Method for preparing concrete aggregate from ore dressing process waste rock and application of concrete aggregate

Abstract

The invention discloses a method for preparing concrete aggregate from ore dressing process waste rocks and application, and belongs to the technical field of solid waste resource utilization and building materials. The method comprises the following steps: (1) crushing and screening: crushing the waste rocks until the particle size is 5-25mm, and sorting the waste rocks into coarse aggregates (5-20mm) and fine aggregates (0.15-5mm); (2) alkaline cleaning is conducted, specifically, a NaOH solution with the pH being 10-12 is adopted for cleaning, and surface sulfide and floating dust are removed; (3) passivating treatment: soaking in a 3-8% sodium phosphate or sodium silicate solution for more than or equal to 20 minutes; and (4) grading optimization: mixing according to the ratio of coarse to fine being (6: 4)-(7: 3), and adding 5-10% of fly ash or natural sand to regulate grading. 90% of waste rock is efficiently utilized, the cost is reduced by 30% compared with that of natural aggregate, the 28-day compressive strength of the obtained concrete is larger than or equal to 35 MPa, the heavy metal content meets the GB 6566-2010 standard, and the concrete is suitable for non-structural engineering with the strength grade of C15-C30. And through the industrial adaptive design, the annual waste rock treatment amount reaches 300,000-600,000 tons, and the method has both environmental protection and economic benefits.

Description

Technical Field

[0001] The present invention belongs to the field of solid waste resource utilization and building materials technology, and specifically relates to a method and application of producing concrete aggregate from mineral processing waste rock, which is particularly suitable for solving environmental problems caused by the accumulation of mineral processing waste rock and the shortage of natural sand and gravel resources. Background Art

[0002] Low-grade waste rock (such as iron ore and copper tailings) generated during the mineral processing process is unable to be economically utilized and is accumulated on a massive scale. The annual stockpile in key domestic mining areas exceeds 200 million tons, with each 10,000 tons of waste rock occupying approximately 1.5 mu (approximately 1.5 acres) of land, resulting in a continuous encroachment on land resources. For example, the Jiugang plant area has a waste rock mountain stockpile of 8 million tons. This not only depletes land resources but also causes soil acidification and groundwater contamination due to the sulfides and heavy metals (lead, cadmium, and arsenic) contained in the waste rock through rainwater leaching. Lead levels in surrounding soils exceed the standard by 12 times, necessitating high environmental remediation costs. Furthermore, the traditional concrete industry's long-standing reliance on natural sand and gravel as aggregate has led to increasingly serious problems such as overexploitation of resources, ecological damage, and escalating costs.

[0003] While existing technologies have attempted to convert waste rock into aggregate, they generally face three major technical bottlenecks: First, the complex composition of waste rock means its direct use may lead to excessive heavy metal leaching or radioactivity risks; second, the physical properties of waste rock (such as compressive strength and water absorption) differ from those of natural aggregate, making it difficult to meet the mechanical requirements of concrete; and third, improper grading leads to poor concrete performance, which in turn affects concrete workability and strength. This leads to unstable production and quality in industrial applications, such as an unbalanced ratio between manufactured sand and manufactured rock. These issues collectively restrict the large-scale resource utilization of mineral processing waste rock in the building materials industry. There is an urgent need to develop a systematic treatment method that simultaneously addresses environmental safety, material performance, and industrial compatibility. Summary of the Invention

[0004] The purpose of the present invention is to provide an efficient treatment method for mineral processing waste rock, which solves its complex composition, high environmental risks, poor physical properties, and grading and output problems in industrial applications, so that it can meet the mechanical properties, environmental protection and durability requirements of concrete aggregate.

[0005] The technical solution of the present invention is: The method for producing concrete aggregate from waste rock from mineral processing of the present invention comprises the following steps: (1) Crushing and screening: crush the waste rock to 5-25 mm and sort it into coarse aggregate (5-20 mm) and fine aggregate (0.15-5 mm); (2) Alkaline cleaning: Use alkaline solution (pH 10-12) to soak and remove surface sulfides and floating dust; (3) Passivation treatment: Soak in 3%-8% phosphate or silicate solution for ≥20 minutes to reduce the heavy metal leaching rate to below the limit of GB 5085.3-2007.

[0006] (4) Gradation optimization: Mix coarse and fine waste rock aggregates according to the mass ratio (coarse:fine = 6:4 to 7:3); add 5%-10% natural sand or fly ash to adjust the gradation to ensure compliance with GB / T 14684-2022 and GB / T 14685-2022 standards.

[0007] Preparation of concrete of the present invention: Proportion (by weight): aggregate 60%-70%, cement 20%-30%, admixture (water reducer or retarder) 1%-3%, water-binder ratio 0.4-0.5; Application scope: Suitable for concrete with strength grade C15-C30, and can be used preferentially in non-structural parts such as floors and roads.

[0008] Beneficial effects of the present invention (1) Environmental benefits: Solving the dual problems of solid waste accumulation and pollution By recycling waste rock (utilization rate reaches 90%), the storage area is significantly reduced.

[0009] The two-stage treatment process of "alkaline cleaning + chemical passivation" reduces the leaching rate of heavy metals (Pb, Cd, As, etc.) to below the limit of "GB5085.3-2007", blocking soil / groundwater pollution caused by rainwater leaching at the source.

[0010] (2) Economic Benefits: The waste rock utilization rate reaches 90%, and the cost is 30% lower than that of natural aggregate. This forms a circular economy industry chain of "waste rock treatment-aggregate production-concrete application", creating a new profit growth point.

[0011] (3) Technical performance: taking into account both mechanical indicators and engineering applicability The 28-day compressive strength of concrete prepared with optimized grading aggregate is ≥35MPa, which fully meets the C15-C30 strength grade requirements and is suitable for non-structural projects such as floors and roads.

[0012] (4) Industrial feasibility: Achieve large-scale production through third-party cooperation model, with an annual waste rock processing capacity of 300,000 to 600,000 tons.

[0013] The aggregate grading complies with "GB / T 14684-2022" and "GB / T 14685-2022", and the concrete environmental protection indicators meet "GB6566-2010", eliminating market access barriers. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a waste rock treatment flow chart; Figure 2This is a schematic diagram of the production line process layout. DETAILED DESCRIPTION

[0015] Example 1 (1) Take the iron ore waste rock, crush it to 5-20 mm, and screen it into coarse (5-25 mm) and fine (0.15-5 mm) aggregates; (2) After cleaning with NaOH solution (pH = 11), soak in 5% sodium phosphate solution for 30 minutes; (3) Mix the coarse and fine materials in a mass ratio of 7:3 and add 8% fly ash to adjust the gradation; (4) Preparation of concrete: waste rock aggregate 65%, cement 25%, water reducer 2%, water-binder ratio 0.45; (5) Test results: 28-day compressive strength 38 MPa, heavy metal leaching amount is lower than the limit of GB 5085.3-2007.

[0016] Example 2 (based on actual production data) (1) Ratio scheme (see Table 1): C30 concrete: aggregate 65% (60% machine-made stone + 5% machine-made sand), cement 25%, water-reducing agent 2%, water-binder ratio 0.45; C20 concrete: aggregate 70% (65% machine-made stone + 5% natural sand), cement 22%, water-reducing agent 1.5%, water-cement ratio 0.5; (2) Application effect: When pouring floors and roads, the concrete has stable working performance and reaches the strength standard after 28 days; (Note: The mix ratio data is referenced from the "202405 Waste Rock and Water Washed Sand Mix Ratio Table").

Claims

1. A method for producing concrete aggregate from waste rock from mineral processing, characterized in that: The following steps are involved: (1) Crushing and screening: crush the waste rock to a particle size of 5-25 mm and sort it into 5-20 mm coarse aggregate and 0.15-5 mm fine aggregate; (2) Alkaline cleaning: Use an alkaline solution with a pH of 10-12 to remove surface sulfides and floating dust; (3) Passivation treatment: Soak in 3%-8% phosphate or silicate solution for ≥20 minutes; (4) Gradation optimization: Mix coarse and fine aggregates in a mass ratio of coarse:fine = 6:4-7:3, and add 5%-10% natural sand or fly ash to adjust the gradation.

2. The method according to claim 1, wherein: The alkaline solution in step (2) is a NaOH solution.

3. The method according to claim 1, wherein: The phosphate in step (3) is sodium phosphate or disodium hydrogen phosphate, and the silicate is sodium silicate; after soaking, the heavy metal leaching rate is lower than the limit of GB 5085.3-2007.

4. The method according to claim 1, wherein: The particle gradation of the aggregate after the gradation optimization described in step (4) complies with the standards of GB / T 14684-2022 and GB / T 14685-2022.

5. Use of aggregate produced according to any one of claims 1 to 4 in concrete, characterized in that: The concrete includes the following components in weight percentage: aggregate 60%-70%, cement 20%-30%, admixture 1%-3%, water-binder ratio 0.4-0.5, the obtained concrete has a 28-day compressive strength of ≥35 MPa, and the heavy metal content complies with GB 6566-2010 standard.

6. The use according to claim 5, characterized in that: The admixture is a polycarboxylate water reducer or a lignin sulfonate retarder.

7. The use according to claim 5, characterized in that: The concrete is suitable for non-structural concrete engineering with strength grades of C15-C30.

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