A composite cementitious material based on lithium slag and synergistic aluminum-based enhancer to stimulate mineral powder and a preparation method thereof

Abstract

The application discloses a kind of based on lithium residue synergistic aluminum-based synergist excitation ore powder Composite Cement and preparation method thereof, belong to solid waste resource reutilization technical field, the composite cement according to weight percentage, including the following raw materials: ore powder: 47%-85%, lithium residue: 5%-30%, desulfurization gypsum: 1%-20%, slaked lime: 0.5%-3%, aluminum-based synergist: 0.1%-7%.Preparation process is: ore powder, lithium residue, desulfurization gypsum, slaked lime and aluminum-based synergist are dry mixed, then gradient stirring is carried out by adding mixing water, form slurry, then shaping and curing are carried out.That is, the application excites ore powder by lithium residue and aluminum-based synergist, realizes excellent mechanical property, good workability and early strength under high solid waste content;And the application process is simple, low in cost, green and low in carbon, significantly better than traditional solid waste excitation system.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource recycling technology, and particularly relates to a composite cementitious material based on lithium slag synergistically activated by aluminum-based synergists and its preparation method. Background Technology

[0002] Lithium slag is a solid waste generated during the lithium extraction process from spodumene or salt lakes. Large-scale open-air stockpiling or landfilling of lithium slag occupies significant amounts of land, causing serious environmental damage and hindering the sustainable development of lithium salts as a clean energy source. Lithium slag possesses abundant potentially active SiO2 and Al2O3; proper activation can reveal its beneficial pozzolanic properties, leading to its widespread use as a mineral admixture in cement and concrete to improve their mechanical properties and durability. While lithium slag has been explored as a substitute material in some areas, its activity in cement and concrete remains low, resulting in low utilization efficiency. Therefore, improving the activity of lithium slag and expanding its high-value-added applications through reasonable activation measures remains a pressing technical challenge.

[0003] Because lithium slag contains relatively few silica-alumina active phases and has large particles, its reactivity with cement is insufficient. Simultaneously, the low calcium content in lithium slag cannot effectively promote the formation of hydrated silicate gels, limiting the activation potential of lithium slag in the cement matrix. To address the problem of insufficient activation effect of lithium slag, this paper seeks methods to fully activate its activity, thereby improving the overall quality and performance of lithium slag-based cementitious materials and better adapting them to various application scenarios.

[0004] Currently, existing research on lithium slag activation still has significant limitations. Most methods employ simple composite activation techniques, lacking systematic process design and parameter optimization. Furthermore, they often only replace cement as a small proportion (≤20%) as auxiliary cementitious materials (SCMs), or directly use unactivated lithium slag to prepare recycled concrete. In addition, the composite activation mechanism of lithium slag and the strength formation mechanism of its recycled concrete remain unclear. Among currently published patents, most mature technologies rely on mechanical / high-temperature treatment or the addition of chemical admixtures to enhance lithium slag activation. Some related research findings are as follows: Patent publication number CN117069400A, entitled "A Method and Application of Low-Carbon Cement Prepared Using Modified Lithium Slag Composite Multi-Source Solid Waste," discloses a method and application for preparing low-carbon cement using modified lithium slag composite multi-source solid waste. By using lithium slag as a raw material for preparing low-carbon cement, modifying it, and combining it with multi-source solid waste, cement clinker, and an activator, a low-carbon cement with low preparation cost and strong mechanical properties is obtained.

[0005] Patent CN118344110A, entitled "A Highly Active Auxiliary Cementitious Material Based on Multi-component Solid Waste and Its Preparation Method," discloses a lithium slag-based multi-component highly active auxiliary cementitious material and its preparation method. The method involves separately grinding industrial byproducts such as lithium slag, blast furnace slag, fly ash, and phosphogypsum, along with limestone, a natural mineral material with abundant reserves and low price, and adding a low-carbon cementitious activator. The process optimizes particle size distribution and then re-blends these materials to obtain a highly active auxiliary cementitious material.

[0006] The lithium slag cementitious materials mentioned above are highly targeted and selective. Patent CN117069400A modifies lithium slag before mixing and compounding. However, the modification process involves high-temperature calcination and alkaline treatment, including the use of sodium hydroxide for alkaline activation, which may lead to the decomposition of sulfate minerals. Furthermore, its two-step modification process significantly increases energy consumption and pretreatment costs compared to simple mechanical grinding or direct blending, forming a significant difference from the direct blending method in this invention. Another patent, CN118344110A, discloses a highly active auxiliary cementitious material that can significantly replace cement clinker. Although it uses various industrial solid wastes such as lithium slag, blast furnace slag, and fly ash, its composition and activity face significant challenges. For example, it uses NaOH as a strong activator, which is costly (sodium hydroxide costs 2000 yuan / ton), and the alkaline activator leads to high alkali content and efflorescence problems. Additionally, the alkaline environment can compromise construction safety.

[0007] To enhance the activity of lithium slag in cementitious materials, address theoretical challenges and construction difficulties, and increase the added value of lithium slag utilization, it is necessary to conduct targeted research and development on composite admixtures acting in the system, explore the influence mechanism and variation law of different components and component contents on the properties of cementitious materials, and provide theoretical support and core technologies for the harmless treatment and large-scale utilization of industrial solid wastes such as lithium slag. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a composite cementitious material based on lithium slag synergistically activated by aluminum-based synergists and its preparation method.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A composite cementitious material based on lithium slag synergistic aluminum-based synergist activated mineral powder, comprising the following raw materials by weight percentage: Mineral powder: 47%-85%, lithium slag: 5%-30%, desulfurized gypsum: 1%-20%, quicklime: 0.5%-3%, aluminum-based synergist: 0.1%-7%.

[0010] Optionally, the mineral powder, by weight percentage, comprises 14.9% Al2O3, 41.0% CaO, 0.058% Cl, 0.349% Fe2O3, 6.99% MgO, 31.8% SiO2, 2.55% SO3, 1.04% TiO2, 0.54% Na2O, and unavoidable impurities.

[0011] Optionally, the lithium slag, by weight percentage, comprises: 18.8% Al2O3, 11.6% CaO, 15.6% SO3, 49% SiO2, 1.85% Fe2O3, 0.59% K2O, 0.28% Na2O, 0.072% Cl, 0.49% P2O5, and unavoidable impurities.

[0012] Optionally, the slaked lime contains ≥99% effective calcium hydroxide.

[0013] Optionally, the aluminum-based synergist is selected from at least two of sulfoaluminate cement, polyaluminum chloride, aluminum sulfate, or calcium aluminate.

[0014] Furthermore, the aluminum-based synergist is a mixture of sulfoaluminate cement and polyaluminum chloride, with a mass ratio of 5:1.

[0015] Beneficial effects: This invention uses lithium slag, mineral powder, sulfoaluminate cement, desulfurized gypsum, quicklime, and polyaluminum chloride as main raw materials. By expanding the range and adjusting the dosage of various components and temperature, a lithium slag-specific active activator is developed to improve the hydration activity of lithium slag, enabling it to participate more effectively in the hydration reaction in cement-based materials, generate cementitious products, and enhance the strength and durability of the materials.

[0016] Optionally, the raw materials of the composite cementitious material also include mixing water, and the water-cement ratio is 0.5.

[0017] A method for preparing a composite cementitious material based on lithium slag synergistically activated mineral powder by an aluminum-based synergist includes the following steps: Weigh the raw materials according to their weight percentages, dry mix the mineral powder, lithium slag, desulfurized gypsum, quicklime and aluminum-based synergist, then add mixing water and perform gradient stirring to form a slurry.

[0018] Optionally, the dry mixing conditions are: dry mixing at a speed of 30-50 rpm for 5-10 minutes.

[0019] Optionally, the gradient stirring conditions are as follows: first, stir at a speed of 140±5 rpm for 60 seconds, pause for 15 seconds, and then stir at a speed of 285±10 rpm for 90 seconds.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects: (1) High utilization rate of solid waste and extremely low cost: The main components of the system of this invention (mineral powder, lithium slag, desulfurization gypsum) are all industrial solid wastes. The raw material cost is much lower than that of traditional alkali-activated materials activated by pure chemical reagents, and also lower than that of ordinary silicate cement, resulting in significant economic benefits.

[0021] (2) High activation efficiency and excellent strength development: This invention achieves a mild and long-lasting activation effect on slag powder through the synergistic effect of lithium slag and aluminum-based synergist. As shown in the example, the compressive strength can reach up to 47.59 MPa after 28 days, and the strength continues to increase in the later stage. The performance is better than that of single lithium slag activation or traditional solid waste activation system.

[0022] (3) Significantly improved early strength: The present invention introduces a trace amount of aluminum-based synergist, which effectively solves the common problem of low early strength in the slag powder (mineral powder)-lithium slag powder system. As can be seen from the examples, the strength of the 3-day composite cementitious material can reach up to 17.80 MPa, which meets the requirements of early bearing capacity in most construction scenarios.

[0023] (4) Workability and setting time are easy to control: The system of the present invention does not require the use of strong alkali, the pH value of the slurry is relatively mild, the initial fluidity is good, and the setting time can be effectively controlled within a large range by adjusting the lithium slag, aluminum-based synergist and water-cement ratio, making it highly adaptable to construction.

[0024] (5) Simple process and easy to industrialize: The preparation process of this invention is only physical mixing and stirring, without the need for high temperature and high pressure or complex chemical reaction equipment, and can be directly used for large-scale production using existing cement concrete production facilities.

[0025] (6) Green, low-carbon and environmentally friendly: The raw materials in the composite cementitious material of this invention are mostly industrial solid waste, which reduces the amount of cement clinker used and significantly reduces carbon dioxide emissions, which is in line with the development direction of the circular economy. Detailed Implementation

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0028] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0029] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0030] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0031] This invention discloses a method for preparing a composite cementitious material based on lithium slag synergistically activated aluminum-based synergist, comprising the following steps: 1. Weigh the raw materials according to their weight percentage: Mineral powder: 47% - 85%, serving as the main source of active silica, aluminum, and calcium and the strength framework of the system.

[0032] Lithium slag: 5% - 30%, as a composite activator, providing an alkaline environment and sulfates, with the optimal dosage range being 10%-30%.

[0033] Desulfurized gypsum: 1% - 20%, provides additional sulfate ions, promotes ettringite formation, and stabilizes the sulfoaluminate phase.

[0034] Quicklime: 0.5% - 3%, to adjust the alkalinity of the system and promote the dissociation of slag glass, preferably 0.5% - 2%.

[0035] Aluminum-based synergist: 0.1% - 7%, preferably 0.5% - 5%.

[0036] 2. Raw material pretreatment: Dry the mineral powder, lithium slag, and desulfurized gypsum separately until the moisture content is less than 1%.

[0037] 3. Dry mixing: Weigh the dry materials of each component according to the above proportions, place them in a high-efficiency mixer, and dry mix at a speed of 30-50 rpm for 5-10 minutes until the color is uniform and there is no clumping.

[0038] 4. Mixing: Transfer the dry mixture to a mixing pot and add mixing water according to the designed water-cement ratio of 0.5. Using a mortar mixer, first mix at low speed for 60 seconds, pause for 15 seconds, and then mix at high speed for 90 seconds to form a uniform new slurry.

[0039] This invention also discloses a composite cementitious material based on lithium slag synergistically activated by an aluminum-based synergist to activate mineral powder. The specific core interaction mechanism between the raw materials is as follows: The combined activating effect of lithium slag: soluble alkali (K) in lithium slag + Na + Sulfates dissolve rapidly, raising the pH of the liquid phase, disrupting the glassy structure of the mineral powder, and releasing Ca. 2+ [SiO4] 4- [AlO4] 5- Plasma. At the same time, gypsum dihydrate and active Al2O3 in lithium slag participate in the reaction, combining with ions dissolved from mineral powder under alkaline conditions, promoting the formation of hydrated calcium aluminosilicate (CASH) gel and ettringite (AFt).

[0040] The synergistic enhancement mechanism of aluminum-based synergists: their main components are aluminum-based minerals C4A3S and aluminum-based chemical substances, such as aluminate AlO3. 2- Upon contact with water, it reacts rapidly, releasing aluminate, hydroxide, and sulfate ions, which helps the slag powder system generate a large amount of ettringite, providing significant early strength. These early-formed ettringite crystals not only possess strength themselves but also act as "nuclei," accelerating subsequent reactions in the lithium slag-mineral powder system, filling pores, and making the microstructure more compact, thereby significantly improving later-stage strength and durability.

[0041] Unless otherwise specified, "room temperature" in this invention refers to 20-30℃.

[0042] All raw materials used in this invention were purchased from the market.

[0043] The technical solution of the present invention will be further illustrated by the following embodiments.

[0044] Examples 1-5 A method for preparing a composite cementitious material based on lithium slag synergistically activated mineral powder by an aluminum-based synergist includes the following steps: 1. Weigh the raw materials according to the weight percentages in Table 1 (based on the sum of the total weight percentages of mineral powder, lithium slag, desulfurization gypsum, quicklime, and aluminum-based synergist being 100%, with a total mass of 450g): Mineral powder: sourced from a steel plant, with main components of Al2O3 14.9%, CaO 41.0%, Cl 0.058%, Fe2O3 0.349%, MgO 6.99%, SiO2 31.8%, SO3 2.55%, TiO2 1.04%, Na2O 0.54%, and unavoidable impurities.

[0045] Lithium slag: sourced from a lithium salt plant, with main components of Al2O3 18.8%, CaO 11.6%, SO3 15.6%, SiO2 49%, Fe2O3 1.85%, K2O 0.59%, Na2O 0.28%, Cl 0.072%, P2O5 0.49%, and unavoidable impurities.

[0046] Desulfurized gypsum: sourced from power plants, purity ≥90%, used after grinding.

[0047] Quicklime: Industrial grade, with an effective calcium hydroxide content of ≥99%.

[0048] Aluminum-based synergists include sulfoaluminate cement, polyaluminum chloride, aluminum sulfate, or calcium aluminate.

[0049] Water: tap water.

[0050] Sand: Standard sand.

[0051] Table 1 2. Raw material pretreatment: Dry the mineral powder, lithium slag, and desulfurized gypsum separately until the moisture content is less than 1%.

[0052] 3. Dry mixing: Weigh the dry materials of each component according to the raw material ratio in Table 1, place them in a high-efficiency mixer, and dry mix at a speed of 30-50 rpm for 5-10 minutes until the color is uniform and there is no clumping.

[0053] 4. Mixing: Transfer the dry mixture to a mixing pot, and add mixing water according to the designed water-cement ratio of 0.5 (wherein, the water-cement ratio is the mass ratio of the mixing water to the sum of the masses of the five raw materials (mineral powder, lithium slag, desulfurized gypsum, quicklime, and aluminum-based synergist)). Using a mortar mixer, first mix at low speed (140±5 rpm) for 60 seconds, pause for 15 seconds, then mix at high speed (285±10 rpm) for 90 seconds to form a uniform new slurry; then add 1350g of standard sand and mix evenly. 5. Molding and Curing: Pour the slurry into the mold and vibrate to compact it. After standing in a standard curing chamber at a temperature of 20±2℃ and a humidity of ≥95% for 24 hours, demold the specimen and then continue to cure it under the same conditions until the specified age for testing.

[0054] Effect verification: The specimens after molding and curing in Examples 1-5 were tested for compressive strength according to the GB / T 17671-2021 test standard. The specific test results are shown in Table 2.

[0055] Table 2. Compressive strength of specimens after molding and curing in Examples 1-5 at 3d, 7d, and 28d. Conclusion: As can be seen from Tables 1 and 2, the introduction of PAC (1%) and the combination of aluminate cement (5%) as aluminum-based synergists resulted in the highest strength of the hardened slurry at 3 days (17.80 MPa) and 7 days (34.05 MPa) among all groups, indicating that the aluminum-based synergists made a significant contribution to early strength. The reasons can be understood from the following two points: (1) PAC provides polynuclear hydroxy aluminum complexes, which can quickly change the ionic environment and surface charge of the slurry, making fine particles (mineral powder, lithium slag, etc.) easier to flocculate and form a "skeleton network", thereby establishing a load-bearing structure more quickly, as shown by the significant improvement at 3 days and 7 days. (2) The active Al source promotes the generation of aluminum phase hydration products, which couple with the calcium source (hydrated lime / aluminate cement hydration products) and sulfate environment (from desulfurized gypsum) in the system, promoting the generation and early filling of aluminum phase-related products and improving early compactness.

[0056] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite cementitious material based on lithium slag synergistically activated mineral powder by an aluminum-based synergist, characterized in that, By weight percentage, it includes the following raw materials: Mineral powder: 47%-85%, lithium slag: 5%-30%, desulfurized gypsum: 1%-20%, quicklime: 0.5%-3%, aluminum-based synergist: 0.1%-7%.

2. The composite cementitious material based on lithium slag synergistically activated mineral powder by an aluminum-based synergist, as described in claim 1, is characterized in that... The mineral powder, by weight percentage, comprises: Al2O3 14.9%, CaO 41.0%, Cl 0.058%, Fe2O3 0.349%, MgO 6.99%, SiO2 31.8%, SO3 2.55%, TiO2 1.04%, Na2O 0.54%, and unavoidable impurities.

3. The composite cementitious material based on lithium slag synergistically activated mineral powder by an aluminum-based synergist, as described in claim 1, is characterized in that... The lithium slag, by weight percentage, comprises: Al2O3 18.8%, CaO 11.6%, SO3 15.6%, SiO2 49%, Fe2O3 1.85%, K2O 0.59%, Na2O 0.28%, Cl 0.072%, P2O5 0.49%, and unavoidable impurities.

4. The composite cementitious material based on lithium slag synergistic aluminum-based synergist activated mineral powder according to claim 1, characterized in that, The slaked lime contains ≥99% effective calcium hydroxide.

5. The composite cementitious material based on lithium slag synergistic aluminum-based synergist activated mineral powder according to claim 1, characterized in that, The aluminum-based synergist is selected from at least two of sulfoaluminate cement, polyaluminum chloride, aluminum sulfate, or calcium aluminate.

6. The composite cementitious material based on lithium slag synergistic aluminum-based synergist activated mineral powder according to claim 5, characterized in that, The aluminum-based synergist is a mixture of sulfoaluminate cement and polyaluminum chloride, with a mass ratio of 5:

1.

7. The composite cementitious material based on lithium slag synergistically activated mineral powder by an aluminum-based synergist, as described in claim 1, is characterized in that... The raw materials of the composite cementitious material also include mixing water, and the water-cement ratio is 0.

5.

8. A method for preparing a composite cementitious material based on lithium slag synergistic aluminum-based synergist activated mineral powder as described in any one of claims 1-7, characterized in that, Includes the following steps: The raw materials are weighed according to the weight percentage, and the mineral powder, lithium slag, desulfurized gypsum, quicklime and aluminum-based synergist are dry mixed. Then, mixing water is added and the mixture is stirred in a gradient to form a slurry, which is the composite cementitious material.

9. The preparation method of the composite cementitious material based on lithium slag synergistic aluminum-based synergist activated mineral powder according to claim 8, characterized in that, The dry mixing conditions are as follows: dry mix at a speed of 30-50 rpm for 5-10 minutes.

10. The preparation method of the composite cementitious material based on lithium slag synergistic aluminum-based synergist activated mineral powder according to claim 8, characterized in that, The gradient stirring conditions are as follows: first, stir at a speed of 140±5 rpm for 60 seconds, pause for 15 seconds, and then stir at a speed of 285±10 rpm for 90 seconds.

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