Fly ash-red mud-based ultrafine powder as well as preparation method and application thereof

Abstract

The invention discloses fly ash-red mud based ultrafine powder and a preparation method and application thereof.The fly ash-red mud based ultrafine powder is prepared from, by weight, 50-70 parts of modified fly ash, 10-35 parts of dealkalized red mud, 4-10 parts of waste glass micro powder and 4-10 parts of nanometer silicon-aluminum sol, the dealkalized red mud is prepared from red mud through calcination-secondary leaching. The fly ash-red mud-based ultrafine powder prepared by the invention can replace S95-grade mineral powder, is remarkably better in working performance, mechanical property and durability after being used for preparing sea sand concrete, can effectively prolong the service life of marine environment concrete engineering while reducing the production cost of the sea sand concrete, and has higher engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixture technology, specifically relating to a fly ash-red mud-based ultrafine powder, its preparation method, and its application. Background Technology

[0002] With the rapid development of the construction industry, the demand for concrete raw materials such as cement and natural sand has surged. To alleviate the crisis of construction sand caused by the shortage of river sand resources and river pollution, sea sand is currently being used as a substitute for river sand in coastal areas and areas with scarce freshwater resources, thus producing sea sand concrete for use in construction projects. However, sea sand contains a large amount of chloride salts. Chloride ions can damage the passivation film on the surface of steel bars, leading to steel corrosion, which in turn causes concrete cracking and spalling, seriously reducing the durability and safety of the structure, and thus limiting its large-scale application. Therefore, sea sand must undergo purification treatment (such as freshwater washing and desalination) to ensure that the chloride ion content meets the standards (e.g., JGJ 206-2010 requires that the chloride ion content not exceed 0.06%).

[0003] Mineral powder, with its fine particles and smooth surface, possesses a micro-aggregate filling effect and ball-bearing lubrication, improving the workability of concrete, reducing bleeding and segregation, and enhancing pumpability. Simultaneously, mineral powder can consume calcium hydroxide (Ca(OH)2) through a secondary hydration reaction, reducing alkaline substances and thus lowering the chloride ion diffusion rate, thereby improving the concrete's resistance to chloride ion penetration and extending the structural service life. However, due to capacity constraints in the metallurgical industry, mineral powder suffers from uneven resource distribution and significant cost fluctuations. Furthermore, its quality is affected by blast furnace raw materials and production processes, with different batches potentially exhibiting differences in activity, fineness, and moisture content, leading to fluctuations in concrete workability and strength, and affecting the consistency of project quality. Therefore, there is an urgent need to find a high-performance, low-cost, and uniform alternative material.

[0004] Chinese patent CN116947402A discloses a high-strength, high-permeability marine sand concrete and its preparation method, which involves ball milling fly ash and manganese slag to a specific surface area ≥17000 m². 2 / kg, 28d activity index ≥110% and specific surface area ≥1000m² 2 With a 28-day activity index ≥95%, it can be used to prepare high-strength, high-permeability sea sand concrete with excellent resistance to chloride ion erosion and good flexural and compressive strength.

[0005] Chinese patent CN111635195A discloses a seawater sand concrete and its preparation method, which involves ball milling reefs and slag to 200 mesh and having a specific surface area ≥6000 cm², respectively. 2 / g, the resulting seawater sand concrete has high density, which can reduce the corrosion of steel bars by chloride ions and improve the durability of concrete structures.

[0006] However, the current processing methods for raw materials of sea sand concrete are mostly simple drying or ball milling, without precise modification to address the defects of low activity and high harmful components in solid waste; moreover, conventional solid waste combinations are mostly used in the raw material system, lacking the synergistic development of "low-activity new solid waste" and "nano-functional components", which limits the improvement of the hydration activity and durability of admixtures. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a fly ash-red mud-based ultrafine powder, its preparation method, and its application. Solid waste deeply modified by "microwave-plasma" combines the micro-aggregate effect of waste glass micropowder with the dual functions of reinforcement and water conduction of nano-silica-alumina sol to construct a "multi-level dense-active self-healing" composite cementitious system. This system can replace mineral powder to reduce the production cost of marine sand concrete, while simultaneously improving the mechanical and durability properties of marine sand concrete.

[0008] To achieve the above objectives, the present invention provides a fly ash-red mud-based ultrafine powder, which, by weight, is composed of 50-70 parts modified fly ash, 10-35 parts dealkalized red mud, 4-10 parts waste glass micro powder and 4-10 parts nano-silica-alumina sol.

[0009] Preferably, the modified fly ash is obtained by microwave activation of fly ash; the particle size of the modified fly ash is 50-100μm, and the modified fly ash contains ≥55% active SiO2 and ≥24% active Al2O3.

[0010] Preferably, the dealkali-treated red mud is obtained by calcining and secondary leaching of red mud; the particle size of the dealkali-treated red mud is 100-200μm, and the main components and contents are SiO2 10%-20%, Al2O3 15%-20%, CaO 5%-15%, and Na2O ≤3%.

[0011] Preferably, the waste glass powder is obtained by ball milling and grading of waste tempered glass from construction, with a particle size of 1-5μm, SiO2 content ≥70%, and glass content ≥90%.

[0012] Preferably, the nano-silica-alumina sol is in sol form, with a particle size of 5-20 nm, an Al2O3 / SiO2 molar ratio of 1:3, a pH value of 8.0-10.0, and a solid content of 20%-30%.

[0013] This invention also provides a method for preparing fly ash-red mud-based ultrafine powder, comprising the following steps: (1) Preparation of modified fly ash: After microwave activation of fly ash for 10-20 min, inert gas is introduced and the process is continued for 3-8 min at a power of 500W and a pressure of 0.1MPa. After collection, the fly ash is dried at 100-110℃ for 10-15 h to obtain modified fly ash. (2) Preparation of dealkalized red mud: After calcination, the red mud is leached twice and then filtered. It is then washed with deionized water until no Cl is present. - It was found that dealkalized red mud was obtained by drying at 100-110℃ for 10-15 hours; (3) Preparation of waste glass powder: The waste glass is crushed, ball-milled for 1-3 hours, and air-classified to collect 1-5 μm particles to obtain waste glass powder; (4) After mixing the modified fly ash, dealkali-reduced red mud and waste glass powder, disperse them at high speed at 3000 r / min for 15-30 min to obtain the primary mixture; (5) Ball mill the primary mixture at 300 r / min for 1-3 h, then add nano-silica-alumina sol and continue ball milling at 400 r / min for 0.5-2 h until the specific surface area of ​​the material is ≥650 m². 2 / kg, aged, dried at 80℃ for 4 hours, and pulverized through a 200-mesh sieve to obtain fly ash-red mud-based ultrafine powder.

[0014] Preferably, the secondary rinsing in step (2) involves a primary rinsing with deionized water followed by a secondary rinsing with ammonium chloride solution.

[0015] More preferably, the liquid-to-solid ratio of the first-stage rinsing is 3:1, and the rinsing time is 20-40 min; the liquid-to-solid ratio of the second-stage rinsing is 2:1, and the rinsing time is 50-70 min; and the solubility of the ammonium chloride solution is 0.1-0.5 mol / L.

[0016] Preferably, the aging conditions in step (5) are aging at 20-25℃ and 60-70% humidity for 20-30 hours.

[0017] The present invention also provides an application of fly ash-red mud-based ultrafine powder in marine sand concrete, wherein the application is to replace mineral powder in the preparation of marine sand concrete.

[0018] The beneficial effects of this invention are as follows: 1. Microwave activation of components in fly ash is used, and dealkalized red mud is prepared by calcination-two-stage rinsing. This solves the industry problem of low fly ash activity and severe alkali damage in red mud. After treatment, the Na2O content of the red mud is ≤3%, and the active components of fly ash are increased by more than 20%, laying the foundation for high-performance admixtures.

[0019] 2. By introducing waste glass micro powder and nano-silica aluminum sol, which work synergistically with industrial solid waste components, the defects of insufficient early strength and poor erosion resistance of sea sand concrete prepared by traditional solid waste admixtures are solved.

[0020] 3. The "pretreatment-dispersion-step ball milling-aging" process reduces ball milling energy consumption by more than 30% compared to traditional processes. At the same time, aging treatment reduces hydration defects in the later stages, achieving a dual optimization of efficiency and energy consumption.

[0021] 4. It effectively disposes of solid waste such as fly ash, red mud, and waste glass, and its performance is superior to that of S95 grade mineral powder, reducing concrete production costs and extending the service life of marine engineering projects. Attached Figure Description

[0022] Figure 1 The XRD pattern of sea sand concrete prepared from fly ash-red mud-based ultrafine powder and S95 grade mineral powder obtained in Example 2 after 28 days of curing.

[0023] Figure 2 The FT-IR spectrum of sea sand concrete prepared from fly ash-red mud-based ultrafine powder and S95 grade mineral powder obtained in Example 2 at 28 days of age.

[0024] Figure 3 The images show SEM images of sea sand concrete prepared from fly ash-red mud-based ultrafine powder and S95 grade mineral powder obtained in Example 2 at 28 days of age. The left image is from Example 2, and the right image is from S95 grade mineral powder. Detailed Implementation

[0025] The technical solution of the present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention should be determined by the contents of the claims. Modifications and substitutions made by those skilled in the art to the technical solution of the present invention without creative effort all fall within the scope of protection of the present invention.

[0026] In the following examples and comparative examples, the fly ash was sourced from Guilin Yongfu Power Plant, with a particle size of 10-100 μm. The main components and their contents are shown in the table below:

[0027] The red mud originated from Guangxi Baise Pingguo Aluminum Industry Co., Ltd., with a particle size of 50-300 μm. Its main components and contents are shown in the table below:

[0028] The waste glass from construction originated from Sichuan Xiong Gang Glass Co., Ltd., and was tempered glass. The nano-silica-alumina sol is sourced from Shanghai Aladdin Biochemical Technology Co., Ltd. It is in sol form with a particle size of 5-20 nm, an Al2O3 / SiO2 molar ratio of 3:1, a pH value of 8.0-10.0, and a solid content of 20%-30%.

[0029] Example 1 A fly ash-red mud-based ultrafine powder for use in sea sand concrete, by weight, is composed of 60 parts modified fly ash, 25 parts dealkalized red mud, 7 parts waste glass micro powder, and 8 parts nano-silica-alumina sol.

[0030] Preparation method: (1) Preparation of modified fly ash: Fly ash was placed in a microwave plasma reactor (power of 1000W) for 15 min to activate it, then argon gas was introduced at 0.1 MPa, and the plasma was treated at 500W for 5 min. Then it was collected and dried at 105℃ for 12 h to obtain modified fly ash. (2) Preparation of dealkalized red mud: The red mud was calcined in a muffle furnace at 800℃ for 3 hours with a heating rate of 10℃ / min. After naturally cooling to room temperature, a first-stage rinsing was performed: deionized water was added to make a liquid-to-solid ratio of 3:1, and the mixture was stirred at 200-300 r / min for 30 min, followed by filtration. A second-stage rinsing was then performed: 0.3 mol / L ammonium chloride solution was added to make a liquid-to-solid ratio of 2:1, and the mixture was stirred at 300-400 r / min for 60 min, followed by filtration and washing with deionized water until no Cl was found. - The red mud was found to be dealkalized after being dried in an oven at 105℃ for 12 hours. (3) Preparation of waste glass powder: After crushing waste building glass, it was ball-milled for 2 hours under the conditions of ball-to-material ratio of 5:1 and rotation speed of 400 r / min, and 1-5 μm particles were collected by air-classification as waste glass powder. (4) Premixing and dispersing: Modified fly ash, dealkali-reduced red mud and waste glass powder are put into a high-speed disperser in proportion and dry-mixed at 3000 r / min for 20 min to obtain a primary mixture; (5) Ball milling and sol doping: The primary mixture is fed into a planetary ball mill, agate balls are added, and the mixture is ball-milled at 300 r / min for 2 hours. Then, nano-silica-alumina sol is added, and the mixture is ball-milled at 400 r / min for 1 hour. The specific surface area of ​​the material is controlled to be ≥650 m². 2 / kg; (6) Aging and post-processing: Take out the ball milled material and age it for 24 hours at a temperature of 20℃ and a humidity of 60%. Then dry it at a low temperature of 80℃ for 4 hours and crush it through a 200-mesh sieve to obtain fly ash-red mud-based ultrafine powder.

[0031] Example 2 A fly ash-red mud-based ultrafine powder for use in sea sand concrete, by weight, is composed of 65 parts modified fly ash, 20 parts dealkalized red mud, 6 parts waste glass micro powder, and 9 parts nano-silica-alumina sol. The preparation method is the same as in Example 1.

[0032] Example 3 A fly ash-red mud-based ultrafine powder for use in sea sand concrete, by weight, is composed of 55 parts modified fly ash, 30 parts dealkalized red mud, 9 parts waste glass micro powder, and 6 parts nano-silica-alumina sol. The preparation method is the same as in Example 1.

[0033] Example 4 A fly ash-red mud-based ultrafine powder for use in sea sand concrete, by weight, is composed of 50 parts modified fly ash, 35 parts dealkalized red mud, 10 parts waste glass micro powder, and 10 parts nano-silica-alumina sol. The preparation method is the same as in Example 1.

[0034] Example 5 A fly ash-red mud-based ultrafine powder for use in sea sand concrete, by weight, is composed of 70 parts modified fly ash, 10 parts dealkalized red mud, 4 parts waste glass micro powder, and 4 parts nano-silica-alumina sol. The preparation method is the same as in Example 1.

[0035] Comparative Example 1 A fly ash-red mud-based ultrafine powder, with the same formulation and preparation method as in Example 1, except that the modified fly ash is replaced with unmodified fly ash.

[0036] Comparative Example 2 A fly ash-red mud-based ultrafine powder, with the same formulation and preparation method as in Example 1, except that the dealkalized red mud is replaced with undealkalized red mud.

[0037] Comparative Example 3 A fly ash-red mud-based ultrafine powder, with the same formulation and preparation method as in Example 1, except that waste glass powder is not used.

[0038] Comparative Example 4 A fly ash-red mud-based ultrafine powder, with the same formulation and preparation method as in Example 1, except that the amount of waste glass powder is changed to 12 parts.

[0039] Comparative Example 5 A fly ash-red mud-based ultrafine powder, with the same formulation and preparation method as in Example 1, except that nano-silica-alumina sol is not used.

[0040] Comparative Example 6 A fly ash-red mud-based ultrafine powder, with the same formulation and preparation method as in Example 1, except that the amount of nano-silica-alumina sol is changed to 12 parts.

[0041] Comparative Example 7 A fly ash-red mud-based ultrafine powder, with the same formulation as Example 1, but prepared by: mixing modified fly ash, dealkali-treated red mud, waste glass micro powder, and nano-silica-alumina sol, and then ball milling at 400 r / min until the material specific surface area is ≥650 m². 2 / kg; then aged for 24 hours at 20℃ and 60% humidity, followed by drying at 80℃ for 4 hours, and then pulverizing through a 200-mesh sieve to obtain fly ash-red mud-based ultrafine powder.

[0042] Comparative Example 8 A fly ash-red mud-based powder, by weight, is composed of 60 parts fly ash and 25 parts red mud; The preparation method involves mixing fly ash and red mud, drying at 80℃ for 4 hours, and then pulverizing the mixture through a 200-mesh sieve to obtain fly ash-red mud base powder.

[0043] Example 6 The fly ash-red mud-based ultrafine powder or fly ash-red mud-based powder prepared in the above examples and comparative examples, as well as commercially available S95 grade mineral powder and commercially available S105 grade mineral powder, were used to prepare sea sand concrete. The mix proportion of the sea sand concrete was: water consumption 160 kg / m³. 3 The water-cement ratio is 0.42, the fly ash content is 15%, the mineral powder / fly ash-red mud-based ultrafine powder content is 25%, the sand ratio is 40%, and the water-reducing agent content is 2.5%. The water-reducing agent is a polycarboxylate water-reducing agent with a solid content of 10% and a water reduction rate of more than 25%. After the sea sand concrete is made, it is cured under standard conditions for 7 days and 28 days, and then its workability, mechanical properties, and durability are tested.

[0044] The testing standards and methods are as follows, and the test results are shown in Table 1: Standard for Test Methods of Performance of Ordinary Concrete Mixtures (GB / T 50080-2016); Standard for Test Methods of Mechanical Properties of Ordinary Concrete (GB / T 50081-2016); Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete (GB / T 50082-2009); "Test Method for Sulfate Attack Resistance of Cement" (GB / T749-2008); "Test Method for Dry and Wet Cyclic Salt Spray of Acidic Corrosive Media" T / CSTM 00151-2019; Table 1. Physicochemical properties of sea sand concrete

[0045] The results showed that the fly ash-red mud-based ultrafine powder prepared in Examples 1-5 was inferior to commercially available S105 grade mineral powder in terms of workability, mechanical properties, and durability, but superior to commercially available S95 grade mineral powder and the comparative example. It can be used to replace S95 grade mineral powder in marine sand concrete, reducing the production cost of marine sand concrete by 10% while effectively extending the service life of marine environment concrete engineering, and has high engineering application value.

[0046] The sea sand concrete prepared using Example 2 and S95 grade mineral powder was tested by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The results showed that the modified fly ash and dealkalized red mud rapidly generated ettringite under the synergistic effect of waste glass micropowder and nano-silica alumina sol, and at the same time reacted with Ca(OH)2 generated by hydration to form CSH gel, which filled the pores of the ettringite network, thereby achieving a positive impact on workability, mechanical properties and durability.

Claims

1. A fly ash-red mud-based ultrafine powder, characterized in that: By weight, it consists of 50-70 parts modified fly ash, 10-35 parts dealkalized red mud, 4-10 parts waste glass powder and 4-10 parts nano-silica-alumina sol.

2. The fly ash-red mud-based ultrafine powder according to claim 1, characterized in that: The modified fly ash is obtained by microwave activation of fly ash.

3. The fly ash-red mud-based ultrafine powder according to claim 1, characterized in that: The dealkali-treated red mud is obtained by calcining red mud and then leaching it in two stages.

4. The fly ash-red mud-based ultrafine powder according to claim 1, characterized in that: The waste glass powder is obtained by ball milling and grading of construction waste glass, with a particle size of 1-5μm.

5. The fly ash-red mud-based ultrafine powder according to claim 1, characterized in that: The nano-silica-alumina sol has a particle size of 5-20 nm, an Al2O3 / SiO2 molar ratio of 1:3, and a solid content of 20-30%.

6. A method for preparing fly ash-red mud-based ultrafine powder as described in claims 1-5, characterized in that: Includes the following steps: (1) Preparation of modified fly ash: After microwave activation of fly ash for 10-20 min, inert gas is introduced and the treatment is continued for 3-8 min. After drying, modified fly ash is obtained. (2) Preparation of dealkali-treated red mud: After calcination, the red mud is leached twice and then filtered until no Cl is found. - The alkali-degraded red mud was detected and dried. (3) Preparation of waste glass powder: Waste glass powder is obtained by crushing, ball milling and classifying construction waste glass; (4) Modified fly ash, dealkali-reduced red mud and waste glass powder are mixed and dispersed to obtain a primary mixture; (5) After ball milling the primary mixture, add the nano-silica-alumina sol and continue ball milling until the specific surface area of ​​the material is ≥650m². 2 / kg, aged, dried, pulverized and sieved to obtain fly ash-red mud-based ultrafine powder.

7. The preparation method according to claim 6, characterized in that: The secondary rinsing in step (2) involves a primary rinsing with deionized water followed by a secondary rinsing with ammonium chloride solution.

8. The preparation method according to claim 7, characterized in that: The liquid-to-solid ratio of the first-stage rinsing is 3:1, and the rinsing time is 20-40 min; the liquid-to-solid ratio of the second-stage rinsing is 2:1, and the rinsing time is 50-70 min; the solubility of the ammonium chloride solution is 0.1-0.5 mol / L.

9. The preparation method according to claim 6, characterized in that: The aging conditions described in step (5) are aging at 20-25℃ and 60-70% humidity for 20-30 hours.

10. The application of fly ash-red mud-based ultrafine powder as described in claims 1-5 in marine sand concrete, characterized in that: The application is to replace mineral powder in the preparation of sea sand concrete.

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