Coarse aggregate for tungsten tailing powder bonding forming concrete and preparation method of coarse aggregate

Abstract

The invention provides coarse aggregate for tungsten tailing powder bonding forming concrete and a preparation method of the coarse aggregate, and belongs to the technical field of industrial solid waste resource utilization. The coarse aggregate is prepared from the following raw materials in percentage by mass: 70-80% of tungsten tailing powder, a composite binder, a skeleton aggregate and an auxiliary additive, the composite binder is compounded with modified starch and sodium polyacrylate on the basis of cement, and the coarse aggregate is prepared through a process of precise batching, static pressure molding and gradient curing. According to the invention, the problems of poor cohesiveness and difficulty in forming when the tungsten tailing powder is directly utilized are solved, the crushing index of the prepared coarse aggregate is less than or equal to 18%, the water absorption rate is less than or equal to 2.8%, the requirements of GB / T14685-2022II type aggregate are met, 5-30% of natural aggregate can be replaced for concrete preparation, and double benefits of large-scale absorption of solid wastes and partial replacement of the natural aggregate are realized.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of building materials and solid waste resource utilization, and particularly relates to a method for preparing coarse aggregate for concrete by using tungsten tailing powder through a bonding forming process. BACKGROUND

[0002] The annual discharge amount of tungsten tailings generated by tungsten ore processing is huge, and long-term stacking not only occupies land resources, but also causes soil and water pollution due to the soluble impurities contained therein. At present, the comprehensive utilization of tungsten tailings is mainly concentrated in the fields of admixture and microcrystalline glass, but there are problems such as low utilization rate and complex process.

[0003] The coarse aggregate for concrete traditionally relies on natural sandstone, and overexploitation leads to ecological destruction, so it is urgent to develop alternative materials. The existing tailing aggregate preparation technology mainly uses a single binder, and has defects such as insufficient strength and high water absorption, and it is difficult to meet the requirements of type II aggregate. Therefore, it is of great practical significance to develop a bonding forming process with high tailing content and high performance. SUMMARY

[0004] Therefore, the application provides a concrete coarse aggregate with high tungsten tailing powder content and excellent mechanical properties and a preparation method thereof, realizing large-scale utilization of solid waste and partial replacement of natural aggregate.

[0005] The technical scheme of the application is implemented as follows:

[0006] (1) Raw material selection

[0007] Tungsten tailing powder: after pretreatment, the particle size and chemical composition meet the standards, and the tungsten tailing powder serves as a core aggregate substrate;

[0008] Composite binder: cement provides basic strength, modified starch enhances interface bonding, and sodium polyacrylate improves the workability of the slurry and reduces the water absorption rate;

[0009] Framework aggregate: waste granite particles form a support structure to reduce the shrinkage of the formed product;

[0010] Auxiliary additive: water reducing agent optimizes fluidity, and adjusting agent controls setting time.

[0011] (2) Preparation process innovation points

[0012] The two-step mixing method of "dry mixing and pre-mixing + wet mixing and homogenization" is adopted to solve the problem of easy agglomeration of the tailing powder; static pressure forming controls the green density to lay a foundation for strength development; gradient steam curing avoids temperature stress cracking and promotes the full hydration of the binder.

[0013] (3) Beneficial effects

[0014] Environmental benefits: tungsten tailings powder content up to 70%, annual consumption of 50-100 tons per production line, reducing solid waste pollution;

[0015] Performance advantage: crushing index ≤18%, water absorption ≤2.8%, better than existing tailings aggregate;

[0016] The aggregate prepared by the process can replace 5-30% of natural aggregate for concrete preparation. DETAILED DESCRIPTION Specific embodiment one:

[0018] (1) Raw material ratio (mass %): tungsten tailings powder 75%, P·O42.5 cement 12%, modified starch 3%, polyacrylic acid sodium 0.8%, waste granite particles 8%, polycarboxylic acid water reducer 0.4%, gypsum powder 0.8%;

[0019] (2) Preparation process: after drying and screening the tailings powder, dry mixing for 2.5 min, wet mixing for 4 min, 18 MPa static pressure forming, gradient steam curing and airing for 4 days;

[0020] (3) Performance test: crushing index 15.2%, water absorption 2.5%, cylinder pressure strength 12.3 MPa, meeting the requirements of class II aggregate. Specific embodiment two:

[0022] (1) Raw material ratio (mass %): tungsten tailings powder 80%, P·O42.5 cement 10%, modified starch 2%, polyacrylic acid sodium 0.8%, waste granite particles 6.6%, polycarboxylic acid water reducer 0.3%, gypsum powder 0.3%;

[0023] (2) Preparation process: after drying and screening the tailings powder, dry mixing for 2.5 min, wet mixing for 4 min, 18 MPa static pressure forming, gradient steam curing and airing for 4 days;

[0024] (3) Performance test: crushing index 17.0%, water absorption 2.7%, cylinder pressure strength 11.8 MPa, meeting the requirements of class II aggregate. Specific embodiment three:

[0026] (1) Raw material ratio (mass %): tungsten tailings powder 70%, P·O42.5 cement 15%, modified starch 3%, polyacrylic acid sodium 1.0%, waste granite particles 10%, polycarboxylic acid water reducer 0.5%, gypsum powder 0.5%;

[0027] (2) Preparation process: after drying and screening the tailings powder, dry mixing for 2.5 min, wet mixing for 4 min, 18 MPa static pressure forming, gradient steam curing and airing for 4 days;

[0028] (3) Performance test: crushing index 13.0%, water absorption 2.7%, cylinder compressive strength 12.8 MPa, meeting the requirements of Class II aggregate.

[0029] In addition, concrete tests are carried out on three embodiments and a comparative sample, and in the concrete mix proportion test, the amount of artificial aggregate replacing gravel is 30%:

[0030] After the concrete mix proportion test, the test results are as follows:

[0031] Table 1 Concrete mix proportion (unit: kg / m 3 )

[0032]

[0033] Table 2 Concrete performance test results of comparative sample and embodiments (30% dosage)

[0034]

[0035]

[0036] According to the test results, when the tungsten tailings powder bonded aggregate for concrete is applied to concrete, the physical and mechanical properties of the prepared concrete can meet the requirements, and the performance is better than that of the comparative sample, so it can directly replace part (5-30%) of natural aggregate for concrete production.

[0037] In summary, in the technical scheme of the present application, since the tungsten tailings powder bonded aggregate for concrete uses tailings as raw material, not only the cost can be reduced, but also the natural environment can be improved, meeting the environmental protection requirements of low carbon and carbon reduction, promoting the sustainable development of mine resources, and having important significance for environmental protection.

[0038] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A coarse aggregate for tungsten tailings powder-bonded formed concrete, characterized by, By mass percentage consists of: tungsten tailings powder 70-80%, composite binder 11.5-19%, skeleton aggregate 5-10%, water reducing agent 0.2-0.5%, adjusting agent 0.3-0.8%; the composite binder includes 10-15% P·O42.5 ordinary Portland cement, 1-3% modified starch and 0.5-1% sodium polyacrylate; the adjusting agent is calcium sulfate dehydrate.

2. The coarse aggregate according to claim 1, characterized in that, The tungsten tailings powder after pretreatment contains ≤3% water, particle size ≤0.15mm, chemical composition meets SiO240-65%, Al2O310-20%, Fe2O3≤8%, and radioactivity meets the requirements of GB6566-2010.

3. The coarse aggregate of claim 1, wherein, The skeleton aggregate is waste granite particles with particle size 5-10mm, and crushing index ≤15%; the water reducing agent is polycarboxylic acid high efficiency water reducing agent.

4. A method of producing the coarse aggregate as claimed in any one of claims 1 to 3, characterized in that, The method comprises the following steps: (1) raw material pretreatment: tungsten tailings powder is dried to ≤3% water content, and impurities with particle size >0.15mm are removed by screening; (2) batching and mixing: tungsten tailings powder, cement, skeleton aggregate and adjusting agent are dry mixed in proportion for 2-3min, then dissolved modified starch, sodium polyacrylate and water reducing agent are added, and water is mixed for 3-5min until the slump is 15-20mm; (3) Static pressure molding: The slurry is injected into a mold, and a pressure of 15-20 MPa is applied for 30-60 s, and the green density is controlled at 2.2-2.4 g / cm 3 ; (4) gradient curing: after the green body is placed at room temperature for 24h, it is cured by steam through the processes of temperature rising (10-15℃ / h to 60-70℃), constant temperature (12-16h, humidity ≥90%), temperature falling (≤10℃ / h), and then is naturally dried for 3-5 days; (5) screening and grading: the vibration screen removes defective products, and the products are graded according to 5-10mm, 10-16mm and 16-25mm.

5. The preparation method according to claim 4, characterized in that, In step (2), the batching error is ≤±0.5%, and in step (4), the temperature and humidity parameters are monitored in real time during the whole curing process.

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