A 3D printing method of tailings blended 3D printing concrete retaining wall material

Abstract

This invention relates to the field of 3D printed concrete materials technology, specifically to a 3D printed concrete retaining wall material incorporating tailings and a 3D printing method. The material comprises aggregates, cement, additives, and water; the aggregates include crushed stone, river sand, and tailings in a mass ratio of 1:4.5-5:1-1.2; the crushed stone particle size ranges from 4.75 to 20 mm, the river sand particle size ranges from 0.16 to 4.75 mm, and the tailings particle size is less than 0.16 mm. The crushed stone, river sand, and tailings form a continuous coarse, medium, and fine gradation system, significantly improving the overall continuity of the aggregate gradation. This helps the slurry uniformly coat each grade of aggregate, reduces interparticle interactions, and ensures that the coarse aggregate remains stably suspended in the slurry without settling. This significantly enhances the anti-segregation ability of the mixture under high fluidity and the compactness after molding, effectively guaranteeing the pumpability, extrusion molding quality, and hardened mechanical strength of the concrete.

Description

Technical Field

[0001] This invention relates to the field of 3D printed concrete materials technology, and more specifically, to a 3D printed concrete retaining wall material mixed with tailings and a 3D printing method. Background Technology

[0002] 3D-printed concrete technology, with its core advantages such as moldless construction, high efficiency, and high adaptability to various shapes, has shown broad application prospects in the engineering construction field. Through highly automated and digitalized construction methods, this technology can significantly reduce labor costs, improve construction accuracy and efficiency, and provide innovative solutions for the rapid prototyping of complex structures and customized components. Introducing this technology into retaining wall construction not only broadens its engineering application scenarios but also provides key technological support for promoting the transformation of related fields towards intelligent and refined construction.

[0003] Existing 3D printed concrete formulations are mostly designed for general building components, and have many compatibility defects when used for retaining wall construction: First, the current aggregate system mainly uses mixed sand with a particle size of 0-3 mm, which has poor gradation continuity and makes it difficult to form an ideal suspended dense structure, affecting the extrudability and constructability of 3D printed concrete; Second, the cementitious system and admixtures have poor synergy, often resulting in uncontrolled setting time. Setting too quickly leads to poor interlayer bonding, while setting too slowly leads to stack collapse; Third, the preparation process lacks specificity, and problems such as fiber agglomeration and uneven mixing of raw materials are common, reducing the performance stability of concrete materials.

[0004] Currently, tailings-infused concrete is mainly geared towards cast-in-place construction techniques and has not yet been systematically optimized for key properties required for 3D printing, such as extrudability, constructability, and interlayer adhesion. Simply increasing the tailings content significantly increases concrete viscosity, affecting its smooth passage through the printing nozzle; while traditional admixture systems struggle to cope with the rapid slump loss caused by the high water absorption of tailings, easily leading to pipe blockage and stack collapse. Furthermore, existing formulations lack synergistic gradation design between tailings and other aggregates, resulting in insufficient material density and limited mechanical properties and durability, making it difficult to balance economy and engineering applicability, thus hindering the large-scale application of 3D printing technology in retaining wall construction. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a 3D printed concrete retaining wall material mixed with tailings and a 3D printing method.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: This invention provides a 3D-printed concrete retaining wall material incorporating tailings, the material comprising aggregate, cement, auxiliary materials and water; the aggregate comprising crushed stone, river sand and tailings in a mass ratio of 1:4.5-5:1-1.2; the crushed stone has a particle size range of 4.75-20 mm, the river sand has a particle size range of 0.16-4.75 mm, and the tailings has a particle size of less than 0.16 mm.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, the tailings are one or more of copper mine tailings, iron mine tailings, zinc mine tailings, and tungsten mine tailings.

[0009] Furthermore, the auxiliary materials include a water-reducing agent, which is one or more of lignin sulfonate, naphthalene sulfonate formaldehyde condensate, sulfonated melamine formaldehyde resin, and polycarboxylic acid polymers.

[0010] Furthermore, the auxiliary materials also include a setting regulator; the setting regulator is one or more of sodium gluconate, calcium chloride, and triethanolamine.

[0011] Furthermore, the mass fractions of each component in the material are as follows: 100-120 parts of crushed stone, 450-550 parts of river sand, 100-150 parts of tailings, 500-600 parts of cement, 1-3 parts of water-reducing agent, 20-60 parts of setting regulator, and 150-250 parts of water.

[0012] Furthermore, the material also includes 200-250 parts by weight of mineral admixture and 100-200 parts by weight of fiber admixture; the mineral admixture is one or more of fly ash, slag powder, phosphorus slag powder, silica powder, and zeolite powder, and the fiber admixture is one or more of polypropylene fiber, polyethylene fiber, polyester fiber, glass fiber, and steel fiber.

[0013] Furthermore, the material also includes 5-15 parts by weight of a modifier and 2-6 parts by weight of a thickener; the modifier is one or more of lime, sodium silicate, and calcium sulfoaluminate, and the thickener is one or more of starch, xanthan gum, carboxymethyl cellulose, and bentonite.

[0014] Furthermore, the cement is one or more of silicate cement, aluminate cement, and sulfoaluminate cement.

[0015] The present invention also provides a method for preparing a 3D printed concrete retaining wall material with tailings as described above, wherein the aggregate and the cement are mixed and stirred, and then water and the auxiliary materials are added and stirred to obtain the material.

[0016] The present invention also provides a 3D printing method for a concrete retaining wall, using the materials described above for 3D printing.

[0017] The beneficial effects of this invention are as follows: (1) The 3D printed concrete retaining wall material with tailings of the present invention is formed by compounding crushed stone, river sand and tailings in a mass ratio of 1:4.5-5:1-1.2 to form a continuous gradation system of coarse, medium and fine aggregates, which significantly improves the overall continuity of aggregate gradation, helps the slurry to uniformly coat the aggregates of each grade, reduces the interaction between particles, and ensures that the coarse aggregates are stably suspended in the slurry without settling, thereby significantly enhancing the anti-segregation ability of the mixture under high flow conditions and the compactness after molding, effectively ensuring the pumpability of concrete, the quality of extrusion molding and the mechanical strength after hardening; (2) The 3D printed concrete retaining wall material with tailings of the present invention broadens the source channels of tailings raw materials, so that various metal tailings from different mines can be used as aggregate resources, significantly improving the raw material adaptability and regional applicability of the formula; at the same time, the particle size distribution characteristics can be optimized by using multiple tailings in combination, further improving the fluidity and density of concrete. (3) The 3D printed concrete retaining wall material with tailings of the present invention forms a complete system with synergistic effect by optimizing the mass ratio of each component. The formula system as a whole ensures that the extrusion is smooth and unblocked in the initial stage of printing and that the structure is stable and does not collapse or deform after stacking. At the same time, it realizes the resource utilization of tailings and the on-site disposal of solid waste. (4) The 3D printed concrete retaining wall material with tailings admixture of the present invention improves the conveying performance of concrete and increases its later strength by incorporating the active effect and lubrication effect of the mineral admixture, while reducing the amount of cement and material cost. By constructing a three-dimensional distributed micro-reinforced skeleton in the concrete through fiber admixture, the brittle matrix is ​​transformed into a composite material with higher toughness and durability, which significantly improves the crack resistance and impact resistance of concrete and effectively solves the technical defects of 3D printed concrete being brittle and prone to cracking. (5) The 3D printed concrete retaining wall material with tailings of the present invention regulates the setting and hardening process from the chemical reaction level by the modifier, and the addition of the thickener effectively improves the cohesiveness and suspension stability of the slurry. The synergistic effect with the setting regulator enables the concrete to quickly establish structural strength after extrusion, ensures the shape of the extruded strip is stable and does not collapse, and significantly improves the molding stability, volume stability and long-term durability of 3D printed concrete. (6) The 3D printed concrete retaining wall material with tailings of the present invention achieves precise control of the performance of the cementitious system by flexibly selecting or using different types of cement in combination. The combination of multiple cements can give full play to their respective advantages and achieve complementary performance, which enhances the adaptability of the formula to different engineering environments and construction requirements, and provides flexible material solutions for diverse application scenarios such as mine underground filling retaining walls, river ecological retaining walls, and slope protection retaining walls. (7) The method for preparing 3D printed concrete retaining wall material with tailings admixture of the present invention is stable and controllable, and can solve problems such as fiber agglomeration, uneven mixing of raw materials and reaction time of admixtures. It also has the advantages of being simple and easy to implement, suitable for industrial mass production, and conducive to the promotion and application of technology. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the bottom first layer of a concrete retaining wall when 3D printing is performed using the method of the present invention; Figure 2 This is a schematic diagram of a completed concrete retaining wall when 3D printed using the method of the present invention. Detailed Implementation

[0019] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0020] The present invention relates to a 3D-printed concrete retaining wall material incorporating tailings, comprising aggregates, cement, additives, and water; the aggregates comprising crushed stone, river sand, and tailings in a mass ratio of 1:4.5-5:1-1.2; the crushed stone has a particle size range of 4.75-20 mm, the river sand has a particle size range of 0.16-4.75 mm, and the tailings has a particle size of less than 0.16 mm.

[0021] The 3D-printed concrete retaining wall material incorporating tailings of this invention forms a continuous gradation system by compounding crushed stone, river sand, and tailings in a specific mass ratio. Crushed stone provides skeletal support, river sand fills medium-sized voids, and tailings fill the finest voids, significantly improving the overall continuity of the aggregate gradation and effectively reducing the system's porosity. This helps the slurry uniformly coat each grade of aggregate, reducing interparticle interactions and ensuring that coarse aggregates remain stably suspended in the slurry without settling. This significantly enhances the mixture's anti-segregation ability under high-flow conditions and its compactness after molding, effectively guaranteeing the concrete's pumpability, extrusion molding quality, and hardened mechanical strength. Simultaneously, it realizes the resource utilization of tailings, solving the environmental pressure problem caused by mine tailings accumulation and providing key technical support for the large-scale application of tailings in 3D-printed concrete.

[0022] The 3D-printed concrete retaining wall material with tailings admixture of the present invention has good rheological and mechanical properties, which can fully meet the requirements of retaining wall for load bearing, impact resistance and deformation resistance.

[0023] Preferably, the tailings are one or more of copper mine tailings, iron mine tailings, zinc mine tailings, and tungsten mine tailings. The availability of these multiple tailings effectively broadens the sources of tailings raw materials, allowing various metal tailings from different mines to be used as aggregate resources. This significantly improves the raw material adaptability and regional applicability of the formula, effectively solving the problem of limited single tailings sources and unstable supply. At the same time, the combined use of multiple tailings can optimize particle size distribution characteristics, further improving the fluidity and density of concrete.

[0024] Preferably, the auxiliary materials include a water-reducing agent, which is one or more of lignin sulfonate, naphthalene sulfonate formaldehyde condensate, sulfonated melamine formaldehyde resin, and polycarboxylic acid polymers.

[0025] The aforementioned water-reducing agent can significantly reduce the water-cement ratio while maintaining the workability of concrete, improve the fluidity and pumpability of the slurry, ensure smooth and unblocked extrusion during the 3D printing process, and improve the dispersibility of cement particles, promoting full hydration reaction, thereby increasing the density and mechanical strength of concrete.

[0026] Preferably, the auxiliary materials also include a setting regulator; the setting regulator is one or more of sodium gluconate, calcium chloride, and triethanolamine.

[0027] Among the above-mentioned setting regulators, using one of them can effectively regulate setting time, while using a mixture of several allows for precise control of concrete setting time through the flexible compounding of components with different setting mechanisms.

[0028] Specifically, sodium gluconate, as a retarder, can delay the hydration reaction and ensure fluidity during the pumping stage; calcium chloride, as a accelerator, can accelerate setting and improve early strength; and triethanolamine, as an early strength agent, can promote hydration and shorten setting time. The synergistic effect of these three agents enables the concrete to maintain high fluidity during transportation and quickly build up structural strength after extrusion, ensuring the stability of the extruded strip shape, preventing collapse, and guaranteeing the quality of interlayer bonding.

[0029] Preferably, in the 3D printed concrete retaining wall material with tailings of the present invention, the mass fractions of each component are: 100-120 parts crushed stone, 450-550 parts river sand, 100-150 parts tailings, 500-600 parts cement, 1-3 parts water-reducing agent, 20-60 parts setting regulator, and 150-250 parts water.

[0030] The specific formulation of the present invention forms a complete system of synergistic effects. Based on the aggregate, 500-600 parts of cement can provide sufficient hydration products to ensure strength development. 1-3 parts of water-reducing agent can significantly reduce the water-cement ratio and ensure fluidity and pumpability in the initial stage of printing. 20-60 parts of setting regulator can achieve precise control of setting time, so that the concrete maintains high fluidity during the transportation stage and quickly builds structural strength after extrusion. 150-250 parts of water can ensure workability while avoiding strength loss caused by excessive water.

[0031] The 3D-printed concrete retaining wall material formulated above exhibits excellent printability through optimized aggregate gradation and synergistic effects with other components. The following rheological parameters were measured using an ICAR rheometer: Freshly mixed concrete (0 min settling time) exhibits a static yield stress of 2500-3200 Pa, a dynamic yield stress of 500-700 Pa, and a plastic viscosity of 20-35 Pa·s; after 30 min settling time, the concrete exhibits a static yield stress of 3200-4000 Pa, a dynamic yield stress of 700-900 Pa, and a plastic viscosity of 35-50 Pa·s. This control of rheological parameters ensures smooth, unobstructed extrusion of the concrete during the initial printing stage, as well as structural stability and prevents collapse deformation after stacking, while also achieving tight interlayer bonding, thus guaranteeing the stability of the printed product quality.

[0032] Meanwhile, the material exhibits excellent mechanical properties, specifically: 1-day compressive strength ≥15 MPa, 28-day compressive strength ≥55 MPa, 1-day flexural strength ≥3 MPa, 28-day flexural strength ≥10 MPa, 1-day interlaminar bond strength ≥0.5 MPa, 28-day interlaminar bond strength ≥3.2 MPa, and shrinkage rate <0.2%, which can fully meet the requirements of retaining wall for load bearing, impact resistance, and deformation resistance.

[0033] Preferably, the material further includes 200-250 parts by weight of mineral admixture and 100-200 parts by weight of fiber admixture; the mineral admixture is one or more of fly ash, slag powder, phosphorus slag powder, silica powder, and zeolite powder, and the fiber admixture is one or more of polypropylene fiber, polyethylene fiber, polyester fiber, glass fiber, and steel fiber.

[0034] The incorporation of mineral admixtures improves the conveying performance of concrete and enhances its later strength by utilizing their active and lubricating effects. At the same time, it reduces cement usage and material costs. By strictly controlling the admixture dosage to within 40% of the cementitious materials, the problem of insufficient hardness in concrete retaining wall materials can be avoided.

[0035] By constructing a three-dimensional micro-reinforced skeleton within concrete using fiber admixtures, the brittle matrix is ​​transformed into a composite material with higher toughness and durability, significantly improving the crack resistance and impact resistance of concrete retaining wall materials.

[0036] The synergistic effect of mineral admixtures and fiber admixtures enables the prepared concrete to achieve a 28-day compressive strength of 55-71.4 MPa and a 28-day flexural strength of 10-15.4 MPa. At the same time, it improves the interlayer bond performance, enabling the 28-day interlayer bond strength to reach 3.2-6.1 MPa. This effectively solves the technical defects of general 3D printed concrete, such as high brittleness and easy cracking, and meets the comprehensive requirements of retaining wall structures for load-bearing capacity, deformation resistance and durability. The flexible selection of different types of mineral admixtures and fiber admixtures enhances the adaptability of the formula to different application scenarios and performance requirements.

[0037] Preferably, the material also includes 5-15 parts by weight of modifier and 2-6 parts by weight of thickener; the modifier is one or more of lime, sodium silicate, and calcium sulfoaluminate, and the thickener is one or more of starch, xanthan gum, carboxymethyl cellulose, and bentonite.

[0038] The aforementioned modifiers can regulate the setting and hardening process at the chemical reaction level. Lime, acting as an alkaline activator, promotes secondary hydration, accelerates setting, and enhances strength. Sodium silicate reacts rapidly to form calcium silicate condensate (CSH), significantly increasing density and impermeability. Calcium sulfoaluminate hydrates to form ettringite (AFt), resulting in moderate volume expansion and reducing the risk of cracking. The specific dosage of the modifiers, within the aforementioned range, can be flexibly selected based on the raw material ratio and actual application.

[0039] The addition of the thickener effectively improves the cohesiveness and suspension stability of the slurry, prevents aggregate settling and bleeding, and works synergistically with the setting regulator to enable the concrete to quickly build up structural strength after extrusion and ensure that the extruded strip shape is stable and does not collapse.

[0040] Furthermore, the combined use of modifiers and thickeners further optimizes the rheological and mechanical properties of concrete, significantly improving the molding stability, volume stability, and long-term durability of 3D printed concrete, providing material assurance for the precise construction of complex retaining wall structures.

[0041] Preferably, the cement is one or more of silicate cement, aluminate cement, and sulfoaluminate cement.

[0042] The present invention discloses a method for preparing 3D printed concrete retaining wall material with tailings, which involves mixing and stirring aggregates and cement, then adding water and auxiliary materials and stirring to obtain the material.

[0043] Preferably, the preparation method includes the following specific steps: S1. Weigh out the crushed stone, river sand, tailings, and cement according to the mass fractions, and mix them.

[0044] Preferably, the mixing equipment is a forced mixing equipment, with a mixing speed of 50-70 r / min and a mixing time of 3-5 min.

[0045] S2. Weigh out water according to the mass fraction and add it to the mixture obtained in S1, and continue stirring.

[0046] Preferably, this step involves stirring at a speed of 50-70 r / min for 3-5 minutes. During stirring, the inner wall of the mixer should be scraped every 1 minute to ensure that the raw materials in the corners are mixed evenly and to avoid localized agglomeration.

[0047] S3. Weigh out the mineral admixture, fiber admixture and modifier according to the mass fractions, add them to the mixture obtained in S2, and continue stirring.

[0048] Preferably, this step involves stirring at a speed of 30-50 r / min for 3-5 min.

[0049] S4. Weigh out the water-reducing agent according to the mass fraction, add it to the mixture obtained in S3, and continue stirring.

[0050] Preferably, this step involves stirring at a speed of 30-50 r / min for 2-3 minutes.

[0051] S5. Weigh out the setting agent and thickener according to the mass fractions, add them to the mixture obtained in S4, and continue stirring.

[0052] Preferably, the 3D printed concrete retaining wall material is prepared by stirring at a speed of 30-50 r / min for 2-3 minutes until homogeneous.

[0053] The preparation method of the present invention is stable and controllable. By optimizing the stirring sequence, speed and time, it effectively solves problems such as fiber agglomeration, uneven mixing of raw materials and reaction time of additives. The preparation process is simple and easy to carry out, the parameters are controllable, it is suitable for industrial mass production, and it is conducive to the promotion and application of the technology.

[0054] The method for 3D printing concrete retaining walls of the present invention uses the materials described above for 3D printing; this method can effectively reduce the risk of cracking of concrete retaining walls, and the materials used have good resistance to sulfate attack, making them suitable for retaining wall projects in harsh environments.

[0055] Specifically, the method for 3D printing concrete retaining walls according to the present invention includes the following steps: the concrete material of the present invention is transported to the concrete 3D printing device by a piston pump, and the concrete is stacked layer by layer by a three-dimensional driven printing head in a continuous extrusion manner. After printing, water is sprayed for curing every 1 hour, and the curing time is not less than 12 hours, so as to realize the automated, efficient and high-quality 3D printing of concrete retaining walls.

[0056] The 3D printing method for concrete retaining walls of this invention provides a flexible material solution for diverse application scenarios such as underground mine filling retaining walls, river ecological retaining walls, and slope protection retaining walls. At the same time, it broadens the sources of raw materials and reduces the impact of regional resource limitations on project implementation.

[0057] Figure 1 This diagram illustrates the first layer during 3D printing using the method of this invention. It shows the extrusion state of the material during the initial stage of 3D printing. As can be seen, the material strip maintains a stable shape and uniform width after being extruded from the printing nozzle, without significant collapse, deformation, or breakage. This demonstrates the excellent flowability achieved by optimizing aggregate gradation and the synergistic effect of the water-reducing agent, ensuring smooth and unobstructed extrusion during the initial printing stage. Simultaneously, the setting regulator and thickener begin to function after extrusion, enabling the concrete to quickly establish initial structural strength, ensuring the shape stability and molding quality of the first layer strip, and laying a good foundation for the bonding of subsequent layers.

[0058] Figure 2 This diagram illustrates a 3D-printed concrete retaining wall created using the method of this invention, showing the stacked state of multiple concrete strips after printing. As can be seen from the diagram, the concrete retaining wall's strips are neatly stacked with tight interlayer bonding. The overall structure shows no obvious delamination, cracking, or collapse deformation, demonstrating the constructability achieved by this invention through the phased addition strategy of setting regulators and thickeners.

[0059] The present invention will be illustrated below through specific embodiments and comparative examples.

[0060] Example 1 The specific formula of the 3D-printed concrete retaining wall material containing tailings in this embodiment is as follows: The composition, by weight, includes: 100 parts crushed stone, 500 parts river sand, 120 parts tailings, 500 parts cement, 1 part water-reducing agent, 30 parts setting regulator, 3 parts thickener, 200 parts mineral admixture, 120 parts fiber admixture, 8 parts modifier, and 160 parts water. The tailings consist of 80 parts copper mine tailings and 40 parts zinc mine tailings.

[0061] The cement is silicate cement, the water-reducing agent is lignosulfonate, the setting regulator is calcium chloride, the thickener is xanthan gum, the mineral admixture is fly ash, the fiber admixture is polypropylene fiber, and the modifier is sodium silicate.

[0062] Based on the above formula, the method for preparing 3D printed concrete retaining wall material mixed with tailings in this embodiment includes the following steps: S1. Weigh out the crushed stone, river sand, copper mine tailings, zinc mine tailings, and silicate cement by mass fraction, and put them into a forced mixing device. Mix at a speed of 50 r / min for 3 min.

[0063] S2. Weigh out the water according to the specified mass percentage and add it to the mixture obtained in S1. Stir at 50 r / min for 3 min. During the stirring process, scrape the inner wall of the mixer every 1 min to ensure that the raw materials in the corners are mixed evenly and to avoid localized agglomeration of raw materials.

[0064] S3. Weigh out fly ash, polypropylene fiber and modifier by mass, add them to the mixture obtained in S2, and stir at 40 r / min for 3 min.

[0065] S4. Weigh out the lignin sulfonate by mass fraction and add it to the mixture obtained in S3. Stir at 40 r / min for 3 min.

[0066] S5. Weigh calcium chloride and xanthan gum according to the mass fractions, add them to the mixture obtained in S4, and stir at 40 r / min for 2 min to obtain the material.

[0067] Example 2 The specific formula of the 3D-printed concrete retaining wall material containing tailings in this embodiment is as follows: The composition, by weight, includes: 100 parts crushed stone, 480 parts river sand, 120 parts tailings, 550 parts cement, 2 parts water-reducing agent, 40 parts setting regulator, 4 parts thickener, 220 parts mineral admixture, 120 parts fiber admixture, 10 parts modifier, and 180 parts water. The tailings are copper mine tailings.

[0068] The cement consists of 500 parts silicate cement and 50 parts sulfoaluminate cement; the water-reducing agent is sulfonated melamine-formaldehyde resin; the setting regulator is sodium gluconate; the thickener is starch; the mineral admixture consists of 150 parts fly ash and 70 parts slag powder; the fiber admixture consists of 100 parts polyethylene fiber and 20 parts steel fiber; and the modifier consists of 5 parts lime and 5 parts sodium silicate.

[0069] Based on the above formula, the method for preparing 3D printed concrete retaining wall material mixed with tailings in this embodiment includes the following steps: S1. Weigh out the crushed stone, river sand, copper mine tailings, silicate cement, and sulfoaluminate cement by mass fraction, and put them into a forced mixing device. Mix at 70 r / min for 4 min.

[0070] S2. Weigh out the water according to the specified mass percentage and add it to the mixture obtained in S1. Stir at 70 r / min for 5 min. During the stirring process, scrape the inner wall of the mixer every 1 min to ensure that the raw materials in the corners are mixed evenly and to avoid localized agglomeration of raw materials.

[0071] S3. Weigh out fly ash, slag powder, polyethylene fiber, steel fiber, lime and sodium silicate by mass fraction, add them to the mixture obtained in S2, and stir at 50 r / min for 3 min.

[0072] S4. Weigh out the sulfonated melamine-formaldehyde resin according to the mass fraction, add it to the mixture obtained in S3, and stir at 50 r / min for 3 min.

[0073] S5. Weigh out sodium gluconate and starch according to the mass fractions, add them to the mixture obtained in S4, and stir at 50 r / min for 2 min until homogeneous to obtain the material.

[0074] Example 3 The specific formula of the 3D-printed concrete retaining wall material containing tailings in this embodiment is as follows: The composition, by weight, includes: 120 parts crushed stone, 500 parts river sand, 100 parts tailings, 550 parts cement, 2 parts water-reducing agent, 50 parts setting regulator, 3 parts thickener, 200 parts mineral admixture, 150 parts fiber admixture, 10 parts modifier, and 200 parts water. The tailings are iron ore tailings.

[0075] The cement is silicate cement, the water-reducing agent is a polycarboxylate polymer, the setting regulator is sodium gluconate, the mineral admixture is 100 parts fly ash, 50 parts slag powder, and 50 parts silica fume, the fiber admixture is glass fiber, and the modifier is 6 parts sodium silicate and 4 parts calcium sulfoaluminate.

[0076] Based on the above formula, the method for preparing 3D printed concrete retaining wall material mixed with tailings in this embodiment includes the following steps: S1. Weigh out the crushed stone, river sand, iron ore tailings, and silicate cement by mass fraction, and put them into a forced mixing device. Mix at a speed of 60 r / min for 5 min.

[0077] S2. Weigh out the water according to the specified mass percentage and add it to the mixture obtained in S1. Stir at 60 r / min for 5 min. During the stirring process, scrape the inner wall of the mixer every 1 min to ensure that the raw materials in the corners are mixed evenly and to avoid localized agglomeration.

[0078] S3. Weigh out fly ash, slag powder, silica powder, glass fiber, sodium silicate and calcium sulfoaluminate according to the mass fractions, add them to the mixture obtained in S2, and stir at 30 r / min for 4 min.

[0079] S4. Weigh out the polycarboxylate polymer by mass fraction and add it to the mixture obtained in S3. Stir at 30 r / min for 3 min.

[0080] S5. Weigh out sodium gluconate and bentonite according to the mass fractions, add them to the mixture obtained in S4, and stir at 30 r / min for 3 min to obtain the material.

[0081] Example 4 The specific formula of the 3D-printed concrete retaining wall material containing tailings in this embodiment is as follows: The composition, by weight, includes: 120 parts crushed stone, 550 parts river sand, 150 parts tailings, 600 parts cement, 3 parts water-reducing agent, 60 parts setting regulator, 240 parts mineral admixture, 150 parts fiber admixture, 12 parts modifier, and 220 parts water. The tailings consist of 100 parts iron ore tailings and 50 parts copper ore tailings.

[0082] The cement is silicate cement, the water-reducing agent is a polycarboxylate polymer, the setting regulator is 40 parts sodium gluconate and 20 parts triethanolamine, the mineral admixture is 160 parts fly ash and 80 parts zeolite powder, the fiber admixture is polyester fiber, and the modifier is lime.

[0083] Based on the above formula, the method for preparing 3D printed concrete retaining wall material mixed with tailings in this embodiment includes the following steps: S1. Weigh out the crushed stone, river sand, iron ore tailings, copper ore tailings, and silicate cement by mass fraction, and put them into a forced mixing device. Mix at a speed of 60 r / min for 5 min.

[0084] S2. Weigh out the water according to the specified mass percentage and add it to the mixture obtained in S1. Stir at 60 r / min for 5 min. During the stirring process, scrape the inner wall of the mixer every 1 min to ensure that the raw materials in the corners are mixed evenly and to avoid localized agglomeration.

[0085] S3. Weigh out fly ash, zeolite powder, polyester fiber and lime according to the mass fractions, add them to the mixture obtained in S2, and stir at a speed of 40 r / min for 3 min.

[0086] S4. Weigh out the polycarboxylate polymer by mass fraction and add it to the mixture obtained in S3. Stir at 40 r / min for 2 min.

[0087] S5. Weigh out sodium gluconate, triethanolamine and carboxymethyl cellulose according to the mass fractions, add them to the mixture obtained in S4, and stir at 40 r / min for 2 min to obtain the material.

[0088] Comparative Example 1 The only difference from Example 1 is that the raw materials do not contain tailings.

[0089] Comparative Example 2 The only difference from Example 1 is that the raw materials do not contain water-reducing agents.

[0090] Comparative Example 3 The only difference from Example 2 is that the raw materials do not contain setting regulators and thickeners.

[0091] Comparative Example 4 The only difference from Example 4 is that the raw material tailings do not contain iron ore tailings.

[0092] The rheological properties of the 3D printed concrete retaining wall formulations obtained in the above embodiments and comparative examples were tested using an ICAR rheometer, and the test results are shown in Table 1.

[0093] Table 1. Rheological property parameters of the 3D printed concrete retaining wall formulations obtained in Examples 1-4 and Comparative Examples 1-4. As can be seen from Table 1, the 0-minute static yield stress, dynamic yield stress, and plastic viscosity of Examples 1-4 of the present invention can ensure that the concrete is extruded smoothly and without blockage in the initial stage of printing. The 30-minute static yield stress, dynamic yield stress, and plastic viscosity are all relatively high, which can ensure that the structure is stable and without collapse deformation after stacking.

[0094] Compared with Example 1, Comparative Example 2 did not contain a water-reducing agent. The static yield stress, dynamic yield stress and plastic viscosity of Comparative Example 2 were all higher at 0 min, which was not conducive to extrusion in the initial stage of printing and was prone to clogging. This shows that the water-reducing agent used in this invention can effectively improve the conveying performance of 3D printed concrete materials.

[0095] Compared with Example 2, Comparative Example 3 did not contain setting regulators or thickeners. The static yield stress, dynamic yield stress and plastic viscosity of Comparative Example 3 were relatively low at 30 min, and it was easy to collapse and deform after stacking. This shows that the setting regulator used in this invention can effectively improve the constructability of 3D printed concrete materials.

[0096] The mechanical properties of the 3D printed concrete retaining wall formulations obtained in the above embodiments and comparative examples were tested using a microcomputer-controlled electro-hydraulic servo pressure testing machine. The shrinkage rate of the 3D printed concrete retaining wall formulations obtained in the above embodiments and comparative examples was tested using a steel cylinder with a diameter of 150 mm and a height of 300 mm. The test results are shown in Table 2.

[0097] Table 2. Mechanical property parameters and shrinkage rates of the 3D-printed concrete retaining wall formulations obtained in Examples 1-4 and Comparative Examples 1-4. As can be seen from Table 2, the compressive strength, flexural strength and interlayer bond strength of Examples 1-4 of the present invention are all high, indicating that the 3D printed fine aggregate concrete material prepared by the present invention has good mechanical properties.

[0098] Compared with Example 1, the compressive strength, flexural strength, and interlaminar bond strength of Comparative Example 1 were significantly reduced, while the shrinkage rate was significantly increased, indicating that the aggregate gradation used in this invention can effectively improve the mechanical properties of 3D printed concrete materials.

[0099] Compared with Example 4, the compressive strength, flexural strength, and interlaminar bond strength of Comparative Example 4 were significantly reduced, while the shrinkage rate was significantly increased, indicating that the tailings gradation used in this invention can effectively improve the mechanical properties of 3D printed concrete materials.

[0100] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0101] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A 3D-printed concrete retaining wall material incorporating tailings, characterized in that, The material includes aggregates, cement, auxiliary materials and water; the aggregates include crushed stone, river sand and tailings in a mass ratio of 1:4.5-5:1-1.2; the crushed stone has a particle size range of 4.75-20 mm, the river sand has a particle size range of 0.16-4.75 mm, and the tailings has a particle size of less than 0.16 mm.

2. The 3D-printed concrete retaining wall material incorporating tailings according to claim 1, characterized in that, The tailings are one or more of copper mine tailings, iron mine tailings, zinc mine tailings, and tungsten mine tailings.

3. The 3D-printed concrete retaining wall material incorporating tailings according to claim 1, characterized in that, The auxiliary materials include water-reducing agents, which are one or more of lignin sulfonate, naphthalene sulfonate formaldehyde condensate, sulfonated melamine formaldehyde resin, and polycarboxylic acid polymers.

4. The 3D-printed concrete retaining wall material incorporating tailings according to claim 3, characterized in that, The auxiliary materials also include a setting regulator; the setting regulator is one or more of sodium gluconate, calcium chloride, and triethanolamine.

5. A 3D-printed concrete retaining wall material incorporating tailings according to claim 4, characterized in that, The material comprises the following components in parts by mass: 100-120 parts crushed stone, 450-550 parts river sand, 100-150 parts tailings, 500-600 parts cement, 1-3 parts water-reducing agent, 20-60 parts setting regulator, and 150-250 parts water.

6. The 3D-printed concrete retaining wall material incorporating tailings according to claim 5, characterized in that, The material also includes 200-250 parts by weight of mineral admixture and 100-200 parts by weight of fiber admixture; the mineral admixture is one or more of fly ash, slag powder, phosphorus slag powder, silica powder, and zeolite powder, and the fiber admixture is one or more of polypropylene fiber, polyethylene fiber, polyester fiber, glass fiber, and steel fiber.

7. A 3D-printed concrete retaining wall material incorporating tailings according to claim 5, characterized in that, The material also includes 5-15 parts by weight of modifier and 2-6 parts by weight of thickener; the modifier is one or more of lime, sodium silicate, and calcium sulfoaluminate, and the thickener is one or more of starch, xanthan gum, carboxymethyl cellulose, and bentonite.

8. A 3D-printed concrete retaining wall material incorporating tailings according to any one of claims 1-7, characterized in that, The cement is one or more of silicate cement, aluminate cement, and sulfoaluminate cement.

9. A method for preparing a 3D-printed concrete retaining wall material incorporating tailings as described in any one of claims 1-8, characterized in that, The aggregate and cement are mixed and stirred, then water and the auxiliary materials are added and stirred to obtain the material.

10. A 3D printing method for a concrete retaining wall, characterized in that, 3D printing is performed using the material described in any one of claims 1-8.

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