Red mud-based lightweight aggregate and preparation method thereof
By using red mud, fly ash and slag powder as cementitious materials, combined with alkali triggers and red mud base polymers, red mud-based lightweight aggregates were prepared, which solved the problems of complex process and poor economicality in the existing technology, and achieved large-scale green utilization and efficient resource recycling of red mud.
Patent Information
- Application Number
- CN202510311715.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-17
- Publication Date
- 2025-05-30
AI Technical Summary
The existing red mud granulation technology requires cementing materials such as cement and high-temperature roasting. The process is complex and economical, making it difficult to achieve large-scale green utilization of red mud.
Red mud, fly ash and slag powder are used as cementing materials, and the preparation of alkali triggers and red mud base polymers and combined with the extrusion granulation process to prepare red mud-based lightweight aggregates, avoiding the use of cement and high-temperature roasting.
It has achieved efficient utilization of red mud, low production energy consumption, low cost, simple preparation process, suitable for large-scale promotion, and has significant economic and environmental benefits.
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Figure CN120058298A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of building materials, and particularly relates to a red mud-based lightweight aggregate and a preparation method thereof. Background Art
[0002] Red mud is a highly alkaline waste generated in the production process of the alumina industry. Its stacking can cause various environmental hazards, mainly including occupying a large amount of land, polluting groundwater and soil, and affecting the production and life of surrounding residents. The alkaline substances in red mud will dissolve out with rain leaching, polluting surface water and groundwater, posing a threat to the ecological environment and human health. In addition, the stacking of red mud may also cause dust pollution and affect air quality. Therefore, studying the utilization of red mud can effectively alleviate the environmental problems caused by red mud stacking. At present, red mud can be used to produce cement, bricks, ceramics, concrete, road materials, etc., and has great potential for comprehensive utilization, but there are still some challenges, including the lack of key technologies for large-scale consumption of red mud.
[0003] Artificial lightweight aggregate is a lightweight aggregate made by high-temperature roasting or other process methods, with the characteristics of low density, high strength, heat insulation, fire resistance, and good seismic performance. Red mud lightweight aggregate is a building material developed using red mud resources. Replacing sand and gravel with it in roads is one of the effective channels for large-scale application of red mud. At present, most red mud granulation technologies require cement and other cementitious materials and high-temperature roasting to ensure performance. However, these technologies are complex in process, poor in economy, and high in cost, and do not meet the development requirements of green industry. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a red mud-based lightweight aggregate and a preparation method thereof in view of the deficiencies of the above-mentioned prior art. It is a high-performance building material developed using red mud resources, with high red mud utilization rate, which can realize the green utilization of red mud. At the same time, no cement and other cementitious materials and high-temperature sintering are required in the preparation process, and it has the characteristics of simple preparation process, low energy consumption, and low cost.
[0005] To solve the above technical problems, the technical solution adopted by the present invention is:
[0006] A preparation method of a red mud-based lightweight aggregate, the method comprising the following steps:
[0007] S1. Preparation of alkali activator: Weigh solid sodium hydroxide and solid sodium silicate in proportion and dissolve them in distilled water a, and age indoors for 2 - 4 h at an aging temperature of 20°C - 25°C to obtain an alkali activator;
[0008] S2. Preparation of red mud geopolymers: Weigh red mud a, fly ash, and slag powder a according to the ratio and pour them into a mixing pan. While stirring, add the alkali activator obtained in S1 at a constant speed. First, stir at 55 - 70 r / min for 1 min, and then increase the speed to 115 - 135 r / min and stir for 2 - 4 min to obtain a red mud geopolymer slurry for standby.
[0009] S3. Preparation of granulation mixture: Weigh red mud b and slag powder b, and add them to the red mud geopolymer slurry obtained in S2 under stirring conditions. Then, continuously and uniformly add distilled water b until the granulation mixture is in a uniformly moist state.
[0010] S4. Extrusion granulation: Pour the granulation mixture obtained in S3 into an extrusion granulator for extrusion molding. After natural curing for 1 d through screening, put it into a sealed bag and cure for 25 - 30 d to obtain red mud-based lightweight aggregates.
[0011] Preferably, the purity of the solid sodium hydroxide ≥ 97%;
[0012] The solid sodium silicate is powdered instant sodium silicate with a modulus of 3.0, a dissolution rate at 30°C ≤ 240 s, and a passing rate through a 120-mesh sieve hole ≥ 95%;
[0013] The red mud is Bayer red mud, and the total content of active SiO 2 and Al 2 O 3 ≥ 40%;
[0014] The content of active effective CaO in the slag powder ≥ 40%;
[0015] The fly ash is fly ash of grade II or above.
[0016] Preferably, in S1, the mass fraction of sodium hydroxide in the alkali activator is 5% - 10%, and the mass ratio of sodium hydroxide to sodium silicate is 1:(2 - 3).
[0017] Preferably, in S2, the mass ratio of red mud a, fly ash, and slag powder a is (5 - 7):1:(2 - 4); the alkali activator accounts for 60% of the total mass of red mud a, fly ash, and slag powder a.
[0018] Preferably, in S3, the mass ratio of red mud b, slag powder b, red mud geopolymer slurry, and distilled water b is (6 - 8):(2 - 4):6.4:1.
[0019] Preferably, the red mud-based lightweight aggregates prepared in S4 meet the following technical standards: particle size is 6 - 10 mm, water absorption is not more than 10%, and bulk density is 950 kg / m 3 -1150 kg / m 3, the cylinder compressive strength is 7.0 - 12.0 MPa.
[0020] The present invention also provides a red mud-based lightweight aggregate prepared by the above method.
[0021] Preferably, the cylinder compressive strength of 7 - 10 MPa is a lightweight aggregate for low-grade road use, and the cylinder compressive strength of 10 - 12 MPa is a lightweight aggregate for high-grade road use.
[0022] Compared with the prior art, the present invention has the following remarkable technical effects:
[0023] 1. The present invention uses industrial solid wastes such as red mud, fly ash and slag powder as cementitious materials, without adding cementitious materials such as cement. The production energy consumption is only 10% - 30% of that of ordinary Portland cement, and can significantly reduce greenhouse gas emissions.
[0024] 2. The red mud-based lightweight aggregate prepared by the present invention has high strength, low water absorption and excellent performance. It can replace natural sand and gravel and be widely used in subgrade materials, lightweight concrete, permeable concrete, etc., reducing the environmental damage and energy consumption caused by the exploitation of natural aggregates and contributing to green development.
[0025] 3. The preparation process of the red mud-based lightweight aggregate of the present invention is simple, the equipment investment cost is low, the economic benefit is remarkable, and it is suitable for wide promotion and use.
[0026] The present invention will be further described in detail below with reference to the drawings and embodiments. Brief Description of the Drawings
[0027] Figure 1 is a physical diagram of the red mud-based lightweight aggregate prepared by the present invention. Detailed Embodiments
[0028] The specifications of the raw materials used in the present invention are as follows:
[0029] The red mud is Bayer red mud, and it is required that the total content of active SiO 2 and Al 2 O 3 ≥ 40%;
[0030] The content of active effective CaO in the slag powder ≥ 40%;
[0031] The fly ash is fly ash of grade II or above;
[0032] The purity of solid sodium hydroxide ≥ 97%;
[0033] The solid sodium silicate is powdered instant sodium silicate, with a required modulus of 3.0, a dissolution rate at 30 °C ≤ 240 s and a passing rate through a 120-mesh sieve ≥ 95%.
[0034] The following raw material dosages are all in parts by mass.
[0035] Example 1
[0036] This example is a preparation method of red mud-based lightweight aggregates, including the following steps:
[0037] S1. Preparation of alkali activator: Take 11 parts of solid sodium silicate and 4 parts of solid sodium hydroxide, dissolve them in 45 parts of distilled water a, and age indoors for 3 h at an aging temperature of 22 °C to obtain the alkali activator.
[0038] S2. Preparation of red mud-based geopolymer: Take 70 parts of red mud a, 10 parts of fly ash, and 20 parts of slag powder a, put them into a mixing pot and stir. While stirring, uniformly and continuously add the aged alkali activator obtained in S1. First, stir at 62 r / min for 1 min and then increase the speed to 125 r / min and stir for 3 min to obtain the red mud-based geopolymer slurry, and set it aside.
[0039] S3. Preparation of granulation mixture: Take 150 parts of red mud b and 100 parts of slag powder b, and uniformly and slowly add them to the red mud-based geopolymer slurry obtained in S2 under stirring conditions. Then, continuously and uniformly add 25 parts of distilled water b until the granulation mixture is in a uniformly wet state.
[0040] S4. Extrusion granulation: Pour the well-stirred granulation mixture obtained in S3 into an extrusion granulator for extrusion molding, cure naturally for 1 d through screening, and then put it into a sealed bag for curing for 25 d to obtain the finished product of red mud-based lightweight aggregates.
[0041] Example 2
[0042] This example is a preparation method of red mud-based lightweight aggregates, including the following steps:
[0043] S1. Preparation of alkali activator: Take 11 parts of solid sodium silicate and 4 parts of solid sodium hydroxide, dissolve them in 45 parts of distilled water a, and age indoors for 2 h at an aging temperature of 25 °C to obtain the alkali activator.
[0044] S2. Preparation of red mud-based geopolymer: Take 60 parts of red mud a, 10 parts of fly ash, and 30 parts of slag powder a, put them into a mixing pot and stir. While stirring, uniformly and continuously add the aged alkali activator obtained in S1. First, stir at 70 r / min for 1 min and then increase the speed to 135 r / min and stir for 2 min to obtain the red mud-based geopolymer slurry, and set it aside.
[0045] S3. Preparation of granulation mixture: Take 150 parts of red mud b and 100 parts of slag powder b, and uniformly and slowly add them to the red mud-based geopolymer slurry obtained in S2 under stirring conditions. Then, continuously and uniformly add 25 parts of distilled water b until the granulation mixture is in a uniformly wet state.
[0046] S4. Extrusion granulation: Pour the granulation mixture well-stirred in S3 into an extrusion granulator for extrusion molding, cure naturally for 1 d through screening, and then cure in a sealed bag for 30 d to obtain the finished product of red mud-based lightweight aggregate.
[0047] Example 3
[0048] This example is a preparation method of red mud-based lightweight aggregate, including the following steps:
[0049] S1. Preparation of alkali activator: Take 11 parts of solid sodium silicate and 4 parts of solid sodium hydroxide, dissolve them in 45 parts of distilled water a, age indoors for 4 h at an aging temperature of 20 °C to obtain the alkali activator.
[0050] S2. Preparation of red mud-based geopolymer: Take 70 parts of red mud a, 10 parts of fly ash, and 20 parts of slag powder a, put them into a mixing pan and stir. While stirring, uniformly and slowly add the aged alkali activator obtained in S1. First, stir at 55 r / min for 1 min and then increase the speed to 115 r / min and stir for 4 min to obtain the red mud-based geopolymer slurry for standby.
[0051] S3. Preparation of granulation mixture: Take 175 parts of red mud b and 75 parts of slag powder b, and uniformly and slowly add them to the red mud-based geopolymer slurry obtained in S2 under stirring conditions. Then continuously and uniformly add 25 parts of distilled water b until the granulation mixture is in a uniformly moist state.
[0052] S4. Extrusion granulation: Pour the granulation mixture well-stirred in S3 into an extrusion granulator for extrusion molding, cure naturally for 1 d through screening, and then cure in a sealed bag for 28 d to obtain the finished product of red mud-based lightweight aggregate.
[0053] Figure 1 It is a physical picture of the lightweight aggregate prepared by the present invention.
[0054] Perform performance tests on the red mud-based lightweight aggregates prepared in Examples 1 - 3:
[0055] Bulk density test: Refer to the national standard "Lightweight Aggregates and Their Test Methods Part 2: Test Methods for Lightweight Aggregates" (GB / T 17431.2 - 2010) for the bulk density test. According to the requirements in "Lightweight Aggregates and Their Test Methods Part 1: Lightweight Aggregates" (GB / T 17431.1 - 2010), the bulk density of the lightweight aggregate shall not be greater than 1200 kg / m 3 .
[0056] Cylinder compressive strength test: The cylinder compressive strength test was carried out with reference to the national standard "Lightweight Aggregates and Their Test Methods - Part 2: Test Methods for Lightweight Aggregates" (GB / T 17431.2~2010). The cylinder compressive strength of lightweight aggregates with a density grade of 1100 should not be less than 5.0 MPa.
[0057] Water absorption test: The water absorption test was carried out with reference to the national standard "Lightweight Aggregates and Their Test Methods - Part 2: Test Methods for Lightweight Aggregates" (GB / T 17431.2~2010). The 1-hour water absorption of lightweight aggregates with a density grade of 1100 should not be more than 10%.
[0058] The test results are shown in Table 1.
[0059] Table 1 Performance test results of red mud-based lightweight aggregates prepared in Examples 1 to 3
[0060]
[0061] According to the experimental results, it can be seen that the cylinder compressive strength and water absorption of the red mud-based lightweight aggregates prepared by the present invention are much higher than the requirements in the specification. With the increase of the red mud dosage, the density of the aggregates decreases, which is beneficial to obtaining lighter aggregates. However, the cylinder compressive strength of the lightweight aggregates decreases and the water absorption increases, and it is not conducive to molding. With the increase of the slag powder dosage, the lightweight aggregates are more easily molded, and due to the high activity of the slag powder, lightweight aggregates with higher strength can be obtained. However, too much slag powder dosage will increase the compactness of the aggregates, which is not conducive to obtaining porous lightweight aggregate balls. Therefore, in practical applications, the best formulation dosage can be comprehensively selected according to the requirements of the application occasion.
[0062] Comparative Example 1
[0063] To verify the influence of different dosages of red mud-based geopolymers on the obtained red mud-based lightweight aggregates. The preparation method includes the following steps:
[0064] S1. Preparation of alkali activator: Take 8 parts of solid sodium silicate and 3 parts of solid sodium hydroxide, dissolve them in 34 parts of distilled water a, and age for 4 h at room temperature with an aging temperature of 20 °C to obtain an alkali activator.
[0065] S2. Preparation of red mud-based geopolymer: Take 52.5 parts of red mud a, 7.5 parts of fly ash, and 15 parts of slag powder a, put them into a mixing pot and stir. While stirring, uniformly add the aged alkali activator obtained in S1 at a constant speed. First, stir at 55 r / min for 1 min and then increase the speed to 115 r / min and stir for 4 min to obtain a red mud-based geopolymer slurry for standby.
[0066] S3. Preparation of granulation mixture: Take 175 parts of red mud b and 75 parts of slag powder b, and uniformly and slowly add them to the red mud-based geopolymer slurry obtained in S2 under stirring conditions. Then continuously and uniformly add 25 parts of distilled water b until the granulation mixture is in a uniformly moist state.
[0067] S4. Extrusion granulation: Pour the granulation mixture stirred in S3 into an extrusion granulator for extrusion molding. After natural curing for 1 d through screening, it is then placed in a sealed bag for curing for 28 d to obtain the finished red mud-based lightweight aggregate. The obtained lightweight aggregates are numbered as comparative specimens 1-1 and comparative specimen 1-2 respectively.
[0068] After performance testing, the results are shown in Table 2 below.
[0069] Table 2 Comparison of performance test results of lightweight aggregates in Comparative Example 1 and Example 3
[0070]
[0071] It can be seen from the test results that after the change of the content of red mud-based geopolymers in Comparative Example 1, the cylinder compressive strength of the obtained lightweight aggregates is lower than the specification requirements, indicating that as a cementitious phase, the content of geopolymers directly determines the strength of red mud-based lightweight aggregates. When the content of red mud-based geopolymer paste decreases, the amount of gel generated decreases, and the pores between red mud and slag powder particles cannot be fully filled, resulting in more defects formed inside the material.
[0072] Comparative Example 2
[0073] Verify the influence of the ratio of red mud and slag powder in the granulation mixture on the obtained red mud-based lightweight aggregates. The preparation method includes the following steps:
[0074] S1. Preparation of alkali activator: Take 11 parts of solid sodium silicate and 4 parts of solid sodium hydroxide, dissolve them in 45 parts of distilled water a, and age indoors for 4 h at a curing temperature of 20 °C to obtain the alkali activator.
[0075] S2. Preparation of red mud-based geopolymer: Take 70 parts of red mud a, 10 parts of fly ash, and 20 parts of slag powder a, put them into a mixing pot for stirring, and while stirring, uniformly and slowly add the aged alkali activator obtained in S1. First, stir at 55 r / min for 1 min and then increase the speed to 115 r / min and stir for 4 min to obtain the red mud-based geopolymer paste for standby.
[0076] S3. Preparation of granulation mixture: Take 250 parts of red mud b, and uniformly and slowly add it to the red mud-based geopolymer paste obtained in S2 under stirring conditions, and then continuously and uniformly add 25 parts of distilled water b until the granulation mixture is in a uniformly moist state.
[0077] S4. Extrusion granulation: Pour the granulation mixture stirred in S3 into an extrusion granulator for extrusion molding. After natural curing for 1 d through screening, it is then placed in a sealed bag for curing for 28 d to obtain the finished red mud-based lightweight aggregate. The obtained lightweight aggregates are numbered as comparative specimens 2-1 and comparative specimen 2-2 respectively.
[0078] After performance testing, the results are shown in Table 3.
[0079] Table 3 Comparison of Lightweight Aggregate Performance Test Results between Comparative Example 2 and Example 3
[0080]
[0081] From the test results, it can be seen that when only red mud is used in the granulation mixture in Comparative Example 2, the cylinder compressive strength of the obtained lightweight aggregate is significantly reduced, not meeting the specification requirements, and the water absorption rate is also higher than the specification requirements. This shows that the slag powder in the granulation mixture plays a key role in reducing the water absorption rate and increasing the strength of the red mud-based lightweight aggregate. The slag powder particles are finer, and the mixed use with red mud optimizes the particle size distribution, making the internal structure of the aggregate after extrusion granulation more uniform, reducing the porosity and increasing the density.
[0082] The above are only the preferred embodiments of the present invention and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent variations made to the above embodiments based on the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.
Claims
1. A method for preparing red mud-based lightweight aggregate, characterized in that: The following steps are involved: S1. Preparation of alkaline activator: Weigh solid sodium hydroxide and solid sodium silicate in proportion and dissolve them in distilled water a, and age them indoors for 2 to 4 hours at an aging temperature of 20° C. to 25° C. to obtain an alkaline activator; S2, preparation of red mud-based polymer: weigh red mud a, fly ash, and slag powder a according to proportion and pour them into a mixing pot, add the alkali activator obtained in S1 at a uniform speed while stirring, first stir at 55-70 r / min for 1 min and then increase to 115-135 r / min and stir for 2-4 min to obtain a red mud-based polymer slurry for standby use; S3, preparation of granulation mixture: weigh red mud b and slag powder b, add them to the red mud-based polymer slurry obtained in S2 under stirring, and then continuously and evenly add distilled water b until the granulation mixture is in a uniformly moist state; S4, extrusion granulation: pour the granulated mixture obtained in S3 into an extrusion granulator for extrusion molding, screen and naturally cure for 1 day, then put it into a sealed bag and cure for 25 to 30 days to obtain red mud-based lightweight aggregate.
2. The method according to claim 1, characterized in that The purity of the solid sodium hydroxide is ≥97%; the solid sodium silicate is powdered instant sodium silicate with a modulus of 3.0, a dissolution rate of ≤240s at 30°C and a 120-mesh sieve pass rate of ≥95%.
3. The method according to claim 1, characterized in that: The red mud is Bayer red mud, and the total content of active SiO2 and Al2O3 is ≥40%; The active effective CaO content in the slag powder is ≥40%; The fly ash is Grade II or above.
4. The method according to claim 1, characterized in that: The mass fraction of sodium hydroxide in the alkaline activator in S1 is 5% to 10%, and the mass ratio of sodium hydroxide to sodium silicate is 1:(2 to 3).
5. The method according to claim 1, characterized in that The mass ratio of the red mud a, fly ash and slag powder a in S2 is (5-7):1:(2-4); the alkali activator accounts for 60% of the total mass of the red mud a, fly ash and slag powder a.
6. The method according to claim 1, characterized in that The mass ratio of the red mud b, slag powder b, red mud-based polymer slurry and distilled water b in S3 is (6-8):(2-4):6.4:
1.
7. The method according to claim 1, characterized in that The red mud-based lightweight aggregate prepared by S4 meets the following technical standards: particle size is 6-10 mm, water absorption is not more than 10%, and bulk density is 950 kg / m 3 ~1150kg / m 3 , cylinder pressure strength is 7.0~12.0MPa.
8. A red mud-based lightweight aggregate prepared by the method according to any one of claims 1 to 7.
9. The red mud-based lightweight aggregate according to claim 8, characterized in that: The cylinder pressure strength is 7-10MPa for low-grade lightweight aggregate for roads, and the cylinder pressure strength is 10-12MPa for high-grade lightweight aggregate for roads.