A 3D printing concrete material with gold tailings sand as full aggregate and hybrid fiber reinforced and a preparation method thereof

Abstract

This invention relates to the field of building materials, and more particularly to a 3D-printed concrete material reinforced with hybrid fibers using gold tailings sand as the sole aggregate, and its preparation method. The 3D-printed concrete material comprises: cement, gold tailings sand, mineral admixtures, water-reducing agent, hybrid fibers, a 3D-printed concrete composite emulsifier, and water; wherein the hybrid fibers include silane coupling agent modified carbon fibers, silane coupling agent modified basalt fibers, and calcium carbonate whiskers. This invention not only enables the large-scale utilization of gold tailings sand, reducing the cost of 3D-printed concrete and improving printing accuracy, but also enhances the performance of concrete through multi-scale hybridization of carbon fibers, basalt fibers, and calcium carbonate whiskers, and utilizes a 3D-printed concrete composite emulsifier to emulsify and increase the wet bulk density of the concrete, thereby enhancing its plasticity and obtaining a 3D-printed concrete material and its preparation method with excellent printability, high mechanical strength, and superior crack resistance.

Description

Technical Field

[0001] This invention relates to the field of building materials, and in particular to a 3D printed concrete material made of gold tailings sand as the whole aggregate and reinforced with fiber, and its preparation method. Background Technology

[0002] 3D printing technology, as an emerging digital construction method, is driving the construction industry towards intelligence, greening, and efficiency. This technology places extremely stringent requirements on the extrudability, cohesiveness, and early strength of materials: the material must be continuously and uniformly extruded during the printing process without clogging the nozzle; it must maintain its shape well after extrusion to prevent collapse or deformation during layer stacking; and it must possess sufficient early strength to support the weight of subsequent printed layers, ensuring structural stability. Traditional 3D printed concrete materials largely rely on natural river sand as fine aggregate. With the rapid development of the construction industry, natural sand and gravel resources are becoming increasingly depleted, and over-exploitation has caused serious damage to the ecological environment. Meanwhile, the large quantities of gold tailings generated during gold mining in my country have been stockpiled for a long time, not only occupying valuable land resources but also posing potential pollution risks to the surrounding soil, water sources, and atmospheric environment, and even posing safety hazards such as tailings dam failures. How to achieve large-scale, high-value utilization of gold tailings has become a major problem that urgently needs to be solved.

[0003] While there are reports of using fiber-reinforced 3D printed concrete in existing technologies, most employ single fibers or traditional fibers (such as polypropylene fibers and steel fibers), which have limitations in multi-scale crack suppression and interface strengthening. For example, macroscopic fibers have poor microcrack suppression effects, while micron-sized fibers, although capable of suppressing microcracks, offer limited improvement in macroscopic mechanical properties. Carbon fiber possesses extremely high strength and modulus, but is expensive and brittle; basalt fibers offer strong alkali resistance and high cost-effectiveness; calcium carbonate whiskers, as a micro-reinforcing material, can effectively improve the density of the cement matrix and early microcrack resistance, and as a nanomaterial, can effectively promote cement hydration and enhance early strength. Organically combining carbon fiber, basalt fiber, and calcium carbonate whiskers can strengthen concrete at multiple scales.

[0004] In addition, due to its high density, concrete has significant limitations on the size of specimens during 3D printing. Larger specimens can only be produced through segmented printing, which greatly restricts the application of concrete in 3D printing. Summary of the Invention

[0005] This invention provides a 3D printed concrete material reinforced with hybrid fibers using gold tailings sand as the entire aggregate and its preparation method. This not only enables the large-scale utilization of gold tailings sand, reducing the cost of 3D printed concrete and improving printing accuracy, but also enhances the performance of concrete through multi-scale hybridization of carbon fiber, basalt fiber and calcium carbonate whiskers. Furthermore, it utilizes a 3D printed concrete composite emulsifier to emulsify and improve the wet bulk density of the concrete, thereby enhancing its plasticity and obtaining a 3D printed concrete material with excellent printability, high mechanical strength and excellent crack resistance, as well as its preparation method.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a 3D-printed concrete material using gold tailings sand as the entire aggregate and hybrid fiber reinforcement, comprising the following raw materials in parts by weight: 300-450 parts cement; Gold tailings sand, 800-1100 parts; 50-150 parts of mineral admixtures; 3-10 parts of water-reducing agent; 5-25 parts of mixed fibers; 12-22 parts of 3D printing concrete composite emulsion; 200-250 parts water; The hybrid fibers include silane coupling agent modified carbon fiber, silane coupling agent modified basalt fiber, and calcium carbonate whiskers.

[0007] This invention innovatively replaces natural sand with gold tailings sand, which has extremely fine particle size and multi-faceted shape and is currently unsuitable as fine aggregate for building materials. This allows the concrete slurry to be extruded from smaller nozzles, thereby giving 3D printed concrete higher printing precision and better slurry cohesion. On this basis, a novel fiber dispersion modification method is used to solve the fiber agglomeration problem, and a multi-scale (macro, meso, and micro) hybrid fiber reinforcement technology is adopted. That is, carbon fiber and basalt fiber provide macroscopic and mesoscopic tensile toughness and impact resistance, while calcium carbonate whiskers effectively inhibit the generation and development of microcracks at the microscale. The three work synergistically to significantly improve the mechanical properties, crack resistance, and shape stability of the material. In addition, by introducing a 3D printed concrete composite emulsifier, the concrete slurry is emulsified, reducing its wet density to about 60% of the original concrete and significantly enhancing its plasticity and cohesion, thus adapting to the continuous printing of larger-sized structures. The starting point of this invention is to organically combine gold tailings sand with three fibers of different scales to exert a multi-scale synergistic enhancement effect, and to achieve synergistic optimization of lightweighting and printing performance by using a composite emulsifier. By emulsifying the concrete slurry with a 3D printing concrete composite emulsifier, the wet density of the concrete can be reduced to about 60% of the original concrete, and the plasticity of the concrete can be enhanced. This allows 3D printed concrete to develop towards larger-scale structures, promoting its application. Ultimately, a gold tailings sand-based 3D printed concrete material with excellent printing performance, mechanical properties and lightweight characteristics is prepared, providing a new path for the high-value utilization of industrial solid waste and the development of green and low-carbon building materials.

[0008] As an example, the mass fraction of cement can be 300, 320, 350, 380, 400, 420, and 450 parts, etc.

[0009] As an example, the mass fractions of gold tailings can be 800, 850, 900, 950, 1000, 1050, and 1100 parts, etc.

[0010] As an example, the mass fractions of the mineral admixture can be 50, 80, 100, 120, 130, and 150 parts, etc.

[0011] As an example, the mass fraction of the water-reducing agent can be 3, 4, 5, 6, 8, and 10 parts, etc.

[0012] As an example, the mass fractions of the blended fibers can be 5, 10, 15, 20, and 25 parts, etc.

[0013] As an example, the mass fraction of 3D printed concrete composite emulsifier can be 12, 15, 18, 20, and 22 parts, etc.

[0014] As an example, the mass fractions of water can be 200, 210, 220, 230, 240, and 250 parts, etc.

[0015] In some specific implementations, the cement includes PO 42.5 R cement.

[0016] In some specific embodiments, the mass ratio of the silane coupling agent modified carbon fiber, the silane coupling agent modified basalt fiber, and the calcium carbonate whiskers in the hybrid fiber is (0.5~1):(1~2):(0.2~0.5). As an example, the mass ratio of the silane coupling agent modified carbon fiber, the silane coupling agent modified basalt fiber, and the calcium carbonate whiskers can be 0.5:1:0.2, 0.8:1:0.2, 0.8:2:0.5, and 1:2:0.5, etc.

[0017] In some specific embodiments, the length of the silane coupling agent modified carbon fiber is 8-15 mm, and the diameter of the silane coupling agent modified carbon fiber is 5-10 μm. As an example, the length of the silane coupling agent modified carbon fiber can be 8, 9, 10, 12, and 15 mm, and the diameter can be 5, 6, 7, 8, 9, and 10 μm, etc.

[0018] In some specific embodiments, the length of the silane coupling agent modified basalt fiber is 5-10 mm, and the diameter of the silane coupling agent modified basalt fiber is 10-20 μm. As an example, the length of the silane coupling agent modified basalt fiber can be 5, 6, 7, 8, 9, and 10 mm, and the diameter can be 10, 12, 15, 18, and 20 μm, etc.

[0019] In some specific embodiments, the radial dimension of the calcium carbonate whisker is 0.1~1.2 μm, the length of the calcium carbonate whisker is 20~30 μm, and the aspect ratio of the calcium carbonate whisker is 20~30. As an example, the radial dimension of the calcium carbonate whisker can be 0.1, 0.5, 1, and 1.2 μm, the length can be 20, 22, 25, 28, and 30 μm, and the aspect ratio can be 20, 22, 25, 28, and 30, etc.

[0020] In some specific embodiments, the preparation of the silane coupling agent modified carbon fiber includes: After physical dispersion, the carbon fibers were soaked and dispersed in acetone, and then soaked and modified in an ethanol solution of silane coupling agent.

[0021] In some specific embodiments, the preparation of the silane coupling agent modified basalt fiber includes: After physical dispersion, basalt fibers were soaked and dispersed in acetone, and then soaked and modified in an ethanol solution of silane coupling agent.

[0022] In this invention, carbon fiber and basalt fiber are dispersed into monofilaments by physical dispersion method, and further dispersed by acetone soaking and modified by silane coupling agent soaking.

[0023] In some specific embodiments, the mud content of the gold tailings is <3%; In some specific embodiments, the gold tailings sand forms a deposited structure with a porosity of 40% to 50%.

[0024] In some specific embodiments, the particle size distribution of the gold tailings sand satisfies the following mass ratio: <0.075mm, 0.075~0.15mm and not equal to 0.15mm, 0.15~0.3mm and not equal to 0.3mm, and 0.3~0.6mm and not equal to 0.6mm (25~35): (15~25): (20~30): (20~35).

[0025] In this invention, after the particle size distribution of the gold tailings meets the above conditions, a close packing fitting is performed to achieve close packing of micro-aggregates, reducing the porosity to 40%~50%. When the mass ratio of the gold tailings particle size distribution satisfies the following conditions: <0.075mm, 0.075~0.15mm and not equal to 0.15mm, 0.15~0.3mm and not equal to 0.3mm, and 0.3~0.6mm and not equal to 0.6mm is 29.9:19.9:23.1:27.1, the porosity is reduced to 46.8%.

[0026] In some specific embodiments, the mineral admixture includes fly ash and silica fume; In some specific embodiments, the mass ratio of fly ash to silica fume is (2~3):1. As examples, the mass ratio of fly ash to silica fume can be 2:1, 2.5:1, and 3:1, etc.

[0027] In some specific embodiments, the 3D printed concrete composite emulsifier includes hydroxypropyl methylcellulose ether, polyalkylbenzene sulfonate, redispersible latex powder, calcium nitrate, and triisopropanolamine; In some specific embodiments, the mass ratio of hydroxypropyl methylcellulose ether, polyalkylbenzene sulfonate, redispersible latex powder, calcium nitrate, and triisopropanolamine is (8~12):(12~18):(3~7):(4~8):(1~5). As an example, the mass ratio of hydroxypropyl methylcellulose ether, polyalkylbenzene sulfonate, redispersible latex powder, calcium nitrate, and triisopropanolamine can be 8:12:3:4:1, 10:15:5:6:3, and 12:18:7:8:5, etc.

[0028] In some specific embodiments, the water-reducing agent includes a polycarboxylate water-reducing agent.

[0029] A second aspect of the present invention also provides a method for preparing the above-mentioned 3D printed concrete material with gold tailings sand as the whole aggregate and mixed fiber reinforcement, comprising the following steps: Cement, gold tailings sand, mineral admixtures, and water-reducing agent are mixed and then stirred for the first time to obtain a dry mixture; Calcium carbonate whiskers are premixed with some water to obtain a suspension; Mix the remaining water and 3D printed concrete composite emulsifier, then add the dry mix, disperse it, and then add the suspension. Stir a second time to obtain a slurry. After mixing silane coupling agent modified carbon fiber and silane coupling agent modified basalt fiber, they are sprinkled into the slurry and stirred a third time to obtain concrete material. The concrete material is left to stand, and then 3D printed concrete material is obtained.

[0030] In some specific embodiments, the first stirring speed is 62 rpm, and the first stirring time is 2 to 5 minutes.

[0031] In some specific embodiments, the second stirring speed is 125 rpm, and the second stirring time is 3 to 6 minutes.

[0032] In some specific embodiments, the third stirring speed is 125 rpm, and the third stirring time is 3 to 5 minutes.

[0033] In some specific embodiments, the settling time is 5 to 15 minutes.

[0034] Compared with the prior art, the present invention has the following beneficial effects: 1. Solid waste utilization and cost control: Gold tailings sand completely replaces natural sand, realizing the high-value utilization of bulk industrial solid waste, reducing material costs and environmental impact.

[0035] 2. Performance Improvement: Gold tailings sand has multi-faceted characteristics. When used as aggregate, the gold tailings sand particles have an interlocking effect, which improves the strength of concrete, especially in terms of flexural strength, and optimizes the problem of concrete brittleness.

[0036] 3. Multi-scale collaborative enhancement mechanism: Microscale (calcium carbonate whiskers): The whiskers are tiny in size and can be uniformly dispersed in cement paste, filling micropores to promote cement hydration, forming a micro-skeleton structure, effectively preventing the initiation and propagation of microcracks, and significantly improving the initial elastic modulus and early crack resistance of the matrix.

[0037] Micro / Macro Scale (Carbon Fiber and Basalt Fiber): Carbon fiber's high modulus provides excellent toughening and tensile strength; basalt fiber exhibits good adhesion to the cement matrix, strong alkali resistance, and provides reliable ductility and impact resistance. Together, they form a main reinforcement network that bears interlayer tensile stress and external loads, preventing macroscopic cracking.

[0038] Synergistic effect: When microcracks bridged by calcium carbonate whiskers develop into macrocracks, they are effectively "captured" and suppressed by carbon fiber and basalt fiber, forming a continuous, multi-level crack-resistant system from micro to macro, which greatly improves the toughness and durability of the material.

[0039] 4. Optimized printing performance: Through precise balance of water-reducing agent and 3D printing concrete composite emulsifier, as well as reasonable fiber content, the material is ensured to have the characteristics of low yield stress (easy to pump and extrude), high viscosity (no deformation after extrusion, can stand upright and not collapse), and low density (larger printing scale), meeting the requirements of 3D printing process.

[0040] 5. Advantages of the preparation method: The "calcium carbonate whisker premix solution" method solves the problems of whiskers being prone to dust generation in dry mixing and agglomeration in wet mixing, ensuring their uniform distribution in the matrix. The stepwise fiber addition process ensures the full dispersion of carbon fiber and basalt fiber, avoiding the formation of fiber balls. Attached Figure Description

[0041] The above and other objects, features, and advantages of the invention will be apparent from the following description of preferred embodiments illustrating the gist of the invention and its use, and the accompanying drawings, in which: Figure 1 This is a test diagram of the extrusion smoothness of the 3D printed concrete material in Example 1.

[0042] Figure 2 This is a comparison of the 3D printing process of concrete material in Example 1. Detailed Implementation

[0043] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. The embodiments of this application are only examples, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] Example 1 A 3D-printed concrete material using gold tailings sand as the sole aggregate and fiber reinforcement is prepared from the following raw materials in parts by weight (kg / m³). 3 ): 400kg of PO 42.5 R cement, 950kg of gold tailings sand, 100kg of mineral admixtures, 8kg of polycarboxylate superplasticizer, 15kg of mixed fibers, 18kg of 3D printing concrete composite emulsifier, and 210kg of water. The particle size distribution of the gold tailings sand meets the following conditions: the mass ratio of <0.075mm, 0.075~0.15mm and not equal to 0.15mm, 0.15~0.3mm and not equal to 0.3mm, and 0.3~0.6mm and not equal to 0.6mm is 29.9:19.9:23.1:27.1. In the mineral admixture, the mass ratio of fly ash to silica fume is 2:1; In the hybrid fibers, the mass ratio of silane coupling agent modified carbon fiber, silane coupling agent modified basalt fiber, and calcium carbonate whiskers is 1:1.6:0.4; the length of the silane coupling agent modified carbon fiber is 10 mm and the diameter is 7 μm; the length of the silane coupling agent modified basalt fiber is 6 mm and the diameter is 15 μm; the radial dimension of the calcium carbonate whiskers is 0.1-1.2 μm, the length is 20-30 μm, and the aspect ratio is 20-30. In the 3D printing concrete composite emulsifier, the mass ratio of hydroxypropyl methylcellulose ether, polyalkylbenzene sulfonate, redispersible latex powder, calcium nitrate, and triisopropanolamine is 10:15:5:6:3. The preparation of silane coupling agent modified carbon fibers includes: Carbon fibers were dispersed into monofilaments by physical dispersion. Then, they were further dispersed by soaking in acetone (the ratio of carbon fiber to acetone was 87.5 g: 100 mL). After that, they were modified by soaking in a mixed solution of silane coupling agent KH550 and ethanol (the ratio of silane coupling agent to ethanol was 6 g: 94 g, and the ratio of carbon fiber to the mixed solution was 87.5: 100 mL). The preparation of silane coupling agent modified basalt fibers includes: Basalt fibers were dispersed into monofilaments by physical dispersion. The monofilaments were then further dispersed by soaking in acetone (basalt fiber to acetone ratio of 132.5g:100mL). The monofilaments were then modified by soaking in a mixed solution of silane coupling agent and ethanol (silane coupling agent to ethanol ratio of 6g:94g, basalt fiber to silane coupling agent ratio of 132.5g:100mL). The preparation of the above-mentioned 3D printed concrete material includes the following steps: (1) Put cement, gold tailings sand, mineral admixtures and water-reducing agent into a planetary mixer and dry mix at 62 rpm for 3 minutes.

[0045] (2) Mix calcium carbonate whiskers with 70kg of water and shear them with a high-speed emulsifier to form a uniform suspension; mix the remaining 140kg of water and 3D printing concrete composite emulsifier and add them to the dry mix. Pour the whisker suspension into the mixture while stirring at 62rpm, and then stir at 125rpm for 4 minutes.

[0046] (3) After mixing the silane coupling agent modified carbon fiber and the silane coupling agent modified basalt fiber, slowly and evenly add them, and continue stirring at 125 rpm for 4 minutes.

[0047] (4) Let it stand for 10 minutes, and the material can be used for 3D printing.

[0048] Performance testing: This material was extruded using nozzles with inner diameters of 5mm and 1.5mm. The 5mm nozzle produced smooth extrusion without any breaks, while the 1.5mm nozzle resulted in slightly reduced extrusion smoothness (e.g., ...). Figure 1 As shown in the figure, the interlayer bonding is good, and the wet bulk density is 0.9. The compressive strength reaches 54.5 MPa after 28 days, the flexural strength reaches 8.5 MPa, and the shape retention rate during the initial setting time is greater than 99%.

[0049] Example 2 A 3D-printed concrete material using gold tailings sand as the sole aggregate and fiber reinforcement is prepared from the following raw materials in parts by weight (kg / m³). 3 ): 450kg of PO 42.5 R cement, 900kg of gold tailings sand, 115kg of mineral admixtures, 9kg of polycarboxylate superplasticizer, 25kg of mixed fibers, 19kg of 3D printing concrete composite emulsifier, and 200kg of water. The particle size distribution of the gold tailings sand meets the following conditions: the mass ratio of <0.075mm, 0.075~0.15mm and not equal to 0.15mm, 0.15~0.3mm and not equal to 0.3mm, and 0.3~0.6mm and not equal to 0.6mm is 29.9:19.9:23.1:27.1. In the mineral admixture, the mass ratio of fly ash to silica fume is 2:1; In the hybrid fibers, the mass ratio of silane coupling agent modified carbon fiber, silane coupling agent modified basalt fiber, and calcium carbonate whiskers is 0.5:1.5:0.5; the length of the silane coupling agent modified carbon fiber is 10 mm and the diameter is 7 μm; the length of the silane coupling agent modified basalt fiber is 6 mm and the diameter is 15 μm; the radial dimension of the calcium carbonate whiskers is 0.1-1.2 μm, the length is 20-30 μm, and the aspect ratio is 20-30. In the 3D printing concrete composite emulsifier, the mass ratio of hydroxypropyl methylcellulose ether, polyalkylbenzene sulfonate, redispersible latex powder, calcium nitrate, and triisopropanolamine is 10:15:5:6:3. The preparation of silane coupling agent modified carbon fiber and silane coupling agent modified basalt fiber are the same as in Example 1.

[0050] The preparation of the above-mentioned 3D printed concrete material includes the following steps: (1) Put cement, gold tailings sand, mineral admixtures and water-reducing agent into a planetary mixer and dry mix at 62 rpm for 3 minutes.

[0051] (2) Mix calcium carbonate whiskers with 66 kg of water and shear them with a high-speed emulsifier to form a uniform suspension. Mix the remaining 134 kg of water and 3D printing concrete composite emulsifier and add them to the dry mix. Pour the whisker suspension into the mixture while stirring at 62 rpm, and then stir at 125 rpm for 4 minutes.

[0052] (3) After mixing the silane coupling agent modified carbon fiber and the silane coupling agent modified basalt fiber, slowly and evenly add them, and continue stirring at 125 rpm for 4 minutes.

[0053] (4) After standing for 10 minutes, the material can be used for 3D printing.

[0054] Performance testing: The material extrudes smoothly without any breaks, exhibits good interlayer adhesion, and has a wet bulk density of 0.92. Its 28-day compressive strength reaches 64 MPa, its flexural strength reaches 9.2 MPa, and its shape retention during initial setting time is greater than 99%.

[0055] Comparative Example 1 3D printed concrete material is made from the following parts by weight of raw materials (kg / m³). 3 ): 450 kg of PO 42.5 R cement, 900 kg of gold tailings sand, 115 kg of mineral admixtures, 9 kg of polycarboxylate superplasticizer, and 200 kg of water. The particle size distribution of the gold tailings sand meets the following conditions: the mass ratio of <0.075mm, 0.075~0.15mm and not equal to 0.15mm, 0.15~0.3mm and not equal to 0.3mm, and 0.3~0.6mm and not equal to 0.6mm is 29.9:19.9:23.1:27.1. In the mineral admixture, the mass ratio of fly ash to silica fume is 2:1.

[0056] The above-mentioned method for preparing 3D printed concrete material includes the following steps: (1) Put cement, gold tailings sand, mineral admixtures and water-reducing agent into a planetary mixer and dry mix at 62 rpm for 3 minutes.

[0057] (2) Add the remaining 200kg of water to the dry mixture, pour in the whisker suspension while stirring at a low speed of 62rpm, and then stir at 125rpm for 4 minutes.

[0058] (3) After standing for 10 minutes, the material can be used for 3D printing.

[0059] Performance testing: The material extrudes smoothly without breaks, but interlayer adhesion is poor and it is prone to collapse. Its wet bulk density is 0.80. The 28-day compressive strength reaches 49 MPa, and the flexural strength reaches 4.5 MPa. However, its high flowability prevents it from maintaining its shape, making it unsuitable for 3D printing. Figure 2 As shown.

[0060] Comparative Example 2 3D printed concrete material is made from the following parts by weight of raw materials (kg / m³). 3 ): 450kg of PO 42.5 R cement, 900kg of gold tailings sand, 115kg of mineral admixtures, 9kg of polycarboxylate superplasticizer, 19kg of 3D printing concrete composite emulsifier, and 200kg of water. The particle size distribution of the gold tailings sand meets the following conditions: the mass ratio of <0.075mm, 0.075~0.15mm and not equal to 0.15mm, 0.15~0.3mm and not equal to 0.3mm, and 0.3~0.6mm and not equal to 0.6mm is 29.9:19.9:23.1:27.1. In the mineral admixture, the mass ratio of fly ash to silica fume is 2:1; In the 3D printing concrete composite emulsifier, the mass ratio of hydroxypropyl methylcellulose ether, polyalkylbenzene sulfonate, redispersible latex powder, calcium nitrate, and triisopropanolamine is 10:15:5:6:3. The preparation of the above-mentioned 3D printed concrete material includes the following steps: (1) Put cement, gold tailings sand, mineral admixtures and water-reducing agent into a planetary mixer and dry mix at 62 rpm for 3 minutes.

[0061] (2) Mix the remaining 200kg of water and the 3D printing concrete composite emulsifier and add them to the dry mix. Pour in the whisker suspension while stirring at a low speed of 62rpm, and then stir at 125rpm for 4 minutes.

[0062] (3) After standing for 10 minutes, the material can be used for 3D printing.

[0063] Performance testing: The material extrudes smoothly without any breaks, exhibits good interlayer adhesion, and has a wet bulk density of 0.83. Its 28-day compressive strength reaches 44 MPa, its flexural strength reaches 4.1 MPa, and its shape retention during initial setting time is greater than 95%.

[0064] The above embodiments demonstrate that the materials and methods provided by this invention can effectively produce high-performance 3D printed concrete, resulting in significant social, environmental, and economic benefits.

[0065] Although preferred embodiments of the invention have been shown and described, it is conceivable that those skilled in the art can devise various modifications to the invention within the spirit and scope of the appended claims.

Claims

1. A 3D-printed concrete material using gold tailings sand as the sole aggregate and hybrid fiber reinforcement, characterized in that, The raw materials include the following parts by weight: 300-450 parts cement; Gold tailings sand, 800-1100 parts; 50-150 parts of mineral admixtures; 3-10 parts of water-reducing agent; 5-25 parts of mixed fibers; 12-22 parts of 3D printing concrete composite emulsion; 200-250 parts water; The hybrid fibers include silane coupling agent modified carbon fiber, silane coupling agent modified basalt fiber, and calcium carbonate whiskers.

2. The 3D printed concrete material according to claim 1, characterized in that, In the hybrid fiber, the mass ratio of the silane coupling agent modified carbon fiber, the silane coupling agent modified basalt fiber, and the calcium carbonate whiskers is (0.5~1):(1~2):(0.2~0.5).

3. The 3D printed concrete material according to claim 1, characterized in that, The length of the silane coupling agent modified carbon fiber is 8~15mm, and the diameter of the silane coupling agent modified carbon fiber is 5~10μm. The length of the silane coupling agent modified basalt fiber is 5~10mm, and the diameter of the silane coupling agent modified basalt fiber is 10~20μm; The radial dimension of the calcium carbonate whisker is 0.1~1.2μm, the length of the calcium carbonate whisker is 20~30μm, and the aspect ratio of the calcium carbonate whisker is 20~30.

4. The 3D printed concrete material according to claim 1, characterized in that, The preparation of the silane coupling agent modified carbon fiber includes: After physical dispersion, the carbon fibers were soaked and dispersed in acetone, and then soaked and modified in an ethanol solution of silane coupling agent. The preparation of the silane coupling agent modified basalt fiber includes: After physical dispersion, basalt fibers were soaked and dispersed in acetone, and then soaked and modified in an ethanol solution of silane coupling agent.

5. The 3D printed concrete material according to claim 1, characterized in that, The mud content of the gold tailings is <3%; The gold tailings sand forms an accumulation structure with a porosity of 40% to 50%. The particle size distribution of the gold tailings sand satisfies the following: <0.075mm, 0.075~0.15mm and not equal to 0.15mm, 0.15~0.3mm and not equal to 0.3mm, and 0.3~0.6mm and not equal to 0.6mm in a mass ratio of (25~35):(15~25):(20~30):(20~35).

6. The 3D printed concrete material according to claim 1, characterized in that, The mineral admixtures include fly ash and silica fume; The mass ratio of fly ash to silica fume is (2~3):

1.

7. The 3D printed concrete material according to claim 1, characterized in that, The 3D printed concrete composite emulsifier includes hydroxypropyl methylcellulose ether, polyalkylbenzene sulfonate, redispersible latex powder, calcium nitrate, and triisopropanolamine; The mass ratio of the hydroxypropyl methylcellulose ether, polyalkylbenzene sulfonate, redispersible latex powder, calcium nitrate and triisopropanolamine is (8~12):(12~18):(3~7):(4~8):(1~5).

8. The 3D printed concrete material according to claim 1, characterized in that, The water-reducing agent includes polycarboxylate water-reducing agents.

9. A method for preparing a 3D-printed concrete material with gold tailings sand as the whole aggregate and hybrid fiber reinforcement as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Cement, gold tailings sand, mineral admixtures, and water-reducing agents are mixed to obtain dry-mixed material; Calcium carbonate whiskers are premixed with some water to obtain a suspension; Mix the remaining water and 3D printed concrete composite emulsifier, then add the dry mix, stir and disperse, then add the suspension, and stir again to obtain a slurry; After mixing silane coupling agent modified carbon fiber and silane coupling agent modified basalt fiber, they are sprinkled into the slurry and stirred to obtain concrete material. The concrete material is left to stand, and then 3D printed concrete material is obtained.

10. The method for preparing 3D printed concrete material according to claim 9, characterized in that, The settling time is 5-15 minutes.

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