Preparation method of modified oyster shell and steel fiber-based 3D printing ecological concrete

Abstract

The application discloses a preparation method of modified oyster shell and steel fiber based 3D printing ecological concrete, which comprises the following steps: (1) calcining oyster shell powder, then mixing the calcined product with a polymer emulsion and performing ultrasonic treatment, drying and grinding the separated solid product to obtain modified oyster shell powder; (2) heating copper-plated steel fibers in air, cooling and then performing surface treatment in weak acid, then performing phosphating treatment on the obtained fibers in a phosphating solution, and then cleaning the obtained fibers to remove residual phosphating solution to obtain modified steel fibers; and (3) taking raw materials in the following proportions: composite cementitious material, fine aggregate, modified oyster shell powder, modified steel fibers and additive, uniformly mixing the above raw materials, and then uniformly stirring the mixture with water to obtain 3D printing ecological concrete. The method can make the concrete have good printability, and can improve the structural stability of a building body after printing and reduce deformation.

Description

Technical Field

[0001] This invention relates to the field of 3D printing material preparation technology, specifically to a method for preparing modified oyster shell and steel fiber-based 3D printed eco-concrete. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] In recent years, millions of tons of discarded oyster shells have been generated globally as marine solid waste. Large quantities of these shells accumulate on coastlines and near rivers, easily leading to soil and water pollution. Oyster shells are rich in carbonates, which can be recycled and reused, for example, in the production of fertilizers and building materials. Concrete 3D printing technology is an emerging building manufacturing technology that gradually constructs building structures or components by layering concrete materials.

[0004] In the process of printing concrete into building structures, it is crucial to ensure two key aspects. First, the concrete material must possess excellent printability to smoothly output from the printing equipment and form the desired shape. Second, the printed structure must maintain good stability to prevent deformation due to insufficient load-bearing capacity. This is because as printing progresses, the load on the underlying concrete material increases, and exceeding its bearing limit can lead to deformation or even collapse. However, while good printability requires good flowability in the concrete material, this can reduce the load-bearing capacity and stability of the printed structure. Therefore, ensuring that 3D-printed concrete materials possess both excellent printability and structural stability is essential for guaranteeing a smooth printing process and the quality of the resulting building. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for preparing modified oyster shell and steel fiber-based 3D-printed eco-concrete, which not only gives the concrete excellent printability but also improves the structural stability of the printed structure and reduces the deformation rate. Specifically, the technical solution of this invention is as follows.

[0006] A method for preparing modified oyster shell and steel fiber-based 3D-printed eco-concrete includes the following steps:

[0007] (1) The oyster shell powder is calcined, and then the calcined product is mixed with polymer emulsion and ultrasonically treated. The solid product is separated, dried and ground to obtain modified oyster shell powder for later use.

[0008] (2) The copper-plated steel fibers are heated in air, cooled, and then surface-treated in a weak acid. After completion, the resulting fibers are placed in a phosphating solution for phosphating treatment, and then the resulting fibers are cleaned to obtain modified steel fibers for later use.

[0009] (3) Take the following raw materials in the following proportions: composite cementitious material, fine aggregate, modified oyster shell powder, modified steel fiber, and admixture. Mix the above raw materials evenly, add water and stir until uniform to obtain 3D printed ecological concrete.

[0010] Furthermore, in step (1), the calcination temperature is 850~950℃ and the time is 40~60min.

[0011] Further, in step (1), the ratio of the calcined product to the polymer emulsion is 1g: 20~50ml. Optionally, the polymer emulsion includes any one of: ethylene-vinyl acetate copolymer emulsion (EVA emulsion), polyacrylate emulsion (PA emulsion), polyvinyl alcohol emulsion, etc. The mass fraction of the polymer emulsion is 30~35%.

[0012] Furthermore, in step (1), the drying temperature is 60~80℃ and the time is 20~35min.

[0013] Furthermore, in step (1), the modified oyster shell powder has a fineness of 300-500 mesh.

[0014] Further, in step (2), the heating temperature is 400~500℃ and the time is 8~15min. Optionally, the copper-plated steel fiber has a length of 5~10mm and a diameter of 0.1~0.15mm.

[0015] Further, in step (2), the weak acid includes at least one of formic acid, acetic acid, citric acid, etc. Optionally, the concentration of the weak acid is 0.25~0.6 mol / L.

[0016] Furthermore, in step (2), the surface treatment time is 130~170s.

[0017] Further, in step (2), the phosphating solution is prepared using the following components: 37-42g of phosphoric acid, 25-30g of zinc oxide, 20-24g of nitric acid, 1-3g of tartaric acid, 0.4-0.7g of ammonium molybdate, and 0.5-0.85g of sodium m-nitrobenzenesulfonate are mixed and then water is added to 1 liter. The mixture is stirred until all components are fully dissolved.

[0018] Furthermore, in step (2), the phosphating treatment is carried out at a temperature of 70~80℃ for 5~10 minutes.

[0019] Further, in step (3), the proportions of each raw material are as follows: 60-100 parts by weight of composite cementitious material, 20-28 parts by weight of fine aggregate, 3-8 parts by weight of modified oyster shell powder, 7-10 parts by weight of modified steel fiber, 1-3 parts by weight of composite additive, and 30-50 parts by weight of water.

[0020] Further, in step (3), the composite cementitious material is composed of lightly calcined magnesium oxide, magnesium sulfate, and silicate cement. The mass ratio of lightly calcined magnesium oxide to magnesium sulfate is 1:2~2.3. The silicate cement is 4~5 times the total mass of the lightly calcined magnesium oxide and magnesium sulfate. The composite cementitious material of this invention can better improve the mid-to-late-stage strength of printed buildings and reduce the occurrence of defects caused by shrinkage in the later stages.

[0021] Further, in step (3), the composite additive includes a water-reducing agent and a thickener, with a mass ratio of 0.5 to 1:1. Optionally, the water-reducing agent includes at least one of polycarboxylate water-reducing agents, naphthalene-based water-reducing agents, and aminosulfonate water-reducing agents. The thickener includes at least one of hydroxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl starch.

[0022] Further, in step (3), the fine aggregate is composed of particles with particle sizes of 0.07~0.15mm, 0.15~0.3mm, and 0.3~1.18mm, graded at a mass ratio of 1:1:3~5. Optionally, the fine aggregate includes at least one of river sand, quartz sand, and manufactured sand.

[0023] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0024] (1) The modified oyster shell powder incorporated into the concrete material of the present invention not only realizes the resource utilization of waste, but also utilizes the pores generated in the oyster shell powder particles after calcination to load polymers. After being incorporated into 3D printed concrete, the hydrophilic properties of the polymer can be used to release water during extrusion printing using extrusion pressure, ensuring that the concrete material has good rheological properties and maintaining good continuous printing capability. At the same time, after extrusion, the polymer reabsorbs the released water, improving the stability of the printed building. Meanwhile, the water absorbed by the polymer is gradually released in the later stage of the hydration of the composite cementitious material, which helps to prevent the drying shrinkage cracking caused by water evaporation and volume shrinkage in the later stage of hydration, thus preventing the deterioration of the building strength. In addition, the calcined oyster shell contains a large amount of calcium oxide, which can effectively promote the curing and hardening process of the composite cementitious material in the printed building, thereby improving the structural stability of the building and reducing the deformation rate.

[0025] (2) The modified steel fibers incorporated into the concrete material of the present invention can not only further improve the structural stability of the printed building, but also improve the mechanical strength and interlayer bonding ability of the building. To this end, the present invention first uses copper-plated steel fibers as a carrier, and uses high-temperature oxidation to transform the copper plating layer on its surface into copper oxide. Then, the surface of the steel fibers is etched by the reaction of weak acid with the copper oxide, making the surface of the steel fibers rough. After further phosphating treatment, the steel fiber matrix exposed by the acid etching reacts with the phosphating solution to form a phosphating film, which can not only prevent the steel fibers from rusting after being incorporated into the concrete material, but also increase the bonding force between the steel fibers and the concrete material. After the above-mentioned modified steel fibers are incorporated into the concrete material and printed into a building, the modified steel fibers can not only play a good supporting role, but also, together with the setting-promoting effect of the modified oyster shell powder, the combination of the two can effectively improve the structural stability of the building and reduce the deformation rate. Furthermore, the ability to improve interlayer bonding can be enhanced by inserting some steel fibers into the lower printing layer. Since the surface of the modified steel fibers has undergone special roughening treatment, it can further overcome the problem of insufficient interlayer strength in 3D printed buildings. Attached Figure Description

[0026] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings, wherein:

[0027] Figure 1 The image shows a sample of modified oyster shell powder prepared in Example 1 below.

[0028] Figure 2 The image shows the compressive strength test results of the 3D-printed eco-concrete prepared in Example 1 below.

[0029] Figure 3 The image shows the flexural strength test results of the 3D-printed eco-concrete prepared in Example 1 below.

[0030] Figure 4 The image shows the compressive strength test results of the 3D-printed eco-concrete prepared in Example 2 below.

[0031] Figure 5 The image shows the flexural strength test results of the 3D-printed eco-concrete prepared in Example 2 below.

[0032] Figure 6 The image shows the compressive strength test results of the 3D-printed eco-concrete prepared in Example 3 below.

[0033] Figure 7 The image shows the flexural strength test results of the 3D-printed eco-concrete prepared in Example 3 below. Detailed Implementation

[0034] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. The present invention will now be further described with reference to specific embodiments.

[0035] Example 1

[0036] A method for preparing modified oyster shell and steel fiber-based 3D-printed eco-concrete includes the following steps:

[0037] (1) After pulverizing the oyster shells, heat them to 900℃ at a rate of 15℃ / min and hold for 45min. Then cool to room temperature. Mix the calcined product with 30% polyacrylate emulsion at a ratio of 1g:20ml. After ultrasonic treatment for 10min, filter out the solid product. Place it in an oven and dry at 70℃ for 25min. Grind it and pass it through a 400-mesh sieve to obtain modified oyster shell powder (e.g. Figure 1 (As shown), for later use.

[0038] (2) Mix 40g of phosphoric acid, 28g of zinc oxide, 22g of nitric acid, 2g of tartaric acid, 0.5g of ammonium molybdate and 0.7g of sodium m-nitrobenzenesulfonate, add water to 1 liter, and stir until all components are fully dissolved to obtain phosphating solution for later use.

[0039] (3) Copper-plated steel fibers (8 mm in length and 0.1 mm in diameter) were heated to 420°C in air at a rate of 10°C / min and held for 10 min. After cooling to room temperature, the obtained steel fibers were added to 0.3 mol / L citric acid and stirred for 150 s. After completion, the steel fibers were filtered out and placed in the phosphating solution heated to 80°C for 6 min. Then the steel fibers were filtered out and washed three times with clean water to obtain modified steel fibers for later use.

[0040] (4) The following proportions of raw materials are used: 85 parts by weight of composite cementitious material, 24 parts by weight of fine aggregate, 5 parts by weight of modified oyster shell powder in this embodiment, 9 parts by weight of modified steel fiber in this embodiment, and 2 parts by weight of composite admixture. Wherein: the composite cementitious material is composed of light-burned magnesium oxide powder, magnesium sulfate powder, and silicate cement (P·O42.5), with a mass ratio of light-burned magnesium oxide to magnesium sulfate of 1:2.2. The silicate cement is 4.5 times the total mass of light-burned magnesium oxide and magnesium sulfate. The composite admixture is composed of polycarboxylate superplasticizer and hydroxyethyl cellulose at a mass ratio of 0.75:1. The fine aggregate is composed of quartz sand with particle sizes distributed at 0.07~0.15mm, 0.15~0.3mm, and 0.3~1.18mm, graded at a mass ratio of 1:1:4.

[0041] (5) Add the above raw materials to the mixer and dry mix for 5 minutes. Then add 40 parts by weight of water and mix for 2 minutes to obtain 3D printed ecological concrete.

[0042] Performance Testing: 1. The 3D-printed eco-concrete prepared in this embodiment was printed using 3D printing equipment and then naturally cured for 28 days. The compressive strength and flexural strength of the specimens were then tested according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GBT 50081-2019). Figure 2 and Figure 3 (As shown). Wherein: the initial direction of the load applied during the flexural strength test is parallel to the interlayer plane of the specimen. The stronger the interlayer bonding ability of the specimen, the higher the flexural strength. 2. The 3D-printed ecological concrete prepared in this embodiment was printed using 3D printing equipment and then naturally cured for 7 days. The structural deformation rate was then calculated based on the average deformation of the obtained specimen in the X, Y, and Z directions, and the results are shown in the table below.

[0043]

[0044] Example 2

[0045] A method for preparing modified oyster shell and steel fiber-based 3D-printed eco-concrete includes the following steps:

[0046] (1) After crushing the oyster shells, heat them to 850°C at a rate of 15°C / min and keep them warm for 60 min. Then cool them to room temperature. Mix the calcined product with 35% polyacrylate emulsion at a ratio of 1 g: 40 ml. After ultrasonic treatment for 10 min, filter out the solid product. Place it in an oven and dry it at 80°C for 20 min. After grinding, pass it through a 500-mesh sieve to obtain modified oyster shell powder for later use.

[0047] (2) Mix 42g of phosphoric acid, 30g of zinc oxide, 24g of nitric acid, 3g of tartaric acid, 0.7g of ammonium molybdate and 0.85g of sodium m-nitrobenzenesulfonate, add water to 1 liter, and stir until all components are fully dissolved to obtain phosphating solution for later use.

[0048] (3) Copper-plated steel fibers (5 mm in length and 0.1 mm in diameter) were heated to 400 °C in air at a rate of 10 °C / min and held for 15 min. After cooling to room temperature, the obtained steel fibers were added to 0.25 mol / L acetic acid and stirred for 170 s. After completion, the steel fibers were filtered out and placed in the phosphating solution heated to 75 °C for 5 min. Then the steel fibers were filtered out and washed three times with clean water to obtain modified steel fibers for later use.

[0049] (4) Take the following raw materials in the following proportions: 100 parts by weight of composite cementitious material, 28 parts by weight of fine aggregate, 8 parts by weight of modified oyster shell powder in this embodiment, 10 parts by weight of modified steel fiber in this embodiment, and 3 parts by weight of composite admixture. Wherein: the composite cementitious material is composed of light-burned magnesium oxide powder, magnesium sulfate powder, and silicate cement (P·O42.5), and the mass ratio of light-burned magnesium oxide to magnesium sulfate is 1:2. The silicate cement is 5 times the total mass of light-burned magnesium oxide and magnesium sulfate. The composite admixture is composed of polycarboxylate superplasticizer and hydroxymethyl cellulose in a mass ratio of 1:1. The fine aggregate is composed of river sand with a particle size distribution of 0.07~0.15mm, 0.15~0.3mm, and 0.3~1.18mm in a mass ratio of 1:1:3.

[0050] (5) Add the above raw materials to the mixer and dry mix for 5 minutes. Then add 50 parts by weight of water and mix for 2 minutes to obtain 3D printed ecological concrete.

[0051] Performance testing: The structural deformation rate, compressive strength, and flexural strength of the 3D-printed eco-concrete prepared in this embodiment were tested using the same method as in Example 1 above. Figure 4 and Figure 5 (As shown in the figure), the results are shown in the table below.

[0052]

[0053] Example 3

[0054] A method for preparing modified oyster shell and steel fiber-based 3D-printed eco-concrete includes the following steps:

[0055] (1) After crushing the oyster shells, heat them to 950°C at a rate of 15°C / min and keep them warm for 40 min. Then cool them to room temperature. Mix the calcined product with 30% ethylene-vinyl acetate copolymer emulsion at a ratio of 1g:50ml. After ultrasonic treatment for 7 min, filter out the solid product. Place it in an oven and dry it at 60°C for 35 min. After grinding, pass it through a 300-mesh sieve to obtain modified oyster shell powder for later use.

[0056] (2) Mix 37g of phosphoric acid, 25g of zinc oxide, 20g of nitric acid, 1g of tartaric acid, 0.4g of ammonium molybdate and 0.5g of sodium m-nitrobenzenesulfonate, add water to 1 liter, and stir until all components are fully dissolved to obtain phosphating solution for later use.

[0057] (3) Copper-plated steel fibers (10 mm in length and 0.15 mm in diameter) were heated to 500 °C in air at a rate of 10 °C / min and held for 8 min. After cooling to room temperature, the obtained steel fibers were added to 0.6 mol / L acetic acid and stirred for 130 s. After completion, the steel fibers were filtered out and placed in the phosphating solution heated to 70 °C for 10 min. Then the steel fibers were filtered out and washed three times with clean water to obtain modified steel fibers for later use.

[0058] (4) The following proportions of raw materials are used: 60 parts by weight of composite cementitious material, 20 parts by weight of fine aggregate, 3 parts by weight of modified oyster shell powder in this embodiment, 7 parts by weight of modified steel fiber in this embodiment, and 1 part by weight of composite admixture. Wherein: the composite cementitious material is composed of light-burned magnesium oxide powder, magnesium sulfate powder, and silicate cement (P·O42.5), and the mass ratio of light-burned magnesium oxide to magnesium sulfate is 1:2.3. The silicate cement is 4 times the total mass of light-burned magnesium oxide and magnesium sulfate. The composite admixture is composed of aminosulfonate water-reducing agent and hydroxypropyl starch in a mass ratio of 0.5:1. The fine aggregate is composed of quartz sand with a particle size distribution of 0.07~0.15mm, 0.15~0.3mm, and 0.3~1.18mm in a mass ratio of 1:1:5.

[0059] (5) Add the above raw materials to the mixer and dry mix for 5 minutes. Then add 30 parts by weight of water and mix for 2 minutes to obtain 3D printed ecological concrete.

[0060] Performance testing: The structural deformation rate, compressive strength, and flexural strength of the 3D-printed eco-concrete prepared in this embodiment were tested using the same method as in Example 1 above. Figure 6 and Figure 7 (As shown in the figure), the results are shown in the table below.

[0061]

[0062] Example 4

[0063] A method for preparing modified oyster shell and steel fiber-based 3D-printed eco-concrete includes the following steps:

[0064] (1) Grind the oyster shells and pass them through a 400-mesh sieve to obtain oyster shell powder, which can be used for later use.

[0065] (2) The following proportions of raw materials are used: 85 parts by weight of composite cementitious material, 24 parts by weight of fine aggregate, 5 parts by weight of oyster shell powder in this embodiment, 9 parts by weight of modified steel fiber prepared in Example 1 above, and 2 parts by weight of composite admixture. Wherein: the composite cementitious material is composed of lightly calcined magnesium oxide powder, magnesium sulfate powder, and silicate cement (P·O42.5), with a mass ratio of lightly calcined magnesium oxide to magnesium sulfate of 1:2.2. The silicate cement is 4.5 times the total mass of lightly calcined magnesium oxide and magnesium sulfate. The composite admixture is composed of polycarboxylate superplasticizer and hydroxyethyl cellulose at a mass ratio of 0.75:1. The fine aggregate is composed of quartz sand with particle sizes distributed at 0.07~0.15mm, 0.15~0.3mm, and 0.3~1.18mm, graded at a mass ratio of 1:1:4.

[0066] (3) Add the above raw materials to the mixer and dry mix for 5 minutes. Then add 40 parts by weight of water and mix for 2 minutes to obtain 3D printed ecological concrete.

[0067] Performance testing: The structural deformation rate, compressive strength, and flexural strength of the 3D printed ecological concrete prepared in this embodiment were tested using the same method as in Example 1 above. The results are shown in the table below.

[0068]

[0069] Example 5

[0070] A method for preparing modified oyster shell and steel fiber-based 3D-printed eco-concrete includes the following steps:

[0071] (1) The following proportions of raw materials are used: 100 parts by weight of composite cementitious material, 28 parts by weight of fine aggregate, 8 parts by weight of modified oyster shell powder prepared in Example 2 above, 10 parts by weight of copper-plated steel fiber (5 mm in length and 0.1 mm in diameter), and 3 parts by weight of composite admixture. Wherein: the composite cementitious material is composed of light-burned magnesium oxide powder, magnesium sulfate powder, and silicate cement (P·O42.5), and the mass ratio of light-burned magnesium oxide to magnesium sulfate is 1:2. The silicate cement is 5 times the total mass of light-burned magnesium oxide and magnesium sulfate. The composite admixture is composed of polycarboxylate superplasticizer and hydroxymethyl cellulose in a mass ratio of 1:1. The fine aggregate is composed of river sand with a particle size distribution of 0.07~0.15 mm, 0.15~0.3 mm, and 0.3~1.18 mm in a mass ratio of 1:1:3.

[0072] (5) Add the above raw materials to the mixer and dry mix for 5 minutes. Then add 50 parts by weight of water and mix for 2 minutes to obtain 3D printed ecological concrete.

[0073] Performance testing: The structural deformation rate, compressive strength, and flexural strength of the 3D printed ecological concrete prepared in this embodiment were tested using the same method as in Example 1 above. The results are shown in the table below.

[0074]

[0075] Example 6

[0076] A method for preparing modified oyster shell and steel fiber-based 3D-printed eco-concrete includes the following steps:

[0077] (1) Copper-plated steel fibers (8 mm in length and 0.1 mm in diameter) were heated to 420 °C in air at a rate of 10 °C / min and held for 10 min. After cooling to room temperature, the obtained steel fibers were added to 0.3 mol / L citric acid and stirred for 150 s. After completion, the steel fibers were filtered out and washed three times with water to obtain modified steel fibers for later use.

[0078] (2) The following proportions of raw materials were used: 85 parts by weight of composite cementitious material, 24 parts by weight of fine aggregate, 5 parts by weight of modified oyster shell powder prepared in Example 1 above, 9 parts by weight of modified steel fiber in this example, and 2 parts by weight of composite admixture. Wherein: the composite cementitious material is composed of lightly calcined magnesium oxide powder, magnesium sulfate powder, and silicate cement (P·O42.5), with a mass ratio of lightly calcined magnesium oxide to magnesium sulfate of 1:2.2. The silicate cement is 4.5 times the total mass of lightly calcined magnesium oxide and magnesium sulfate. The composite admixture is composed of polycarboxylate superplasticizer and hydroxyethyl cellulose at a mass ratio of 0.75:1. The fine aggregate is composed of quartz sand with particle sizes distributed at 0.07~0.15mm, 0.15~0.3mm, and 0.3~1.18mm, graded at a mass ratio of 1:1:4.

[0079] (4) Add the above raw materials to the mixer and dry mix for 5 minutes. Then add 40 parts by weight of water and mix for 2 minutes to obtain 3D printed ecological concrete.

[0080] Performance testing: The structural deformation rate, compressive strength, and flexural strength of the 3D printed ecological concrete prepared in this embodiment were tested using the same method as in Example 1 above. The results are shown in the table below.

[0081]

[0082] Example 7

[0083] A method for preparing modified oyster shell and steel fiber-based 3D-printed eco-concrete includes the following steps:

[0084] (1) Mix 37g of phosphoric acid, 25g of zinc oxide, 20g of nitric acid, 1g of tartaric acid, 0.4g of ammonium molybdate and 0.5g of sodium m-nitrobenzenesulfonate, add water to 1 liter, stir until all components are fully dissolved, and the phosphating solution is obtained for later use.

[0085] (2) Add copper-plated steel fibers (10 mm in length and 0.15 mm in diameter) to acetic acid with a concentration of 0.6 mol / L and stir for 130 s. After completion, filter out the steel fibers, place them in the phosphating solution heated to 70°C and let them stand for 10 min, then filter out the steel fibers and wash them three times with clean water to obtain modified steel fibers for later use.

[0086] (3) The following proportions of raw materials are used: 60 parts by weight of composite cementitious material, 20 parts by weight of fine aggregate, 3 parts by weight of modified oyster shell powder prepared in Example 3 above, 7 parts by weight of modified steel fiber in this example, and 1 part by weight of composite admixture. Wherein: the composite cementitious material is composed of light-burned magnesium oxide powder, magnesium sulfate powder, and silicate cement (P·O42.5), with a mass ratio of light-burned magnesium oxide to magnesium sulfate of 1:2.3. The silicate cement is 4 times the total mass of light-burned magnesium oxide and magnesium sulfate. The composite admixture is composed of aminosulfonate water-reducing agent and hydroxypropyl starch in a mass ratio of 0.5:1. The fine aggregate is composed of quartz sand with particle sizes distributed at 0.07~0.15mm, 0.15~0.3mm, and 0.3~1.18mm, graded in a mass ratio of 1:1:5.

[0087] (4) Add the above raw materials to the mixer and dry mix for 5 minutes. Then add 30 parts by weight of water and mix for 2 minutes to obtain 3D printed ecological concrete.

[0088] Performance testing: The structural deformation rate, compressive strength, and flexural strength of the 3D printed ecological concrete prepared in this embodiment were tested using the same method as in Example 1 above. The results are shown in the table below.

[0089]

[0090] Example 8

[0091] A method for preparing modified oyster shell and steel fiber-based 3D-printed eco-concrete includes the following steps:

[0092] (1) Mix 42g of phosphoric acid, 30g of zinc oxide, 24g of nitric acid, 3g of tartaric acid, 0.7g of ammonium molybdate and 0.85g of sodium m-nitrobenzenesulfonate, add water to 1 liter, and stir until all components are fully dissolved to obtain phosphating solution for later use.

[0093] (2) The copper-plated steel fiber (5 mm in length and 0.1 mm in diameter) is heated to 400°C in air at a rate of 10°C / min and held for 15 min. After cooling to room temperature, the obtained steel fiber is placed in the phosphating solution heated to 75°C and left to stand for 5 min. Then the steel fiber is filtered out and washed three times with clean water to obtain the modified steel fiber for later use.

[0094] (3) The following proportions of raw materials are used: 100 parts by weight of composite cementitious material, 28 parts by weight of fine aggregate, 8 parts by weight of modified oyster shell powder prepared in Example 2 above, 10 parts by weight of modified steel fiber in this example, and 3 parts by weight of composite admixture. Wherein: the composite cementitious material is composed of lightly calcined magnesium oxide powder, magnesium sulfate powder, and silicate cement (P·O42.5), with a mass ratio of lightly calcined magnesium oxide to magnesium sulfate of 1:2. The silicate cement is 5 times the total mass of lightly calcined magnesium oxide and magnesium sulfate. The composite admixture is composed of polycarboxylate superplasticizer and hydroxymethyl cellulose in a mass ratio of 1:1. The fine aggregate is composed of river sand with particle sizes distributed at 0.07~0.15mm, 0.15~0.3mm, and 0.3~1.18mm, graded in a mass ratio of 1:1:3.

[0095] (4) Add the above raw materials to the mixer and dry mix for 5 minutes. Then add 50 parts by weight of water and mix for 2 minutes to obtain 3D printed ecological concrete.

[0096] Performance testing: The structural deformation rate, compressive strength, and flexural strength of the 3D printed ecological concrete prepared in this embodiment were tested using the same method as in Example 1 above. The results are shown in the table below.

[0097]

[0098] Example 9

[0099] A method for preparing modified oyster shell and steel fiber-based 3D-printed eco-concrete includes the following steps:

[0100] (1) The following raw materials were prepared in the following proportions: 60 parts by weight of silicate cement (P·O42.5), 20 parts by weight of fine aggregate, 3 parts by weight of modified oyster shell powder prepared in Example 3 above, 7 parts by weight of modified steel fiber prepared in Example 3 above, and 1 part by weight of composite admixture. The composite admixture was composed of aminosulfonate water-reducing agent and hydroxypropyl starch in a mass ratio of 0.5:1. The fine aggregate was composed of quartz sand with particle sizes of 0.07~0.15mm, 0.15~0.3mm, and 0.3~1.18mm graded in a mass ratio of 1:1:5.

[0101] (2) Add the above raw materials to the mixer and dry mix for 5 minutes. Then add 30 parts by weight of water and mix for 2 minutes to obtain 3D printed ecological concrete.

[0102] Performance testing: The 28-day compressive strength of the 3D printed ecological concrete prepared in this embodiment was tested using the same method as in Example 1 above, and the result was 53.16 MPa.

[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing modified oyster shell and steel fiber-based 3D-printed eco-concrete, characterized in that, Includes the following steps: (1) The oyster shell powder is calcined, and then the calcined product is mixed with polymer emulsion and ultrasonically treated. The solid product is separated, dried and ground to obtain modified oyster shell powder for later use. (2) The copper-plated steel fiber is heated in air, cooled and then placed in a weak acid for surface treatment; after completion, the obtained fiber is placed in a phosphating solution for phosphating treatment, and then the obtained fiber is cleaned to obtain modified steel fiber for later use. (3) Take the following proportions of raw materials: 60-100 parts by weight of composite cementitious material, 20-28 parts by weight of fine aggregate, 3-8 parts by weight of modified oyster shell powder, 7-10 parts by weight of modified steel fiber, and 1-3 parts by weight of composite admixture; mix the above raw materials evenly and add 30-50 parts by weight of water and stir evenly to obtain 3D printed ecological concrete. In step (3), the composite cementitious material is composed of light-burned magnesium oxide, magnesium sulfate, and silicate cement; wherein: the mass ratio of light-burned magnesium oxide to magnesium sulfate is 1:2~2.3; and the silicate cement is 4~5 times the total mass of light-burned magnesium oxide and magnesium sulfate; In step (3), the composite additive includes a water-reducing agent and a thickener, with a mass ratio of 0.5 to 1:1; In step (3), the fine aggregate is composed of particles with particle sizes of 0.07~0.15mm, 0.15~0.3mm, and 0.3~1.18mm graded in a mass ratio of 1:1:3~5; In step (3), the fine aggregate includes at least one of river sand, quartz sand, and manufactured sand.

2. The method for preparing modified oyster shell and steel fiber-based 3D printed eco-concrete according to claim 1, characterized in that, In step (1), the calcination temperature is 850~950℃ and the time is 40~60min.

3. The method for preparing modified oyster shell and steel fiber-based 3D printed eco-concrete according to claim 1, characterized in that, In step (1), the ratio of the calcined product to the polymer emulsion is 1g: 20~50ml; In step (1), the polymer emulsion includes any one of ethylene-vinyl acetate copolymer emulsion, polyacrylate emulsion, and polyvinyl alcohol emulsion; In step (1), the polymer emulsion has a mass fraction of 30-35%; In step (1), the drying temperature is 60~80℃ and the time is 20~35min; In step (1), the modified oyster shell powder has a fineness of 300-500 mesh.

4. The method for preparing modified oyster shell and steel fiber-based 3D printed eco-concrete according to claim 1, characterized in that, In step (2), the heating temperature is 400~500℃ and the time is 8~15min; in step (2), the length of the copper-plated steel fiber is 5~10mm and the diameter is 0.1~0.15mm.

5. The method for preparing modified oyster shell and steel fiber-based 3D printed eco-concrete according to claim 1, characterized in that, In step (2), the weak acid includes at least one of formic acid, acetic acid, and citric acid; In step (2), the concentration of the weak acid is 0.25~0.6 mol / L; In step (2), the surface treatment time is 130~170s.

6. The method for preparing modified oyster shell and steel fiber-based 3D printed eco-concrete according to claim 1, characterized in that, In step (2), the phosphating solution is prepared using the following components: 37-42g of phosphoric acid, 25-30g of zinc oxide, 20-24g of nitric acid, 1-3g of tartaric acid, 0.4-0.7g of ammonium molybdate, and 0.5-0.85g of sodium m-nitrobenzenesulfonate are mixed and then water is added to 1 liter. The mixture is stirred until all components are fully dissolved. In step (2), the phosphating treatment temperature is 70-80℃ and the time is 5-10min.

7. The method for preparing modified oyster shell and steel fiber-based 3D printed eco-concrete according to claim 1, characterized in that, The water-reducing agent includes at least one of polycarboxylate water-reducing agent, naphthalene-based water-reducing agent, and aminosulfonate water-reducing agent; the thickener includes at least one of hydroxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl starch.

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