An eco-friendly ultra-high performance concrete material and its preparation method

Abstract

This invention proposes an eco-friendly ultra-high performance concrete material and its preparation method. First, ultra-activated tailings powder is prepared from metal tailings using ultrafine active analysis grinding and coating, and a mechano-chemical activation method, to replace cement. Then, through particle shaping, surface strengthening, and gradation sorting, the tailings particle size and shape are shaped into tailings sand to replace quartz sand. Finally, ultrasonic atomization is used to uniformly anchor colloidal silica onto the fiber surface to improve fiber surface roughness. A cementitious material composed of cement, fly ash, and ultra-activated tailings powder is dry-mixed with quartz sand and tailings sand in a specific ratio. After uniform mixing, mixing water and a water-reducing agent are added and stirred to form a homogeneous slurry. Finally, pretreated fibers are added, and after uniform mixing, the eco-friendly ultra-high performance concrete is obtained.

Description

Technical Field

[0001] This invention relates to ultra-high performance concrete, specifically to an eco-friendly ultra-high performance concrete material prepared using metal tailings and its preparation method. Background Technology

[0002] Ultra-high performance concrete (UHPC) is formulated based on the theory of closest packing of particles. By optimizing the particle size of raw materials, it achieves the closest packing state, giving UHPC extremely high mechanical properties, toughness, and durability. It solves the problems of low strength, poor toughness, and easy cracking found in ordinary concrete, and can be applied to bridge deck paving, marine structures, and highly abrasive and corrosive environments. However, conventional UHPC uses a large amount of high-quality raw materials such as cementitious materials, active mineral admixtures, quartz sand, and high-strength steel fibers, resulting in large volume shrinkage and high adiabatic temperature rise, making it unsuitable for large-volume concrete construction. Furthermore, its production cost is dozens of times higher than that of ordinary concrete, limiting its widespread application. In addition, because UHPC has a low water-cement ratio, typically 0.14-0.20, the hydration degree of the cementitious material is only 30%-40%. Unhydrated cement particles act as fillers in the matrix, and the cementitious effect of the cement is not fully utilized.

[0003] Metal tailings are industrial waste generated during mining and metal smelting processes. Their main components are generally oxides such as silicon dioxide, aluminum oxide, iron oxide, calcium oxide, and magnesium oxide. Based on ore processing methods, metal tailings can generally be divided into two categories: one is tailings slag formed after ore beneficiation processes such as filtering, concentration, and dewatering; this type has no hydration activity. The other is water-quenched slag formed after high-temperature molten metal ore has had its effective components extracted and then rapidly cooled in water; this type possesses hydration activity. Limited by technological levels and local economic development constraints, the comprehensive utilization rate of metal tailings in my country is less than 30%. Some metal tailings are dumped into tailings ponds or tailings dams, occupying large amounts of land and causing serious pollution to the local atmosphere, water, and soil environment, while also posing risks of natural disasters such as landslides and debris flows. With the increasing depletion of metal mineral resources in my country and the deepening implementation of national environmental protection policies, the resource-based reuse of metal tailings can effectively reduce its environmental damage and supplement increasingly depleted mineral resources, becoming an inevitable development trend. At present, the comprehensive utilization of metal tailings at home and abroad includes: recovery of valuable components, backfilling of mined-out areas, and preparation of building materials. However, further processing and purification of tailings have the problem of low economic efficiency. When used for backfilling, there are problems such as low resource utilization, low added value, and pollution of the surrounding environment caused by the leaching of heavy metals. Using tailings for building materials is an effective way to reduce the volume of tailings and dispose of them on a large scale.

[0004] Therefore, it is necessary to develop an eco-friendly ultra-high performance concrete material and its preparation method that utilizes metal tailings to reduce cement usage, decrease the thermal rise and volume shrinkage of UHPC, reduce production costs, and dispose of industrial waste. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide an eco-friendly ultra-high performance concrete material prepared from metal tailings and its preparation method. This reduces the thermal rise and volume shrinkage of UHPC, lowers production costs, disposes of industrial waste, and the prepared ultra-high performance concrete can not only achieve high performance, long life and greenness of buildings and structures, but also solidify heavy metals in tailings.

[0006] The technical solution of this invention is: an eco-friendly ultra-high performance concrete material, characterized in that it comprises a cementitious material system, an aggregate system, mixing water, a water-reducing agent, and silica pretreated fibers.

[0007] The mass ratio of the cementitious material system, aggregate system, mixing water, and water-reducing agent is 1:(0.9-1.2):(0.14-0.2):(0.02-0.05), and the volumetric dosage of the silica pretreated fiber in the eco-friendly ultra-high performance concrete material is 1%-3%.

[0008] The cementitious material system includes 40-60% cement, 5-15% fly ash, and 30-50% ultra-activated tailings powder by mass percentage, and the sum of the mass percentages of cement, fly ash, and ultra-activated tailings powder in the cementitious material system is 100%.

[0009] The aggregate system comprises 40-60% quartz sand and 40-60% tailings sand by mass percentage, and the sum of the mass percentages of quartz sand and tailings sand in the aggregate system is 100%.

[0010] Preferably, the ultra-activated tailings powder has a particle size of 10-40 μm and is prepared by a method comprising the following steps:

[0011] a. Grind metal tailings to obtain tailings powder, wherein the tailings powder has a fineness of not more than 5% residue on a 45μm square hole sieve and an average particle size range of 5-10μm. The tailings powder is then thoroughly mixed with ultrafine active powder with an average particle size range of 50-100nm under a high-speed airflow to fully coat the tailings powder, thereby obtaining preliminarily activated tailings powder.

[0012] b. The pre-activated tailings powder is mixed and ground with nano-oxidation powder to allow the nano-oxidation powder to complex or anchor on the surface of the tailings powder, thereby obtaining super-activated tailings powder with a particle size of 10-40μm.

[0013] Furthermore, in step a, the metal tailings are composed of one or more of the following: manganese tailings, copper tailings, lead-zinc tailings, molybdenum tailings, tungsten-tin tailings, water-quenched manganese slag, water-quenched copper slag, and water-quenched lead-zinc slag; the ultrafine active powder is one or more of the following: silica fume, nano-silica, and nano-calcium carbonate; and the mass ratio of tailings powder to ultrafine active powder is 1:(0.2-0.5).

[0014] Furthermore, in step b, the nano-oxidation powder is a mixture of nano-calcium oxide and nano-magnesium oxide, wherein the mass percentage of nano-calcium oxide in the nano-oxidation powder is 40-60%, and the remainder is nano-magnesium oxide; the mass ratio of the initially activated tailings powder to the nano-oxidation powder is 1:(0.1-0.3).

[0015] The average particle size of the nano-oxidation powder of the present invention ranges from 10 to 50 nm, and the mixing and grinding time in step b is 15 to 45 min.

[0016] Preferably, the quartz sand in the aggregate system is continuously graded, divided into three particle size ranges: 0.18-0.42 mm, 0.42-0.84 mm, and 0.84-2 mm, with mass percentages of 14-22%, 45-53%, and 27-33% respectively, and the sum of the mass percentages of the three particle size ranges is 100%.

[0017] Preferably, the tailings sand in the aggregate system is obtained after processing tailings slag, which includes one or more tailings slags selected from manganese tailings, copper tailings, lead-zinc tailings, molybdenum tailings, tungsten-tin tailings, etc. The processing method includes particle shaping, surface strengthening, and gradation separation.

[0018] The particle shaping process involves first screening out tailings with a particle size greater than 4.75 mm, and then shaping the tailings using a sand and gravel shaping machine.

[0019] The surface strengthening is achieved by uniformly spraying a surface strengthening agent onto the surface of the tailings slag.

[0020] The gradation and sorting process involves separating the shaped and strengthened tailings slag into three particle size ranges: 0.18-0.42 mm, 0.42-0.84 mm, and 0.84-2 mm. The tailings slag is then formulated with mass percentages of 14-22%, 45-53%, and 27-33% respectively. The sum of the mass percentages of the three particle size ranges is 100%, which yields the tailings sand.

[0021] Preferably, the silica pretreated fiber is obtained by ultrasonic atomization to uniformly disperse saturated colloidal silica onto the fiber surface, with a volume ratio of saturated colloidal silica to fiber of 1:(20-50), and the fiber is one or more of high-strength steel fiber and high-strength polyoxymethylene fiber.

[0022] Preferably, the water-reducing agent is a polycarboxylate high-efficiency water-reducing agent with a water reduction rate greater than 30% and a solid content greater than 30%.

[0023] Preferably, the cement is silicate cement, and the grade can be selected from P·Ⅱ42.5, P·O42.5R, P·II52.5, P·II52.5R, and P·O52.5, with an average particle size of 10-40 μm; the fly ash has a fineness of no more than 5% residue on a 45 μm square-hole sieve, and an average particle size of 1-5 μm. The spherical particles in the fly ash can improve the fluidity of the slurry and exert a "pozzolanic effect," thereby improving the later-stage strength of the material.

[0024] This invention also provides a method for preparing any of the above-mentioned eco-friendly ultra-high performance concrete materials, comprising:

[0025] Cement, fly ash, super-activated tailings powder, quartz sand, and tailings sand are dry-mixed in a mixer, then mixing water and water-reducing agent are added to form a uniform slurry. Finally, silica pretreated fibers are added and mixed evenly to produce eco-friendly ultra-high performance concrete.

[0026] This invention enhances the activity of tailings through ultrafine active powder grinding and coating, and a mechano-chemical activation method (i.e., mixing and grinding with nano-oxidation powder). This tailings can replace cement and silica fume to reduce the viscosity, early hydration heat, adiabatic temperature rise, and volume shrinkage of UHPC, thus meeting the requirements of large-volume concrete construction. Through particle shaping, surface strengthening, and gradation sorting, the tailings particle size and shape are shaped into tailings sand to replace quartz sand, reducing the use of high-quality raw materials in UHPC production. Ultrasonic atomization is used to uniformly anchor colloidal silica onto the fiber surface, increasing fiber surface roughness and enhancing the adhesion between the fiber and the matrix, thereby reducing fiber usage. Different tailings treatment methods can be employed based on the type and characteristics of tailings in different regions, achieving full utilization of tailings, disposing of industrial waste, reducing carbon emissions during UHPC production, and utilizing the ultra-low porosity and ultra-high impermeability of UHPC to solidify heavy metals in the tailings, realizing the green utilization of tailings and the production of eco-friendly UHPC.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. Metal tailings are ground and activated using ultrafine powder grinding and coating and mechanical-chemical activation methods to replace cement and silica fume. This reduces the amount of adhesive used, lowers the viscosity, early hydration heat, and adiabatic temperature rise of UHPC, thus meeting the requirements of large-volume concrete construction. At the same time, the addition of calcium oxide, magnesium oxide, and other components during the mechanical-chemical activation process can further enhance the activity of the tailings. In addition, the exothermic reaction with water and the increase in slurry alkalinity can accelerate the hydration process. The increased volume of the reaction products can fill the slurry pores, improve the material strength and density, and reduce the volume shrinkage of the material.

[0029] 2. By applying particle shaping, surface strengthening, and gradation sorting, and replacing quartz sand with shaped metal tailings, the use of high-quality raw materials can be reduced, thus lowering material costs. Pre-treating the fiber surface with colloidal silica can improve fiber surface roughness, thereby enhancing the adhesion between the fiber and the matrix, increasing material toughness, and simultaneously reducing fiber usage, saving costs.

[0030] 3. The invention can make full use of local metal tailings resources and dispose of industrial waste. The technology is versatile, and the ultra-high performance concrete prepared can not only achieve high performance, long service life and greenness of buildings and structures, but also solidify heavy metals in tailings. Attached Figure Description

[0031] Figure 1 Flowchart for the preparation of ultra-activated tailings powder

[0032] Figure 2 Tailings sand preparation process Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the following embodiments provide a more detailed description of the invention. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Unless otherwise specified, the pharmaceuticals used in the embodiments are commercially available products, and the methods used are conventional methods in the art.

[0034] The requirements for the materials used in this embodiment are as follows:

[0035] The cement is commercially available silicate cement, with grades including P·Ⅱ42.5, P·O42.5R, P·II52.5, P·II52.5R, and P·O52.5, and an average particle size range of 10-40μm.

[0036] Fly ash should at least meet the performance requirements of Grade I ash, with a residue of no more than 5% on a 45μm square-hole sieve and an average particle size of 1-5μm. Spherical particles in fly ash can improve the fluidity of the slurry and exert a "volcanic ash effect," thereby improving the later-stage strength of the material.

[0037] like Figure 1 As shown, the super-activated tailings powder is prepared by a two-step method:

[0038] a. First, the tailings are ground into tailings powder. The finely ground tailings powder has a residue of less than 5% when sieved through a 45μm square-hole sieve, and an average particle size range of 5-10μm. Its particle size is slightly smaller than that of cement particles, requiring relatively moderate energy and having low requirements for grinding equipment; conventional mills are sufficient. The ground tailings powder is then thoroughly mixed with ultrafine active powder under a high-speed airflow of 200-500m / s, allowing the ultrafine powder to fully coat the tailings powder, resulting in preliminarily activated tailings powder. The ultrafine active powder is one or more of silica fume, nano-silica, and nano-calcium carbonate, with an average particle size range of 50-100nm. The mass ratio of tailings powder to ultrafine active powder is 1:(0.2-0.5). Under the action of high-speed airflow, the ultrafine active powder can fully coat the surface of the tailings powder, improving the dispersion effect of the ultrafine powder in the slurry and accelerating the cement hydration process due to the nucleation effect of the ultrafine powder, while simultaneously enhancing the hydration activity of the tailings powder.

[0039] b. Subsequently, the pre-activated tailings powder is mixed and milled with nano-oxidation powder for 15-45 minutes to produce a mechanochemical activation effect, causing calcium oxide and magnesium oxide to complex or anchor on the surface of the tailings powder, thus obtaining super-activated tailings powder. The particle size range of the super-activated tailings powder is 10-40 μm. Since its particle size is similar to that of cement particles, it will not affect the particle packing state when it replaces cement. The nano-oxidation powder is a mixture of nano-calcium oxide and nano-magnesium oxide, with a mass ratio of pre-activated tailings powder to nano-oxidation powder of 1:(0.1-0.3). The mechanochemical activation effect produced by the mixing and milling of nano-calcium oxide and nano-magnesium oxide with the pre-activated tailings powder can further enhance the activity of the tailings powder. Nano-calcium oxide and nano-magnesium oxide react with water exothermically and increase the alkalinity of the slurry. On the one hand, this helps the hydration reaction to proceed, and on the other hand, the reaction products can fill the pores of the slurry, improving the material strength, density, and volume stability. The mass percentage of nano-calcium oxide in the nano-oxidation powder is 40-60%. Taking advantage of the different volume increases and reaction rates of nano-calcium oxide and nano-magnesium oxide after reacting with water, they can act as expansion agents in the early and late stages, respectively, to improve the volume stability of the material.

[0040] The average particle size range of the nano-magnesium oxide and nano-calcium oxide of this invention is 10-50 nm.

[0041] The quartz sand is continuously graded and divided into three particle size ranges: 0.18-0.42mm, 0.42-0.84mm, and 0.84-2mm. The mass percentage of each particle size range is (14-22):(45-53):(27-33).

[0042] Tailings sand is composed of one or more tailings slags from manganese tailings, copper tailings, lead-zinc tailings, molybdenum tailings, tungsten-tin tailings, etc., after treatment, and the 28-day hydration activity of the tailings is less than 80%. The specific tailings can be selected based on the local tailings resources, making full use of local tailings resources and achieving comprehensive utilization of local materials.

[0043] like Figure 2 As shown, the process of producing tailings sand from tailings slag includes three steps: particle shaping, surface strengthening, and gradation separation. First, tailings slag particles larger than 4.75 mm are screened out. Then, a sand and gravel shaping machine is used to shape the tailings slag, which both breaks it down to smaller particle sizes and optimizes its shape, improving particle roundness. Next, existing surface strengthening agents (such as modified mesoporous silica nanoparticles made from condensed phosphoric acid or sodium aluminate) are uniformly sprayed onto the tailings slag surface. The modified mesoporous silica nanoparticles can fill the microcracks created during the shaping process, increasing the strength of the tailings slag. Furthermore, the mesoporous silica nanoparticles can serve as a carrier for subsequent matrix hydration nucleation, which helps refine the size of hydration products. The hydration products also tightly fill the interfacial transition zone between the mesopores, the matrix, and the tailings slag, improving interfacial strength. After the surface strengthening agent is anchored on the surface of the tailings slag, the shaped and strengthened tailings slag is sorted into three particle size ranges: 0.18-0.42mm, 0.42-0.84mm, and 0.84-2mm. The tailings slag is then mixed according to the mass percentage of (14-22):(45-53):(27-33) to obtain tailings sand.

[0044] The fiber is one or more of high-strength steel fiber and high-strength polyoxymethylene fiber, used to improve the toughness of materials. Because polyoxymethylene fiber has metal-like strength and high elongation, and its mass is significantly lower than that of steel fiber at the same volume content, it can be used as a substitute for high-strength steel fiber.

[0045] The fiber pretreatment method is ultrasonic atomization. Specifically, the required saturated silica gel and fiber are weighed according to the ratio, and ultrasonic atomization is used to uniformly disperse the saturated colloidal silica onto the fiber surface, thereby forming uniform anchoring points on the fiber surface, improving the surface roughness of the fiber, and thus improving the adhesion between the fiber and the matrix, resulting in silica pretreated fiber.

[0046] Example 1

[0047] This embodiment provides an eco-friendly ultra-high performance concrete material, per 1m 3 Including the following raw materials:

[0048] Cementitious material system: 560 kg cement, 112 kg fly ash, 448 kg super-activated tailings powder;

[0049] Aggregate system: Quartz sand is supplied in 112 kg, 280 kg, and 168 kg per cubic meter of 0.18-0.42 mm, 0.42-0.84 mm, and 0.84-2 mm particle sizes; tailings sand is supplied in 112 kg, 280 kg, and 168 kg per cubic meter of 0.18-0.42 mm, 0.42-0.84 mm, and 0.84-2 mm particle sizes.

[0050] The volumetric admixture of the following materials in eco-friendly ultra-high performance concrete is 1.5%, consisting of 201.6 kg of mixing water, 28 kg of water-reducing agent, and 118 kg of silica pretreated fiber.

[0051] In this embodiment, the specific preparation steps of the super-activated tailings powder are as follows:

[0052] a. Metal tailings (water-quenched manganese slag) are ground using a cement ball mill for 45 minutes to obtain finely ground tailings powder. The residue on a 45μm square hole sieve is 3.4%, and the average particle size range is 5-10μm. 100 parts by weight of the finely ground tailings powder are mixed with 25 parts by weight of ultrafine active powder (i.e., nano-calcium carbonate, particle size 50-100nm) using a high-speed airflow to uniformly coat the surface of the finely ground tailings powder, thus obtaining preliminarily activated tailings powder.

[0053] b. Mix and grind the pre-activated tailings powder obtained in step a with 10 parts by mass of nano-magnesium oxide and 10 parts by mass of nano-calcium oxide for 30 minutes to produce a mechanical-chemical activation effect, so that the nano-oxide powder complexes with the tailings powder or anchors on the surface of the tailings powder to obtain super-activated tailings powder with a particle size of 10-40μm.

[0054] In this embodiment, the tailings sand is made by screening out manganese tailings with a particle size greater than 4.75mm, crushing and shaping it with a sand and gravel shaping machine, and then performing surface strengthening and gradation screening. According to the particle size, it is divided into three gradations: 0.18-0.42mm, 0.42-0.84mm and 0.84-2mm.

[0055] The silica pretreated fiber is obtained by uniformly dispersing saturated colloidal silica onto the surface of steel fiber using ultrasonic atomization, with a volume ratio of saturated colloidal silica to steel fiber of 1:25.

[0056] The preparation method of eco-friendly ultra-high performance concrete material is as follows:

[0057] The above-mentioned weights of cement, fly ash, super-activated tailings powder, quartz sand, and tailings sand are dry-mixed in a mixer for 1 minute. Then, mixing water and water-reducing agent are added and mixed for 5-7 minutes to form a uniform slurry. Finally, silica pretreated fibers are added and mixed for 30-60 seconds to obtain eco-friendly ultra-high performance concrete.

[0058] Example 2

[0059] This embodiment provides an eco-friendly ultra-high performance concrete material, per 1m 3 Including the following raw materials:

[0060] Cementitious material system: 560 kg cement, 112 kg fly ash, 448 kg super-activated tailings powder;

[0061] Aggregate system: Quartz sand is supplied in 112 kg, 280 kg, and 168 kg per cubic meter of 0.18-0.42 mm, 0.42-0.84 mm, and 0.84-2 mm particle sizes; tailings sand is supplied in 112 kg, 280 kg, and 168 kg per cubic meter of 0.18-0.42 mm, 0.42-0.84 mm, and 0.84-2 mm particle sizes.

[0062] The volumetric dosage of 201.6 kg of mixing water, 28 kg of water-reducing agent, and 118 kg of silica pretreated fiber in the eco-friendly ultra-high performance concrete material is 1.5%.

[0063] In this embodiment, the specific preparation steps of the super-activated tailings powder are as follows:

[0064] a. Metal tailings (manganese tailings and copper tailings mixed at a mass ratio of 6:4) are ground using a cement ball mill for 60 minutes to obtain finely ground tailings powder. The residue on a 45μm square hole sieve is 4.1%, and the average particle size range is 5-10μm. 100 parts by mass of the finely ground tailings powder are mixed with 30 parts by mass of ultrafine active powder (i.e., silica fume, particle size 50-100nm) using a high-speed airflow to uniformly coat the surface of the finely ground tailings powder, thus obtaining preliminarily activated tailings powder.

[0065] b. Mix and grind the pre-activated tailings powder obtained in step a with 10 parts by mass of nano-magnesium oxide and 10 parts by mass of nano-calcium oxide for 30 minutes to produce a mechanical-chemical activation effect, so that the nano-oxide powder complexes with the tailings powder or anchors on the surface of the tailings powder to obtain super-activated tailings powder with a particle size of 10-40μm.

[0066] In this embodiment, the tailings sand is made by screening out manganese tailings with a particle size greater than 4.75mm, crushing and shaping it with a sand and gravel shaping machine, and then performing surface strengthening and gradation screening. According to the particle size, it is divided into three gradations: 0.18-0.42mm, 0.42-0.84mm and 0.84-2mm.

[0067] The silica pretreated fiber is obtained by uniformly dispersing saturated colloidal silica onto the surface of steel fiber using ultrasonic atomization, with a volume ratio of saturated colloidal silica to steel fiber of 1:25.

[0068] The preparation method of eco-friendly ultra-high performance concrete material is as follows:

[0069] The above-mentioned weights of cement, fly ash, super-activated tailings powder, quartz sand, and tailings sand are dry-mixed in a mixer for 1 minute. Then, mixing water and water-reducing agent are added and mixed for 5-7 minutes to form a uniform slurry. Finally, silica pretreated fibers are added and mixed for 30-60 seconds to obtain eco-friendly ultra-high performance concrete.

[0070] Example 3

[0071] This embodiment provides an eco-friendly ultra-high performance concrete material, per 1m 3 Including the following raw materials:

[0072] Cementitious material system: 560 kg cement, 112 kg fly ash, 448 kg super-activated tailings powder;

[0073] Aggregate system: Quartz sand is supplied in 112 kg, 280 kg, and 168 kg per cubic meter of 0.18-0.42 mm, 0.42-0.84 mm, and 0.84-2 mm particle sizes; tailings sand is supplied in 112 kg, 280 kg, and 168 kg per cubic meter of 0.18-0.42 mm, 0.42-0.84 mm, and 0.84-2 mm particle sizes.

[0074] The volumetric dosage of 201.6 kg of mixing water, 28 kg of water-reducing agent, and 118 kg of silica pretreated fiber in the eco-friendly ultra-high performance concrete material is 1.5%.

[0075] In this embodiment, the specific preparation steps of the super-activated tailings powder are as follows:

[0076] a. Metal tailings (water-quenched manganese slag, manganese tailings, and copper tailings mixed in a mass ratio of 4:4:2) are ground using a cement ball mill for 50 minutes each time to obtain finely ground tailings powder. The residue on a 45μm square hole sieve is 3.8%, and the average particle size range is 5-10μm. 100 parts by mass of the finely ground tailings powder are mixed with 30 parts by mass of ultrafine active powder (i.e., 25 parts by mass of silica fume + 5 parts by mass of nano-calcium carbonate, particle size 50-100nm) using a high-speed airflow to uniformly coat the surface of the finely ground tailings powder, thus obtaining preliminarily activated tailings powder.

[0077] b. Mix and grind the pre-activated tailings powder obtained in step a with 10 parts by mass of nano-magnesium oxide and 10 parts by mass of nano-calcium oxide for 30 minutes to produce a mechanical-chemical activation effect, so that the nano-oxide powder complexes with the tailings powder or anchors on the surface of the tailings powder to obtain super-activated tailings powder with a particle size of 10-40μm.

[0078] In this embodiment, the tailings sand is made by screening out manganese tailings with a particle size greater than 4.75mm, crushing and shaping it with a sand and gravel shaping machine, and then performing surface strengthening and gradation screening. According to the particle size, it is divided into three gradations: 0.18-0.42mm, 0.42-0.84mm and 0.84-2mm.

[0079] The silica pretreated fiber is obtained by uniformly dispersing saturated colloidal silica onto the surface of steel fiber using ultrasonic atomization, with a volume ratio of saturated colloidal silica to steel fiber of 1:25.

[0080] The preparation method of eco-friendly ultra-high performance concrete material is as follows:

[0081] The above-mentioned weights of cement, fly ash, super-activated tailings powder, quartz sand, and tailings sand are dry-mixed in a mixer for 1 minute. Then, mixing water and water-reducing agent are added and mixed for 5-7 minutes to form a uniform slurry. Finally, silica pretreated fibers are added and mixed for 30-60 seconds to obtain eco-friendly ultra-high performance concrete.

[0082] Comparative Example 1

[0083] This comparative example provides an ultra-high performance concrete material, per 1m 3 Including the following raw materials:

[0084] Cementitious material system: 728 kg cement, 112 kg fly ash, 280 kg silica fume;

[0085] Aggregate system: Quartz sand with three particle sizes of 0.18-0.42mm, 0.42-0.84mm, and 0.84-2mm weighs 224kg, 560kg, and 336kg respectively;

[0086] 201.6 kg of mixing water; 28 kg of water-reducing agent; 157 kg of silica pretreated fiber, with a volumetric admixture of 2% in the eco-friendly ultra-high performance concrete material.

[0087] The method for pretreating silica fibers is the same as in Example 1.

[0088] The preparation method of ultra-high performance concrete material is as follows:

[0089] The above-mentioned weights of cement, fly ash, silica fume, and quartz sand are dry-mixed in a mixer for 1 minute. Then, mixing water and water-reducing agent are added and mixed for 5-7 minutes to form a uniform slurry. Finally, silica pretreated fibers are added and mixed for 30-60 seconds to obtain eco-friendly ultra-high performance concrete.

[0090] In Examples 1 to 3 above, the mass ratio of the metal tailings powder for ultra-activated tailings powder (total mass of tailings is 100) is shown in Table 1 below.

[0091] Table 1. Grinding ratio of metal tailings (total tailings are 100).

[0092]

[0093] In Examples 1-3 above, the mass ratio of finely ground tailings powder to ultrafine active powder and nano-oxidation powder (the total mass of finely ground tailings powder is calculated as 100) is shown in Table 2 below.

[0094] Table 2 Activation mix ratio of metal tailings (total amount of ground tailings powder is 100)

[0095]

[0096] The amounts of cementitious material system, mixing water water-reducing agent, and silica pretreated fiber used in Examples 1-3 and Comparative Example 1 are shown in Table 3 below, and the amounts of quartz sand and tailings sand used are shown in Table 4 below.

[0097] Table 3. Mix proportions for eco-friendly ultra-high performance concrete materials (kg / m³) 3 )

[0098]

[0099] Table 4. Mix proportions for eco-friendly ultra-high performance concrete materials (kg / m³) 3 )

[0100]

[0101] Performance testing

[0102] The performance of the eco-friendly ultra-high performance concrete prepared in Examples 1-3 and the product prepared in the comparative example were tested, and the results are shown in Table 5 below.

[0103] Table 5 Performance data of the examples and comparative examples

[0104]

[0105] Table 5 shows that the fluidity of the eco-friendly ultra-high performance concrete prepared by replacing cement and silica fume with ultra-activated tailings powder, replacing quartz sand with tailings sand, and using pretreated steel fibers is significantly improved compared to the control group. This is because the amount of steel fibers used is reduced by 25%. Although the amount of steel fibers is significantly reduced, the mechanical properties of the material do not show a significant decrease, with a decrease of less than 5%. However, the compressive strength is still greater than 130 MPa, and the tensile strength is greater than 9 MPa. The porosity results show that the eco-friendly ultra-high performance concrete has a slight increase compared to the control group, but it is not significant. Its porosity is still at a low level, and it still has a significant effect on solidifying heavy metal ions in the tailings.

Claims

1. An eco-friendly ultra-high performance concrete material, characterized in that: This includes the cementitious material system, aggregate system, mixing water, water-reducing agent, and silica pretreated fibers. The mass ratio of the cementitious material system, aggregate system, mixing water, and water-reducing agent is 1:(0.9-1.2):(0.14-0.2):(0.02-0.05), and the volumetric dosage of the silica pretreated fiber in the eco-friendly ultra-high performance concrete material is 1%-1.5%. The cementitious material system comprises, by mass percentage, 40-60% cement, 5-15% fly ash, and 30-50% ultra-activated tailings powder, wherein the sum of the mass percentages of cement, fly ash, and ultra-activated tailings powder in the cementitious material system is 100%. The ultra-activated tailings powder has a particle size of 10-40 μm and is prepared by a method including the following steps: a. Grind metal tailings to obtain tailings powder. The tailings powder has a fineness of no more than 5% residue on a 45μm square hole sieve and an average particle size range of 5-10μm. The tailings powder is then thoroughly mixed with ultrafine active powder with an average particle size range of 50-100nm under a high-speed airflow to fully coat the tailings powder with the ultrafine active powder, thus obtaining preliminarily activated tailings powder. The metal tailings are one or more of manganese tailings, copper tailings, lead-zinc tailings, molybdenum tailings, tungsten-tin tailings, water-quenched manganese slag, water-quenched copper slag, and water-quenched lead-zinc slag. The ultrafine active powder is one or more of silica fume, nano-silica, and nano-calcium carbonate. The mass ratio of tailings powder to ultrafine active powder is 1:(0.2-0.5). b. The pre-activated tailings powder and nano-oxidation powder are mixed and ground to allow the nano-oxidation powder to complex or anchor on the surface of the tailings powder, thereby obtaining super-activated tailings powder with a particle size of 10-40 μm. The nano-oxidation powder is a mixture of nano-calcium oxide and nano-magnesium oxide, with the mass percentage of nano-calcium oxide in the nano-oxidation powder being 40-60% and the remainder being nano-magnesium oxide. The mass ratio of pre-activated tailings powder to nano-oxidation powder is 1:(0.1-0.3). The aggregate system comprises 40-60% quartz sand and 40-60% tailings sand by mass percentage, wherein the sum of the mass percentages of quartz sand and tailings sand in the aggregate system is 100%. The tailings sand in the aggregate system is obtained after processing tailings slag, which includes one or more tailings slag selected from manganese tailings, copper tailings, lead-zinc tailings, molybdenum tailings, and tungsten-tin tailings. The processing method includes particle shaping, surface strengthening, and gradation separation. The particle shaping process involves first screening out tailings with a particle size greater than 4.75 mm, and then shaping the tailings using a sand and gravel shaping machine. The surface strengthening is achieved by uniformly spraying a surface strengthening agent onto the surface of the tailings slag. The gradation and sorting process involves separating the shaped and strengthened tailings slag into three particle size ranges: 0.18-0.42 mm, 0.42-0.84 mm, and 0.84-2 mm. The tailings slag is then sized and mixed according to the following mass percentages: 14-22%, 45-53%, and 27-33%, respectively. The sum of the mass percentages of the three particle size ranges is 100%, which yields the tailings sand. The silica pretreated fiber is obtained by uniformly dispersing saturated colloidal silica onto the fiber surface using ultrasonic atomization. The volume ratio of saturated colloidal silica to fiber is 1:(20-50). The fiber is one or more of high-strength steel fiber and high-strength polyoxymethylene fiber.

2. The eco-friendly ultra-high performance concrete material as described in claim 1, characterized in that, The quartz sand in the aggregate system is continuously graded, divided into three particle size ranges: 0.18-0.42mm, 0.42-0.84mm, and 0.84-2mm, with mass percentages of 14-22%, 45-53%, and 27-33% respectively. The sum of the mass percentages of the three particle size ranges is 100%.

3. The eco-friendly ultra-high performance concrete material as described in claim 1, characterized in that, The water-reducing agent is a polycarboxylate high-efficiency water-reducing agent with a water reduction rate of more than 30% and a solid content of more than 30%.

4. The eco-friendly ultra-high performance concrete material as described in claim 1, characterized in that, The cement is silicate cement, and the grade can be selected from one of P•Ⅱ42.5, P•O42.5R, P•II52.5, P•II52.5R, and P•O52.5, with an average particle size of 10-40μm; the fly ash has a fineness of not more than 5% residue on a 45μm square hole sieve, and an average particle size of 1-5μm.

5. A method for preparing an eco-friendly ultra-high performance concrete material as described in any one of claims 1 to 4, characterized in that, include: Cement, fly ash, super-activated tailings powder, quartz sand, and tailings sand are dry-mixed in a mixer, then mixing water and water-reducing agent are added to form a uniform slurry. Finally, silica pretreated fibers are added and mixed evenly to produce eco-friendly ultra-high performance concrete.

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