5, and the modified bacteria liquid is used for mixing with the recycled fine aggregate.

[0030] (4) 5 g of bacillus powder is mixed with 300 ml of water and fully stirred, 10 ml of supernatant is taken after standing for 20 min, and is injected into an LB culture medium, and is placed in a shaking box for 24 h, so that active bacteria liquid is obtained, OD600 is 1, and the active bacteria liquid is used for mixing with the recycled micro powder.

[0031] (5) The recycled fine aggregate and the recycled micro powder are mixed with the corresponding bacteria liquid respectively at a solid-liquid ratio of 1.0, and are placed in a carbonization box for carbonization. The recycled fine aggregate is carbonized for 24 h, and the recycled micro powder is carbonized for 7 d.

[0032] (6) Each component is accurately weighed according to the mass percentage: fine sand 43 parts, cement 24 parts, recycled fine aggregate 11 parts, recycled micro powder 3 parts, water 11 parts, water reducing agent 3 parts and thickening agent 5 parts.

[0033] (7) The fine sand, cement, recycled fine aggregate, recycled micro powder and thickening agent are placed in a double-shaft mixer, mixed and stirred for 5 min, and uniform mixing is ensured.

[0034] (8) The water reducing agent is dissolved in water, and then the liquid is added into the mixer, mixed and stirred for 5 min, and uniform mixing is ensured, so that the novel 3D printing material is obtained.

[0035] (9) The stirred printing material is put into a gantry type 3D printer, after printing according to the set model, film curing is performed for 24 h, and the test piece is cut into a standard test piece size (70.7 mm cube).

[0036] (10) After 28 days of curing, the compressive strength of the test piece is measured. The 28-day compressive strength reaches 58.5 MPa.

[0037] Example 2

[0038] The purpose of this example is to optimize the concentration of modified bacteria solution and active bacteria solution. Bacillus powder is mixed with different volumes of water and stirred thoroughly. After 20 minutes of standing, 10 ml of supernatant is injected into LB medium and placed in a shaking incubator for 24 hours to obtain a series of modified bacteria solutions. The OD600 of the modified bacteria solution is shown in Table 1. The modified bacteria solution is used to mix with recycled fine aggregate. Bacillus powder is mixed with different volumes of water and stirred thoroughly. After 20 minutes of standing, 10 ml of supernatant is injected into LB medium and placed in a shaking incubator for 24 hours to obtain a series of active bacteria solutions. The OD600 of the active bacteria solution is shown in Table 2. The active bacteria solution is used to mix with recycled fine powder.

[0039] The recycled fine aggregate and recycled fine powder are mixed with the corresponding bacteria solution at a solid-liquid ratio of 1.0 and placed in a carbonization box for carbonization. The recycled fine aggregate is carbonized for 24 hours, and the recycled fine powder is carbonized for 7 days. The water absorption rate of the recycled fine aggregate and the activity index of the recycled fine powder are tested.

[0040] Table 1 Influence of modified bacteria solution OD600 on water absorption rate of recycled fine aggregate

[0041] Modified bacteria solution OD600 1 1.5 2 Water absorption of recycled fine aggregate / % 3.22 2.63 2.85

[0042] Table 2 Influence of active bacteria solution OD600 on activity index of recycled fine powder

[0043] Activated bacteria solution OD600 0.8 1 1.2 Recycled fine powder activity index / % 71.56 76.35 69.82

[0044] As shown in Tables 1 and 2, when the OD600 of the modified bacteria solution is 1.5, the water absorption rate of the recycled fine aggregate decreases to 2.63%; when the OD600 of the active bacteria solution is 1, the activity index of the recycled fine powder increases to 76.35%.

[0045] Example 3

[0046] The example of the present application provides a new type of 3D printing material. The fine sand accounts for 43 parts by weight, the cement accounts for 21 parts by weight, the recycled fine aggregate accounts for 11 parts by weight, the recycled fine powder accounts for 6 parts by weight, the water accounts for 11 parts by weight, the water reducing agent accounts for 3 parts by weight, and the thickening agent accounts for 5 parts by weight.

[0047] The example of the present application provides a preparation method of a new type of 3D printing material, which comprises the following steps:

[0048] (1) The construction waste concrete purchased is placed in a crusher, and graded through a 2.36 mm aperture vibrating screen to screen out recycled fine aggregate with a particle size of 0.15 mm to 2.36 mm to obtain recycled fine aggregate.

[0049] (2) The acquired waste concrete from the construction site is placed in a ball mill, and the powder obtained by ball milling is sieved by a vibrating sieve machine to a particle size of less than 75 μm to obtain recycled micropowder.

[0050] (3) Mix 10 g of Bacillus powder with 300 ml of water and stir thoroughly. After standing for 20 min, take 10 ml of the supernatant and inject it into LB medium. Place it in an oscillating box for 24 h to obtain a modified bacterial solution.

[0051] (4) Mix 5 g of Bacillus powder with 300 ml of water and stir thoroughly. After standing for 20 min, take 10 ml of the supernatant and inject it into LB culture medium. Place it in an oscillating box for 24 h to obtain an activated bacterial liquid.

[0052] (5) Recycled fine aggregate and recycled micropowder were mixed with the corresponding bacterial solution at a solid-liquid ratio of 1.0 and placed in a carbonization box for carbonization. Recycled fine aggregate was carbonized for 24 hours, and recycled micropowder was carbonized for 7 days.

[0053] (6) Accurately weigh each component by mass percentage: 43 parts of fine sand, 21 parts of cement, 11 parts of recycled fine aggregate, 6 parts of recycled micro powder, 11 parts of water, 3 parts of water reducer, and 5 parts of thickener.

[0054] (7) Place fine sand, cement, recycled fine aggregate, recycled micro powder and thickener into a twin-shaft mixer and mix for 5 minutes to ensure uniform mixing.

[0055] (8) Dissolve the water reducer in water, add the liquid into a blender, and mix and stir for 5 minutes to ensure uniform mixing to obtain a new 3D printing material.

[0056] (9) The mixed printing material is put into the gantry-type 3D printer. After printing according to the set model, the film is coated and cured for 24 hours, and the specimen is cut into the standard specimen size (70.7 mm cube).

[0057] (10) The compressive strength of the specimen was measured after 28 days of curing. The compressive strength reached 51.4 MPa after 28 days.

[0058] Example 4

[0059] An embodiment of the present invention provides a new 3D printing material, which comprises, by weight, 43 parts of fine sand, 18 parts of cement, 11 parts of recycled fine aggregate, 9 parts of recycled micropowder, 11 parts of water, 3 parts of water reducer, and 5 parts of thickener.

[0060] An embodiment of the present invention provides a method for preparing a novel 3D printing material, comprising the following steps:

[0061] (1) The acquired construction site waste concrete is placed in a crusher and classified through a vibrating screen with an aperture of 2.36 mm to screen out recycled fine aggregate with a particle size of 0.15 mm to 2.36 mm to obtain recycled fine aggregate.

[0062] (2) The acquired waste concrete from the construction site is placed in a ball mill, and the powder obtained by ball milling is sieved by a vibrating sieve machine to a particle size of less than 75 μm to obtain recycled micropowder.

[0063] (3) Mix 10 g of Bacillus powder with 300 ml of water and stir thoroughly. After standing for 20 min, take 10 ml of the supernatant and inject it into LB medium. Place it in an oscillating box for 24 h to obtain a modified bacterial solution.

[0064] (4) Mix 5 g of Bacillus powder with 300 ml of water and stir thoroughly. After standing for 20 min, take 10 ml of the supernatant and inject it into LB culture medium. Place it in an oscillating box for 24 h to obtain an activated bacterial liquid.

[0065] (5) Recycled fine aggregate and recycled micropowder were mixed with the corresponding bacterial solution at a solid-liquid ratio of 1.0 and placed in a carbonization box for carbonization. Recycled fine aggregate was carbonized for 24 hours, and recycled micropowder was carbonized for 7 days.

[0066] (6) Accurately weigh each component by mass percentage: 43 parts of fine sand, 18 parts of cement, 11 parts of recycled fine aggregate, 9 parts of recycled micro powder, 11 parts of water, 3 parts of water reducer, and 5 parts of thickener.

[0067] (7) Place fine sand, cement, recycled fine aggregate, recycled micro powder and thickener into a twin-shaft mixer and mix for 5 minutes to ensure uniform mixing.

[0068] (8) Dissolve the water reducer in water, add the liquid into a blender, and mix and stir for 5 minutes to ensure uniform mixing to obtain a new 3D printing material.

[0069] (9) The mixed printing material is put into the gantry-type 3D printer. After printing according to the set model, the film is coated and cured for 24 hours, and the specimen is cut into the standard specimen size (70.7 mm cube).

[0070] (10) The compressive strength of the specimen was measured after 28 days of curing. The compressive strength reached 42.8 MPa after 28 days.

[0071] Example 5

[0072] An embodiment of the present invention provides a new 3D printing material, which comprises, by weight, 32 parts of fine sand, 24 parts of cement, 22 parts of recycled fine aggregate, 3 parts of recycled micropowder, 11 parts of water, 3 parts of water reducer, and 5 parts of thickener.

[0073] An embodiment of the present invention provides a method for preparing a novel 3D printing material, comprising the following steps:

[0074] (1) The acquired construction site waste concrete is placed in a crusher and classified through a vibrating screen with an aperture of 2.36 mm to screen out recycled fine aggregate with a particle size of 0.15 mm to 2.36 mm to obtain recycled fine aggregate.

[0075] (2) The acquired waste concrete from the construction site is placed in a ball mill, and the powder obtained by ball milling is sieved by a vibrating sieve machine to a particle size of less than 75 μm to obtain recycled micropowder.

[0076] (3) Mix 10 g of Bacillus powder with 300 ml of water and stir thoroughly. After standing for 20 min, take 10 ml of the supernatant and inject it into LB medium. Place it in an oscillating box for 24 h to obtain a modified bacterial solution.

[0077] (4) Mix 5 g of Bacillus powder with 300 ml of water and stir thoroughly. After standing for 20 min, take 10 ml of the supernatant and inject it into LB culture medium. Place it in an oscillating box for 24 h to obtain an activated bacterial liquid.

[0078] (5) Recycled fine aggregate and recycled micropowder were mixed with the corresponding bacterial solution at a solid-liquid ratio of 1.0 and placed in a carbonization box for carbonization. Recycled fine aggregate was carbonized for 24 hours, and recycled micropowder was carbonized for 7 days.

[0079] (6) Accurately weigh each component by mass percentage: 32 parts of fine sand, 24 parts of cement, 22 parts of recycled fine aggregate, 3 parts of recycled micro powder, 11 parts of water, 3 parts of water reducer, and 5 parts of thickener.

[0080] (7) Place fine sand, cement, recycled fine aggregate, recycled micro powder and thickener into a twin-shaft mixer and mix for 5 minutes to ensure uniform mixing.

[0081] (8) Dissolve the water reducer in water, add the liquid into a blender, and mix and stir for 5 minutes to ensure uniform mixing to obtain a new 3D printing material.

[0082] (9) The mixed printing material is put into the gantry-type 3D printer. After printing according to the set model, the sample is coated and cured for 24 hours, and the sample is cut into the standard sample size (70.7 mm cube).

[0083] (10) The compressive strength of the specimen was measured after 28 days of curing. The compressive strength reached 53.3 MPa after 28 days.

[0084] Example 6

[0085] An embodiment of the present invention provides a new 3D printing material, which comprises, by weight, 48 parts of fine sand, 24 parts of cement, 6 parts of recycled fine aggregate, 3 parts of recycled micropowder, 11 parts of water, 3 parts of water reducer, and 5 parts of thickener.

[0086] An embodiment of the present invention provides a method for preparing a novel 3D printing material, comprising the following steps:

[0087] (1) The acquired construction site waste concrete is placed in a crusher and classified through a vibrating screen with an aperture of 2.36 mm to screen out recycled fine aggregate with a particle size of 0.15 mm to 2.36 mm to obtain recycled fine aggregate.

[0088] (2) The acquired waste concrete from the construction site is placed in a ball mill, and the powder obtained by ball milling is sieved by a vibrating sieve machine to a particle size of less than 75 μm to obtain recycled micropowder.

[0089] (3) Mix 10 g of Bacillus powder with 300 ml of water and stir thoroughly. After standing for 20 min, take 10 ml of the supernatant and inject it into LB medium. Place it in an oscillating box for 24 h to obtain a modified bacterial solution.

[0090] (4) Mix 5 g of Bacillus powder with 300 ml of water and stir thoroughly. After standing for 20 min, take 10 ml of the supernatant and inject it into LB culture medium. Place it in an oscillating box for 24 h to obtain an activated bacterial liquid.

[0091] (5) Recycled fine aggregate and recycled micropowder were mixed with the corresponding bacterial solution at a solid-liquid ratio of 1.0 and placed in a carbonization box for carbonization. Recycled fine aggregate was carbonized for 24 hours, and recycled micropowder was carbonized for 7 days.

[0092] (6) Accurately weigh each component by mass percentage: 48 parts of fine sand, 24 parts of cement, 6 parts of recycled fine aggregate, 3 parts of recycled micro powder, 11 parts of water, 3 parts of water reducer, and 5 parts of thickener.

[0093] (7) Place fine sand, cement, recycled fine aggregate, recycled micro powder and thickener into a twin-shaft mixer and mix for 5 minutes to ensure uniform mixing.

[0094] (8) Dissolve the water reducer in water, add the liquid into a blender, and mix and stir for 5 minutes to ensure uniform mixing to obtain a new 3D printing material.

[0095] (9) The mixed printing material is put into the gantry-type 3D printer. After printing according to the set model, the sample is coated and cured for 24 hours, and the sample is cut into the standard sample size (70.7 mm cube).

[0096] (10) The compressive strength of the specimen was measured after 28 days of curing. The compressive strength reached 56.4 MPa after 28 days.

[0097] Example 7

[0098] An embodiment of the present invention provides a new 3D printing material, which comprises, by weight, 43 parts of fine sand, 24 parts of cement, 11 parts of recycled fine aggregate, 3 parts of recycled micropowder, 11 parts of water, 3 parts of water reducer, 5 parts of thickener, 0.42 parts of concentrated urease, 0.55 parts of urea solution, and 0.32 parts of calcium chloride solution.

[0099] The application provides a preparation method of a novel 3D printing material, which comprises the following steps:

[0100] (1) placing the purchased construction waste concrete in a crusher, grading through a 2.36 mm aperture vibrating screen, screening out recycled fine aggregates with a particle size of 0.15 mm to 2.36 mm, and obtaining the recycled fine aggregates.

[0101] (2) placing the purchased construction waste concrete in a ball mill, screening the powder obtained by ball milling to a particle size of <75 μm through a vibrating shaker, and obtaining recycled micro powder.

[0102] (3) mixing 10 g of bacillus powder with 300 ml of water, fully stirring, standing for 20 min, taking 10 ml of supernatant, injecting into an LB culture medium, and placing in a shaking box for 24 h to obtain a modified bacteria solution.

[0103] (4) mixing 5 g of bacillus powder with 300 ml of water, fully stirring, standing for 20 min, taking 10 ml of supernatant, injecting into an LB culture medium, and placing in a shaking box for 24 h to obtain an active bacteria solution.

[0104] (5) mixing the recycled fine aggregates and the recycled micro powder with the corresponding bacteria solution at a solid-liquid ratio of 1.0, and placing in a carbonization box for carbonization; the recycled fine aggregates are carbonized for 24 h, and the recycled micro powder is carbonized for 7 d.

[0105] (6) accurately weighing each component according to the mass percentage: 43 parts of fine sand, 24 parts of cement, 11 parts of recycled fine aggregates, 3 parts of recycled micro powder, 11 parts of water, 3 parts of water reducing agent and 5 parts of thickening agent.

[0106] (7) selecting dry and mildew-free soybeans, crushing into fine powder (passing through a 100 mesh sieve), and increasing the extraction contact area;

[0107] (8) according to the ratio of soybean powder: distilled water = 1:5, adding the powder into pre-cooled distilled water (4 ℃), stirring uniformly, and soaking for 2 hours (adding 0.05M Tris-HCl buffer to adjust the pH to 7.5 to improve the extraction rate);

[0108] (9) fully stirring the mixed solution with a magnetic stirrer, centrifuging (3000 rpm, 15 min) at 4 ℃, and collecting the supernatant;

[0109] (10) slowly adding ammonium sulfate to the supernatant to a saturation degree of 40%, standing for 1 hour, centrifuging (10000 rpm, 20 min) again at 4 ℃, dissolving the precipitate with a small amount of buffer, and obtaining a concentrated urease solution;

[0110] (11) Dissolve urea and calcium chloride in distilled water respectively, prepare 0.5M urea solution and 0.5M calcium chloride solution, take 0.55 parts of urea solution and 0.32 parts of calcium chloride solution for standby;

[0111] (12) Take the concentrated soybean urease solution, dilute it to 10U / mL with buffer solution (pH 7.5), mix it with urea and calcium chloride solution, and obtain the soybean urease solution, the enzyme activity of the soybean urease solution is stable;

[0112] (13) Put fine sand, cement, recycled fine aggregate, recycled micro powder and thickening agent into a double-shaft mixer, mix and stir for 5 minutes to ensure uniform mixing.

[0113] (14) Dissolve the water reducing agent in water, the amount of soybean urease solution is 20% of the total amount of water, then add the liquid into the mixer, mix and stir for 5 minutes to ensure uniform mixing, and obtain the new 3D printing material.

[0114] (15) Put the stirred printing material into the gantry type 3D printer, after printing according to the set model, cover and maintain for 24h. Cut the test piece into a standard test piece size (70.7mm cube).

[0115] (16) Measure the compressive strength after 28d of curing of the test piece. The 28d compressive strength reaches 60.2MPa.

[0116] Example 8

[0117] The embodiment of the application provides a new 3D printing material, according to weight parts, fine sand 43 parts, cement 24 parts, recycled fine aggregate 11 parts, recycled micro powder 3 parts, water 11 parts, water reducing agent 3 parts, thickening agent 5 parts, concentrated urease 0.42 parts, urea solution 0.55 parts, and calcium chloride solution 0.32 parts.

[0118] The embodiment of the application provides a preparation method of a new 3D printing material, comprising the following steps:

[0119] (1) Put the purchased construction waste concrete into a crusher, grade the recycled fine aggregate with a particle size of 0.15mm-2.36mm through a 2.36mm aperture vibrating screen, and obtain the recycled fine aggregate.

[0120] (2) Put the purchased construction waste concrete into a ball mill, screen the powder obtained by ball milling to a particle size of <75μm through a vibrating shaker, and obtain the recycled micro powder.

[0121] (3) Mix 10g of bacillus powder with 300ml of water, stir fully, stand for 20min, take 10ml of supernatant and inject into LB culture medium, and put into a shaking box for 24h, and obtain modified bacteria liquid.

[0122] (4) 5g Bacillus powder is mixed with 300ml water and stirred thoroughly, and after standing for 20min, 10ml of supernatant is injected into LB culture medium and placed in a shaking box for 24h to obtain an activated bacteria solution.

[0123] (5) The recycled fine aggregate and recycled micro powder are mixed with the corresponding bacteria solution at a solid-liquid ratio of 1.0 and placed in a carbonization box for carbonization. The recycled fine aggregate is carbonized for 24h, and the recycled micro powder is carbonized for 7d.

[0124] (6) Each component is accurately weighed according to the mass percentage: fine sand 43 parts, cement 24 parts, recycled fine aggregate 11 parts, recycled micro powder 3 parts, water 11 parts, water reducing agent 3 parts, and thickening agent 5 parts.

[0125] (7) Dry and mildewed soybeans are selected and crushed into fine powder (passed through a 100-mesh sieve) to increase the extraction contact area;

[0126] (8) According to the ratio of soybean powder to distilled water = 1:8, the powder is added to pre-cooled distilled water (4℃) and stirred uniformly, and soaked for 2 hours (0.05M Tris-HCl buffer is added to adjust the pH to 7.5 to improve the extraction rate);

[0127] (9) The mixed solution is thoroughly stirred with a magnetic stirrer, and centrifuged at 4℃ (3000rpm, 15min), and the supernatant is collected;

[0128] (10) Ammonium sulfate is slowly added to the supernatant to a saturation degree of 40%, and after standing for 1 hour, it is centrifuged again at 4℃ (10000rpm, 20min), and the precipitate is dissolved with a small amount of buffer to obtain a concentrated urease solution;

[0129] (11) Urea and calcium chloride are dissolved in distilled water to prepare a 0.5M urea solution and a 0.5M calcium chloride solution, respectively, for standby;

[0130] (12) The concentrated soybean urease solution is diluted with buffer (pH 7.5) to a concentration of 10U / mL, and mixed with the urea and calcium chloride solutions to obtain a soybean urease solution, and the enzyme activity of the soybean urease solution is stable;

[0131] (13) Fine sand, cement, recycled fine aggregate, recycled micro powder, and thickening agent are placed in a double-shaft mixer and mixed and stirred for 5min to ensure uniform mixing.

[0132] (14) The water reducing agent is dissolved in water, and the soybean urease solution is added in an amount of 20% of the total water, and then the liquid is added to the mixer and mixed and stirred for 5min to ensure uniform mixing, to obtain a new 3D printing material.

[0133] (15) The stirred printing material is put into the gantry type 3D printer, and after printing according to the set model, the film is cured for 24 h. The test piece is cut into a standard test piece size (70.7 mm cube).

[0134] (16) The compressive strength of the test piece is measured after curing for 28 d. The 28 d compressive strength reaches 59.6 MPa.

[0135] Example 9

[0136] The difference between this example and example 8 is that the proportions of soybean urease, urea and calcium chloride are different. Specifically, the present example provides a new type of 3D printing material, wherein the proportions by weight are as follows: fine sand 43 parts, cement 24 parts, recycled fine aggregate 11 parts, recycled micro powder 3 parts, water 11 parts, water reducing agent 3 parts, thickening agent 5 parts, concentrated urease 0.36 parts, urea solution 0.45 parts, and calcium chloride solution 0.27 parts. The preparation method is the same as that of example 8. The compressive strength of the test piece is measured after curing for 28 d. The 28 d compressive strength reaches 55.4 MPa.

[0137] Example 10

[0138] The difference between this example and example 8 is that the proportions of soybean urease, urea and calcium chloride are different. Specifically, the present example provides a new type of 3D printing material, wherein the proportions by weight are as follows: fine sand 43 parts, cement 24 parts, recycled fine aggregate 11 parts, recycled micro powder 3 parts, water 11 parts, water reducing agent 3 parts, thickening agent 5 parts, concentrated urease 0.48 parts, urea solution 0.6 parts, and calcium chloride solution 0.36 parts. The preparation method is the same as that of example 8. The compressive strength of the test piece is measured after curing for 28 d. The 28 d compressive strength reaches 57.2 MPa.

[0139] Comparative Example 1

[0140] Compared with example 1, the difference of the present comparative example is that the recycled fine aggregate is not induced by microorganisms to mineralize, and the specific steps are as follows:

[0141] (1) The purchased construction waste concrete is placed in a crusher, and the recycled fine aggregate with a particle size of 0.15 mm to 2.36 mm is screened out by a 2.36 mm aperture vibrating screen, to obtain the recycled fine aggregate.

[0142] (2) The purchased construction waste concrete is placed in a ball mill, and the powder obtained by ball milling is screened to a particle size of <75 μm by a vibrating shaker, to obtain the recycled micro powder.

[0143] (3) 10 g of bacillus powder is mixed with 300 ml of water and stirred thoroughly, 10 ml of supernatant is taken after standing for 20 min, and injected into LB culture medium, and placed in a shaking box for 24 h, to obtain an active bacteria liquid.

[0144] (4) The recycled fine powder is mixed with the corresponding bacterial solution at a solid-liquid ratio of 1.0 and placed in a carbonization box for carbonization for 7 days.

[0145] (5) Each component is accurately weighed according to the mass percentage: fine sand 43 parts, cement 24 parts, recycled fine aggregate 11 parts, recycled fine powder 3 parts, water 11 parts, water reducing agent 3 parts, thickening agent 5 parts.

[0146] (6) The fine sand, cement, recycled fine aggregate, recycled fine powder and thickening agent are placed in a double-shaft mixer and mixed and stirred for 5 minutes to ensure uniform mixing.

[0147] (7) The water reducing agent is dissolved in water, and then the liquid is added to the mixer and mixed and stirred for 5 minutes to ensure uniform mixing, obtaining a new 3D printing material.

[0148] (8) The mixed printing material is placed in a gantry type 3D printer, and after printing according to the set model, it is covered and cured for 24 hours. The test piece is cut into a standard test piece size (70.7mm cube).

[0149] (9) The compressive strength of the test piece is measured after 28 days of curing. The 28-day compressive strength reaches 51.6MPa

[0150] Comparative Example 2

[0151] Compared with Example 1, the difference of the present comparative example is that the recycled fine powder is not induced by microorganisms to mineralize, and the specific steps are as follows: (1) The construction waste concrete purchased is placed in a crusher, and the recycled fine aggregate with a particle size of 0.15mm-2.36mm is screened out by a 2.36mm aperture vibrating screen, obtaining recycled fine aggregate.

[0152] (2) The construction waste concrete purchased is placed in a ball mill, and the powder obtained by ball milling is screened to a particle size of <75μm by a vibrating shaker, obtaining recycled fine powder.

[0153] (3) 5g of Bacillus powder is mixed with 300ml of water and stirred thoroughly, and after standing for 20min, 10ml of supernatant is injected into LB culture medium and placed in a shaking box for 24h, obtaining modified bacterial solution.

[0154] (4) The recycled fine aggregate is mixed with the modified bacterial solution at a solid-liquid ratio of 1.0 and placed in a carbonization box for carbonization. The recycled fine aggregate is carbonized for 24h, and the recycled fine powder is carbonized for 7d.

[0155] (5) Each component is accurately weighed according to the mass percentage: fine sand 43 parts, cement 24 parts, recycled fine aggregate 11 parts, recycled fine powder 3 parts, water 11 parts, water reducing agent 3 parts, thickening agent 5 parts.

[0156] (6) The fine sand, cement, recycled fine aggregate, recycled fine powder and thickening agent are placed in a double-shaft mixer and mixed and stirred for 5 minutes to ensure uniform mixing.

[0157] (7) Dissolve the water reducing agent in water, then add the liquid into the blender, mix and stir for 5 minutes to ensure uniform mixing, to obtain a new 3D printing material.

[0158] (8) Put the mixed printing material into the gantry type 3D printer, and after printing according to the set model, film curing is performed for 24 h, and the test piece is cut into a standard test piece size (70.7 mm cube).

[0159] (9) Measure the compressive strength of the test piece after 28 d of curing. The 28 d compressive strength reaches 45.3 MPa

[0160] Comparative Example 3

[0161] Compared with Example 1, the difference of the present comparative example is that neither the recycled fine aggregate nor the recycled micro powder is induced by microorganisms to mineralize, and the specific steps are as follows:

[0162] (1) Put the purchased construction waste concrete into a crusher, and grade it through a 2.36 mm aperture vibrating screen, screen out the recycled fine aggregate with a particle size of 0.15 mm to 2.36 mm, and obtain the recycled fine aggregate.

[0163] (2) Put the purchased construction waste concrete into a ball mill, and screen the powder obtained by ball milling to a particle size of <75 μm through a vibrating shaker, to obtain the recycled micro powder.

[0164] (3) Accurately weigh each component according to the mass percentage: fine sand 43 parts, cement 24 parts, recycled fine aggregate 11 parts, recycled micro powder 3 parts, water 11 parts, water reducing agent 3 parts, and thickening agent 5 parts.

[0165] (4) Put the fine sand, cement, recycled fine aggregate, recycled micro powder, and thickening agent into a double-shaft blender, mix and stir for 5 minutes to ensure uniform mixing.

[0166] (5) Dissolve the water reducing agent in water, then add the solution into the blender, mix and stir for 5 minutes to ensure uniform mixing, to obtain a new 3D printing material.

[0167] (6) Put the mixed printing material into the gantry type 3D printer, and after printing according to the set model, film curing is performed for 24 h, and the test piece is cut into a standard test piece size (70.7 mm cube).

[0168] (7) Measure the compressive strength of the test piece after 28 d of curing. The 28 d compressive strength reaches 40.4 MPa

[0169] Comparative Example 4

[0170] The difference between the present comparative example and Example 7 is that the urease solution is prepared from commercially purchased Bacillus pasteurii powder instead of self-made soybean urease solution. The preparation method is as follows: the Bacillus pasteurii powder is added to the recovery medium (urea 20 g / L, yeast extract 0.5 g / L) and shaken for 24 h, the bacterial cells are collected by centrifugation, and the bacterial slurry is resuspended in PBS to an OD600 of 1. The preparation of the urease solution of the present comparative example is completed.

[0171] The specific steps are as follows:

[0172] (1) The construction waste concrete purchased is placed in a crusher, and the recycled fine aggregate with a particle size of 0.15-2.36 mm is obtained by grading through a 2.36 mm aperture vibrating screen.

[0173] (2) The construction waste concrete purchased is placed in a ball mill, and the recycled micro-powder is obtained by screening the powder obtained by ball milling to a particle size of <75 μm.

[0174] (3) 10 g of Bacillus pasteurii powder is mixed with 300 ml of water and stirred thoroughly, 10 ml of supernatant is taken after standing for 20 min, and injected into LB medium, and placed in a shaking box for 24 h to obtain a modified bacterial solution.

[0175] (4) 5 g of Bacillus pasteurii powder is mixed with 300 ml of water and stirred thoroughly, 10 ml of supernatant is taken after standing for 20 min, and injected into LB medium, and placed in a shaking box for 24 h to obtain an active bacterial solution.

[0176] (5) The recycled fine aggregate and the recycled micro-powder are mixed with the corresponding bacterial solution at a solid-liquid ratio of 1.0, and placed in a carbonization box for carbonization. The recycled fine aggregate is carbonized for 24 h, and the recycled micro-powder is carbonized for 7 d.

[0177] (6) Each component is accurately weighed according to the mass percentage: fine sand 43 parts, cement 24 parts, recycled fine aggregate 11 parts, recycled micro-powder 3 parts, water 11 parts, water reducing agent 3 parts, thickening agent 5 parts, urease 0.42 parts, urea 0.55 parts, calcium chloride 0.32 parts.

[0178] (7) The urease solution is diluted with buffer (pH 7.5) to a concentration of 10 U / mL to ensure stable enzyme activity after mixing with urea and calcium chloride solutions;

[0179] (8) The fine sand, cement, recycled fine aggregate, recycled micro-powder, and thickening agent are placed in a double-shaft mixer and mixed and stirred for 5 min to ensure uniform mixing.

[0180] (9) The water reducing agent is dissolved in water, the urease solution is added in an amount of 20% of the total water, and then the liquid is added to the mixer and mixed and stirred for 5 min to ensure uniform mixing, to obtain a new 3D printing material.

[0181] (10) The stirred printing material is put into the gantry type 3D printer, and after printing according to the set model, the film curing is maintained for 24h. The test piece is cut into a standard test piece size (70.7mm cube).

[0182] (11) The compressive strength of the test piece is measured after 28d curing. The 28d compressive strength reaches 59.2MPa.

[0183] The application develops a new type of 3D printing material based on recycled micro powder and recycled fine aggregate blending and an internal interlayer gap repair method thereof, realizes high-value resource of industrial solid waste through microbial assisted mineralization activation, replaces part of fine sand with recycled fine aggregate and part of lime with recycled micro powder, and greatly reduces the cost. The new type of 3D printing material has high fluidity, and the initial fluidity reaches more than 180mm. The 3D printing material has excellent compressive strength. The application also provides a method for deep repair of internal interlayer gaps of test pieces, so that the mechanical properties of the 3D printing test piece are more excellent.

[0184] The technology provides a high-performance and low-cost systematic solution for large-scale utilization of industrial solid waste, and promotes the transformation of building material industry to collaborative development of "resources-environment-engineering".

Claims

1. A new type of 3D printing material based on the blending of recycled micro powder and recycled fine aggregate, characterized in that: The invention comprises, by weight, 32 to 48 parts of fine sand, 18 to 24 parts of cement, 6 to 22 parts of recycled fine aggregate, 3 to 9 parts of recycled micropowder, 3 parts of water reducer, and 5 parts of thickener; wherein the recycled fine aggregate is modified recycled fine aggregate induced by Bacillus, and the recycled micropowder is activated recycled micropowder induced by Bacillus.

2. The novel 3D printing material according to claim 1, characterized in that: It also includes soybean urease: 0.36 parts to 0.48 parts, urea solution: 0.45 parts to 0.6 parts, and calcium chloride solution: 0.27 parts to 0.36 parts; The concentrations of the urea solution and the calcium chloride solution are both 0.5M.

3. The novel 3D printing material according to claim 1, characterized in that: The water reducing agent is sodium gluconate, and the thickening agent is hydroxypropyl methylcellulose.

4. The novel 3D printing material according to claim 1, characterized in that: The fine sand is river sand with a particle size of 0.15 mm to 2.36 mm, and the type of cement is 42.5 ordinary Portland cement.

5. The novel 3D printing material according to claim 1, characterized in that: The recycled fine aggregate is a modified recycled fine aggregate that has been mineralized by inducing a Bacillus bacterial solution with an OD600 of 1-2, and the recycled micropowder is an activated recycled micropowder that has been mineralized by inducing a Bacillus bacterial solution with an OD600 of 0.8-1.

2.

6. A method for preparing the novel 3D printing material according to any one of claims 1 to 5, characterized in that: The cement, modified recycled fine aggregate, activated recycled micropowder and thickener are mixed evenly to obtain a dry mix; the water reducer is dissolved in water, and the obtained liquid is mixed with the dry mix and stirred thoroughly to obtain a new 3D printing material.

7. The preparation method according to claim 6, characterized in that Cement, modified recycled fine aggregate, activated recycled micropowder, and thickener are uniformly mixed to obtain a dry mix; soybean urease solution, urea solution, and calcium chloride solution are mixed to obtain a mixed solution a; a water reducer is dissolved in water to obtain a mixed solution b; the mixed solution a and the mixed solution b are mixed to obtain a mixed solution c; the mixed solution c is mixed with the dry mix and fully stirred to obtain a new 3D printing material.

8. The preparation method according to claim 6 or 7, characterized in that The preparation method of the modified recycled fine aggregate is as follows: crushing industrial waste concrete blocks, screening out recycled fine aggregate with a particle size of 0.15mm to 2.36mm, placing the recycled fine aggregate soaked in Bacillus liquid in a carbonization box for carbonization, taking it out and drying it to obtain the modified recycled fine aggregate.

9. The preparation method according to claim 6 or 7, characterized in that: The preparation method of the activated regenerated micropowder is as follows: screening out the regenerated micropowder with a particle size of less than 75 μm, soaking the regenerated micropowder in a bacillus liquid, and then placing the regenerated micropowder in a carbonization box for carbonization to obtain the activated regenerated micropowder.

10. The preparation method according to claim 7, characterized in that The preparation method of soybean urease is as follows: soak soybean powder in water, stir and mix, centrifuge and take the supernatant; add ammonium sulfate to the supernatant and collect the precipitate to obtain soybean urease.

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