Method for preparing cement by utilizing modified lithium slag composite multi-source solid waste
By using targeted solidification and gradient excitation technology of modified lithium slag, combined with multi-component synergistic design, the problems of low activity and impurity suppression of lithium slag were solved, and high-performance cement was prepared. This solved the bottleneck of lithium slag application in cement and achieved high dosage stability and performance improvement.
Patent Information
- Application Number
- CN202511613741.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-06
- Publication Date
- 2026-01-27
AI Technical Summary
The low activity and harmful impurities in existing lithium slag limit its application in cement concrete. Furthermore, the lack of synergistic design in the physical mixing of various solid wastes leads to performance fluctuations, making it difficult to produce high-quality cement.
Lithium slag was modified using targeted solidification and gradient activation methods, and cement was prepared by multi-component synergistic design. The cement consisted of modified lithium slag, granulated blast furnace slag, fly ash, silicate cement, and composite gypsum. A composite activator was used for gradient activation to form an orderly hydration process.
Stable application of high-content lithium slag has been achieved, significantly improving the early strength of cement, and its later strength surpasses that of traditional cement of the same grade. Drying shrinkage is reduced, performance is more stable, and volume stability is improved.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of building materials and solid waste resource utilization technology, and more specifically relates to a method for preparing cement using modified lithium slag composite multi-source solid waste. Background Technology
[0002] Cement is a crucial material for national economic development, but its traditional production process (primarily relying on silicate cement clinker) suffers from high energy consumption, high resource consumption, and high carbon dioxide emissions. The accumulation of these solid wastes not only occupies vast amounts of land but also poses a potential threat to the environment.
[0003] Lithium slag is an acidic waste residue generated during the extraction of lithium from spodumene in the lithium salt industry. It has low activity and contains a certain amount of residual lithium, fluorine, and other harmful impurities, limiting its large-scale application in cement concrete. Currently, the utilization rate of lithium slag is low, with most being stockpiled, resulting in serious resource waste and environmental pressure. Although solid wastes such as fly ash and slag are widely used in cement admixtures, their added value needs further improvement.
[0004] In existing technologies, the modification of lithium slag is mostly limited to simple mechanical grinding or alkali activation, failing to fundamentally solve the strong inhibitory effect of residual lithium salts (such as Li2CO3 and LiF) on cement hydration. This inhibitory effect leads to abnormal cement setting and extremely slow early strength development, which is the core bottleneck limiting the amount of lithium slag added. In addition, simply physically mixing various solid wastes without considering the synergistic design of the hydration process of each component in the system can easily lead to performance fluctuations and make it difficult to stably produce high-quality cement.
[0005] Therefore, developing a method that can target and eliminate the side effects of lithium salts and precisely stimulate the synergistic hydration activity of multi-source solid waste is the key to realizing the high-value utilization of lithium slag. Summary of the Invention
[0006] The purpose of this invention is to provide a method for preparing cement using modified lithium slag and other multi-source solid waste, in order to solve the problems existing in the prior art. This invention provides a method for preparing cement using modified lithium slag and other multi-source solid waste with high dosage and high performance through synergistic activation and optimized cementitious system design.
[0007] To achieve the above objectives, the present invention provides the following solution:
[0008] One of the technical solutions of this invention is to provide cement prepared using modified lithium slag composite multi-source solid waste, comprising the following raw materials in parts by weight:
[0009] The mixture contains 30-60 parts modified lithium slag, 15-35 parts granulated blast furnace slag, 5-15 parts fly ash, 8-20 parts silicate cement, 4-8 parts composite gypsum, and 1.5-3.5 parts composite activator.
[0010] The preparation steps of the modified lithium slag are as follows:
[0011] Pretreatment: The lithium slag is pretreated by spraying with aluminum salt solution, and then cured;
[0012] Mechanical-chemical composite grinding: Pretreated lithium slag is mixed with calcined magnesium oxide and then ground.
[0013] Gradient excitation: Sodium silicate powder is first added to the pulverized lithium slag powder for aging, and then calcium sulfate whiskers are added for mixing to obtain modified lithium slag.
[0014] The core function of the preprocessing step is to utilize AI 3+ With soluble Li in lithium slag + The reaction generates insoluble lithium aluminum salts (such as LiAlO2) or embedded structures, achieving "targeted solidification" and fundamentally eliminating the lithium-inhibiting effect. In the mechanical-chemical composite grinding step, the introduction of MgO not only acts as a mill synergist, but its microcrystals can also generate brucite during subsequent hydration, contributing to the stability of the early structure. Gradient excitation first deeply disrupts the glass matrix with strongly alkaline sodium silicate, followed by calcium sulfate whiskers (providing highly active Ca). 2+ and SO4 2- (And has fiber reinforcement effect) In the middle and late stages, it is continuously stimulated to form an orderly hydration process.
[0015] Preferably, the aluminum salt solution includes an aluminum sulfate solution; the concentration of the aluminum salt solution is 5-10 wt%; and the solid-liquid ratio of the lithium slag and the aluminum salt solution is 0.1-0.15 g:1 mL.
[0016] Preferably, the curing temperature is 50~70℃ and the time is 6~12h.
[0017] Preferably, the mass of the calcined magnesium oxide is 1-3% of the dry weight of the pretreated lithium slag; and it is ground to a specific surface area of 550-750 m². 2 / kg.
[0018] Preferably, the mass of the sodium silicate powder is 1.5-3% of the dry basis mass of the milled lithium slag powder; the aging time is 8-24 hours; and the mass of the calcium sulfate whiskers is 0.5-2% of the dry basis mass of the milled lithium slag powder.
[0019] Preferably, the composite gypsum is prepared by mixing desulfurized gypsum and phosphogypsum in a mass ratio of 7~8:2~3.
[0020] Preferably, the composite activator is composed of solid water glass, triisopropanolamine, and calcium formate in a mass ratio of 2~3:0.5~1:1.
[0021] The second technical solution of the present invention provides a method for preparing cement using modified lithium slag composite multi-source solid waste, comprising the following steps:
[0022] Modified lithium slag, granulated blast furnace slag, fly ash, silicate cement, and composite gypsum are mixed and ground according to the specified dosage; a composite activator is added to the mixture after co-grinding, and homogenization is carried out to obtain the cement prepared by using modified lithium slag and multi-source solid waste.
[0023] Preferably, the fineness of the grinding is controlled as follows: specific surface area ≥ 450 m². 2 / kg, and the residue on a 45μm square hole sieve is ≤8%.
[0024] The third technical solution of this invention provides the application of the cement prepared by using modified lithium slag composite multi-source solid waste in the construction field.
[0025] The technical mechanism of this invention is as follows:
[0026] This invention fundamentally solves the two major problems of "activity inhibition" and "volume instability" in the high-dosage application of lithium slag in cement systems through the physicochemical synergistic mechanism of "targeted solidification-gradient excitation-system reconstruction", and achieves synergistic effect of multi-source solid waste.
[0027] First, the targeted solidification mechanism solves the problem of chemical inhibition of lithium ions. The residual soluble lithium salts (such as Li₂CO₃ and LiF) in lithium slag are the root cause of the strong inhibition of cement hydration. These lithium ions preferentially adsorb onto the surface of silicate cement clinker particles and hydration products (such as CSH gel), forming a dense "lithium ion barrier," which greatly delays the degradation of calcium ions. 2+ and OH - The dissolution and diffusion of aluminum salts hinder the formation and growth of hydrated crystal nuclei, leading to abnormal solidification and early strength loss. The innovation of this invention lies in introducing an aluminum salt solution (such as aluminum sulfate) during the pretreatment stage. The Al in the solution... 3+ Ions can react with soluble Li in lithium slag + The reaction produces insoluble or very poorly soluble lithium-aluminum composite compounds (such as LiAlO2) or immobilizes them within an amorphous aluminum hydroxide gel network. This process achieves "targeted solidification" of harmful free lithium ions, transforming them from soluble inhibitors into stable solid components, thus removing the biggest chemical obstacle to the application of high-dosage lithium slag.
[0028] Secondly, the gradient activation and microstructure optimization mechanisms synergistically enhance the activity and stability of the cementitious system. After removing the inhibition of lithium, effectively activating the potential cementitious activity of solid wastes such as lithium slag and mineral slag becomes crucial. Although single strong alkali activation can destroy the glassy structure, the reaction is too rapid, easily leading to early structural defects and weak strength growth in the later stages. The "alkali first, then sulfur" gradient activation strategy adopted in this invention conforms to the hydration kinetics of cementitious materials. The strongly alkaline environment (high concentration of OH-) provided by sodium silicate... - This process rapidly disrupts the glassy network structure of lithium slag and mineral slag, exposing the internal active SiO2 and Al2O3. The subsequent introduction of calcium sulfate whiskers provides highly active Ca... 2+ and SO4 2- The hydrated gel reacts with the previously dissolved Al2O3 to form expandable ettringite (AFt), which effectively fills the pores and makes the structure dense. On the other hand, its unique fibrous crystal morphology acts as a microfiber reinforcement in the slurry, improving the toughness of the microstructure. This time-sequential excitation mode ensures the continuous and orderly generation of hydration products (CSH gel and AFt), resulting in a denser and more robust slurry structure.
[0029] Finally, the reconstruction of the multi-component system achieved synergistic and optimized performance. This invention, through formulation design, eliminated steel slag with complex composition and questionable volume stability, constructing a purer cementitious system centered on "modified lithium slag-blast furnace slag-fly ash". The introduction of phosphogypsum into the composite gypsum not only provides SO3, but its P2O5 can also participate in the reaction to generate phosphate products with lower solubility, further enhancing the system's density and impermeability. The specially formulated composite activator (solid water glass / triisopropanolamine / calcium formate) plays a role from different dimensions: water glass provides continuous alkalinity; triisopropanolamine specifically catalyzes the iron phase components of blast furnace slag, promoting their dissolution; and calcium formate, as a highly efficient early-strength agent, significantly accelerates early hydration. The synergy of these components ultimately manifests macroscopically as higher early and later strength, lower drying shrinkage, and excellent volume stability in cement products.
[0030] The present invention discloses the following technical effects:
[0031] 1. Pioneering "Targeted Solidification" Technology: Through pretreatment with aluminum salt solution, soluble lithium ions in lithium slag are specifically solidified, solving the industry problem of lithium inhibiting cement hydration and removing a fundamental obstacle to significantly increasing the lithium slag content (up to 60%). This is a key technical approach not addressed in existing technologies.
[0032] 2. "Gradient activation" strategy: This strategy changes the traditional method of adding activators all at once and adopts a "gradient activation mode of alkali first and then sulfur", which conforms to the hydration kinetics of the lithium slag-slag composite system. This achieves a stable, continuous and efficient hydration reaction and significantly improves the later strength growth rate of cement.
[0033] 3. Synergistic effect of multiple components:
[0034] The introduction of phosphogypsum into composite gypsum provides additional P2O5, which can form a denser phosphate complex hydration product with Al and Ca in the system, thereby enhancing impermeability.
[0035] By abandoning the steel slag formulation design, unstable factors are avoided, allowing the system to focus on leveraging the synergistic cementing effect of lithium slag, blast furnace slag, and fly ash, resulting in more stable performance.
[0036] Calcium formate in the composite activator, as a strong early-stage activator, works synergistically with triisopropanolamine (which is particularly effective for slag) to overcome the shortcoming of low early-stage strength in solid waste cement.
[0037] By combining the above technologies, the cement prepared by this invention not only has 100% qualified stability, but also has a 3-day strength that can reach more than 90% of that of ordinary cement, a 28-day strength that surpasses that of traditional cement of the same grade by 5-10%, and a drying shrinkage value that is reduced by more than 15%, demonstrating significant advantages in comprehensive performance. Detailed Implementation
[0038] 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.
[0039] 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. Any stated value or intermediate value within a stated range, as well as each smaller range between 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.
[0040] 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.
[0041] 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 readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.
[0042] 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.
[0043] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.
[0044] The following embodiments and comparative examples of this invention describe the raw materials used:
[0045] Lithium slag: taken from local lithium salt plants, with a chemical composition mainly of SiO2 (55-60%), Al2O3 (20-25%), a water content of 20%, and a soluble lithium content (calculated as Li2O) of 0.8%.
[0046] Aluminum salt solution: An 8 wt% aqueous solution was prepared using analytical grade aluminum sulfate (Al2(SO4)3·18H2O).
[0047] Calcined magnesium oxide: Lightly calcined MgO, with an activity content ≥85%.
[0048] Sodium silicate powder: solid water glass powder with a modulus of 2.0~2.4.
[0049] Calcium sulfate whiskers: diameter 1~5μm, aspect ratio >20.
[0050] Composite gypsum: Desulfurized gypsum (from a local power plant) and phosphogypsum (from a local phosphate fertilizer plant, after purification) are mixed at a mass ratio of 7.5:2.5.
[0051] Composite activator: solid water glass, triisopropanolamine, and calcium formate are mixed and ground in a mass ratio of 2.5:0.7:1.
[0052] Other raw materials: S95 grade granulated blast furnace slag, II grade fly ash, and 42.5 grade silicate cement, all conforming to national standards.
[0053] Example 1
[0054] Preparation of modified lithium slag:
[0055] Pretreatment (targeted solidification): Take 1000g of raw wet lithium slag (800g on dry basis), spray it with 8% aluminum sulfate solution at a solid-liquid ratio of 1:10 (80mL solution), mix well, and cure at 60℃ for 8 hours.
[0056] Mechanical-chemical composite grinding: After curing, dry at 105℃, and grind together with 2% (by dry weight) calcined magnesium oxide (16g) to a specific surface area of approximately 650m². 2 / kg.
[0057] Gradient excitation: First, add 2% sodium silicate powder (16g) by dry weight and age for 12 hours; then add 1% calcium sulfate whiskers (8g) by dry weight and mix evenly to obtain modified lithium slag.
[0058] Cement preparation:
[0059] Formula: 50 parts modified lithium slag, 25 parts granulated blast furnace slag, 10 parts fly ash, 10 parts silicate cement, 7 parts composite gypsum, and 2.5 parts composite activator.
[0060] Process: All solid raw materials (except the composite activator) are mixed and ground together until the specific surface area is 460 m² / kg and the residue on a 45μm sieve is 6.5%. The composite activator is added and homogenized in a mixer for 5 minutes to obtain cement E1 of the present invention.
[0061] Example 2
[0062] The amount of modified lithium slag was adjusted to 40 parts, the amount of granulated blast furnace slag was increased to 35 parts, and the amount of silicate cement was 12 parts.
[0063] In the preparation of modified lithium slag, the amount of calcium sulfate whiskers is increased to 1.5%.
[0064] The remaining steps are the same as in Example 1, and cement E2 is obtained.
[0065] Comparative Example 1: Non-targeted curing
[0066] The only difference from Example 1 is that the "aluminum salt solution pretreatment" step is omitted during lithium slag modification. The original lithium slag is directly dried and then subjected to subsequent mechanical-chemical composite grinding and gradient excitation.
[0067] Cement C1 was obtained.
[0068] Comparative Example 2: Gradient-free excitation
[0069] The only difference from Example 1 is that during lithium slag modification, sodium silicate powder and calcium sulfate whiskers are added all at once during grinding, rather than being added in stages.
[0070] Cement C2 was obtained.
[0071] Comparative Example 3: Traditional Composite Activator
[0072] The only difference from Example 1 is that the composite activator is replaced with an equal amount of conventional alkali-free liquid activator (prepared by mixing triethanolamine and sodium thiosulfate in a mass ratio of 1:2).
[0073] Cement C3 was obtained.
[0074] Comparative Example 4: Commercially Available Products
[0075] Commercially available grade 42.5 ordinary slag silicate cement (P·S·A 42.5) was used.
[0076] All cement samples prepared according to the various embodiments and comparative examples were tested for performance in accordance with the following Chinese national standards (GB):
[0077] Standard consistency water requirement, setting time, and soundness: GB / T 1346-2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement";
[0078] Mortar strength: GB / T 17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)";
[0079] Drying shrinkage: GB / T 751-2023 "Test Method for Drying Shrinkage of Cement Mortar";
[0080] Cement mortar fluidity: GB / T 2419-2005 "Method for Determination of Flowability of Cement Mortar" (for evaluating workability).
[0081] The test results are shown in Tables 1 and 2.
[0082] Table 1 Test results of physical and mechanical properties of cement
[0083]
[0084] Table 2 Results of Long-Term Performance and Workability Tests for Cement
[0085]
[0086] Analysis of Tables 1 and 2 leads to the following conclusions:
[0087] 1. The decisive role of "targeted curing" technology (E1 vs. C1):
[0088] Comparative Example C1 (without targeted curing) exhibited an unusually long setting time and extremely low strength at 3 days, directly demonstrating the strong inhibitory effect of soluble lithium ions on cement hydration. In contrast, Example E1 set normally and showed good strength development at all ages. This eloquently proves that "targeted curing" of lithium ions through aluminum salt solution pretreatment is a necessary and crucial step in solving this technical challenge and achieving high lithium slag content (50%), with significant differences in technical effectiveness and outstanding substantive characteristics.
[0089] 2. The superiority of the "gradient activation" strategy (E1 vs. C2):
[0090] The 3-day and 28-day compressive strengths of Comparative Example C2 (one-time activation) were significantly lower than those of E1. This indicates that the stepwise "alkali-first, sulfur-later" gradient activation can more orderly and fully activate the lithium slag and mineral slag, avoid mutual interference between different activators, optimize the hydration process, and thus achieve a higher strength growth rate.
[0091] 3. Synergistic effect of composite activators (E1 vs. C3):
[0092] The comparative example C3 (traditional activator) showed lower early and late strengths than E1, and a greater shrinkage value. This demonstrates that the specific solid water glass / triisopropanolamine / calcium formate composite activator system of this invention has superior compatibility and synergistic activation effect on the specific solid waste system of this invention, especially with calcium formate and triisopropanolamine playing a significant role in improving early strength.
[0093] The overall advantages of the product of this invention (E1 / E2 vs. C4):
[0094] Strength: The 28-day compressive strength (53.5MPa and 54.2MPa) of cement E1 and E2 of this invention is significantly higher than that of commercially available 42.5 grade slag cement C4 (48.5MPa), exceeding the requirements of grade 42.5 and even reaching the strength level of grade 52.5.
[0095] Durability: 28-day drying shrinkage values for E1 and E2 (285 × 10⁻⁶) -6 and 278×10 -6 () is far lower than the comparison ratio and commercially available products (~330×10) -6 The reduction exceeded 13%. This indicates that the cement of this invention has better volume stability and crack resistance, which is an unexpected technical effect.
[0096] Workability: While ensuring high strength, the flowability of the cement of this invention is comparable to that of ordinary cement, indicating that it has good workability.
[0097] Through a systematic comparison of the examples and comparative examples, it is fully demonstrated that the "targeted solidification-gradient excitation-multi-component synergy" technical solution provided by the present invention has successfully solved the core obstacle of high-volume utilization of lithium slag. The cement prepared by the invention shows significant and unexpected improvements in mechanical properties and durability (especially drying shrinkage properties), which are superior to traditional processes and commercially available products.
[0098] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.
[0099] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A type of cement prepared using modified lithium slag composite multi-source solid waste, characterized in that, The raw materials include the following parts by weight: The mixture contains 30-60 parts modified lithium slag, 15-35 parts granulated blast furnace slag, 5-15 parts fly ash, 8-20 parts silicate cement, 4-8 parts composite gypsum, and 1.5-3.5 parts composite activator. The preparation steps of the modified lithium slag are as follows: Pretreatment: The lithium slag is pretreated by spraying with aluminum salt solution, and then cured; Mechanical-chemical composite grinding: Pretreated lithium slag is mixed with calcined magnesium oxide and then ground. Gradient excitation: Sodium silicate powder is first added to the pulverized lithium slag powder for aging, and then calcium sulfate whiskers are added for mixing to obtain modified lithium slag.
2. The cement prepared using modified lithium slag composite multi-source solid waste according to claim 1, characterized in that, The aluminum salt solution includes an aluminum sulfate solution; the concentration of the aluminum salt solution is 5~10wt%; the solid-liquid ratio of the lithium slag and the aluminum salt solution is 0.1~0.15g:1mL.
3. The cement prepared using modified lithium slag composite multi-source solid waste according to claim 1, characterized in that, The curing temperature is 50~70℃, and the time is 6~12h.
4. The cement prepared using modified lithium slag composite multi-source solid waste according to claim 1, characterized in that, The mass of the calcined magnesium oxide is 1-3% of the dry weight of the pretreated lithium slag; it is ground to a specific surface area of 550-750 m². 2 / kg.
5. The cement prepared using modified lithium slag composite multi-source solid waste according to claim 1, characterized in that, The mass of the sodium silicate powder is 1.5-3% of the dry basis mass of the ground lithium slag powder; the aging time is 8-24 hours; and the mass of the calcium sulfate whiskers is 0.5-2% of the dry basis mass of the ground lithium slag powder.
6. The cement prepared using modified lithium slag composite multi-source solid waste according to claim 1, characterized in that, The composite gypsum is made by mixing desulfurized gypsum and phosphogypsum in a mass ratio of 7~8:2~3.
7. The cement prepared using modified lithium slag composite multi-source solid waste according to claim 1, characterized in that, The composite activator is composed of solid water glass, triisopropanolamine, and calcium formate in a mass ratio of 2~3:0.5~1:
1.
8. The method for preparing cement using modified lithium slag composite multi-source solid waste as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Modified lithium slag, granulated blast furnace slag, fly ash, silicate cement, and composite gypsum are mixed and ground according to the specified dosage; a composite activator is added to the mixture after co-grinding, and homogenization is carried out to obtain the cement prepared by using modified lithium slag and multi-source solid waste.
9. The method according to claim 8, characterized in that, The fineness of the grinding process is controlled as follows: specific surface area ≥ 450 m². 2 / kg, and the residue on a 45μm square hole sieve is ≤8%.
10. The application of cement prepared using modified lithium slag composite multi-source solid waste as described in any one of claims 1 to 7 in the construction field.