Mine fine tailing-based non-fired light aggregate and preparation method thereof

Abstract

The present application relates to a kind of mine fine tailings base baking-free light aggregate and its preparation method, the mine fine tailings base baking-free light aggregate includes the component as follows by mass fraction: mine fine tailings 50-450 parts, light sand 50-100 parts, cement 550-950 parts, additive 0.5-18 parts, water 200-250 parts;Wherein, the additive is sodium bicarbonate and ammonium bicarbonate mixture;The mass ratio of sodium bicarbonate and ammonium bicarbonate is (5-9):(1-5). The preparation method of the mine fine tailings base baking-free light aggregate includes: microwave high fire heating treatment is carried out to mine fine tailings;Light aggregate is covered with preservative film curing, curing in the environment with relative humidity 20%-35%, carbon dioxide curing.The present application can realize the comprehensive utilization of mine fine tailings, the light aggregate prepared has the advantages of light weight, high strength, low water absorption, and has good application prospect.

Description

[0001] This invention patent is a divisional application of invention patent 202211309346.0 filed on October 25, 2022. Technical Field

[0002] This invention relates to the field of building materials technology, and in particular to a non-fired lightweight aggregate based on fine tailings from mining and its preparation method. Background Technology

[0003] Using mine tailings as the main raw material for preparing lightweight aggregates not only solves the environmental pollution and land resource occupation problems caused by the stockpiling of mine tailings, but also broadens the source of raw materials for lightweight aggregate preparation. However, traditional non-fired lightweight aggregates have low strength and high density. Therefore, the selection of additives and the preparation process become the key to preparing lightweight, high-strength lightweight aggregates.

[0004] Existing technologies, such as patent application CN202110549128.3, disclose a method for preparing high-volume fly ash non-fired lightweight aggregate. This method involves mixing fly ash and cement in a specific ratio, then adding water glass to the mixture in a pelletizing machine to form green pellets. After drying the green pellets, they are cured at room temperature with water to form lightweight aggregate microspheres. However, the lightweight aggregate prepared by this invention has a high density, similar to concrete spheres, and does not possess the characteristic of being lightweight. Therefore, current technology is still difficult to meet market demands and has many shortcomings.

[0005] In conclusion, it is necessary to develop a new technical solution to address the problems existing in the current technology and meet the current needs of the industry. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a non-fired lightweight aggregate based on mine tailings. The lightweight aggregate of this invention features a simple preparation method, eliminates the need for sintering, saves energy, enables comprehensive utilization of mine tailings, and possesses advantages such as light weight, high strength, and low water absorption, overcoming the shortcomings and deficiencies of the prior art.

[0007] One object of the present invention is to provide a non-fired lightweight aggregate based on mine tailings, wherein the non-fired lightweight aggregate based on mine tailings comprises the following components in parts by weight:

[0008]

[0009] The additive is a mixture of sodium bicarbonate and ammonium bicarbonate.

[0010] Furthermore, the mass ratio of sodium bicarbonate to ammonium bicarbonate is (5-9):(1-5).

[0011] Furthermore, the fine tailings from the mine contain 50-60% inactive SiO2, 15-20% Al2O3, and 5-8% CaO.

[0012] Furthermore, the non-reactive SiO2 content in the mine tailings is 53.93%, the Al2O3 content is 17.41%, and the CaO content is 6.23%.

[0013] Furthermore, the bulk density of the light sand is 140-150 kg / m³. 3 The particle size is 0.1-0.8 mm.

[0014] Furthermore, the cement is silicate cement with a strength grade of P.II52.5 and a specific surface area of ​​400-500 m². 2 / kg, apparent density is 3000-3200 kg / m³ 3 The bulk density is 1000-1300 kg / m³ 3 .

[0015] Furthermore, the cement is silicate cement with a strength grade of P.II52.5 and a specific surface area of ​​470 m². 2 / kg, apparent density is 3050kg / m³ 3 The bulk density is 1200 kg / m³. 3 .

[0016] Furthermore, the particle size of the lightweight aggregate is 5-20 mm.

[0017] Another object of the present invention is to provide a method for preparing the above-mentioned mine tailings-based non-fired lightweight aggregate, comprising the following steps:

[0018] S1. Grind the fine tailings from the mine and heat them in a microwave oven on medium-high heat for 10-20 minutes to obtain pretreated fine tailings from the mine, A.

[0019] S2. Pour the additive into water and stir well to obtain solution B;

[0020] S3. Mix light sand, part of pretreated mine tailings A, and part of cement evenly to obtain dry material C;

[0021] S4. Mix the remaining pretreated mine tailings A with cement evenly to obtain dry material D;

[0022] S5. Place dry material C in a container, and while rotating the container horizontally, spray some solution B into dry material C to obtain lightweight aggregate core E.

[0023] S6. Add the dry material D into the core E of the lightweight aggregate, continue to rotate the container horizontally, and slowly spray the remaining solution B into the container to obtain lightweight aggregate F.

[0024] S7. Cover the lightweight aggregate F with plastic wrap and cure for 24-36 hours, then place it in an environment with a relative humidity of 20%-35% for 24-36 hours, and finally place it in a carbon dioxide curing chamber for 24-36 hours to obtain the mine fine tailings-based non-fired lightweight aggregate.

[0025] Further, in step S1, the mine tailings are mechanically ground to a particle size of less than 20 μm.

[0026] Furthermore, in step S5, the particle size of the aggregate core E is 3-15 mm.

[0027] Preferably, the method for preparing the mine tailings-based non-fired lightweight aggregate includes the following steps:

[0028] S1. Grind 50-450 parts of mine tailings mechanically until the particle size is less than 20μm, and then heat it in a microwave oven on medium-high heat for 10-20 minutes to obtain pretreated mine tailings A.

[0029] S2. Pour 0.5-18 parts of the additive into 200-250 parts of water and stir until homogeneous to obtain solution B;

[0030] S3. Mix 50-100 parts of light sand, 40-340 parts of pretreated mine tailings A, and 160-460 parts of cement evenly to obtain dry material C.

[0031] S4. Mix the remaining pretreated mine tailings A with 390-490 parts of cement evenly to obtain dry material D;

[0032] S5. Place the dry material C on a disc, and while rotating the disc horizontally, slowly and evenly spray 100-130 parts of solution B into the dry material C to obtain the lightweight aggregate core E.

[0033] S6. Put the dry material D into the disc, continue to rotate the disc horizontally, and at the same time slowly spray the remaining solution B into the disc to obtain lightweight aggregate F.

[0034] S7. Cover the lightweight aggregate F with plastic wrap and cure for 24 hours, then place it in an environment with a relative humidity of 20%-35% for 24 hours, and finally place it in a carbon dioxide curing chamber for 24 hours to obtain the mine fine tailings-based non-fired lightweight aggregate.

[0035] The present invention has the following beneficial effects:

[0036] 1. The lightweight aggregate prepared by this invention has a core-shell structure. Its outer shell is mainly made of cement, which improves the strength of the lightweight aggregate. Its core is mainly made of mine tailings, which solves the problem of mine tailings storage, reduces the occupation of land resources, reduces dust, and reduces environmental pollution. At the same time, it broadens the source of raw materials for aggregates, reduces the exploitation of natural resources, realizes the secondary utilization of waste resources, turns waste into treasure, and has certain economic and environmental benefits.

[0037] 2. This invention does not use traditional activators such as sodium hydroxide, water glass, quicklime, or gypsum, but instead uses sodium bicarbonate and ammonium bicarbonate as activators. This causes the Si-O bonds in the inactive SiO2 of the mine tailings to break and recombine under alkaline conditions, forming a glassy phase that becomes the active phase. This phase then undergoes a secondary hydration reaction with the hydration product Ca(OH)2, forming CSH gel and improving the strength of the lightweight aggregate. Simultaneously, the addition of sodium bicarbonate and ammonium bicarbonate to the lightweight aggregate acts as a foaming agent, generating CO2 and NH3. The pores left by the escaping gases reduce the density of the lightweight aggregate. Furthermore, the addition of lightweight sand also reduces the density of the lightweight aggregate. The lightweight sand, with its specific particle size, can also serve as nucleation sites for cement and mine tailings, causing the powder to continuously spherize on the lightweight sand.

[0038] 3. This invention utilizes mechanical activation, microwave activation, and chemical activation to activate inactive SiO2 in mine tailings. Mechanical grinding disrupts the crystal structure of SiO2, reducing its crystallinity and increasing its activity. Furthermore, mechanical grinding reduces the particle size of the mine tailings, providing a filling effect and improving the strength of the lightweight aggregate. Microwave radiation also disrupts the structure of SiO2, breaking Si-O bonds and increasing the activity of the mine tailings. The addition of sodium bicarbonate and ammonium bicarbonate for chemical activation further disrupts the silicon-oxygen tetrahedral structure, enhancing the activity of the mine tailings. The coupled effect of these three processes further enhances the activity of SiO2. The activated SiO2 consumes the low-strength Ca(OH)2, generating high-strength CSH gel, thus improving the strength of the lightweight aggregate.

[0039] 4. This invention does not employ traditional natural curing or steam curing, but instead uses a three-stage curing system: film curing, low-humidity curing, and carbon dioxide curing. Initially, film curing is performed for 24-36 hours to prevent moisture evaporation. Simultaneously, CO2 generated from sodium bicarbonate and ammonium bicarbonate serves as a carbon source, reducing CO2 emissions into the environment. Then, curing is conducted in an environment with a relative humidity of 20%-35% to remove excess moisture from the lightweight aggregate, allowing external CO2 to diffuse into it. Finally, curing is performed in a CO2 environment, where the hydration product Ca(OH)2 generates CaCO3, increasing the density and strength of the lightweight aggregate. Detailed Implementation

[0040] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0041] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0042] It should be understood that, except in any operational instance or otherwise indicated, all figures representing the amounts of ingredients used, for example, in the specification and claims, should be understood to be modified in all cases by the term "about". Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximations varying with the desired performance to be obtained according to the invention.

[0043] In the embodiments of the present invention, the content of non-active SiO2 in the mine tailings is 53.93%, the content of Al2O3 is 17.41%, and the content of CaO is 6.23%.

[0044] The bulk density of the lightweight sand in this embodiment of the invention is 150 kg / m³. 3 The particle size is 0.1-0.8 mm.

[0045] The cement used in this embodiment of the invention is silicate cement with a strength grade of P.II52.5 and a specific surface area of ​​470 m². 2 / kg, apparent density is 3050kg / m³ 3 The bulk density is 1200 kg / m³. 3 .

[0046] The particle size of the lightweight aggregate in this embodiment of the invention is 5-20 mm.

[0047] Example 1

[0048] A non-fired lightweight aggregate based on mine tailings mud comprises the following components in parts by weight:

[0049]

[0050] The additive is a mixture of 1 part sodium bicarbonate and 1 part ammonium bicarbonate.

[0051] The preparation method of the above-mentioned mine tailings-based non-fired lightweight aggregate includes the following steps:

[0052] S1. Grind 100 parts of mine tailings mechanically until the particle size is less than 20 μm, and then heat them in a microwave oven on medium-high heat for 15 minutes to obtain pretreated mine tailings A.

[0053] S2. Pour 1 part sodium bicarbonate and 1 part ammonium bicarbonate into 220 parts water and stir until well mixed to obtain solution B;

[0054] S3. Mix 50 parts of light sand, 75 parts of pretreated mine tailings A, and 425 parts of cement evenly to obtain dry material C.

[0055] S4. Mix the remaining 25 parts of pretreated mine tailings A and 475 parts of cement evenly to obtain dry material D.

[0056] S5. Place the dry material C on a disc, and while rotating the disc horizontally, slowly and evenly spray 112 parts of solution B into the dry material C to obtain a lightweight aggregate core E with a particle size of 3-10 mm.

[0057] S6. Put the dry material D into the disc, continue to rotate the disc horizontally, and at the same time slowly spray the remaining 110 parts of solution B into the disc to obtain lightweight aggregate F.

[0058] S7. Cover the lightweight aggregate F with plastic wrap and cure for 24 hours, then place it in an environment with a relative humidity of 20%-35% for 24 hours, and finally place it in a carbon dioxide curing chamber for 24 hours to obtain the mine fine tailings-based non-fired lightweight aggregate.

[0059] Comparative Example 1

[0060] A non-fired lightweight aggregate based on mine tailings mud comprises the following components in parts by weight:

[0061]

[0062] The additive is a mixture of 1 part sodium bicarbonate and 1 part ammonium bicarbonate.

[0063] The preparation method of the above-mentioned mine tailings-based non-fired lightweight aggregate includes the following steps:

[0064] S1. Mechanically grind 100 parts of mine tailings to a particle size of less than 20μm to obtain pretreated mine tailings A;

[0065] S2. Pour 1 part sodium bicarbonate and 1 part ammonium bicarbonate into 220 parts water and stir until well mixed to obtain solution B;

[0066] S3. Mix 50 parts of light sand, 75 parts of pretreated mine tailings A, and 425 parts of cement evenly to obtain dry material C.

[0067] S4. Mix the remaining 25 parts of pretreated mine tailings A and 475 parts of cement evenly to obtain dry material D.

[0068] S5. Place the dry material C on a disc, and while rotating the disc horizontally, slowly and evenly spray 112 parts of solution B into the dry material C to obtain a lightweight aggregate core E with a particle size of 3-10 mm.

[0069] S6. Put the dry material D into the disc, continue to rotate the disc horizontally, and at the same time slowly spray the remaining 110 parts of solution B into the disc to obtain lightweight aggregate F.

[0070] S7. Cover the lightweight aggregate F with plastic wrap and cure for 24 hours, then place it in an environment with a relative humidity of 20%-35% for 24 hours, and finally place it in a carbon dioxide curing chamber for 24 hours to obtain the mine fine tailings-based non-fired lightweight aggregate.

[0071] Comparative Example 2

[0072] A non-fired lightweight aggregate based on mine tailings mud comprises the following components in parts by weight:

[0073]

[0074]

[0075] The preparation method of the above-mentioned mine tailings-based non-fired lightweight aggregate includes the following steps:

[0076] S1. Grind 100 parts of mine tailings mechanically until the particle size is less than 20 μm, and then heat them in a microwave oven on medium-high heat for 15 minutes to obtain pretreated mine tailings A.

[0077] S2. Pour 2 parts of sodium hydroxide into 220 parts of water and stir until homogeneous to obtain solution B;

[0078] S3. Mix 50 parts of light sand, 75 parts of pretreated mine tailings A, and 425 parts of cement evenly to obtain dry material C.

[0079] S4. Mix the remaining 25 parts of pretreated mine tailings A and 475 parts of cement evenly to obtain dry material D.

[0080] S5. Place the dry material C on a disc, and while rotating the disc horizontally, slowly and evenly spray 112 parts of solution B into the dry material C to obtain a lightweight aggregate core E with a particle size of 3-10 mm.

[0081] S6. Put the dry material D into the disc, continue to rotate the disc horizontally, and at the same time slowly spray the remaining 110 parts of solution B into the disc to obtain lightweight aggregate F.

[0082] S7. Cover the lightweight aggregate F with plastic wrap and cure for 24 hours, then place it in an environment with a relative humidity of 20%-35% for 24 hours, and finally place it in a carbon dioxide curing chamber for 24 hours to obtain the mine fine tailings-based non-fired lightweight aggregate.

[0083] Comparative Example 3

[0084] A non-fired lightweight aggregate based on mine tailings mud comprises the following components in parts by weight:

[0085]

[0086] The additive is a mixture of 1 part sodium bicarbonate and 1 part ammonium bicarbonate.

[0087] The preparation method of the above-mentioned mine tailings-based non-fired lightweight aggregate includes the following steps:

[0088] S1. Grind 100 parts of mine tailings mechanically until the particle size is less than 20 μm, and then heat them in a microwave oven on medium-high heat for 15 minutes to obtain pretreated mine tailings A.

[0089] S2. Pour 1 part sodium bicarbonate and 1 part ammonium bicarbonate into 220 parts water and stir until well mixed to obtain solution B;

[0090] S3. Mix 50 parts of light sand, 75 parts of pretreated mine tailings A, and 425 parts of cement evenly to obtain dry material C.

[0091] S4. Mix the remaining 25 parts of pretreated mine tailings A and 475 parts of cement evenly to obtain dry material D.

[0092] S5. Place the dry material C on a disc, and while rotating the disc horizontally, slowly and evenly spray 112 parts of solution B into the dry material C to obtain a lightweight aggregate core E with a particle size of 3-10 mm.

[0093] S6. Put the dry material D into the disc, continue to rotate the disc horizontally, and at the same time slowly spray the remaining 110 parts of solution B into the disc to obtain lightweight aggregate F.

[0094] S7. Naturally cure lightweight aggregate F for 72 hours to obtain mine tailings-based non-fired lightweight aggregate.

[0095] Test case

[0096] Test method:

[0097] The compressive strength, bulk density and water absorption of the mine tailings-based non-fired lightweight aggregates of Example 1 and Comparative Examples 1-3 were tested.

[0098] The test results are shown in Table 1.

[0099] Table 1 Performance Test Results

[0100]

[0101] Table 1 shows that the performance of the non-fired lightweight aggregate based on mine tailings prepared in Example 1 is significantly better than that of Comparative Examples 1-3. The performance difference between Example 1 and Comparative Example 1 indicates that the coupled effect of mechanical activation, microwave activation, and chemical activation can improve the compressive strength of the lightweight aggregate. The performance difference between Example 1 and Comparative Example 2 indicates that, compared with sodium hydroxide modification, using sodium bicarbonate and ammonium bicarbonate as chemical activators and foaming agents can reduce the density of the lightweight aggregate. The performance difference between Example 1 and Comparative Example 3 indicates that the three-stage curing system of film curing, low-humidity curing, and carbon dioxide curing can greatly improve the compressive strength and density of the lightweight aggregate, and reduce its water absorption. This invention enables the comprehensive utilization of mine tailings, and the prepared lightweight aggregate has the advantages of light weight, high strength, and low water absorption, showing good application prospects.

[0102] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0103] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A non-fired lightweight aggregate based on fine tailings from mining, characterized in that, The mine tailings-based non-fired lightweight aggregate comprises the following components in parts by weight: 50-450 parts of fine tailings from the mine 50-100 parts of light sand 550-950 parts cement Additives 0.5-18 parts 200-250 parts water; The additive is a mixture of sodium bicarbonate and ammonium bicarbonate; The preparation method of the non-fired lightweight aggregate based on fine tailings from the mine is as follows: S1. Grind the fine tailings from the mine and heat them in a microwave oven on medium-high heat for 10-20 minutes to obtain pretreated fine tailings from the mine, A. S2. Pour the additive into water and stir well to obtain solution B; S3. Mix light sand, part of pretreated mine tailings A, and part of cement evenly to obtain dry material C; S4. Mix the remaining pretreated mine tailings A with cement evenly to obtain dry material D; S5. Place dry material C in a container, and while rotating the container horizontally, spray some solution B into dry material C to obtain lightweight aggregate core E. S6. Add the dry material D into the core E of the lightweight aggregate, continue to rotate the container horizontally, and slowly spray the remaining solution B into the container to obtain lightweight aggregate F. S7. Cover the lightweight aggregate F with plastic wrap and cure for 24-36 hours, then place it in an environment with a relative humidity of 20%-35% for 24-36 hours, and finally place it in a carbon dioxide curing chamber for 24-36 hours to obtain the mine fine tailings-based non-fired lightweight aggregate.

2. The mine tailings-based non-fired lightweight aggregate according to claim 1, characterized in that, The mass ratio of sodium bicarbonate to ammonium bicarbonate is (5-9):(1-5).

3. The mine tailings-based non-fired lightweight aggregate according to claim 1, characterized in that, The tailings from the mine contain 50-60% inactive SiO2, 15-20% Al2O3, and 5-8% CaO.

4. The mine tailings-based non-fired lightweight aggregate according to claim 1, characterized in that, The bulk density of the light sand is 140-150 kg / m³ 3 The particle size is 0.1-0.8 mm.

5. The non-fired lightweight aggregate based on fine tailings from mining according to claim 1, characterized in that, The cement is silicate cement with a strength grade of P.II52.5 and a specific surface area of ​​400-500 m². 2 / kg, apparent density is 3000-3200 kg / m³ 3 The bulk density is 1000-1300 kg / m³ 3 .

6. The non-fired lightweight aggregate based on fine tailings from mining according to claim 1, characterized in that, The particle size of the lightweight aggregate is 5-20 mm.

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