Lithium-excited blast furnace slag-based geopolymer material and preparation method thereof

Abstract

The invention relates to the technical field of inorganic cementing materials, in particular to a lithium-excited blast furnace slag-based geopolymer material and a preparation method thereof, and aims to solve the problems of unstable alkali-aggregate reaction inhibition effect and insufficient durability in an existing geopolymer system. According to the material, granulated blast furnace slag is taken as a main raw material, lithium salt is taken as an exciting agent, sodium silicate is matched for auxiliary excitation, and a stable and compact geopolymer gel structure is constructed by controlling the lithium ion content, the silicon-aluminum ratio and the water-binder ratio. The preparation method comprises the steps of raw material pretreatment, lithium activator and auxiliary activator solution preparation, mixing and stirring, casting molding, constant-temperature and constant-humidity maintenance and the like. Through regulation and control of lithium ions on gel structure formation and aggregate interface reaction, effective inhibition of alkali-aggregate reaction is realized, and mechanical properties and volume stability of the material are improved. The material disclosed by the invention is simple in preparation process and can be used for preparing low-carbon and high-durability cementing materials for buildings and civil engineering.

Description

Technical Field

[0001] This invention belongs to the field of inorganic cementitious materials and solid waste resource utilization technology, specifically involving a lithium-activated blast furnace slag-based geopolymer material and its preparation method, particularly involving a geopolymer system in which lithium ions participate in activation and gel structure regulation to achieve alkali-aggregate reaction inhibition and durability improvement. Background Technology

[0002] Blast furnace slag, an important industrial byproduct of iron and steel smelting, possesses potential cementitious activity. Through alkali activation, it can be used to prepare geopolymer materials, showing broad application prospects in the field of low-carbon building materials. However, traditional alkali activation systems typically rely on high-alkalinity activators, which easily trigger alkali-aggregate reactions in the material, leading to volume expansion, cracking, and durability degradation, severely restricting its engineering applications.

[0003] Existing research indicates that lithium salts have a certain inhibitory effect on alkali-aggregate reactions in cement-based materials, mainly by regulating the composition of reaction products or reducing gel swelling. However, in geopolymer systems with blast furnace slag as the main raw material, the mechanisms by which lithium ions participate in the activation reaction, gel structure formation, and their synergistic regulation of interfacial reactions and macroscopic properties remain unclear, and systematic and scalable technical solutions for related material systems and preparation methods are still lacking.

[0004] Therefore, there is an urgent need to develop a lithium-activated blast furnace slag-based polymer material that combines low carbon content, high mechanical properties, and excellent volume stability, and to establish a controllable preparation method for it, in order to solve the problem of insufficient durability in the existing technology. Summary of the Invention

[0005] This invention addresses the problems of existing blast furnace slag-based polymer materials, such as susceptibility to alkali-aggregate reactions, insufficient volume stability, and limited long-term durability under alkali-activated conditions. It proposes a lithium-activated blast furnace slag-based polymer material and its preparation method. Existing technologies commonly employ high-alkali activation systems to activate blast furnace slag, but this often results in excessively high alkalinity, making the reaction process difficult to control and easily inducing the dissolution of active silica in the aggregate and the formation of expansive reaction products, thus adversely affecting the material's service performance. This invention introduces lithium ions to participate in the activation and structure regulation process, ensuring sufficient reaction of the blast furnace slag while effectively suppressing the alkali-aggregate reaction, and simultaneously improving both the material's mechanical properties and durability.

[0006] To achieve the above objectives, this invention provides a lithium-activated blast furnace slag-based polymer material. Using blast furnace slag as the main cementing raw material, the activation reaction is completed under the combined action of a lithium activator and an auxiliary activator. The lithium activator is a lithium salt capable of providing lithium ions, preferably one or a combination of lithium hydroxide and lithium nitrate. Its dosage is controlled within a reasonable range relative to the mass of the blast furnace slag, allowing lithium ions to participate in the formation and rearrangement of the gel structure during the activation process. The auxiliary activator is sodium silicate, which, by adjusting the reaction environment of silicon and aluminum species in the system, forms a synergistic activation effect with the lithium activator, thereby promoting the release of the potential activity of the blast furnace slag. By controlling the water-cement ratio, the activation reaction process is stabilized, forming a dense and stable gel network.

[0007] In the aforementioned material system, lithium ions not only participate in the early-stage activation reaction but also regulate the coordination environment and bonding state during the gel structure evolution, promoting the densification and stabilization of the gel network. Simultaneously, lithium ions adsorb and react at the aggregate-cement interface, reducing the dissolution rate of reactive silica and inhibiting the formation of expansive gels, thereby achieving effective control over the alkali-aggregate reaction. The resulting geopolymer material exhibits excellent comprehensive performance in terms of volume stability, mechanical properties, and long-term durability.

[0008] This invention also provides a method for preparing the above-mentioned lithium-activated blast furnace slag-based geopolymer material. The method includes pretreatment of blast furnace slag, preparation of a lithium activation solution, mixing the activation solution with the blast furnace slag to form a slurry, and molding and curing the slurry. Through the above preparation process, lithium ions fully participate in the reaction and structural regulation during the material formation stage, ensuring a controllable activation reaction process and a stable gel structure, thereby obtaining a geopolymer material with balanced performance.

[0009] Compared with existing technologies, this invention achieves effective suppression of the alkali-aggregate reaction without relying on high alkalinity conditions through lithium excitation and synergistic excitation, while simultaneously improving the structural stability and durability of blast furnace slag-based polymer materials. This material, using blast furnace slag as the main raw material, is beneficial for the resource utilization of industrial solid waste and has promising engineering application prospects and widespread application value. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments are briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of the preparation process of the lithium-activated blast furnace slag-based polymer material of the present invention. Detailed Implementation

[0012] To enable those skilled in the art to better understand and implement the present invention, the lithium-activated blast furnace slag-based polymer material and its preparation method of the present invention are further described in detail below with reference to specific embodiments. It should be noted that the following embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Equivalent substitutions or modifications made by those skilled in the art without departing from the technical concept of the present invention should all fall within the scope of protection of the present invention.

[0013] The raw materials used in this invention include granulated blast furnace slag, a lithium activator, an auxiliary activator, and water. The granulated blast furnace slag is water-quenched blast furnace slag produced during iron and steel smelting, obtained after drying and grinding. Its main chemical components include CaO, SiO2, Al2O3, and MgO, possessing potential hydraulic properties and geopolymerization reactivity. The lithium activator is selected from lithium salts or lithium-alkali compounds capable of providing Li+ in an alkaline environment, used to regulate the dissolution behavior and gel structure evolution of the blast furnace slag. The auxiliary activator is sodium silicate, used to provide a soluble silicon source and synergistically regulate the alkalinity of the system. The mixing water is deionized water or standard-compliant industrial water.

[0014] In the specific preparation process, granulated blast furnace slag is first weighed according to the set ratio, and the lithium activator and sodium silicate are pretreated. The lithium activator can be directly dissolved in the mixing water to form a homogeneous solution, and the sodium silicate is diluted according to the required modulus to ensure the stability of the system's alkalinity and silicon source supply. Subsequently, the lithium activator solution and the sodium silicate solution are mixed to form a composite activation solution.

[0015] The composite activation solution was added to granulated blast furnace slag, and the mixture was thoroughly stirred under controlled water-cement ratio conditions to ensure uniform contact between the activator and the blast furnace slag particles and to initiate an initial dissolution reaction. During stirring, the system gradually formed a reaction precursor structure dominated by calcium aluminosilicate gel. Li+ ions participated in regulating the migration and rearrangement of silica-alumina species, thereby affecting the densification of the gel structure and the evolution of its pore structure. The stirred slurry was poured into a pre-prepared mold, and air bubbles were removed by vibration or static settling to ensure the uniformity of the sample structure.

[0016] The molded samples were cured under controlled environmental conditions. The curing temperature was controlled within the normal range, and the curing environment was kept at a high relative humidity to promote the continuous geopolymerization reaction. During the curing process, the active components in the blast furnace slag continuously dissolved and repolymerized, gradually forming a continuous and dense gel network structure. Li+ in this process influenced the interfacial chemical reaction and the stability of the gel structure, thereby regulating the volume stability and durability of the material.

[0017] Example 1

[0018] This example provides a method for preparing blast furnace slag-based geopolymer materials using lithium hydroxide as a lithium activator and its performance testing process.

[0019] Granulated blast furnace slag is selected as the main cementing raw material. After drying, the granulated blast furnace slag has a specific surface area of ​​420-450 m². 2 / kg. The lithium activator is analytical grade lithium hydroxide, the auxiliary activator is liquid sodium silicate with a modulus of 2.0 to 2.2, and the mixing water is deionized water.

[0020] Lithium hydroxide is added as a lithium activator based on 100 parts by weight of granulated blast furnace slag, with an addition amount of 2 wt% of the blast furnace slag mass. Liquid sodium silicate is also added as an auxiliary activator to meet the alkaline environment required for the geological polymerization reaction. The water-binder ratio is controlled at 0.35.

[0021] In the preparation process, the weighed granulated blast furnace slag is first dry-mixed with lithium hydroxide for 2-3 minutes to ensure that the lithium activator is uniformly dispersed in the blast furnace slag particles. Then, a pre-prepared sodium silicate solution and mixing water are added, and the mixture is stirred in a planetary mixer. The mixture is first stirred at low speed for 2 minutes, and then at high speed for 3 minutes, until a uniform slurry without obvious agglomeration is formed.

[0022] The obtained slurry was poured into a standard mold, and internal air bubbles were removed by vibration molding. The molded sample was then covered with a plastic film to reduce moisture evaporation. The molded sample was cured for 28 days at 20°C and 95% relative humidity.

[0023] After the curing period, the compressive strength of the samples was tested and their volume stability was examined, including the determination of the shrinkage rate and the observation of whether macroscopic cracks appeared, in order to evaluate the basic mechanical properties and volume stability of the prepared blast furnace slag-based polymer material.

[0024] Example 2

[0025] This example is based on Example 1, but the type of lithium activator is adjusted, while the composition of other raw materials, proportioning parameters and preparation process conditions remain the same.

[0026] Specifically, lithium hydroxide used in Example 1 was replaced with lithium nitrate as the lithium activator. To eliminate the influence of differences in the total amount of lithium ions on the experimental results, the amount of lithium nitrate added was controlled according to the principle of having the same molar amount of lithium ions provided by lithium hydroxide in Example 1. Liquid sodium silicate with a modulus of 2.0 to 2.2 was still used as the auxiliary activator, and the water-cement ratio was maintained at 0.35.

[0027] The mixing, molding, and curing processes for the samples were the same as in Example 1, i.e., cured for 28 days at 20℃ and 95% relative humidity. After curing, the compressive strength and volume stability of the resulting samples were tested.

[0028] By comparing and analyzing the performance of samples under different lithium activators, the influence of lithium activator type on the polymerization reaction process and final material properties of blast furnace slag-based materials under the same lithium ion content is verified.

[0029] Example 3

[0030] This example, based on Example 1, keeps the lithium activator type unchanged and only adjusts the lithium activator dosage to study the influence of changes in lithium activator dosage on material properties.

[0031] Specifically, lithium hydroxide was still used as the lithium activator, and its dosage was adjusted to 3 wt% of the granulated blast furnace slag mass. The type and modulus of the auxiliary activator, the water-binder ratio (0.35), the stirring process, the molding method and the curing regime were the same as in Example 1.

[0032] The prepared samples were cured for 28 days at a temperature of 20℃ and a relative humidity of 95%. After the curing period, the compressive strength, volume stability, and macroscopic structural integrity of the samples were tested and observed.

[0033] This example is used to verify the impact of changes in lithium activator dosage on the degree of polymerization reaction, material structure characteristics, and volume stability of blast furnace slag-based substrates, thereby providing a basis for the reasonable dosage range of lithium activator systems.

Claims

1. A lithium-activated blast furnace slag-based polymer material, characterized in that, The material uses granulated blast furnace slag as the main cementing raw material, lithium salt as the activator, and sodium silicate as an auxiliary activator. Through the participation of lithium ions in the gel structure construction, a dense and stable geopolymer system is formed, thereby inhibiting the alkali-aggregate reaction and improving the mechanical properties and volume stability of the material.

2. The lithium-activated blast furnace slag-based polymer material according to claim 1, characterized in that, The lithium salt is one or a combination of lithium hydroxide and lithium nitrate.

3. The lithium-activated blast furnace slag-based polymer material according to claim 1 or 2, characterized in that, The lithium salt content is 1–5 wt% of the blast furnace slag mass.

4. The lithium-activated blast furnace slag-based polymer material according to claim 1, characterized in that, The modulus of the sodium silicate is 1.0–2.

0.

5. The lithium-activated blast furnace slag-based polymer material according to claim 1, characterized in that, The water-to-binder ratio of the material is 0.30–0.

40.

6. The lithium-activated blast furnace slag-based polymer material according to claim 1, characterized in that, Lithium ions passivate the interface of reactive aggregates by regulating the coordination and pore structure of geopolymer gels.

7. A method for preparing a lithium-activated blast furnace slag-based polymer material as described in any one of claims 1-6, characterized in that, Includes the following steps: Granulated blast furnace slag is pretreated; an activation solution containing lithium salt and sodium silicate is prepared; the activation solution is mixed and stirred with blast furnace slag to form a slurry; The slurry was cast into a mold and cured to obtain a lithium-activated blast furnace slag-based polymer material.

8. The preparation method according to claim 7, characterized in that, The maintenance conditions are a temperature of 15–30℃ and a relative humidity of not less than 90%.

9. The preparation method according to claim 7, characterized in that, The maintenance period is 7–28 days.

10. The use of the lithium-activated blast furnace slag-based geopolymer material according to any one of claims 1–6 in the preparation of low-carbon, high-durability cementitious materials for building or civil engineering.

Images