Ultra-high performance concrete for resource utilization of pyrite tailings and preparation method of ultra-high performance concrete

Abstract

The invention relates to ultra-high performance concrete for resource utilization of pyrite tailings and a preparation method thereof, and the method comprises the following steps: carrying out a series of treatment processes such as drying desulfurization, alkaline etching and calcium salt complexation on pyrite tailings, mechanically sieving, screening the pyrite tailings after desulfurization according to a range of 25-85 meshes, and preparing the ultra-high performance concrete for resource utilization of pyrite tailings. And finally, mixing according to a set ratio, so as to obtain the ultra-high performance concrete. By combining a series of treatment processes such as drying desulfurization, alkaline etching and calcium salt complexation, free sulfate ions in the pyrite tailings are effectively eliminated, sulfides such as SO2 and SO3 are neutralized, then the physical and chemical compatibility of the pyrite tailings in the alkaline UHPC product is improved, it is ensured that doping of the pyrite tailings does not bring negative influence on the UHPC product, and the UHPC product quality is improved. Therefore, the UHPC product which is excellent in performance, low in carbon and environmentally friendly can be prepared, and the problem of resource utilization of building material products of pyrite tailings can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of building material production, in particular to an ultra-high performance concrete for resource utilization of pyrite tailings and a preparation method thereof. Background Art

[0002] Pyrite tailings are industrial solid wastes discharged after separating and enriching useful components from crushed and ground iron ores during mineral processing. Due to the lack of effective resource utilization means, a large amount of pyrite tailings are stockpiled, seriously occupying land. More importantly, the environmental hazards brought by sulfide ore tailings are particularly prominent. When exposed to the air, the sulfur element contained in them is easily oxidized to form acidic gases such as SO2 and SO3, which are prone to form acid rain. This not only reduces the pH value of the soil, leading to soil infertility, but also corrodes buildings, instruments, etc., reducing the strength of equipment. And the heavy metal ions in the tailings form acidic mine wastewater under the leaching action of acid rain, polluting the surrounding water sources and destroying the ecological balance. Some beneficiation reagents remaining in the tailings, such as xanthate, black powder, cyanide, etc., are toxic to a certain extent and will directly endanger human health.

[0003] Building materials products have the potential to resourcefully utilize a large amount of industrial solid wastes. However, due to the beneficiation process, the particle size of pyrite tailings is relatively fine, making it difficult to replace fine aggregates such as natural sand and manufactured sand to prepare cement concrete products. Moreover, directly incorporating pyrite tailings into building materials products, their relatively high sulfur content will not only cause retardation of cement products and sulfate erosion, but also the slow release of sulfides such as SO2 and SO3 in the cement concrete products will generate a large number of pores, affecting the structural integrity of the materials, which greatly limits the resource utilization of pyrite tailings in cement concrete products.

[0004] Ultra-high performance concrete (UHPC) is a new type of concrete material with high strength, high toughness and high durability, and has now been widely used in infrastructure construction projects such as bridges and wind power tower barrels. Its excellent performance is mainly attributed to the low water-binder ratio, the close packing effect between cementitious material particles, and the incorporation of steel fibers. And during the preparation of UHPC, quartz sand with a relatively fine particle size is often required. If the particle size of pyrite tailings is further screened and subdivided, it just matches the particle size distribution of these building materials raw materials. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: to provide a super high performance concrete for resource utilization of pyrite tailings and its preparation method. By combining a series of treatment processes such as drying desulfurization, alkaline etching, and calcium salt complexation, the free sulfate ions in the pyrite tailings can be effectively eliminated, and sulfides such as SO2 and SO3 can be neutralized, thereby improving the physical and chemical compatibility of the pyrite tailings in alkaline UHPC products, ensuring that the incorporation of pyrite tailings does not have a negative impact on UHPC products. Therefore, not only can UHPC products with excellent performance and low carbon environmental protection be prepared, but also it can help solve the problem of resource utilization of building materials products made from pyrite tailings.

[0006] The technical solution adopted by the present invention to solve its technical problem is: a super high performance concrete for resource utilization of pyrite tailings, which is prepared by mixing according to the ratio of 800 - 1000 kg / m 3 of cement, 850 - 920 kg / m 3 of pyrite tailings sand, 140 - 170 kg / m 3 of silica fume, 100 - 240 kg / m 3 of S95 slag or secondary fly ash, 190 - 250 kg / m 3 of steel fiber, 8 - 13 kg / m 3 of polycarboxylate superplasticizer, and 200 - 240 kg / m 3 of water.

[0007] Furthermore, the slump flow of the concrete prepared by the present invention is: 800 - 1200 mm, cured at normal temperature for 28 d; the compressive strength is: 120 - 150 MPa, and the flexural strength is: 26 - 32 MPa.

[0008] Meanwhile, the present invention also provides a preparation method of a super high performance concrete for resource utilization of pyrite tailings, including the following steps,

[0009] S1. The pyrite tailings sand is placed in a blast drying equipment for drying desulfurization;

[0010] S2. The alkaline salts are mixed with the pyrite tailings sand according to a mass percentage of 2 - 5% and then co - milled to complete alkaline etching;

[0011] S3. The calcium - containing salts are mixed with the pyrite tailings sand according to a mass percentage of 1% - 2% and then co - milled to further consume the sulfur - containing ions in the pyrite tailings sand through a complexation sedimentation reaction;

[0012] S4. Through mechanical sieving, the sulfur - removed pyrite tailings sand is screened in the range of 25 - 85 mesh to obtain the sulfur - removed and sieved pyrite tailings sand;

[0013] S5. According to 800 - 1000 kg / m 3, 850 - 920 kg / m of pyrite tailings sand 3 , 140 - 170 kg / m of silica fume 3 , 100 - 240 kg / m of S95 slag or class II fly ash 3 , 190 - 250 kg / m of steel fiber 3 , 8 - 13 kg / m of polycarboxylate superplasticizer solid 3 , 200 - 240 kg / m of water 3 Mix in the above proportions to obtain ultra-high performance concrete.

[0014] Furthermore, in step S1 of the present invention, the drying temperature is set at 40 - 80 °C and the drying time is 3 - 6 h.

[0015] Furthermore, in step S2 of the present invention, the alkaline salts are at least one of sodium carbonate, sodium silicate or sodium hydroxide.

[0016] Furthermore, in step S2 of the present invention, the ball milling frequency is set at 10 - 30 r / min, the ball-to-material ratio is set at 1:1, and the ball milling time is 10 - 30 min.

[0017] Furthermore, in step S3 of the present invention, the calcium-containing salts are at least one of calcium hydroxide, calcium oxide or calcium chloride.

[0018] Furthermore, in step S5 of the present invention, the slump flow of the concrete is 800 - 1200 mm, the normal temperature curing is 28 d; the compressive strength is 120 - 150 MPa, and the flexural strength is 26 - 32 MPa.

[0019] The beneficial effect of the present invention is to solve the defects existing in the background technology.

[0020] 1. Through a series of sulfur removal processes for pyrite tailings sand such as drying desulfurization - alkaline etching - calcium salt complexation, sulfides existing in the form of SO2, SO3 sulfides or sulfates in the tailings sand are eliminated, ensuring that the incorporation of the tailings sand will not affect the hydration of cement in UHPC or cause sulfate erosion, and improving the chemical compatibility of the tailings sand in UHPC products; pyrite tailings sand with sulfides and sulfates (calculated by the mass of SO3) ≤ 0.5% can be obtained, which meets the requirements of GB / T 14684 for the harmful substance content of construction sand.

[0021] 2. Screen the pyrite tailings sand based on the principle of close packing. By adjusting the mesh number of the tailings sand, meet the usage requirements of UHPC products for pyrite tailings sand, improve the physical compatibility of the tailings sand in UHPC products, and then replace quartz sand to prepare UHPC products with excellent performance; use the desulfurized and sieved pyrite tailings sand to prepare UHPC. Each cubic meter of UHPC can consume 850 - 920 kg of pyrite tailings sand, which can become an effective way to utilize pyrite tailings sand in a high-value way. At the same time, the prepared UHPC meets the strength grade requirements of UC120 specified in GB / T31387. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a flow chart of the preparation method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] Now, the present invention will be further described in detail with reference to the accompanying drawings and preferred embodiments. These drawings are all simplified schematic diagrams, only illustrating the basic structure of the present invention in a schematic way, so they only show the components related to the present invention.

[0024] As Figure 1 shown, a preparation method of ultra-high performance concrete for resource utilization of pyrite tailings is as follows:

[0025] 1. Drying and desulfurization, that is, placing the pyrite tailings sand in a blast drying oven for drying, setting the temperature at 40 - 80 °C, and controlling the time at 3 - 6 h appropriately. The purpose is to release the SO2 and SO3 sulfides contained in the tailings sand through thermal action.

[0026] 2. Alkaline etching, that is, mixing sodium carbonate, sodium silicate, sodium hydroxide and other alkaline salts with the pyrite tailings sand according to a mass percentage of 2 - 5%, and then carrying out co - ball milling. The ball milling frequency is set at 10 - 30 r / min, the ball - to - material ratio is set at 1:1, and ball milling is carried out for 10 - 30 min to ensure that the alkaline activator fully contacts the pyrite tailings particles and etches on the surface, initially consuming sulfur - containing ionic groups such as sulfite and sulfate, and at the same time reducing the acidity of the pyrite tailings.

[0027] 3. Calcium salt complexation, that is, mixing calcium hydroxide, calcium oxide, calcium chloride and other calcium - containing salts with the pyrite tailings sand according to a mass percentage of 1% - 2%, and then carrying out co - ball milling. Through the complexation sedimentation reaction, further consume sulfite and sulfate and other sulfur - containing ions in the pyrite tailings sand to ensure the safety of using pyrite tailings.

[0028] 4. Through mechanical sieving, screen the desulfurized pyrite tailings sand in the range of 25 - 85 mesh to obtain the desulfurized and sieved pyrite tailings sand.

[0029] Example 1

[0030] Mix according to the ratio of 800 kg / m³ of P.O42.5 cement 3 ,850 kg / m³ of pyrite tailings sand 3 ,140 kg / m³ of silica fume 3 ,240 kg / m³ of S95 slag 3 ,250 kg / m³ of steel fiber 3 ,8 kg / m³ of polycarboxylate superplasticizer solid 3 ,200 kg / m³ of water 3 to obtain a UHPC material with a slump flow of 800 mm, cured at normal temperature for 28 days, with a compressive strength of 150 MPa and a flexural strength of 26 MPa.

[0031] Example 2

[0032] Mix according to the ratio of 1000 kg / m³ of P.O42.5 cement 3 ,900 kg / m³ of pyrite tailings sand 3 ,150 kg / m³ of silica fume 3 ,240 kg / m³ of class II fly ash 3 ,192 kg / m³ of steel fiber 3 ,13 kg / m³ of polycarboxylate superplasticizer solid 3 ,200 kg / m³ of water 3 to obtain a UHPC material with a slump flow of 820 mm, cured at normal temperature for 28 days, with a compressive strength of 148 MPa and a flexural strength of 32 MPa.

[0033] Example 3

[0034] Mix according to the ratio of 1000 kg / m³ of P.O42.5 cement 3 ,920 kg / m³ of pyrite tailings sand 3 ,170 kg / m³ of silica fume 3 ,240 kg / m³ of S95 slag 3 ,250 kg / m³ of steel fiber 3 ,13 kg / m³ of polycarboxylate superplasticizer solid 3 ,240 kg / m³ of water 3 to obtain a UHPC material with a slump flow of 1200 mm, cured at normal temperature for 28 days, with a compressive strength of 150 MPa and a flexural strength of 32 MPa.

[0035] What is described in the above specification is only the specific embodiments of the present invention. Various examples do not constitute a limitation to the essence of the present invention. Those of ordinary skill in the art can make modifications or variations to the previously described specific embodiments after reading the specification without departing from the essence and scope of the invention.

Claims

1. Ultra-high performance concrete for resource utilization of pyrite tailings, characterized in that: According to the proportion of 800 - 1000 kg / m of cement 3 , 850 - 920 kg / m of pyrite tailings sand 3 , 140 - 170 kg / m of silica fume 3 , 100 - 240 kg / m of S95 slag or class II fly ash 3 , 190 - 250 kg / m of steel fiber 3 , 8 - 13 kg / m of polycarboxylate superplasticizer (solid form) 3 , 200 - 240 kg / m of water 3 and mixed and prepared.

2. The ultra-high performance concrete for resource utilization of pyrite tailings according to claim 1, characterized in that: The slump flow of the prepared concrete: 800 - 1200 mm, cured at normal temperature for 28 days; compressive strength: 120 - 150 MPa, flexural strength: 26 - 32 MPa.

3. A method for preparing ultra-high performance concrete for resource utilization of pyrite tailings as described in claim 1, characterized in that: It includes the following steps. S1. The pyrite tailing sand is placed in a blast drying device for drying and desulfurization. S2. The alkaline salts are mixed with the pyrite tailing sand according to a mass percentage of 2 - 5% and then co - ball - milled to complete alkaline etching. S3. The calcium - containing salts are mixed with the pyrite tailing sand according to a mass percentage of 1% - 2% and then co - ball - milled to further consume the sulfur - containing ions in the pyrite tailing sand through a complexation sedimentation reaction. S4. Through mechanical sieving, the desulfurized pyrite tailing sand is screened in the range of 25 - 85 mesh to obtain the desulfurized and sieved pyrite tailing sand. S5. Mix according to the ratio of 800 - 1000 kg / m of P.O42.5 cement 3 , 850 - 920 kg / m of pyrite tailings sand 3 , 140 - 170 kg / m of silica fume 3 , 100 - 240 kg / m of S95 slag or class II fly ash 3 , 190 - 250 kg / m of steel fiber 3 , 8 - 13 kg / m of polycarboxylate superplasticizer solid 3 , 200 - 240 kg / m of water 3 to obtain ultra-high performance concrete.

4. The preparation method of a super high performance concrete for resource utilization of pyrite tailings according to claim 3, characterized in that: In the step S1, the drying temperature is set at 40 - 80 °C, and the drying time is 3 - 6 h.

5. The preparation method of an ultra-high performance concrete for resource utilization of pyrite tailings according to claim 3, characterized in that: In the step S2, the alkaline salts are at least one of sodium carbonate, sodium silicate or sodium hydroxide.

6. The preparation method of a super high-performance concrete for resource utilization of pyrite tailings according to claim 3, characterized in that: In the step S2, the ball - milling frequency is set at 10 - 30 r / min, the ball - to - material ratio is set at 1:1, and the ball - milling time is 10 - 30 min.

7. The preparation method of a super high performance concrete for resource utilization of pyrite tailings according to claim 3, characterized in that: In the step S3, the calcium - containing salts are at least one of calcium hydroxide, calcium oxide or calcium chloride.

8. The preparation method of an ultra-high performance concrete for resource utilization of pyrite tailings as claimed in claim 3, wherein: In the step S5, the slump flow of the concrete: 800 - 1200 mm, cured at normal temperature for 28 days; compressive strength: 120 - 150 MPa, flexural strength: 26 - 32 MPa.

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