An activator for geopolymer, a method for preparing the same and use thereof in geopolymer materials

Abstract

The application discloses an activator for geopolymer, a preparation method thereof and application of the activator in geopolymer materials. The preparation method comprises the following steps: determining target modulus and target alkali equivalent of the activator according to characteristics of a precursor material and mechanical property requirements; determining mass ratio of two kinds of powders according to the target parameters and component content and modulus of the first instant sodium silicate powder and the second instant sodium silicate powder; and mixing the two kinds of powders uniformly in a dry environment according to the mass ratio. The prepared activator can be used for preparing geopolymer grouting material, mortar or concrete and other materials. Different modulus instant sodium silicate powders are physically compounded, and without additional introduction of sodium hydroxide or sodium carbonate and other additional alkalis, effective activation of silico-alumina precursor materials can be realized, and the activation efficiency and construction operability are considered, and the comprehensive requirements of geopolymer reaction on alkalinity and silicon source are met.

Description

Technical Field

[0001] This application belongs to the field of building materials technology, and more specifically, relates to an activator for geopolymers, its preparation method, and its application in geopolymer materials. Background Technology

[0002] Geopolymers are a three-dimensional network of inorganic polymer materials with excellent properties such as early strength, high temperature resistance, corrosion resistance, low shrinkage, and low carbon and environmental friendliness. They are considered to be green cementitious materials that are expected to partially replace traditional silicate cement.

[0003] Geopolymers are primarily prepared from aluminosilicate solid raw materials through processes such as dissolution, gelation, and polycondensation under the action of an alkaline activator. The alkaline activator provides the necessary alkalinity for the reaction, dissolves the aluminosilicate phase, and participates in subsequent polymerization. Currently, the mainstream alkaline activator in research and application is a mixture of liquid sodium silicate and sodium hydroxide, typically based on commercially available sodium silicate with the addition of solid sodium hydroxide to adjust its modulus. However, this adjustment process disrupts the original polymer structure of the silicate, leading to a decrease in system viscosity and poor stability. Furthermore, the prepared activator requires a relatively long aging period (usually about 24 hours) before use. This not only prolongs preparation time but also increases the complexity and uncertainty of on-site construction.

[0004] To overcome the inconvenience of storing and transporting alkaline activators in liquid systems and the need for pre-prepared aging, the industry has explored solid activator solutions, mainly including two types: The first is a solid monomodulus fast-dissolving sodium silicate and sodium hydroxide compound system. Although this system solves the liquid storage and transportation problem, sodium hydroxide releases a large amount of heat instantly upon contact with water, causing a rapid rise in slurry temperature, excessively fast reaction, and rapid loss of fluidity, resulting in a very short application window and posing a strong alkaline safety risk. The second is a solid sodium silicate and weakly alkaline compound system such as sodium carbonate. To reduce the reaction intensity, some studies have attempted to replace part or all of the sodium hydroxide with sodium carbonate. This system has a mild reaction and maintains good performance, but introduces a new core drawback: sodium carbonate is much less alkaline than sodium hydroxide, resulting in severely insufficient activation and dissolution efficiency for silicon-aluminum precursors, leading to a slow early reaction rate of geopolymers and sluggish strength development, making it difficult to meet the application requirements of most projects; at the same time, the introduction of sodium carbonate may generate a small number of bubbles, affecting the material's density.

[0005] In summary, existing activator technologies face a dilemma: using highly efficient but dangerous strong alkalis sacrifices construction safety and controllability; using safe weak alkalis sacrifices early performance and activation efficiency.

[0006] Therefore, there is an urgent need to develop a new solid activator system that does not require the addition of alkali and has both high activation efficiency and excellent construction performance. Summary of the Invention

[0007] The technical effect to be achieved by this application is to provide an activator for geopolymers, its preparation method and its application in geopolymer materials, which can effectively activate siliceous aluminum precursor materials without the need for the introduction of external alkalis such as sodium hydroxide or sodium carbonate, while taking into account both activation efficiency and construction operability.

[0008] To achieve the above-mentioned technical effects, this application provides a method for preparing an activator for geopolymers, comprising the following steps:

[0009] S1: Determine the target modulus and target alkali equivalent of the activator based on the characteristics of the precursor material used in the geopolymer to be activated and the preset mechanical property requirements.

[0010] S2: Based on the target modulus, target alkali equivalent, and the component content and modulus of the first and second instant sodium silicate powders, determine the mass ratio of the first and second instant sodium silicate powders; the modulus of the first instant sodium silicate powder is less than the modulus of the second instant sodium silicate powder.

[0011] S3: Mix the first fast-dissolving sodium silicate powder and the second fast-dissolving sodium silicate powder evenly in a dry environment according to the mass ratio to obtain the activator.

[0012] In this scheme, by designing the mass ratio of fast-dissolving sodium silicate powder with different moduli, the resulting activator can simultaneously provide the alkalinity source and active silicic acid components required for the reaction during the water dissolution process, thereby meeting the comprehensive requirements of geopolymer reaction for alkalinity and silicon source.

[0013] To achieve the above-mentioned technical effects, this application also provides an activator for geopolymers, which is prepared by the above-described method for preparing an activator for geopolymers;

[0014] The first fast-dissolving sodium silicate powder has a modulus of 1.0-1.2, and the second fast-dissolving sodium silicate powder has a modulus of 2.0-3.0.

[0015] In this scheme, low-modulus fast-dissolving sodium silicate powder and high-modulus fast-dissolving sodium silicate powder are physically compounded. The low-modulus component dissolves first, creating a high pH environment to promote the dissolution of the precursor. The high-modulus component then continuously dissolves active silicate ions, which condense with the dissolved aluminosilicate monomers. This allows the activator to form a more balanced dissolution and reaction environment during hydration, thereby forming a denser and more uniform gel network without the need for additional alkalis such as sodium hydroxide or sodium carbonate.

[0016] Furthermore, the target modulus of the activator is 1.2-2.0, and the target base equivalent is 5%-9%.

[0017] Furthermore, the modulus of the first fast-dissolving sodium silicate powder is 1.0.

[0018] Furthermore, the modulus of the second fast-dissolving sodium silicate powder is 2.0, 2.3, or 2.85.

[0019] To achieve the above-mentioned technical effects, this application also provides an application of an activator in geopolymer materials. The preparation of geopolymer materials using the aforementioned activator, by weight, includes the following preparation steps:

[0020] 9-16 parts of activator and 64-69 parts of aluminosilicate precursor material are mixed evenly in a dry environment to obtain a solid mixture; the aluminosilicate precursor material includes slag powder and / or fly ash.

[0021] Add 20-22 parts of mixing water to the solid mixture and stir until a homogeneous slurry is formed; the homogeneous slurry is the geopolymer material.

[0022] Further, the step of mixing 9-16 parts of the activator with 64-69 parts of the aluminosilicate precursor material uniformly under a dry environment to obtain a solid mixture includes:

[0023] 9-16 parts of activator, 64-69 parts of silicon-aluminum precursor material, and 64-69 parts of aggregate are mixed evenly in a dry environment to obtain a solid mixture.

[0024] Furthermore, after adding mixing water to the solid mixture and stirring until a homogeneous mortar is formed, the process further includes:

[0025] Add 10-11 parts of steel fiber to the homogeneous mortar and stir continuously to disperse the steel fiber evenly.

[0026] Furthermore, the geopolymer material includes one of geopolymer grouting material, geopolymer mortar, or geopolymer concrete.

[0027] The beneficial effects of this application are as follows:

[0028] 1. The solution provided in this application designs the mass ratio of fast-dissolving sodium silicate powder with different moduli so that the resulting activator can simultaneously provide the alkalinity source and active silicic acid components required for the reaction during the water dissolution process, thereby meeting the comprehensive requirements of geopolymer reaction for alkalinity and silicon source.

[0029] 2. The solution provided in this application physically combines low-modulus fast-dissolving sodium silicate powder with high-modulus fast-dissolving sodium silicate powder. The low-modulus component dissolves first, creating a high pH environment to promote the dissolution of the precursor. The high-modulus component then continuously dissolves active silicate ions, which undergo condensation with the dissolved aluminosilicate monomers. This allows the activator to form a more balanced dissolution and reaction environment during hydration, thereby forming a denser and more uniform gel network without the need for additional alkalis such as sodium hydroxide or sodium carbonate. Detailed Implementation

[0030] The embodiments of the technical solution of this application will be described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0031] This application provides a method for preparing an activator for geopolymers, comprising the following steps:

[0032] S1: Determine the target modulus and target alkali equivalent of the activator based on the characteristics of the precursor material used in the geopolymer to be activated and the preset mechanical property requirements.

[0033] Specifically, in this step, the chemical composition characteristics of the selected silica-alumina precursor material (such as finely ground slag, fly ash, metakaolin) are first used to preliminarily determine the range of alkali equivalent and modulus required for the target geopolymer system. Within the preliminary range, further adjustments are made based on the mechanical performance requirements of the geopolymer material (such as fluidity, setting time, or compressive strength) to determine the target modulus and target alkali equivalent required for the activator.

[0034] For example, the main oxide composition of the precursor material is obtained by X-ray fluorescence spectroscopy (XRF), and the preliminary ranges of modulus and alkali equivalent are determined with reference to Table 1 below:

[0035] Table 1. Comparison of Preliminary Ranges of Precursor Types, Moduli, and Alkali Equivalents

[0036]

[0037] After determining the initial range of modulus and alkali equivalent using Table 1 above, fine-tuning is performed within this initial range according to the specific requirements of the mechanical properties, as follows:

[0038] If the focus is on early strength (e.g., requiring a 3d compressive strength of 40 MPa or more): the modulus is taken from the lower limit of the preliminary range to the lower limit, and the alkali equivalent is taken from the upper limit of the preliminary range to the upper limit + 0.5%.

[0039] If the focus is on fluidity and workability (e.g., the fluidity is required to be no more than 15 s): the modulus is taken from the upper limit of the preliminary range to the upper limit + 0.2, and the alkali equivalent is taken from the lower limit of the preliminary range to the lower limit - 0.5%.

[0040] To balance early strength and workability, it is recommended to use a modulus of 1.2-1.4 and an alkali equivalent of 7%-8%.

[0041] S2: Determine the mass ratio of the first and second instant sodium silicate powders based on the target modulus, target alkali equivalent, and the component content and modulus of the first and second instant sodium silicate powders.

[0042] Specifically, this embodiment can be achieved through the following process (alkali equivalent is expressed as Na2O by mass):

[0043] The target alkali equivalent of the geopolymer alkali activator is set as follows: The target modulus is The modulus is defined as the total Number of moles With the general mole number Ratio, i.e.

[0044]

[0045] Assume the mass of the first batch of rapidly soluble sodium silicate powder to be mixed is The mass of the second fast-dissolving sodium silicate powder is ;

[0046] In the first fast-dissolving sodium silicate powder mass fraction is mass fraction is ;

[0047] In the second fast-dissolving sodium silicate powder mass fraction is mass fraction is ;

[0048] Based on the principle of conservation of mass, the following system of equations is established:

[0049]

[0050] in, The total mass of the silicon-aluminum raw materials. and These are the molar masses of silicon dioxide and sodium oxide, respectively.

[0051] Solving the above system of two linear equations in two variables yields the mass ratio of the first and second fast-dissolving sodium silicate powders. .

[0052] S3: Mix the first fast-dissolving sodium silicate powder and the second fast-dissolving sodium silicate powder evenly in a dry environment according to the mass ratio to obtain the activator.

[0053] Specifically, the mixing of the first and second fast-dissolving sodium silicate powders can be carried out using common dry powder mixing equipment, such as V-type mixers, trough mixers, or double-spiral conical mixers. The mixing time is generally 3-10 minutes to ensure the uniform distribution of the two powders and prevent local over-concentration or over-diluteness from causing fluctuations in the activator performance.

[0054] This application also provides an activator for geopolymers, which is prepared using the preparation method described in the above embodiments;

[0055] The first fast-dissolving sodium silicate powder has a modulus of 1.0-1.2, and the second fast-dissolving sodium silicate powder has a modulus of 2.0-3.0.

[0056] Preferably, the target modulus of the activator is 1.2-2.0, and the target base equivalent is 5%-9%.

[0057] Specifically, when the modulus of the first rapidly soluble sodium silicate powder is 1.0-1.2, its sodium oxide content is relatively high, which can rapidly provide a large number of hydroxide ions upon contact with water, quickly establishing a high pH environment and promoting the rapid dissolution of the silica-alumina phase in the silica-alumina precursor materials (such as slag and fly ash). If the modulus is too high (>1.5), the initial alkalinity of the system is insufficient, which may lead to incomplete dissolution of the precursor. Preferably, the modulus of the first rapidly soluble sodium silicate powder is 1.0.

[0058] When the modulus of the second type of rapidly soluble sodium silicate powder is in the range of 2.0-3.0, a better balance can be achieved between reactivity, structure formation, and workability. The preferred modulus is 2.0, 2.3, or 2.85.

[0059] Specifically, from a material properties perspective, the lower the modulus of sodium silicate, the higher the proportion of free Na₂O in its chemical structure, resulting in greater heat release during alkali dissolution in water, a faster dissolution rate, and a more vigorous alkali-activated reaction with the precursor. If the modulus of the second rapidly dissolving sodium silicate powder is too low, its rapid dissolution and exothermic reaction will produce a strong synergistic exothermic effect with the highly alkaline first rapidly dissolving sodium silicate powder, leading to an overly concentrated system reaction and an excessively high exothermic peak. This not only accelerates solidification, resulting in a short construction window, but may also cause microcracks due to uneven early thermal stress and shrinkage, impairing the final strength and durability of the slurry. Conversely, an excessively high modulus of sodium silicate indicates a very high degree of polymerization in its silicon-oxygen structure, resulting in a slow dissolution rate and difficulty in rapidly releasing sufficient effective alkali to activate the precursor at room temperature, leading to delayed reaction initiation and insufficient early hydration kinetics. This directly manifests as poor initial fluidity of the slurry, excessively long setting time, and slow development of early strength (3d, 7d), failing to meet the timeliness requirements for rapid load-bearing and reinforcement in engineering.

[0060] From the perspective of the formulation constraints of the compound system, under the condition of fixed alkali equivalent and target comprehensive modulus, the higher the modulus of the second fast-dissolving sodium silicate powder, the greater the proportion of the first fast-dissolving sodium silicate powder with a modulus of 1.0 required to achieve the system's modulus balance. The alkali content of the modulus 1.0 component is extremely high, and a significant increase in its dosage will drastically increase the initial alkali concentration of the system, which theoretically may exacerbate the intensity of the reaction. However, in reality, the high-modulus second fast-dissolving sodium silicate powder dissolves slowly, and the effective silicon and alkali it provides are insufficient to immediately support the formation of the reaction network. Instead, it results in a situation where the system has a high alkali concentration in the initial stage but cannot effectively initiate the structuring process. The result is still a deterioration in workability: rapid loss of initial fluidity and short workable time, while setting and strength development are abnormally slow, forming a contradictory phenomenon of "rapid loss of fluidity and slow hardening".

[0061] Within the preferred range of 2.0-2.85:

[0062] Modulus 2.0 is at the lower limit of this equilibrium range. Its dissolution rate and alkali release capacity are moderate. When combined with components of modulus 1.0, it can provide the necessary rapid start-up activation without causing the system reaction to runaway. It tends to optimize early reaction kinetics and is conducive to obtaining higher early strength.

[0063] Modulus 2.3 is the optimal equilibrium point within this equilibrium range. Its solubility characteristics are optimally complementary to those of the modulus 1.0 component, ensuring an ideal match between the alkali release rate of the composite activator and the supply rate of active silicon. This guarantees a stable and continuous reaction, achieving the best combination of workability, early strength development, and long-term microstructure density.

[0064] A modulus of 2.85 is at the upper limit of this equilibrium range. It significantly increases the relative supply of active silicon. Although its own dissolution and alkali release are relatively slower, in the compound system, it effectively "buffers" the excessively high alkali concentration impact from the modulus 1.0 component, making the reaction more moderate and sustained. This is particularly beneficial for the high polymerization degree development of the silicon-aluminum network in the later stages, thereby optimizing long-term strength and chemical stability. In summary, this embodiment, through the synergistic effect of two fast-dissolving sodium silicate powders with different moduli, enables the activator system to achieve an effective activation effect without the need for an external strong alkali.

[0065] This application also provides an application of an activator in geopolymer materials. The preparation of geopolymer materials using the activator in the above embodiments, by weight, includes the following preparation steps:

[0066] 9-16 parts of activator and 64-69 parts of silicon-aluminum precursor material are mixed evenly in a dry environment to obtain a solid mixture;

[0067] Add 20-22 parts of mixing water to the solid mixture and stir until a homogeneous slurry is formed; the homogeneous slurry is the geopolymer material.

[0068] Specifically, the silica-alumina precursor material includes slag powder and / or fly ash. In this embodiment, the geopolymer material is a geopolymer grouting material.

[0069] Preferably, the step of mixing 9-16 parts of activator with 64-69 parts of aluminosilicate precursor material uniformly under a dry environment to obtain a solid mixture comprises:

[0070] 9-16 parts of activator, 64-69 parts of silicon-aluminum precursor material, and 64-69 parts of aggregate are mixed evenly in a dry environment to obtain a solid mixture.

[0071] Specifically, the geopolymer material in this embodiment is a geopolymer mortar. When the geopolymer material described in this embodiment is used to prepare mortar, an appropriate amount of fine aggregate, such as river sand or quartz sand, is usually added to the activator and aluminosilicate precursor material. The addition of aggregate can improve the physical properties of the geopolymer mortar.

[0072] Preferably, after adding mixing water to the solid mixture and stirring until a homogeneous mortar is formed, the process further includes:

[0073] Add 10-11 parts of steel fiber to the homogeneous mortar and stir continuously to disperse the steel fiber evenly.

[0074] Specifically, the geopolymer material in this embodiment is geopolymer concrete. The addition of steel fibers can significantly improve the tensile strength, crack resistance, and toughness of geopolymer concrete, giving it better performance under large loads and impacts. It is suitable for engineering structures with high requirements for concrete performance, such as roads, bridges, and industrial plants.

[0075] Based on the embodiments provided in this application, some specific experiments have been conducted, namely, examples of preparing geopolymer materials using the activators in the above embodiments, and some comparative examples are given. It should be noted that the following embodiments are only for illustrating the invention in detail and do not limit the scope of protection of the invention in any way.

[0076] Example 1

[0077] This embodiment aims to prepare a geopolymer grouting material that meets the following performance indicators:

[0078] Flowability: ≤ 20 s;

[0079] Setting time: initial setting ≥ 30 min, final setting ≤ 90 min;

[0080] Compressive strength: 3d ≥ 40 MPa, 7d ≥ 55 MPa, 28d ≥ 65 MPa.

[0081] Water-to-binder ratio: 0.32.

[0082] The precursor material is a mixture of slag and fly ash powder, with slag accounting for 70% of the total mass and fly ash accounting for 30%. The specific surface area of ​​the slag is 370 m² / kg, and the specific surface area of ​​the fly ash is 350 m² / kg. The chemical compositions of the two powders are shown in Table 2 below.

[0083] Table 2 Chemical composition of precursor materials

[0084]

[0085] S1: Based on the characteristics of the precursor material and the preset mechanical property requirements, the target alkali equivalent N of the geopolymer activator is set to 8%, and the target modulus is set to... It is 1.2.

[0086] Specifically, the precursor consists of 70% slag and 30% fly ash, and the equivalent calcium oxide content of this precursor composite system is calculated to be 28.23% according to the following formula:

[0087] 0.7 × 37.65% + 0.3 × 6.24% = 28.23%

[0088] The calcium-to-silicon ratio of this precursor composite system is calculated to be 0.74 according to the following formula:

[0089] Ca / Si= (0.7×37.65%+0.3×6.24%) / (0.7×33.65%+0.3×49.28%)=0.74

[0090] Therefore, the system was determined to fall within the "medium-calcium system" range in Table 1. The initial target modulus range for the activator was selected as 1.4-1.6, and the target alkali equivalent range as 7%-8%. Based on this, parameter optimization was performed in conjunction with preset performance targets (flowability ≤ 20 s; initial setting ≥ 30 min, final setting ≤ 90 min; 3-day, 7-day, and 28-day compressive strengths > 40 MPa, 55 MPa, and 65 MPa, respectively). To meet the strength and setting time requirements, the modulus was appropriately reduced to accelerate reaction initiation. Simultaneously, to balance flowability and ensure activation efficiency, the upper limit of the alkali equivalent range was chosen. Finally, the target modulus was determined to be 1.2, and the target alkali equivalent to 8%.

[0091] S2: Based on the target modulus, target alkali equivalent, and the component content and modulus of the first and second fast-dissolving sodium silicate powders, the above parameters are substituted into the relevant formulas for calculation to determine the mass ratio of the first and second fast-dissolving sodium silicate powders.

[0092] Specifically, the activator raw material is a compound of two types of fast-dissolving sodium silicate powder with different moduli:

[0093] The first instant sodium silicate powder has a modulus of 1.0, with a SiO2 content of 47.5 wt% and a Na2O content of 50.0 wt% (denoted as a1=0.5, b1=0.475).

[0094] The second fast-dissolving sodium silicate powder has a modulus of 2.3, with a SiO2 content of 54.1 wt% and a Na2O content of 24.2 wt% (denoted as a2=0.242, b2=0.541).

[0095] The detailed process is as follows:

[0096]

[0097]

[0098] Solving the system of equations, we get m1 = 8.8 and m2 = 3.6.

[0099] S3: Mix the first fast-dissolving sodium silicate powder and the second fast-dissolving sodium silicate powder evenly in a dry environment according to the mass ratio to obtain the activator.

[0100] The activator used in this embodiment and the preparation method of the geopolymer grout are as follows:

[0101] Raw material composition by mass: 46 parts slag powder, 20 parts fly ash, 9 parts quick-dissolving sodium silicate powder with a modulus of 1.0, 4 parts quick-dissolving sodium silicate powder with a modulus of 2.3, and 21 parts mixing water.

[0102] The preparation method includes the following steps:

[0103] S1: Add slag powder and fly ash to a mixer and dry mix for 3 minutes in a dry environment with humidity ≤50% to obtain a uniform precursor material;

[0104] S2: Add fast-dissolving sodium silicate powder with moduli of 1.0 and 2.3 to the above precursor material, and continue to dry mix for 2 minutes until uniformly distributed;

[0105] S3: Add all the mixing water and stir rapidly at 2000 rpm for 2 minutes to obtain the geopolymer grouting material.

[0106] The difference between Examples 2-3 and Example 1 lies in the different amounts of each component and the different application scenarios during the preparation of the geopolymer material. Example 2 was used to prepare geopolymer mortar, and Example 3 was used to prepare geopolymer ultra-high performance concrete. Everything else is the same as Example 1. The amounts of each component are shown in Table 3.

[0107] Table 3. Component dosages in Examples 1-3

[0108]

[0109] The performance of the geopolymer materials in Examples 1-3 above was tested. The flowability test for Example 1 was performed according to the flow cone flowability test method in GB / T50448-2015 "Technical Specification for Application of Cement-based Grouting Materials". The flowability tests for Examples 2 and 3 were performed according to GB / T 2419 2005 "Method for Determination of Flowability of Cement Mortar". The setting time test was performed according to GB / T1346-2024 "Test Method for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". The compressive strength test was performed according to GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)", with compressive strength tested at 3d, 7d, and 28d. The test results are shown in Table 4.

[0110] Table 4 Performance test results of Examples 1-3

[0111]

[0112] Experimental conclusion:

[0113] The results of Examples 2 and 3 show that the composite activator system of the present invention can adapt to the needs of different application scenarios.

[0114] To further investigate the effect of the modulus of the second fast-dissolving sodium silicate powder on the performance of geopolymer grouting materials, this application sets up Examples 4 and 5 based on Example 1.

[0115] The only differences between Examples 4-5 and Example 1 are the modulus of the second fast-dissolving sodium silicate powder used and the different proportions adjusted to maintain the target alkali equivalent and target modulus. The component amounts for each example are shown in Table 5, and the performance test results are shown in Table 6.

[0116] Table 5. Component dosages in Examples 1, 4, and 5

[0117]

[0118] Table 6 Performance test results of Examples 1, 4, and 5

[0119]

[0120] Experimental conclusion:

[0121] Experimental results show that Examples 1, 4 and 5 all produced high-performance geopolymer grouting materials, with a 28-day compressive strength exceeding 73 MPa. This fully verifies that the composite activator system described in this application has a high-efficiency activating ability within the preferred range of 2.0-2.85 for the second component modulus, and can form a dense and stable hardened structure.

[0122] Further comparison of the performance of each group revealed that the rheological properties and reaction kinetics of the material exhibited regular differences with the change of the modulus of the second fast-dissolving sodium silicate powder. Regarding fluidity and setting time, the lower the modulus, the faster the dissolution rate and the more vigorous the reaction. Example 4 (modulus 2.0), while exhibiting good fluidity, had a shortened initial setting time of 24 minutes due to excessively rapid alkali release, resulting in a tight construction window. Example 5 (modulus 2.85), on the other hand, suffered from delayed dissolution of the high-polymerization-degree silica structure, leading to increased initial viscosity, poorer fluidity, and a delayed reaction initiation. In terms of strength development patterns, Example 4 exhibited an "early strength" characteristic, with high early strength but limited later growth; Example 5 exhibited a "late strength" characteristic, with relatively insufficient early activation, but the largest increase in strength from 7 to 28 days due to continuous silica-alumina network reorganization in the later stages.

[0123] In summary, Example 1 is at the equilibrium point of reaction kinetics, which avoids the risk of "rapid loss of flow" caused by low modulus and overcomes the defect of "slow start" caused by high modulus. While maintaining the best fluidity and suitable construction time, it achieves a balanced and steady increase in strength at all ages.

[0124] To further verify the advancement of the activator proposed in this application compared with conventional activation systems in the prior art, this application sets up comparative examples 1-4 based on Example 1.

[0125] Comparative Example 1

[0126] The difference from Example 1 is that a traditional liquid activator system is used instead of the activator of the present invention, that is, 15 parts of sodium silicate with a modulus of 2.4 and 3 parts of sodium hydroxide with a purity of 96% are used instead of sodium silicate powder with moduli of 1.0 and 2.3. The proportions of other materials are the same and the preparation method is the same.

[0127] It should be noted that the liquid activator in Comparative Example 1 needs to be prepared in advance and allowed to stand for 24 hours before use.

[0128] Comparative Example 2

[0129] The difference from Example 1 is that a sodium silicate + sodium hydroxide system is used to replace the composite activator of the present invention. Specifically, 11 parts of fast-dissolving sodium silicate powder with a modulus of 2.3 and 3 parts of sodium hydroxide with a purity of 96% are used to replace the fast-dissolving sodium silicate powder with moduli of 1.0 and 2.3. The proportions of other materials are the same, and the preparation method is the same.

[0130] Comparative Example 3

[0131] The difference from Example 1 is that a sodium silicate + sodium carbonate system is used to replace the composite activator of the present invention. Specifically, 7 parts of instant sodium silicate powder with a modulus of 1.0 and 6 parts of anhydrous sodium carbonate powder are used to replace instant sodium silicate powder with moduli of 1.0 and 2.3. The proportions of other materials are the same, and the preparation method is the same.

[0132] Comparative Example 4

[0133] The difference from Example 1 is that sodium silicate powder with a single modulus of 1.2 is used instead of the composite activator of the present invention, while the proportions of other materials are the same and the preparation method is the same.

[0134] The amounts of each component in Example 1 and Comparative Examples 1-4 are shown in Table 7.

[0135] Table 7. Amounts of each component in Example 1 and Comparative Examples 1-4

[0136]

[0137] The performance of the geopolymer materials of Example 1 and Comparative Examples 1-4 was tested, and the test results are shown in Table 8.

[0138] Table 8 Performance test results of Example 1 and Comparative Examples 1-4

[0139]

[0140] Experimental conclusion:

[0141] By comparing the performance test results of Example 1 and Comparative Example 1, it can be seen that the present invention exhibits significant advantages in improving the performance of geopolymer grouting materials. The grouting material prepared in Example 1 maintains good working performance in terms of fluidity, even slightly better than traditional liquid systems. More importantly, the activator system of the present invention significantly improves both the early and late strength of the geopolymer grouting material: the 3-day compressive strength is increased by approximately 28.6% compared to Comparative Example 1; the 28-day compressive strength is increased by approximately 26.0% compared to Comparative Example 1. In addition, the present invention uses a dry powder form, avoiding the 24-hour aging process of the liquid activator required in Comparative Example 1, significantly shortening the preparation time and simplifying the construction process.

[0142] Comparative Example 2 used a system of solid sodium silicate and strong alkali sodium hydroxide. While this system had some effect on activating strength, it also brought some construction problems. Data showed that the grouting material of Comparative Example 2 had extremely poor fluidity, reaching 31.5s, and the setting time was too fast. This could easily lead to rapid hardening of the material and loss of workability in actual engineering. In contrast, Example 1 of this invention had a fluidity of 13.7s and a moderate setting time, providing a sufficient construction window. In terms of strength, the 28-day compressive strength of Example 1 was much higher than that of Comparative Example 2, indicating that this invention can achieve better mechanical properties while ensuring excellent workability, avoiding the "flash setting" and safety risks of traditional strong alkali solid activators.

[0143] Comparative Example 3 reduced the reaction intensity by introducing a weak base, sodium carbonate. Although its fluidity was similar to that of Example 1 of this invention, its insufficient activation efficiency was a significant drawback. Specifically, the setting time was too long, resulting in extremely slow early strength development. The 3-day compressive strength was only 10.5 MPa, far lower than the 48.6 MPa of Example 1; the 28-day compressive strength was also significantly lower than that of Example 1. This indicates that Comparative Example 3, in practical engineering applications, is unlikely to meet most of the requirements for early strength and rapid curing of geopolymer materials. This invention, however, significantly improves both early and late strength while ensuring good workability, avoiding the drawbacks of "insufficient activation and slow strength development" inherent in weak base systems.

[0144] The initial fluidity of the grout in Comparative Example 4 was 14.3 s, which was basically the same as that of Example 1 (13.7 s), indicating that its dispersibility was acceptable in the initial stage of water addition. However, the fluidity was lost very quickly over time; the setting time was also significantly shortened, with an initial setting time of only 22 min and a final setting time of 41 min. In practical engineering, this rapid hardening could easily reduce workability. In terms of strength development, the 3-day compressive strength of Comparative Example 4 reached 52.8 MPa, slightly higher than that of Example 1 (48.6 MPa), exhibiting typical "early strength" characteristics. However, the strength growth in the later stages was weak. The 7-day strength (60.1 MPa) was already lower than that of Example 1 (61.5 MPa), and the 28-day strength (64.5 MPa) was significantly lower than that of Example 1 (73.1 MPa). This indicates that although the 1.2-modulus single activator can provide sufficient initial alkalinity to promote precursor dissolution, the lack of a high-modulus component to continuously replenish the active silicon source, coupled with the excessively rapid reaction in the early stages leading to poor structural density, limited the development of the three-dimensional network structure.

[0145] In summary, the activator for geopolymers, its preparation method, and its application in geopolymer materials provided by this invention achieve a balance between activation efficiency and workability by compounding readily soluble sodium silicate powders of different moduli without introducing additional strong or weak alkalis. The geopolymer materials prepared by this invention not only possess excellent mechanical properties but also exhibit good flowability and controllable setting time, while avoiding the problems of aging and waiting associated with traditional liquid activators, "flash solidification" of strong alkali solid activators, and low activation efficiency of weak alkali solid activators.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an activator for geopolymers, characterized in that, Includes the following steps: S1: Determine the target modulus and target alkali equivalent of the activator based on the characteristics of the precursor material used in the geopolymer to be activated and the preset mechanical property requirements. S2: Based on the target modulus, target alkali equivalent, and the component content and modulus of the first and second instant sodium silicate powders, determine the mass ratio of the first and second instant sodium silicate powders; the modulus of the first instant sodium silicate powder is less than the modulus of the second instant sodium silicate powder. S3: Mix the first and second fast-dissolving sodium silicate powders uniformly in a dry environment according to the mass ratio to obtain the activator; the modulus of the first fast-dissolving sodium silicate powder is 1.0-1.2, and the modulus of the second fast-dissolving sodium silicate powder is 2.0-3.

0.

2. An activator for geopolymers, characterized in that, It was prepared by the preparation method described in claim 1; The first fast-dissolving sodium silicate powder has a modulus of 1.0-1.2, and the second fast-dissolving sodium silicate powder has a modulus of 2.0-3.

0.

3. The activator as described in claim 2, characterized in that, The target modulus of the activator is 1.2-2.0, and the target base equivalent is 5%-9%.

4. The activator as described in claim 2, characterized in that, The modulus of the first fast-dissolving sodium silicate powder is 1.

0.

5. The activator as described in claim 2, characterized in that, The modulus of the second fast-dissolving sodium silicate powder is 2.0, 2.3 or 2.

85.

6. The application of an activator in geopolymer materials, characterized in that, Geopolymer materials prepared using the activator as described in any one of claims 2-5, by weight, include the following preparation steps: 9-16 parts of activator and 64-69 parts of aluminosilicate precursor material are mixed evenly in a dry environment to obtain a solid mixture; the aluminosilicate precursor material includes slag powder and / or fly ash. Add 20-22 parts of mixing water to the solid mixture and stir until a homogeneous slurry is formed; the homogeneous slurry is the geopolymer material.

7. The application according to claim 6, characterized in that, The step involves uniformly mixing 9-16 parts of activator with 64-69 parts of aluminosilicate precursor material under a dry environment to obtain a solid mixture, comprising: 9-16 parts of activator, 64-69 parts of silicon-aluminum precursor material, and 64-69 parts of aggregate are mixed evenly in a dry environment to obtain a solid mixture.

8. The application according to claim 7, characterized in that, After adding mixing water to the solid mixture and stirring until a homogeneous mortar is formed, the process further includes: Add 10-11 parts of steel fiber to the homogeneous mortar and stir continuously to disperse the steel fiber evenly.

9. The application according to any one of claims 6-8, characterized in that, The geopolymer material includes one of geopolymer grouting material, geopolymer mortar, or geopolymer concrete.

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