Alkaline residue-based geopolymer and method for preparing the same

Abstract

This invention belongs to the technical field of industrial solid waste resource utilization and novel inorganic cementitious materials. It discloses an alkaline slag-based geopolymer and its preparation method, with the core being the synthesis and application of a special composite activator. The special composite activator uses industrial by-products as the main raw material and is synthesized through modification, compounding, and low-temperature calcination processes. This overcomes the technical defects of traditional activators, such as low activation efficiency, slow strength development of geopolymers, high brittleness, and high cost. It can efficiently activate the activity of silicon-aluminum components in alkaline slag, promoting the full progress of the geopolymerization reaction. The alkaline slag-based geopolymer of this invention uses alkaline slag as the main raw material (with a dosage of up to 60%-85%), supplemented with appropriate amounts of silicon-aluminum admixtures, a special composite activator, and a modifier. It is prepared through pretreatment, batching, stirring, molding, and curing steps. Its 28-day compressive strength can reach 40-85 MPa, and its flexural strength can reach 5-12 MPa. It also possesses excellent water resistance, corrosion resistance, and freeze resistance. Furthermore, the preparation process has low energy consumption and no harmful gas emissions, realizing the large-scale resource utilization of alkaline slag. This invention also discloses in detail the synthesis process of special composite activators, which is simple, highly controllable, and has low production costs. It is easy to scale up industrial production and solves the problems of imperfect and limited application of existing alkaline residue base polymer activation systems. It has environmental, economic and social benefits.

Description

Technical Field

[0001] This invention belongs to the technical field of industrial solid waste resource utilization and novel inorganic cementitious materials. Specifically, it relates to an alkaline slag-based polymer and its preparation method. More specifically, it relates to an alkaline slag-based polymer with a special composite activator as the core and its preparation method, which is applicable to multiple fields such as building materials, road engineering, foundation treatment, and environmental protection seepage prevention. Background Technology

[0002] Alkali residue is an industrial waste generated during the production of soda ash using the ammonia-soda process or the combined alkali process. Approximately 0.8-1.2 tons of alkali residue are produced for every ton of soda ash produced. my country's annual alkali residue discharge reaches tens of millions of tons. The long-term accumulation of large amounts of alkali residue not only occupies valuable land resources, but also causes soluble salts (such as NaCl and CaCl2) to seep into the soil and groundwater due to rainwater runoff, resulting in soil salinization and groundwater pollution. At the same time, the dust in the alkali residue pollutes the air, seriously endangering the ecological environment and human health. Therefore, the resource utilization of alkali residue has become an urgent environmental and resource problem to be solved.

[0003] Geopolymers are a novel inorganic cementitious material formed through low-temperature polymerization of aluminosilicates as the main raw material under the action of an activator. They possess advantages such as high strength, good durability, low energy consumption, and low carbon footprint, and are considered the most promising new material to replace ordinary silicate cement. Alkali slag contains certain amounts of SiO2, Al2O3, CaO, and other components, providing the basic conditions for preparing geopolymers. Using alkali slag to prepare geopolymers not only enables large-scale resource utilization of alkali slag and reduces environmental pollution, but also lowers the production cost of geopolymers, resulting in significant environmental and economic benefits.

[0004] Activators are a core component in the preparation of geopolymers. Their role is to break the Si-O-Si and Al-O-Si bonds in the aluminosilicate raw materials, promoting the dissolution and polymerization of the aluminosilicate components to form a gel with a three-dimensional network structure, thereby endowing the geopolymer with excellent mechanical properties and durability. Currently, the activators used for geopolymers in alkaline slag bases are mainly traditional alkaline activators, such as single activators like sodium hydroxide, potassium hydroxide, and water glass, or simple composite activators. However, these traditional activators have many drawbacks:

[0005] 1. Low activation efficiency: The activity of silicon and aluminum components in alkaline slag is low. Traditional alkaline activators are unable to fully break the internal chemical bonds, resulting in insufficient dissolution of silicon and aluminum components, incomplete geopolymerization reaction, slow strength development of geopolymer, especially low early strength. The 28-day compressive strength is usually below 30 MPa, which is difficult to meet the requirements of practical engineering applications.

[0006] 2. High cost: The raw materials such as sodium hydroxide and water glass in traditional alkali activators are expensive and used in large quantities, which leads to high production costs of alkali slag-based polymers, limiting their industrial application.

[0007] 3. Poor durability: Alkali slag-based polymers prepared using traditional activators have high internal porosity and insufficiently dense structure. They have poor water resistance, corrosion resistance, and freeze resistance. When exposed to humid, corrosive, or cold environments for a long time, their strength is prone to decrease, they are prone to cracking, and their service life is short.

[0008] 4. High brittleness: Geopolymers prepared by traditional alkali activators have high brittleness and poor toughness, with low tensile and flexural strength, and are prone to brittle fracture, making them difficult to apply in engineering fields that require toughness.

[0009] 5. Insufficient environmental friendliness: Traditional alkaline activators are highly corrosive and hygroscopic, which can easily cause corrosion to equipment during production and use, threaten the personal safety of operators, and cause secondary pollution to the environment after disposal. At the same time, the production process of some traditional activators has high energy consumption and a large carbon footprint, which does not conform to the development trend of low carbon and environmental protection.

[0010] In the existing technology, the preparation of geopolymers based on alkali slag still has the following problems: the pretreatment of alkali slag is not perfect, and the easily soluble salts and impurities are not effectively removed, affecting the progress of the geopolymer reaction and the performance of the geopolymer; the selection and proportion of silica-alumina admixtures are unreasonable, resulting in poor synergy with alkali slag and difficulty in fully exerting their filling and reinforcing effects; the control of preparation process parameters (such as stirring speed, stirring time, curing temperature, curing time, etc.) is not precise enough, leading to large fluctuations in the performance of the geopolymer and unstable product quality; the selection and use of modifiers are unreasonable, making it difficult to effectively improve the brittleness and durability of the geopolymer.

[0011] Therefore, developing a special activator with high activation efficiency, low cost, good environmental performance, and strong compatibility with alkali slag, optimizing the preparation process of geopolymers based on alkali slag, and solving the problems of low strength, poor durability, high brittleness, high cost, and insufficient environmental performance in existing technologies, so as to realize the large-scale resource utilization of alkali slag and the industrial promotion and application of geopolymers, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0012] The purpose of this invention is to overcome the shortcomings of existing technologies, such as low activation efficiency, high cost, and insufficient environmental friendliness of geopolymer activators for alkali slag-based materials, as well as the low strength, poor durability, high brittleness, and imperfect preparation process of geopolymers. This invention provides a geopolymer for alkali slag-based materials and its preparation method. The core lies in the synthesis and application of a special composite activator. By optimizing the raw material ratio and synthesis process of the activator, the activation efficiency and environmental friendliness of the activator are improved, and the cost is reduced. Simultaneously, by optimizing the raw material ratio and preparation process of the geopolymer, the mechanical properties and durability of the geopolymer are improved, enabling large-scale resource utilization of alkali slag.

[0013] To achieve the above objectives, the present invention adopts the following technical solution:

[0014] A special composite activator for the preparation of alkaline slag-based polymers, comprising the following raw materials in parts by weight: 30-50 parts of industrial by-product silica fume;

[0015] 15-25 parts of water glass

[0016] 8-15 parts of sodium hydroxide

[0017] 2-6 parts of aluminum tripolyphosphate

[0018] 1-4 parts of nano-SiO2

[0019] 3-8 parts of calcium-based modifier

[0020] 1-3 parts of co-solvent;

[0021] The calcium-based modifier is a compound of calcium hydroxide and gypsum, with a weight ratio of 2:1 to 3:1.

[0022] The co-solvent is a mixture of sodium carbonate and potassium chloride, with a weight ratio of 1:1 to 1:2.

[0023] The special composite activator of this invention uses industrial by-product silica fume as one of the main raw materials, which not only reduces the production cost of the activator but also realizes the resource utilization of industrial by-product silica fume, conforming to the development concept of low carbon and environmental protection; water glass and sodium hydroxide serve as basic alkaline activating components, providing sufficient OH- - The process involves breaking the chemical bonds of the silicon and aluminum components in the alkaline residue, promoting their dissolution; aluminum tripolyphosphate, as an auxiliary activator, synergistically enhances the activation efficiency with the alkaline activating components, promoting the full progress of the geopolymer reaction, and improving the corrosion resistance and impermeability of the geopolymer; nano-SiO2, with its extremely high specific surface area and activity, fills the pores inside the geopolymer, refines the pore structure, and improves the density and strength of the geopolymer; calcium hydroxide and gypsum in the calcium-based modifier replenish the Ca in the system. 2+ Ca 2+It can combine with the silica-alumina gel produced by the geopolymer reaction to form C-(A)-SH gel, which works synergistically with NASH gel to further improve the mechanical properties and durability of geopolymers. At the same time, gypsum can also regulate the rate of the geopolymer reaction, avoiding excessively fast reaction leading to excessively rapid slurry setting, or excessively slow reaction leading to slow strength development. Sodium carbonate and potassium chloride in the cosolvent can reduce the activation energy of the system, promote the fusion reaction between raw materials, improve the stability and uniformity of the activator, and improve the compatibility between the activator and alkaline slag, promoting the full play of the activator.

[0024] Furthermore, the industrial by-product silica fume has a specific surface area of ​​20,000-30,000 cm² / g and a SiO₂ content of ≥90%; the water glass has a modulus of 1.5-2.5 and a solid content of 30%-45%; the sodium hydroxide has a purity of ≥96%; the aluminum tripolyphosphate has a purity of ≥98%; the nano-SiO₂ has a particle size of 50-100 nm and a specific surface area of ​​150-250 m² / g; and the gypsum is building gypsum with a CaSO₄·2H₂O content of ≥95%.

[0025] Limiting the specific surface area and SiO2 content of industrial by-product silica fume ensures its sufficient activity to fully participate in the synthesis reaction of the activator and subsequent geopolymerization reaction; limiting the modulus and solid content of water glass ensures the supply of sufficient SiO3. 2- , with OH - Synergistic effect enhances activation efficiency while preventing the activator's stability from decreasing due to excessively high or low modulus; limiting the purity of sodium hydroxide ensures a sufficient supply of OH-. - To avoid impurities affecting the activation effect; limiting the purity of aluminum tripolyphosphate ensures its full auxiliary activation effect; limiting the particle size and specific surface area of ​​nano-SiO2 ensures sufficient activity and filling effect, refining the pore structure of geopolymers; limiting the purity of gypsum ensures its ability to supplement Ca. 2+ This helps to prevent impurities from affecting the geopolymerization reaction.

[0026] This invention also discloses a method for synthesizing the above-mentioned special composite activator, comprising the following steps:

[0027] S1. Raw material pretreatment: Dry the industrial by-product silica fume in an oven at 105±5℃ for 4-6 hours to remove moisture, then crush it and pass it through a 200-mesh sieve for later use; crush the calcium hydroxide and gypsum in the calcium-based modifier separately, pass them through a 180-mesh sieve, and mix them evenly in proportion for later use; crush the sodium carbonate and potassium chloride in the co-solvent and mix them evenly for later use.

[0028] The purpose of raw material pretreatment is to remove moisture and impurities from the raw materials, refine the particle size of the raw materials, make the raw materials more uniformly mixed, and promote the full progress of subsequent reactions. Industrial by-product silica fume is dried and crushed through a 200-mesh sieve to ensure that its particle size is uniform and its activity is fully utilized. Calcium-based modifiers and co-solvents are pretreated separately and then mixed evenly to ensure that they are evenly dispersed in subsequent reactions and to avoid uneven reactions caused by excessively high or low local concentrations.

[0029] S2. Primary modification: Add the pretreated industrial by-product silica fume into a high-speed mixer, adjust the speed to 300-500 r / min, slowly add nano-SiO2 and co-solvent, mix for 15-25 min to obtain primary modified silica fume;

[0030] During the initial modification process, high-speed stirring can ensure that nano-SiO2 and co-solvent are uniformly dispersed in industrial by-product silica fume. The co-solvent can promote the bonding between nano-SiO2 and industrial by-product silica fume, enhance the activity of silica fume, and lay the foundation for subsequent composite reactions. Controlling the stirring speed and time can ensure the uniformity of mixing and avoid agglomeration.

[0031] S3. Composite reaction: Add water glass to the reactor, heat to 40-60℃, adjust the stirring speed to 200-300r / min, slowly add sodium hydroxide, stir until completely dissolved, then add aluminum tripolyphosphate, and continue stirring for 30-40min to obtain a composite solution;

[0032] Heating to 40-60℃ can promote the dissolution of sodium hydroxide and accelerate the rate of the composite reaction; controlling the stirring speed and time can ensure that the sodium hydroxide is completely dissolved and that the aluminum tripolyphosphate is uniformly dispersed in the water glass solution to form a stable composite solution; avoid adding sodium hydroxide too quickly, which may lead to excessively high local concentrations, clumping, and affect the stability of the composite solution.

[0033] S4. Fusion Modification: The primary modified silica fume obtained in step S2 is slowly added to the composite solution obtained in step S3, and the pretreated calcium-based modifier is added at the same time. The temperature is raised to 70-90℃, the stirring speed is increased to 400-600r / min, and the mixture is kept at this temperature and stirred for 60-90min. During this period, the viscosity of the system is checked every 15min, and the viscosity of the system is controlled to be 800-1200mPa·s.

[0034] Heating to 70-90℃ can increase the fusion reaction rate between raw materials and promote the full reaction of primary modified silica fume, calcium-based modifier, and composite solution. Increasing the stirring speed can ensure uniform mixing of raw materials and avoid stratification and agglomeration. Controlling the system viscosity at 800-1200 mPa·s can ensure the fluidity and stability of the activator, which is convenient for subsequent mixing with raw materials such as alkali slag and can also ensure the activation effect of the activator. If the system viscosity is lower than 800 mPa·s, add an appropriate amount of primary modified silica fume to increase the system viscosity. If it is higher than 1200 mPa·s, add a small amount of deionized water to adjust the viscosity to ensure that the viscosity meets the requirements.

[0035] S5. Low-temperature calcination: The fusion product obtained in step S4 is placed in a calcination furnace and heated to 200-300℃ at a heating rate of 5-10℃ / min. The temperature is maintained for calcination for 2-4 hours, and then naturally cooled to room temperature. After pulverization, it is passed through a 180-mesh sieve to obtain the special composite activator product.

[0036] The purpose of low-temperature calcination is to remove residual moisture and volatile impurities from the fusion product, promote the stability of the internal structure of the activator, and enhance its activity. Controlling the heating rate to 5-10℃ / min can prevent the fusion product from cracking and agglomerating due to excessively rapid heating, which would affect the performance of the activator. Holding the calcination at this temperature for 2-4 hours ensures that moisture and volatile impurities are completely removed and the activator structure is stable. Natural cooling to room temperature can prevent excessively rapid cooling from causing stress inside the activator and resulting in cracking. After pulverizing, passing the activator through an 180-mesh sieve ensures that the fineness of the activator is uniform, which facilitates uniform mixing with raw materials such as alkali residue and fully exerts the activating effect. Preferably, nitrogen gas is introduced during the calcination process for protection, with a nitrogen flow rate of 0.5-1L / min, to prevent product oxidation and ensure the activity and stability of the activator.

[0037] S6. Finished Product Inspection and Storage: The performance of the special composite activator finished product shall be inspected. The inspection indicators include activation activity, moisture content and fineness. The activation activity shall be ≥95%, the moisture content shall be ≤0.5% and the fineness (residue on 180 mesh sieve) shall be ≤5%. After passing the inspection, the product shall be sealed and stored for future use.

[0038] Finished product testing ensures that the performance of special composite activators meets the requirements and avoids unqualified activators from affecting the performance of geopolymers; sealed storage prevents activators from absorbing moisture and oxidizing, ensuring their performance stability during storage and extending their shelf life.

[0039] This invention also discloses an alkaline residue-based polymer, composed of the following raw materials in parts by weight: 60-85 parts of alkaline residue,

[0040] 10-25 parts of silicon-aluminum admixture

[0041] 3-8 parts of the above-mentioned special composite activator

[0042] Modifier 0.5-2 parts

[0043] 15-25 parts deionized water;

[0044] The silica-aluminate admixture is a mixture of metakaolin and fly ash, with a weight ratio of 3:1 to 5:1.

[0045] The modifier is a compound of polyvinyl alcohol and basalt fiber, with a weight ratio of 2:1 to 4:1.

[0046] The alkaline slag-based geopolymer of this invention uses alkaline slag as the main raw material, with an admixture content of 60%-85%, realizing large-scale resource utilization of alkaline slag and reducing environmental pollution caused by alkaline slag accumulation. The metakaolin in the silica-alumina admixture has high activity, which can supplement the silica-alumina components in the system and promote the full geopolymerization reaction. Fly ash can fill the pores inside the geopolymer, refine the pore structure, and improve the density and strength of the geopolymer. The two are compounded in a specific ratio, working synergistically to significantly improve the mechanical properties of the geopolymer. A special composite activator can efficiently activate the activity of the silica-alumina components in the alkaline slag and silica-alumina admixture, promoting the full geopolymerization reaction and improving the geopolymer's performance. The modifier improves the strength and durability of the geopolymer. Polyvinyl alcohol in the modifier has good adhesion and toughness, which can improve the adhesion and toughness of the geopolymer and reduce cracking. Basalt fiber has extremely high tensile strength and toughness, which can play a role in strengthening and toughening, delaying the generation and propagation of internal cracks in the geopolymer. When the two are compounded in a specific ratio, they can effectively improve the brittleness of the geopolymer and improve its tensile strength and flexural strength. The amount of deionized water is controlled at 15-25 parts to ensure that the slurry has good fluidity and is easy to form. At the same time, it avoids that too much water will increase the porosity of the geopolymer and reduce its strength, or that too little water will make the slurry difficult to form and the geopolymer reaction will be incomplete.

[0047] Furthermore, the alkali residue is an industrial waste residue generated from the production of soda ash using the ammonia-soda process, with a pH value of 8-12, a moisture content of ≤10%, and is pulverized and passed through a 100-mesh sieve. The residue contains 15%-25% SiO2, 5%-15% Al2O3, 30%-45% CaO, and 2%-8% MgO, with easily soluble salts (NaCl, CaCl2) content ≤5%. The metakaolin is calcined at 700-800℃ and has a specific surface area of ​​10000. The fly ash has a specific surface area of ​​15000 cm² / g, a SiO₂ content ≥50%, and an Al₂O₃ content ≥30%; the fly ash is grade I fly ash with a specific surface area of ​​5000-8000 cm² / g, a SiO₂ content ≥40%, and an Al₂O₃ content ≥20%; the polyvinyl alcohol has a degree of polymerization of 1700-2000 and a degree of alcoholysis of 88%-90%; the basalt fiber has a length of 3-6 mm, a diameter of 10-20 μm, and a tensile strength ≥3000 MPa.

[0048] Limiting the source, pH value, moisture content, particle size, and chemical composition of alkali slag ensures sufficient activity for geopolymer preparation while avoiding excessive soluble salt content that could negatively impact geopolymer performance and durability. Limiting the calcination temperature, specific surface area, and chemical composition of metakaolin ensures high activity for full participation in the geopolymerization reaction. Limiting the grade, specific surface area, and chemical composition of fly ash ensures its full filling and reinforcing effects. Limiting the degree of polymerization and alcoholysis of polyvinyl alcohol ensures good adhesion and toughness, resulting in a tight bond with the geopolymer matrix. Limiting the length, diameter, and tensile strength of basalt fibers ensures their full reinforcement and toughening effects, delaying crack propagation.

[0049] This invention also discloses a method for preparing the above-mentioned alkaline residue-based geopolymer, comprising the following steps:

[0050] Step 1: Raw material pretreatment

[0051] 1.1 Pretreatment of alkali residue: The alkali residue from the ammonia-soda process is placed in an open-air storage yard for natural drying for 24-48 hours to remove surface free moisture. Then it is sent to a dryer and dried at 105±5℃ for 6-8 hours. After drying, it is sent to a pulverizer for pulverization. After pulverization, it is passed through a 100-mesh sieve. The residue is returned to the pulverizer for re-pulverization. The pulverized alkali residue is placed in a sealed container for later use. The moisture content of the alkali residue after pretreatment is controlled to be ≤8%.

[0052] The purpose of alkali residue pretreatment is to remove free water and some soluble salts, refine the particle size of the alkali residue, and make the silicon and aluminum components in the alkali residue easier to be activated by the activator. At the same time, it avoids excessive water or excessively large particle size from affecting subsequent mixing and molding. Natural air drying followed by drying can reduce drying energy consumption and save costs. Crushing and passing through a 100-mesh sieve can ensure that the alkali residue has a uniform particle size, which is convenient for uniform mixing with other raw materials. Controlling the moisture content of the alkali residue after pretreatment to ≤8% can avoid excessive water content leading to excessive slurry fluidity, increased porosity of the geopolymer, and decreased strength. Preferably, the alkali residue is turned over regularly during the drying process to ensure uniform evaporation of moisture.

[0053] 1.2 Pretreatment of silica-alumina admixture: Mix metakaolin and fly ash evenly in proportion, send to a dryer, dry at 110±5℃ for 3-4 hours to remove moisture, then send to a high-speed mixer, adjust the speed to 200-300 r / min, mix for 10-15 minutes to obtain a uniform silica-alumina admixture for later use.

[0054] The purpose of pretreatment of silica-alumina admixtures is to remove moisture and ensure that they are mixed evenly with raw materials such as alkali slag and activators, so as to give full play to their filling and reinforcing effects. Drying at 110±5℃ for 3-4 hours can completely remove moisture and avoid moisture affecting the geopolymerization reaction. High-speed mixing can ensure that metakaolin and fly ash are mixed evenly and avoid local concentrations that are too high or too low.

[0055] 1.3 Modifier pretreatment: Add polyvinyl alcohol to deionized water, heat to 80-90℃, stir until completely dissolved to obtain a polyvinyl alcohol solution; cut basalt fibers to the specified length, immerse them in the polyvinyl alcohol solution for 20-30 minutes, remove them and air dry to obtain the pretreated modifier for later use;

[0056] The purpose of the pretreatment with modifier is to improve the bonding performance between the modifier and the geopolymer matrix, and to give full play to its reinforcing and toughening effects. Heating the polyvinyl alcohol to 80-90℃ to dissolve it can accelerate the dissolution rate and ensure that it is completely dissolved. Soaking the basalt fiber in the polyvinyl alcohol solution can allow the fiber surface to adsorb polyvinyl alcohol, improve the adhesion between the fiber and the geopolymer matrix, prevent the fiber from agglomerating in the slurry, and ensure its uniform dispersion. Preferably, the basalt fiber is stirred once every 5 minutes during the soaking process to ensure that the fiber adsorbs the polyvinyl alcohol solution uniformly.

[0057] 1.4 Pretreatment of special composite activator: Place the above-mentioned special composite activator in a dryer and dry it at 100±5℃ for 1-2 hours to remove moisture and set aside for later use;

[0058] The purpose of pretreatment of special composite activators is to remove the moisture absorbed during storage, ensure their activation activity, and avoid moisture affecting the activation effect and the fluidity of the slurry.

[0059] Step 2: Ingredient Preparation and Mixing

[0060] 2.1 Dry material mixing: The pretreated alkali residue and silica-alumina admixture are fed into a forced mixer, the speed is adjusted to 300-400 r / min, and the mixture is mixed for 20-30 min to obtain a uniform dry material mixture;

[0061] The purpose of dry material mixing is to ensure that the alkali residue and the silica-alumina admixture are mixed evenly, laying the foundation for the subsequent addition of activator and water. Forced mixers have the advantages of uniform mixing and high efficiency. By controlling the speed and time, the dry materials can be mixed evenly and the stratification phenomenon can be avoided.

[0062] 2.2 Activator Mixing: Slowly add the pretreated special composite activator to the dry material mixture and continue stirring for 15-20 minutes to ensure that the activator is evenly dispersed in the dry material;

[0063] Slowly adding the special composite activator while continuing to stir can prevent the local concentration of the activator from being too high, ensuring that it is evenly dispersed in the dry material, so that each dry material particle can fully contact the activator, laying the foundation for the full progress of the subsequent geopolymerization reaction.

[0064] 2.3 Wet Mixing: Add the pretreated modifier to the dry material-activator mixture, then slowly add deionized water, adjust the stirring speed to 200-300 r / min, and continue stirring for 25-35 min to obtain a uniform geopolymer slurry; during the stirring process, check the slurry flowability every 10 min, and control the slurry flowability to 180-220 mm. If the flowability is too low, add a small amount of deionized water; if the flowability is too high, add a small amount of dry material mixture to adjust.

[0065] The purpose of wet mixing is to fully mix the modifier, deionized water, and dry material-activator mixture to form a uniform slurry, which is convenient for molding. Controlling the stirring speed and time can ensure the uniformity of the slurry and avoid agglomeration and stratification. Controlling the slurry flowability to 180-220mm can ensure that the slurry has good fluidity, which is convenient for pouring into the mold for molding. At the same time, it can avoid excessive flowability, which will increase the porosity of the geopolymer and reduce its strength, or insufficient flowability, which will make it difficult for the slurry to fill the mold and cause voids and defects. Preferably, constant temperature stirring is used during the stirring process, and the stirring environment temperature is controlled at 20±3℃ to prevent the slurry from setting too quickly or too slowly.

[0066] Step 3: Molding

[0067] Pour the geopolymer slurry obtained in step two into a mold pre-coated with a release agent. The mold size is selected according to actual needs (such as a standard test mold of 40mm×40mm×160mm). After pouring, place the mold on a vibration table, adjust the vibration frequency to 50-60Hz, and the vibration time to 2-3 minutes to remove air bubbles in the slurry and ensure that the slurry is densely filled. After vibration, use a scraper to smooth the excess slurry on the surface of the mold and place it in a room temperature (20±5℃) environment for 1-2 hours for pre-curing.

[0068] Applying a release agent to the mold facilitates subsequent demolding and prevents the geopolymer preform from sticking to the mold and damaging the preform. Vibration treatment removes air bubbles from the slurry, preventing them from remaining inside the geopolymer and forming pores that affect its strength and durability. Controlling the vibration frequency and time ensures that air bubbles are fully removed while avoiding excessive vibration that could cause slurry stratification. Pre-curing at room temperature for 1-2 hours allows the slurry to initially solidify, preventing cracking and deformation during subsequent curing. Preferably, the mold release agent is a mixture of engine oil and diesel oil in a 1:1 weight ratio, which provides good demolding effect and has no impact on the properties of the geopolymer.

[0069] Step 4: Maintenance

[0070] 4.1 Primary curing: Place the pre-cured mold into the curing chamber, control the curing temperature at 25±3℃ and the relative humidity at 85%-95%, and cure for 24-48 hours. During this period, check the temperature and humidity of the curing environment every 8 hours to ensure that they meet the requirements.

[0071] The purpose of primary curing is to promote further solidification of the slurry, initiate the geopolymer reaction, and enable the geopolymer green body to develop initial strength, thus preventing cracking and deformation. Controlling the curing temperature to 25±3℃ and the relative humidity to 85%-95% provides a suitable environment for the geopolymer reaction, accelerates the reaction rate, and avoids cracking of the green body due to excessively high or low temperatures or insufficient humidity. Regularly monitoring the temperature and humidity ensures a stable curing environment and guarantees uniform green body performance. Preferably, an automatic temperature and humidity control system is installed in the curing chamber to monitor and adjust the temperature and humidity in real time, reducing manual operation and improving curing efficiency and stability.

[0072] 4.2 Intermediate curing: After the primary curing is completed, the mold is removed to obtain the geopolymer green body. The green body is then placed in the curing chamber, and the curing temperature is adjusted to 35±3℃ and the relative humidity to 80%-90%. The curing is carried out for 3-5 days to promote the further geopolymerization reaction.

[0073] The purpose of intermediate curing is to promote the further progress of the geopolymer reaction and improve the strength and density of the geopolymer green body. Appropriately increasing the curing temperature to 35±3℃ can accelerate the geopolymer reaction rate, promote the full polymerization of silicon and aluminum components, and form a dense three-dimensional network structure. Adjusting the relative humidity to 80%-90% can prevent the surface moisture of the green body from evaporating too quickly and causing cracking, while providing sufficient moisture for the geopolymer reaction.

[0074] 4.3 Final Curing: After intermediate curing, the geopolymer green body is transferred to a standard curing room, where the curing temperature is controlled at 20±2℃ and the relative humidity at 90%-95% for 20-22 days until the specified strength is reached. During the curing process, a small amount of deionized water is sprayed on the surface of the green body every day to prevent surface cracking.

[0075] The purpose of final curing is to ensure that the geopolymer reaction proceeds fully and that the geopolymer reaches the specified strength and durability. The temperature and humidity conditions of the standard curing room can simulate the actual engineering application environment and ensure that the performance of the geopolymer meets the actual application requirements. Spraying a small amount of deionized water every day can prevent the surface moisture of the green body from evaporating too quickly and causing surface cracking, and ensure that the overall performance of the green body is uniform.

[0076] Step 5: Finished Product Inspection and Packaging

[0077] 5.1 Performance Testing: The finished geopolymer product after final curing will undergo performance testing. Testing indicators include compressive strength, flexural strength, water resistance, corrosion resistance, freeze-thaw resistance, density, and porosity. Specifically, the following parameters must be met: 28-day compressive strength ≥ 40 MPa, 28-day flexural strength ≥ 5 MPa, softening coefficient ≥ 0.85, hydrochloric acid corrosion resistance (immersion in 5% HCl solution for 7 days) with strength loss ≤ 10%, freeze-thaw resistance (25 freeze-thaw cycles at -20℃) with strength loss ≤ 8%, density 1.8-2.2 g / cm³, and porosity ≤ 20%.

[0078] Performance testing ensures that the performance of geopolymer products meets the requirements of actual engineering applications, preventing substandard products from entering the market. Three parallel samples are selected for each test indicator, and the test results are averaged. If the test result of a single sample deviates from the average value by more than 10%, a new sample is selected for testing to ensure the accuracy and reliability of the test results. The limitation of each test indicator ensures that the geopolymer has good mechanical properties and durability, making it suitable for multiple engineering fields.

[0079] 5.2 Packaging and Storage: Qualified finished products are cut and polished according to specifications, then packaged with waterproof packaging materials and stored in a dry, ventilated, and cool warehouse. During storage, they should be protected from moisture and pressure. The shelf life is 6 months. Qualified finished products are returned to the raw material pretreatment step for reprocessing.

[0080] Waterproof packaging prevents finished products from absorbing moisture and avoids a decrease in strength; a dry, ventilated, and cool storage environment ensures the stability of finished product performance; reprocessing unqualified finished products can improve raw material utilization, reduce production costs, and avoid waste.

[0081] Furthermore, the alkaline slag-based geopolymer of the present invention can be supplemented with 0.1-0.5 parts of pigment or 0.3-1 parts of defoamer in the raw materials according to actual application requirements. The defoamer is an organosilicon defoamer, which is added during the wet material mixing process in step 2.3, simultaneously with deionized water. Adding pigment can give the finished geopolymer different colors to meet the aesthetic requirements of different application scenarios. Adding defoamer can further remove air bubbles in the slurry, reduce the porosity inside the geopolymer, and improve its density and strength. The organosilicon defoamer has a good defoaming effect and has no negative impact on the performance of the geopolymer.

[0082] Beneficial effects

[0083] Compared with the prior art, the present invention has the following significant advantages:

[0084] 1. Special composite activator with high activation efficiency, good environmental performance, and low cost: The special composite activator of this invention uses industrial by-product silica fume as one of the main raw materials, combined with water glass, sodium hydroxide, aluminum tripolyphosphate, nano-SiO2, calcium-based modifier, and co-solvent. The synergistic effect of each component significantly improves the activation efficiency, effectively breaking the chemical bonds of the silica-alumina components in the alkaline slag, promoting the dissolution of the silica-alumina components and the full progress of the geopolymerization reaction, thus solving the problem of low activation efficiency of traditional activators. At the same time, the application of industrial by-product silica fume not only reduces the production cost of the activator (compared to traditional alkaline activators, the cost is reduced by 20%-30%), but also realizes the resource utilization of industrial by-product silica fume, which is in line with the development concept of low carbon and environmental protection. The activator synthesis process adopts a low-temperature calcination process, which has low energy consumption, no harmful gas emissions, and the finished product has low corrosivity and weak hygroscopicity, significantly improving environmental protection and safety, and solving the problem of insufficient environmental protection of traditional activators.

[0085] 2. High utilization rate of alkali residue and significant environmental benefits: The alkali residue-based polymer of this invention has an alkali residue content of 60%-85%, realizing large-scale resource utilization of alkali residue and effectively solving the problems of alkali residue accumulation occupying land and polluting the environment. At the same time, the preparation process has low energy consumption and no harmful gas, wastewater and waste residue emissions. Compared with traditional cement production, energy consumption is reduced by 40%-50% and CO2 emissions are reduced by 60%-70%, resulting in significant environmental benefits and meeting the national policy requirements for low-carbon environmental protection and solid waste resource utilization.

[0086] 3. Excellent mechanical properties and durability of geopolymers: The alkaline slag-based geopolymers prepared using the special composite activator of this invention can achieve a 28-day compressive strength of 40-85 MPa and a 28-day flexural strength of 5-12 MPa, which is 30%-80% higher than that of geopolymers prepared with traditional alkali activators. At the same time, the geopolymers have low internal porosity and dense structure, with a softening coefficient ≥0.85, hydrochloric acid corrosion resistance strength loss ≤10%, and frost resistance strength loss ≤8%. The water resistance, corrosion resistance, and frost resistance are significantly improved, and the service life can reach more than 50 years, which can meet the application requirements of different engineering fields. In addition, the addition of modifiers effectively improves the brittleness of geopolymers, enhances their tensile strength and toughness, and avoids the defects of traditional geopolymers that are brittle and prone to cracking.

[0087] 4. The preparation process is simple, highly controllable, and easy to scale up for industrial production: The synthesis process of the special composite activator of this invention includes only six steps: raw material pretreatment, primary modification, composite reaction, fusion modification, low-temperature calcination, and finished product testing and storage. The steps are simple, requiring no complex production equipment or harsh production conditions. All process parameters (such as temperature, stirring speed, time, etc.) can be precisely controlled, with good repeatability, facilitating industrial scale-up production. The preparation process of the alkaline residue-based geopolymer is also simple. It can be mass-produced using conventional building material production equipment (such as dryers, crushers, mixers, vibrating tables, curing boxes, etc.) without the need for additional special equipment, further reducing production costs and promoting industrial application.

[0088] 5. Wide Applicability: The alkaline slag-based polymer of this invention has excellent mechanical properties and good durability. According to actual application needs, the raw material ratio and preparation process parameters can be adjusted to prepare products with different strength grades and different properties. It is applicable to many fields such as building materials (such as blocks, boards, concrete admixtures, etc.), road engineering (such as road base courses, roadbed fillers, etc.), foundation treatment (such as soft foundation reinforcement materials, etc.), environmental protection seepage prevention (such as landfill seepage prevention layers, sewage treatment pond linings, etc.), with broad application prospects. Attached Figure Description

[0089] Figure 1 This is a process flow diagram for preparing an alkaline residue-based geopolymer according to the present invention. Detailed Implementation

[0090] Example

[0091] To more clearly illustrate the technical solution of the present invention, the present invention will be further described in detail below with reference to specific embodiments. The following embodiments are only for explaining the present invention and are not intended to limit the scope of protection of the present invention. All technical solutions based on the present invention fall within the scope of protection of the present invention.

[0092] In this embodiment, the specifications of the raw materials used are as follows:

[0093] 1. Industrial by-product silica fume: specific surface area of ​​25000cm² / g, SiO2 content of 92%, purchased from an industrial by-product of a metallurgical plant;

[0094] 2. Water glass: Modulus 2.0, solid content 38%, industrial grade, purchased from a chemical company;

[0095] 3. Sodium hydroxide: 98% purity, flakes, industrial grade, purchased from a chemical reagent factory;

[0096] 4. Aluminum tripolyphosphate: 98.5% purity, industrial grade, purchased from a new materials company;

[0097] 5. Nano SiO2: Particle size 70nm, specific surface area 200m² / g, industrial grade, purchased from a nanomaterials company;

[0098] 6. Calcium-based modifier: Calcium hydroxide (96% purity, industrial grade) and building gypsum (CaSO4·2H2O content 96%, industrial grade) were compounded and purchased from a building materials company.

[0099] 7. Co-solvent: Sodium carbonate (98% purity, industrial grade) and potassium chloride (98% purity, industrial grade) were mixed and purchased from a chemical company.

[0100] 8. Alkali residue: Industrial waste residue produced by the ammonia-soda process for producing soda ash. The pH value is 10 and the moisture content is 8%. After being crushed and passed through a 100-mesh sieve, the residue contains 20% SiO2, 10% Al2O3, 38% CaO, 5% MgO, and 3% easily soluble salts (NaCl, CaCl2). It is taken from a soda ash plant.

[0101] 9. Silica-alumina admixture: Metakaolin (calcination temperature 750℃, specific surface area 12000cm² / g, SiO2 content 55%, Al2O3 content 32%) and Grade I fly ash (specific surface area 6500cm² / g, SiO2 content 45%, Al2O3 content 22%) were compounded and purchased from a building materials company.

[0102] 10. Modifier: Polyvinyl alcohol (degree of polymerization 1800, degree of alcoholysis 89%, industrial grade) and basalt fiber (length 4mm, diameter 15μm, tensile strength 3200MPa, industrial grade) were compounded and purchased from a chemical company and a fiber company.

[0103] 11. Deionized water: homemade, conductivity ≤10μS / cm;

[0104] 12. Defoamer: Silicone defoamer, industrial grade, purchased from a chemical company;

[0105] 13. Pigment: Titanium dioxide (white), industrial grade, purchased from a pigment company.

[0106] In this embodiment, the performance testing method is as follows:

[0107] 1. Performance testing of special composite activators:

[0108] (1) Activation activity: The strength comparison method of the granulated pulp was adopted. The special composite activator of the present invention and the traditional composite activator (sodium hydroxide + water glass, weight ratio 1:2) were used to prepare alkali slag base polymer granulated pulp test blocks. After curing for 28 days, the compressive strength was tested. Activation activity = (28-day compressive strength of granulated pulp prepared with the activator of the present invention / 28-day compressive strength of granulated pulp prepared with the traditional activator) × 100%;

[0109] (2) Moisture content: determined according to the method in GB / T 17669.3-1999 "Building gypsum Part 3: Determination of mechanical properties";

[0110] (3) Fineness: The content of residue on a 180-mesh sieve was determined by standard sieve sieving method.

[0111] 2. Performance testing of polymers in alkaline residue-based substrates:

[0112] (1) Compressive strength and flexural strength: determined according to GB / T 17671-1999 "Test method for strength of cement mortar (ISO method)" with a mold size of 40mm×40mm×160mm and tested after curing for 28 days;

[0113] (2) Water resistance: The softening coefficient of the test block after curing for 28 days was determined according to the method in GB / T 17671-1999 (softening coefficient = compressive strength in saturated state / compressive strength in dry state).

[0114] (3) Corrosion resistance: The test block after curing for 28 days was immersed in 5% HCl solution. After immersion for 7 days, the strength loss rate of the test block was measured (strength loss rate = (compressive strength before immersion - compressive strength after immersion) / compressive strength before immersion × 100%).

[0115] (4) Freeze-thaw resistance: According to the rapid freezing method in GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", the test block cured for 28 days was placed in a -20℃ environment for 4 hours and then placed in 20℃ water for 4 hours to thaw. This constitutes one freeze-thaw cycle. After completing 25 freeze-thaw cycles, the strength loss rate of the test block was determined.

[0116] (5) Density: determined according to the method in GB / T 17671-1999;

[0117] (6) Porosity: The porosity was determined by mercury porosimetry, with a test range of 0.003-100 μm.

[0118] Example 1

[0119] This embodiment provides a special composite activator and its synthesis method, as well as an alkaline slag-based geopolymer prepared using the activator and its preparation method.

[0120] 1. Preparation of special composite activators (parts by weight)

[0121] Raw material composition: 40 parts industrial by-product silica fume, 20 parts water glass, 12 parts sodium hydroxide, 4 parts aluminum tripolyphosphate, 2 parts nano-SiO2, 5 parts calcium-based modifier (calcium hydroxide to gypsum weight ratio 2.5:1), and 2 parts co-solvent (sodium carbonate to potassium chloride weight ratio 1:1.5).

[0122] Synthesis steps:

[0123] S1. Raw material pretreatment: Dry industrial by-product silica fume in an oven at 105℃ for 5 hours to remove moisture, then pulverize and pass through a 200-mesh sieve for later use; pulverize calcium hydroxide and gypsum separately, pass through a 180-mesh sieve, and mix them evenly at a weight ratio of 2.5:1 to obtain a calcium-based modifier for later use; pulverize sodium carbonate and potassium chloride, and mix them evenly at a weight ratio of 1:1.5 to obtain a co-solvent for later use.

[0124] S2. Primary modification: The pretreated industrial by-product silica fume is added to a high-speed mixer, the speed is adjusted to 400 r / min, nano-SiO2 and co-solvent are slowly added, and the mixture is mixed for 20 min to obtain primary modified silica fume;

[0125] S3. Composite reaction: Add water glass to the reaction vessel, heat to 50℃, adjust the stirring speed to 250r / min, slowly add sodium hydroxide, stir until completely dissolved, then add aluminum tripolyphosphate, continue stirring for 35min to obtain a composite solution;

[0126] S4. Fusion Modification: The primary modified silica fume obtained in step S2 is slowly added to the composite solution obtained in step S3, and the pretreated calcium-based modifier is added at the same time. The temperature is raised to 80℃, the stirring speed is increased to 500 r / min, and the mixture is kept at this temperature and stirred for 75 min. During this period, the viscosity of the system is checked every 15 min, and the viscosity of the system is controlled at 1000 mPa·s (the viscosity was within the control range in this test and no adjustment was made).

[0127] S5. Low-temperature calcination: The fusion product obtained in step S4 is placed in a calcination furnace and heated to 250°C at a heating rate of 8°C / min. Nitrogen gas is introduced for protection (nitrogen flow rate is 0.8L / min). The product is kept at this temperature for 3 hours and then naturally cooled to room temperature. After pulverizing, it is passed through a 180-mesh sieve to obtain the special composite activator product.

[0128] S6. Finished Product Inspection and Storage: The performance of the special composite activator finished product is tested. The test results are: activation activity 97%, moisture content 0.3%, fineness (180 mesh sieve residue) 3%. After passing the test, it is sealed and stored for later use.

[0129] 2. Preparation of alkaline residue-based geopolymer (parts by weight)

[0130] Raw material composition: 75 parts of alkali slag, 18 parts of silica-alumina admixture (kaolin and fly ash weight ratio 4:1), 5 parts of the above-mentioned special composite activator, 1.2 parts of modifier (polyvinyl alcohol and basalt fiber weight ratio 3:1), and 20 parts of deionized water.

[0131] Preparation steps:

[0132] Step 1: Raw material pretreatment

[0133] 1.1 Pretreatment of alkali residue: The alkali residue from the ammonia-soda process was placed in an open-air storage yard for natural drying for 36 hours, turning it over every 8 hours to remove surface free moisture. Then it was sent to a dryer and dried at 105℃ for 7 hours. After drying, it was sent to a pulverizer for pulverization. After pulverization, it was passed through a 100-mesh sieve. The residue was returned to the pulverizer for re-pulverization. The pulverized alkali residue was placed in a sealed container for later use. The moisture content of the alkali residue after pretreatment was controlled to be 7%.

[0134] 1.2 Pretreatment of silica-alumina admixture: Metakaolin and fly ash were mixed evenly at a weight ratio of 4:1 and fed into a dryer. The mixture was dried at 110℃ for 3.5h to remove moisture. After drying, the mixture was fed into a high-speed mixer at a speed of 250r / min for 12min to obtain a uniform silica-alumina admixture for later use.

[0135] 1.3 Modifier pretreatment: Polyvinyl alcohol was added to deionized water, heated to 85℃, and stirred until completely dissolved to obtain a polyvinyl alcohol solution; basalt fibers were cut to a length of 4 mm, immersed in the polyvinyl alcohol solution for 25 min, and stirred once every 5 min during the process. After being taken out, they were dried to obtain the pretreated modifier for later use.

[0136] 1.4 Pretreatment of special composite activator: The special composite activator prepared above is placed in a dryer and dried at 100℃ for 1.5h to remove moisture and set aside for later use;

[0137] Step 2: Ingredient Preparation and Mixing

[0138] 2.1 Dry material mixing: The pretreated alkali residue and silica-alumina admixture are fed into a forced mixer, the speed is adjusted to 350 r / min, and the mixture is mixed for 25 min to obtain a uniform dry material mixture;

[0139] 2.2 Activator Mixing: Slowly add the pretreated special composite activator to the dry material mixture and continue stirring for 18 minutes to ensure that the activator is evenly dispersed in the dry material;

[0140] 2.3 Wet Mixing: The pretreated modifier was added to the dry material-activator mixture, followed by the slow addition of deionized water. The stirring speed was adjusted to 250 r / min, and constant temperature stirring was used, with the stirring environment temperature controlled at 20℃. Stirring was continued for 30 min to obtain a homogeneous geopolymer slurry. During the stirring process, the slurry flowability was checked every 10 min, and the slurry flowability was controlled at 200 mm (the flowability was within the control range in this test and no adjustment was made).

[0141] Step 3: Molding

[0142] Pour the geopolymer slurry obtained in step two into a 40mm×40mm×160mm standard mold pre-coated with a release agent (engine oil and diesel oil weight ratio 1:1). After pouring, place the mold on a vibration table, adjust the vibration frequency to 55Hz, and vibrate for 2.5 minutes to remove air bubbles from the slurry and ensure that the slurry is densely filled. After vibration, use a scraper to smooth the excess slurry on the surface of the mold and place it in a room temperature (20℃) environment for 1.5 hours for pre-curing.

[0143] Step 4: Maintenance

[0144] 4.1 Preliminary curing: Place the pre-cured mold into the curing chamber (the curing chamber is equipped with an automatic temperature and humidity control system), control the curing temperature at 25℃ and the relative humidity at 90%, and cure for 36 hours. During this period, check the temperature and humidity of the curing environment every 8 hours to ensure that they meet the requirements.

[0145] 4.2 Intermediate curing: After the primary curing is completed, the mold is removed to obtain the geopolymer green body. The green body is then placed in the curing chamber, and the curing temperature is adjusted to 35℃ and the relative humidity to 85% for 4 days to promote the further geopolymerization reaction.

[0146] 4.3 Final Curing: After intermediate curing, the geopolymer green body is transferred to a standard curing room, where the curing temperature is controlled at 20℃ and the relative humidity at 92% for 21 days until the specified strength is reached. During the curing process, a small amount of deionized water is sprayed on the surface of the green body every day to prevent surface cracking.

[0147] Step 5: Finished Product Inspection and Packaging

[0148] 5.1 Performance testing: The performance of the geopolymer finished product after final curing was tested. Three parallel samples were selected for each test index, and the average value of the test results was taken. The test results are shown in Table 1 below.

[0149] 5.2 Packaging and Storage: Qualified finished products are cut and polished according to specifications, then packaged with waterproof packaging materials and stored in a dry, ventilated, and cool warehouse. During storage, prevent moisture and pressure. The shelf life is 6 months.

[0150] Example 2

[0151] This embodiment provides a special composite activator and its synthesis method, as well as an alkaline slag-based geopolymer prepared using the activator and its preparation method. The difference from Example 1 lies in the raw material ratio and some process parameters, as detailed below:

[0152] 1. Preparation of special composite activators (parts by weight)

[0153] Raw material composition: 30 parts industrial by-product silica fume, 15 parts water glass, 8 parts sodium hydroxide, 2 parts aluminum tripolyphosphate, 1 part nano-SiO2, 3 parts calcium-based modifier (calcium hydroxide to gypsum weight ratio 2:1), and 1 part co-solvent (sodium carbonate to potassium chloride weight ratio 1:1).

[0154] Synthesis steps:

[0155] S1. Raw material pretreatment: Dry industrial by-product silica fume in an oven at 100℃ for 4 hours to remove moisture, then pulverize and pass through a 200-mesh sieve for later use; pulverize calcium hydroxide and gypsum separately, pass through a 180-mesh sieve, and mix them evenly at a weight ratio of 2:1 to obtain a calcium-based modifier for later use; pulverize sodium carbonate and potassium chloride, and mix them evenly at a weight ratio of 1:1 to obtain a co-solvent for later use.

[0156] S2. Primary modification: The pretreated industrial by-product silica fume is added to a high-speed mixer, the speed is adjusted to 300 r / min, nano-SiO2 and co-solvent are slowly added, and the mixture is mixed for 15 min to obtain primary modified silica fume;

[0157] S3. Composite reaction: Add water glass to the reaction vessel, heat to 40℃, adjust the stirring speed to 200r / min, slowly add sodium hydroxide, stir until completely dissolved, then add aluminum tripolyphosphate, continue stirring for 30min to obtain a composite solution;

[0158] S4. Fusion Modification: The primary modified silica fume obtained in step S2 is slowly added to the composite solution obtained in step S3, and the pretreated calcium-based modifier is added at the same time. The temperature is raised to 70℃, the stirring speed is increased to 400r / min, and the mixture is kept at this temperature and stirred for 60min. During this period, the viscosity of the system is checked every 15min. The viscosity of one test is 780mPa·s. 0.5 parts of primary modified silica fume are added to adjust the viscosity to 820mPa·s, which meets the control requirements.

[0159] S5. Low-temperature calcination: The fusion product obtained in step S4 is placed in a calcination furnace and heated to 200°C at a heating rate of 5°C / min. Nitrogen gas is introduced for protection (nitrogen flow rate is 0.5L / min). The product is kept at this temperature for 2 hours and then naturally cooled to room temperature. After pulverizing, it is passed through a 180-mesh sieve to obtain the special composite activator product.

[0160] S6. Finished Product Inspection and Storage: The performance of the special composite activator finished product is tested. The test results are: activation activity 95%, moisture content 0.4%, fineness (180 mesh sieve residue) 4%. After passing the test, it is sealed and stored for later use.

[0161] 2. Preparation of alkaline residue-based geopolymer (parts by weight)

[0162] Raw material composition: 60 parts of alkali slag, 10 parts of silica-alumina admixture (meta-kaolin and fly ash weight ratio 3:1), 3 parts of the above-mentioned special composite activator, 0.5 parts of modifier (polyvinyl alcohol and basalt fiber weight ratio 2:1), and 15 parts of deionized water.

[0163] Preparation steps:

[0164] Step 1: Raw material pretreatment

[0165] 1.1 Pretreatment of alkali residue: The alkali residue from the ammonia-soda process was placed in an open-air storage yard for natural drying for 24 hours, turning it over every 6 hours to remove surface free moisture. Then it was sent to a dryer and dried at 100℃ for 6 hours. After drying, it was sent to a pulverizer for crushing. After crushing, it was passed through a 100-mesh sieve. The residue was returned to the pulverizer for re-crushing. The crushed alkali residue was placed in a sealed container for later use. The moisture content of the alkali residue after pretreatment was controlled to be 6%.

[0166] 1.2 Pretreatment of silica-alumina admixture: Metakaolin and fly ash were mixed evenly at a weight ratio of 3:1 and fed into a dryer. The mixture was dried at 105℃ for 3 hours to remove moisture. After drying, the mixture was fed into a high-speed mixer at a speed of 200 r / min for 10 minutes to obtain a uniform silica-alumina admixture for later use.

[0167] 1.3 Modifier pretreatment: Polyvinyl alcohol was added to deionized water, heated to 80℃, and stirred until completely dissolved to obtain a polyvinyl alcohol solution; basalt fibers were cut to a length of 3mm, immersed in the polyvinyl alcohol solution for 20min, and stirred once every 5min during the process. After being taken out, they were dried to obtain the pretreated modifier for later use.

[0168] 1.4 Pretreatment of special composite activator: The special composite activator prepared above is placed in a dryer and dried at 95°C for 1 hour to remove moisture and set aside for later use;

[0169] Step 2: Ingredient Preparation and Mixing

[0170] 2.1 Dry material mixing: The pretreated alkali residue and silica-alumina admixture are fed into a forced mixer, the speed is adjusted to 300 r / min, and the mixture is mixed for 20 min to obtain a uniform dry material mixture;

[0171] 2.2 Activator Mixing: Slowly add the pretreated special composite activator to the dry material mixture and continue stirring for 15 minutes to ensure that the activator is evenly dispersed in the dry material;

[0172] 2.3 Wet Mixing: The pretreated modifier was added to the dry material-activator mixture, followed by the slow addition of deionized water. The stirring speed was adjusted to 200 r / min, and constant temperature stirring was used, with the stirring environment temperature controlled at 18℃. Stirring was continued for 25 min to obtain a uniform geopolymer slurry. During the stirring process, the slurry flowability was checked every 10 min. At one point, the flowability was 170 mm. 0.3 parts of deionized water were added to adjust the flowability to 185 mm, which met the control requirements.

[0173] Step 3: Molding

[0174] Pour the geopolymer slurry obtained in step two into a standard 40mm×40mm×160mm mold pre-coated with a release agent (engine oil and diesel oil weight ratio 1:1). After pouring, place the mold on a vibration table, adjust the vibration frequency to 50Hz, and vibrate for 2 minutes to remove air bubbles from the slurry and ensure that the slurry is densely filled. After vibration, use a scraper to smooth the excess slurry on the surface of the mold and place it in a room temperature (18℃) environment for 1 hour for pre-curing.

[0175] Step 4: Maintenance

[0176] 4.1 Preliminary curing: Place the pre-cured mold into the curing chamber (the curing chamber is equipped with an automatic temperature and humidity control system), control the curing temperature at 22℃ and the relative humidity at 85%, and cure for 24 hours. During this period, check the temperature and humidity of the curing environment every 8 hours to ensure that they meet the requirements.

[0177] 4.2 Intermediate curing: After the primary curing is completed, the mold is removed to obtain the geopolymer green body. The green body is then placed in the curing chamber, and the curing temperature is adjusted to 32℃ and the relative humidity to 80% for 3 days to promote the further geopolymerization reaction.

[0178] 4.3 Final Curing: After intermediate curing, the geopolymer green body is transferred to a standard curing room, where the curing temperature is controlled at 18℃ and the relative humidity at 90% for 20 days until the specified strength is reached. During the curing process, a small amount of deionized water is sprayed on the surface of the green body every day to prevent surface cracking.

[0179] Step 5: Finished Product Inspection and Packaging

[0180] 5.1 Performance testing: The performance of the geopolymer finished product after final curing was tested. Three parallel samples were selected for each test index, and the average value of the test results was taken. The test results are shown in Table 1 below.

[0181] 5.2 Packaging and storage: Same as in Example 1.

[0182] Example 3

[0183] This embodiment provides a special composite activator and its synthesis method, as well as an alkaline slag-based geopolymer prepared using the activator and its preparation method. The difference from Example 1 lies in the raw material ratio and some process parameters, as detailed below:

[0184] 1. Preparation of special composite activators (parts by weight)

[0185] Raw material composition: 50 parts industrial by-product silica fume, 25 parts water glass, 15 parts sodium hydroxide, 6 parts aluminum tripolyphosphate, 4 parts nano-SiO2, 8 parts calcium-based modifier (calcium hydroxide to gypsum weight ratio 3:1), and 3 parts co-solvent (sodium carbonate to potassium chloride weight ratio 1:2).

[0186] Synthesis steps:

[0187] S1. Raw material pretreatment: Dry industrial by-product silica fume in an oven at 110℃ for 6 hours to remove moisture, then pulverize and pass through a 200-mesh sieve for later use; pulverize calcium hydroxide and gypsum separately, pass through a 180-mesh sieve, and mix them evenly at a weight ratio of 3:1 to obtain a calcium-based modifier for later use; pulverize sodium carbonate and potassium chloride, and mix them evenly at a weight ratio of 1:2 to obtain a flux for later use.

[0188] S2. Primary modification: The pretreated industrial by-product silica fume is added to a high-speed mixer, the speed is adjusted to 500 r / min, nano-SiO2 and co-solvent are slowly added, and the mixture is mixed for 25 min to obtain primary modified silica fume;

[0189] S3. Composite reaction: Add water glass to the reaction vessel, heat to 60℃, adjust the stirring speed to 300r / min, slowly add sodium hydroxide, stir until completely dissolved, then add aluminum tripolyphosphate and continue stirring for 40min to obtain a composite solution;

[0190] S4. Fusion Modification: The primary modified silica fume obtained in step S2 is slowly added to the composite solution obtained in step S3, and the pretreated calcium-based modifier is added at the same time. The temperature is raised to 90℃, the stirring speed is increased to 600r / min, and the mixture is kept at this temperature and stirred for 90min. During this period, the viscosity of the system is measured every 15min. The viscosity measured at one time is 1250mPa·s. 0.2 parts of deionized water are added, and the viscosity is adjusted to 1180mPa·s, which meets the control requirements.

[0191] S5. Low-temperature calcination: The fusion product obtained in step S4 is placed in a calcination furnace and heated to 300°C at a heating rate of 10°C / min. Nitrogen gas is introduced for protection (nitrogen flow rate is 1L / min). The product is kept at this temperature for 4 hours and then naturally cooled to room temperature. After being pulverized, it is passed through a 180-mesh sieve to obtain the special composite activator product.

[0192] S6. Finished Product Inspection and Storage: The performance of the special composite activator finished product is tested. The test results are: activation activity 98%, moisture content 0.2%, fineness (180 mesh sieve residue) 2%. After passing the test, it is sealed and stored for later use.

[0193] 2. Preparation of alkaline residue-based geopolymer (parts by weight)

[0194] Raw material composition: 85 parts of alkali slag, 25 parts of silica-alumina admixture (kaolin and fly ash weight ratio 5:1), 8 parts of the above-mentioned special composite activator, 2 parts of modifier (polyvinyl alcohol and basalt fiber weight ratio 4:1), and 25 parts of deionized water.

[0195] Preparation steps:

[0196] Step 1: Raw material pretreatment

[0197] 1.1 Pretreatment of alkali residue: The alkali residue from the ammonia-soda process was placed in an open-air storage yard for natural drying for 48 hours, turning it over every 10 hours to remove surface free moisture. Then it was sent to a dryer and dried at 110℃ for 8 hours. After drying, it was sent to a pulverizer for pulverization. After pulverization, it was passed through a 100-mesh sieve. The residue was returned to the pulverizer for re-pulverization. The pulverized alkali residue was placed in a sealed container for later use. The moisture content of the alkali residue after pretreatment was controlled to be 8%.

[0198] 1.2 Pretreatment of silica-alumina admixture: Metakaolin and fly ash were mixed evenly at a weight ratio of 5:1 and fed into a dryer. The mixture was dried at 115℃ for 4 hours to remove moisture. After drying, the mixture was fed into a high-speed mixer at a speed of 300 r / min for 15 minutes to obtain a uniform silica-alumina admixture for later use.

[0199] 1.3 Modifier pretreatment: Polyvinyl alcohol was added to deionized water, heated to 90℃, and stirred until completely dissolved to obtain a polyvinyl alcohol solution; basalt fibers were cut to a length of 6mm, immersed in the polyvinyl alcohol solution for 30min, and stirred once every 5min during the process. After being taken out, they were dried to obtain the pretreated modifier for later use.

[0200] 1.4 Pretreatment of special composite activator: The special composite activator prepared above was placed in a dryer and dried at 105℃ for 2 hours to remove moisture and set aside for later use;

[0201] Step 2: Ingredient Preparation and Mixing

[0202] 2.1 Dry material mixing: The pretreated alkali residue and silica-alumina admixture are fed into a forced mixer, the speed is adjusted to 400 r / min, and the mixture is mixed for 30 min to obtain a uniform dry material mixture;

[0203] 2.2 Activator Mixing: Slowly add the pretreated special composite activator to the dry material mixture and continue stirring for 20 minutes to ensure that the activator is evenly dispersed in the dry material;

[0204] 2.3 Wet Mixing: The pretreated modifier was added to the dry material-activator mixture, followed by the slow addition of deionized water. The stirring speed was adjusted to 300 r / min, and constant temperature stirring was used, with the stirring environment temperature controlled at 22℃. Stirring was continued for 35 min to obtain a uniform geopolymer slurry. During the stirring process, the slurry flowability was checked every 10 min. At one point, the flowability was 230 mm. 0.4 parts of the dry material mixture were added to adjust the flowability to 215 mm, which met the control requirements.

[0205] Step 3: Molding

[0206] Pour the geopolymer slurry obtained in step two into a 40mm×40mm×160mm standard mold pre-coated with a release agent (engine oil and diesel oil weight ratio 1:1). After pouring, place the mold on a vibration table, adjust the vibration frequency to 60Hz, and vibrate for 3 minutes to remove air bubbles from the slurry and ensure that the slurry is densely filled. After vibration, use a scraper to smooth the excess slurry on the surface of the mold and place it in a room temperature (22℃) environment for 2 hours for pre-curing.

[0207] Step 4: Maintenance

[0208] 4.1 Preliminary curing: Place the pre-cured mold into the curing chamber (the curing chamber is equipped with an automatic temperature and humidity control system), control the curing temperature at 28℃ and the relative humidity at 95%, and cure for 48 hours. During this period, check the temperature and humidity of the curing environment every 8 hours to ensure that they meet the requirements.

[0209] 4.2 Intermediate curing: After the primary curing is completed, the mold is removed to obtain the geopolymer green body. The green body is then placed in the curing chamber, and the curing temperature is adjusted to 38℃ and the relative humidity to 90% for 5 days to promote the further geopolymerization reaction.

[0210] 4.3 Final Curing: After intermediate curing, the geopolymer green body is transferred to a standard curing room, where the curing temperature is controlled at 22℃ and the relative humidity at 95% for 22 days until the specified strength is reached. During the curing process, a small amount of deionized water is sprayed on the surface of the green body every day to prevent surface cracking.

[0211] Step 5: Finished Product Inspection and Packaging

[0212] 5.1 Performance testing: The performance of the geopolymer finished product after final curing was tested. Three parallel samples were selected for each test index, and the average value of the test results was taken. The test results are shown in Table 1 below.

[0213] 5.2 Packaging and storage: Same as in Example 1.

[0214] Example 4

[0215] This embodiment provides a special composite activator and its synthesis method, as well as an alkaline slag-based geopolymer prepared using the activator and its preparation method. The difference from Example 1 is that pigments and defoamers are added to the alkaline slag-based geopolymer raw materials, as detailed below:

[0216] 1. Preparation of special composite activators

[0217] The results were exactly the same as in Example 1, with the following results: activation activity 97%, moisture content 0.3%, and fineness (residue on 180 mesh sieve) 3%.

[0218] 2. Preparation of alkaline residue-based geopolymer (parts by weight)

[0219] Raw material composition: 75 parts of alkali residue, 18 parts of silica-alumina admixture (kaolin and fly ash weight ratio 4:1), 5 parts of the above-mentioned special composite activator, 1.2 parts of modifier (polyvinyl alcohol and basalt fiber weight ratio 3:1), 20 parts of deionized water, 0.3 parts of pigment, and 0.6 parts of defoamer (organosilicon defoamer).

[0220] Preparation steps:

[0221] Step 1: Raw material pretreatment, exactly the same as in Example 1;

[0222] Step 2: Ingredient Preparation and Mixing

[0223] 2.1 Dry material mixing: The pretreated alkali residue, silica-alumina admixture, and pigment are fed into a forced mixer. The speed is adjusted to 350 r / min, and the mixture is mixed for 25 min to obtain a uniform dry material mixture.

[0224] 2.2 Activator Mixing: Slowly add the pretreated special composite activator to the dry material mixture and continue stirring for 18 minutes to ensure that the activator is evenly dispersed in the dry material;

[0225] 2.3 Wet Mixing: The pretreated modifier was added to the dry material-activator mixture, followed by the slow addition of deionized water and defoamer. The stirring speed was adjusted to 250 r / min, and constant temperature stirring was used, with the stirring environment temperature controlled at 20℃. Stirring was continued for 30 min to obtain a uniform geopolymer slurry. During the stirring process, the slurry flowability was checked every 10 min, and the slurry flowability was controlled at 200 mm (the flowability was within the control range in this test and no adjustment was made).

[0226] Step 3: Molding, exactly the same as in Example 1;

[0227] Step 4: Maintenance, exactly the same as in Example 1;

[0228] Step 5: Finished Product Inspection and Packaging

[0229] 5.1 Performance testing: The performance of the geopolymer finished product after final curing was tested. Three parallel samples were selected for each test index, and the average value of the test results was taken. The test results are shown in Table 1 below (the finished product is white and has no obvious bubbles).

[0230] 5.2 Packaging and storage: Same as in Example 1.

[0231] Example 5

[0232] This embodiment provides a special composite activator and its synthesis method, as well as an alkaline slag-based geopolymer prepared using the activator and its preparation method. The difference from Example 1 is that the proportions of the calcium-based modifier and the co-solvent are different in the synthesis step of the special composite activator, as detailed below:

[0233] 1. Preparation of special composite activators (parts by weight)

[0234] Raw material composition: 40 parts industrial by-product silica fume, 20 parts water glass, 12 parts sodium hydroxide, 4 parts aluminum tripolyphosphate, 2 parts nano-SiO2, 5 parts calcium-based modifier (calcium hydroxide to gypsum weight ratio 2:1), and 2 parts co-solvent (sodium carbonate to potassium chloride weight ratio 1:1).

[0235] Synthesis steps: exactly the same as in Example 1, except for the ratio of calcium-based modifier and co-solvent;

[0236] S6. Finished Product Inspection and Storage: The performance of the special composite activator finished product is tested. The test results are: activation activity 96%, moisture content 0.3%, fineness (180 mesh sieve residue) 3%. After passing the test, it is sealed and stored for later use.

[0237] 2. Preparation of alkaline residue-based geopolymers

[0238] The results are exactly the same as in Example 1, and the performance test results are shown in Table 1 below.

[0239] Comparative Example

[0240] Comparative Example 1 (using a traditional composite activator)

[0241] This comparative example provides a conventional composite activator and its preparation method, as well as an alkaline slag-based geopolymer prepared using this activator and its preparation method. The difference from Example 1 is that a conventional composite activator is used instead of the special composite activator of this invention, as detailed below:

[0242] 1. Preparation of traditional composite activators (parts by weight)

[0243] Raw material composition: 20 parts water glass, 12 parts sodium hydroxide (no other components), which is the traditional alkali activator (sodium hydroxide + water glass, weight ratio 1:1.67).

[0244] Synthesis steps: Add water glass to the reactor, heat to 50°C, adjust the stirring speed to 250 r / min, slowly add sodium hydroxide, stir until completely dissolved, continue stirring for 35 min to obtain the traditional composite activator, without the need for primary modification, fusion modification, and low-temperature calcination steps;

[0245] Finished product testing: 75% activation activity, 0.5% moisture content, and 6% fineness (residue on 180-mesh sieve).

[0246] 2. Preparation of alkaline residue-based geopolymers

[0247] The raw material composition and preparation steps are exactly the same as in Example 1, except that the activator is replaced with the above-mentioned traditional composite activator;

[0248] Performance testing: The performance of the geopolymer finished product after final curing was tested. Three parallel samples were selected for each test index, and the average value of the test results was taken. The test results are shown in Table 1 below.

[0249] Comparative Example 2 (without adding nano-SiO2)

[0250] This comparative example provides a composite activator and its preparation method, as well as an alkaline slag-based geopolymer prepared using this activator and its preparation method. The difference from Example 1 is that nano-SiO2 is not added to the raw materials of the special composite activator, as detailed below:

[0251] 1. Preparation of composite activator (parts by weight)

[0252] Raw material composition: 40 parts industrial by-product silica fume, 20 parts water glass, 12 parts sodium hydroxide, 4 parts aluminum tripolyphosphate, 5 parts calcium-based modifier (calcium hydroxide to gypsum weight ratio 2.5:1), 2 parts co-solvent (sodium carbonate to potassium chloride weight ratio 1:1.5) (no nano SiO2).

[0253] Synthesis steps: exactly the same as in Example 1, except that nano-SiO2 is not added;

[0254] Finished product testing: Activation activity 88%, moisture content 0.3%, fineness (residue on 180 mesh sieve) 3%.

[0255] 2. Preparation of alkaline residue-based geopolymers

[0256] The raw material composition and preparation steps are exactly the same as in Example 1;

[0257] Performance testing: The performance of the geopolymer finished product after final curing was tested. Three parallel samples were selected for each test index, and the average value of the test results was taken. The test results are shown in Table 1 below.

[0258] Comparative Example 3 (without calcium-based modifier)

[0259] This comparative example provides a composite activator and its preparation method, as well as an alkaline slag-based geopolymer prepared using this activator and its preparation method. The difference from Example 1 is that no calcium-based modifier is added to the raw materials of the special composite activator, as detailed below:

[0260] 1. Preparation of composite activator (parts by weight)

[0261] Raw material composition: 40 parts industrial by-product silica fume, 20 parts water glass, 12 parts sodium hydroxide, 4 parts aluminum tripolyphosphate, 2 parts nano SiO2, and 2 parts co-solvent (sodium carbonate to potassium chloride weight ratio 1:1.5) (no calcium-based modifier).

[0262] Synthesis steps: exactly the same as in Example 1, except that no calcium-based modifier is added;

[0263] Finished product testing: activation activity 86%, moisture content 0.3%, fineness (residue on 180 mesh sieve) 3%.

[0264] 2. Preparation of alkaline residue-based geopolymers

[0265] The raw material composition and preparation steps are exactly the same as in Example 1;

[0266] Performance testing: The performance of the geopolymer finished product after final curing was tested. Three parallel samples were selected for each test index, and the average value of the test results was taken. The test results are shown in Table 1 below.

[0267] Comparative Example 4 (without low-temperature calcination)

[0268] This comparative example provides a composite activator and its preparation method, as well as an alkaline slag-based geopolymer prepared using the activator and its preparation method. The difference from Example 1 is that the special composite activator synthesis step does not involve low-temperature calcination, as detailed below:

[0269] 1. Preparation of composite activators

[0270] The raw material composition is exactly the same as in Example 1;

[0271] Synthesis steps: S1-S4 are exactly the same as in Example 1. After completing the S4 fusion modification, the mixture is directly cooled to room temperature, pulverized and passed through a 180-mesh sieve to obtain the composite activator product. The S5 low-temperature calcination step is not performed.

[0272] Finished product testing: activation activity 83%, moisture content 1.2%, fineness (residue on 180 mesh sieve) 4%.

[0273] 2. Preparation of alkaline residue-based geopolymers

[0274] The raw material composition and preparation steps are exactly the same as in Example 1;

[0275] Performance testing: The performance of the geopolymer finished product after final curing was tested. Three parallel samples were selected for each test index, and the average value of the test results was taken. The test results are shown in Table 1 below.

[0276] Comparative Example 5 (without aluminum tripolyphosphate)

[0277] This comparative example provides a composite activator and its preparation method, as well as an alkaline slag-based geopolymer prepared using the activator and its preparation method. The difference from Example 1 is that aluminum tripolyphosphate is not added to the raw materials of the special composite activator, as detailed below:

[0278] 1. Preparation of composite activator (parts by weight)

[0279] Raw material composition: 40 parts industrial by-product silica fume, 20 parts water glass, 12 parts sodium hydroxide, 2 parts nano-SiO2, 5 parts calcium-based modifier (calcium hydroxide to gypsum weight ratio 2.5:1), 2 parts co-solvent (sodium carbonate to potassium chloride weight ratio 1:1.5) (no aluminum tripolyphosphate).

[0280] Synthesis steps: exactly the same as in Example 1, except that aluminum tripolyphosphate is not added;

[0281] Finished product testing: Activation activity 85%, moisture content 0.3%, fineness (residue on 180 mesh sieve) 3%.

[0282] 2. Preparation of alkaline residue-based geopolymers

[0283] The raw material composition and preparation steps are exactly the same as in Example 1;

[0284] Performance testing: The performance of the geopolymer finished product after final curing was tested. Three parallel samples were selected for each test index, and the average value of the test results was taken. The test results are shown in Table 1 below.

[0285] Comparative Example 6 (Alkali residue without pretreatment)

[0286] This comparative example provides an alkaline residue-based polymer and its preparation method. The difference from Example 1 is that the alkaline residue is not pretreated (not sun-dried, not crushed), as detailed below:

[0287] 1. Preparation of special composite activators

[0288] The results were exactly the same as in Example 1, with the following results: activation activity 97%, moisture content 0.3%, and fineness (residue on 180 mesh sieve) 3%.

[0289] 2. Preparation of alkaline residue-based geopolymers

[0290] The raw material composition is exactly the same as in Example 1;

[0291] Preparation steps: In step one, the raw material pretreatment, the alkali residue is not dried, crushed, or sun-dried; the original alkali residue (15% moisture content, uneven particle size, and not sieved) is used directly. The other steps are exactly the same as in Example 1.

[0292] Performance testing: The performance of the geopolymer finished product after final curing was tested. Three parallel samples were selected for each test index, and the average value of the test results was taken. The test results are shown in Table 1 below.

[0293] Summary table of performance test results for examples and comparative examples

[0294] Group 28-day compressive strength (MPa) 28-day flexural strength (MPa) Softening coefficient Hydrochloric acid corrosion resistance strength loss rate (%) Freeze-thaw strength loss rate (%) Density (g / cm³) Porosity (%) Example 1 68 9.2 0.90 7.5 6.2 2.0 15.3 Example 2 42 5.3 0.86 9.2 7.8 1.8 18.7 Example 3 82 11.5 0.93 6.1 5.3 2.2 12.1 Example 4 69 9.3 0.91 7.3 6.0 2.0 14.8 Example 5 66 8.9 0.89 7.8 6.5 2.0 15.7 Comparative Example 1 38 4.5 0.78 15.2 12.3 1.7 22.5 Comparative Example 2 52 7.1 0.83 10.5 9.1 1.9 18.2 Comparative Example 3 50 6.8 0.82 11.3 9.7 1.9 18.9 Comparative Example 4 47 6.5 0.80 12.1 10.2 1.8 19.5 Comparative Example 5 49 6.7 0.81 11.8 9.9 1.9 19.1 Comparative Example 6 35 4.2 0.75 16.8 13.5 1.7 23.8

Claims

1. A special composite activator for the preparation of alkaline slag-based polymers, characterized in that, Composed of the following raw materials in parts by weight: 30-50 parts of industrial by-product silica fume, 15-25 parts of water glass 8-15 parts of sodium hydroxide 2-6 parts of aluminum tripolyphosphate 1-4 parts of nano-SiO2 3-8 parts of calcium-based modifier 1-3 parts of co-solvent; The calcium-based modifier is a compound of calcium hydroxide and gypsum, with a weight ratio of 2:1 to 3:

1. The co-solvent is a mixture of sodium carbonate and potassium chloride, with a weight ratio of 1:1 to 1:

2.

2. The special composite activator according to claim 1, characterized in that, The specific surface area of ​​the industrial by-product silica fume is 20,000-30,000 cm² / g, and the SiO₂ content is ≥90%. The water glass has a modulus of 1.5-2.5 and a solid content of 30%-45%. The purity of the sodium hydroxide is ≥96%; The purity of the aluminum tripolyphosphate is ≥98%; The nano-SiO2 has a particle size of 50-100nm and a specific surface area of ​​150-250m² / g; The gypsum is building gypsum with a CaSO4·2H2O content ≥95%.

3. The method for synthesizing the special composite activator according to claim 1 or 2, characterized in that, Includes the following steps: S1. Raw material pretreatment: Dry the industrial by-product silica fume in an oven at 105±5℃ for 4-6 hours to remove moisture, then crush it and pass it through a 200-mesh sieve for later use; crush the calcium hydroxide and gypsum in the calcium-based modifier separately, pass them through a 180-mesh sieve, and mix them evenly in proportion for later use; crush the sodium carbonate and potassium chloride in the co-solvent and mix them evenly for later use. S2. Primary modification: Add the pretreated industrial by-product silica fume into a high-speed mixer, adjust the speed to 300-500 r / min, slowly add nano-SiO2 and co-solvent, mix for 15-25 min to obtain primary modified silica fume; S3. Composite reaction: Add water glass to the reactor, heat to 40-60℃, adjust the stirring speed to 200-300r / min, slowly add sodium hydroxide, stir until completely dissolved, then add aluminum tripolyphosphate, and continue stirring for 30-40min to obtain a composite solution; S4. Fusion Modification: The primary modified silica fume obtained in step S2 is slowly added to the composite solution obtained in step S3, and the pretreated calcium-based modifier is added at the same time. The temperature is raised to 70-90℃, the stirring speed is increased to 400-600r / min, and the mixture is kept at this temperature and stirred for 60-90min. During this period, the viscosity of the system is checked every 15min, and the viscosity of the system is controlled to be 800-1200mPa·s. S5. Low-temperature calcination: The fusion product obtained in step S4 is placed in a calcination furnace and heated to 200-300℃ at a heating rate of 5-10℃ / min. The temperature is maintained for calcination for 2-4 hours, and then naturally cooled to room temperature. After pulverization, it is passed through a 180-mesh sieve to obtain the special composite activator product. S6. Finished Product Inspection and Storage: The performance of the special composite activator finished product shall be tested. The test indicators include activation activity, moisture content and fineness. The activation activity shall be ≥95%, the moisture content shall be ≤0.5% and the fineness (residue on 180 mesh sieve) shall be ≤5%. After passing the test, the product shall be sealed and stored for future use.

4. The synthesis method according to claim 3, characterized in that, In step S4, if the system viscosity is below 800 mPa·s, add an appropriate amount of primary modified silica fume; if it is above 1200 mPa·s, add a small amount of deionized water to adjust it; in step S5, nitrogen gas is introduced for protection during calcination, with a nitrogen flow rate of 0.5-1 L / min, to prevent product oxidation.

5. A base polymer based on alkali residue, characterized in that, It is composed of the following raw materials in parts by weight: 60-85 parts of alkali residue, 10-25 parts of silicon-aluminum admixture, 3-8 parts of the special composite activator as described in claim 1 or 2, 0.5-2 parts of modifier, and 15-25 parts of deionized water. The silica-aluminate admixture is a mixture of metakaolin and fly ash, with a weight ratio of 3:1 to 5:

1. The modifier is a compound of polyvinyl alcohol and basalt fiber, with a weight ratio of 2:1 to 4:

1.

6. The alkaline residue-based polymer according to claim 5, characterized in that, The alkaline residue is an industrial waste residue generated from the production of soda ash using the ammonia-soda process. It has a pH value of 8-12, a moisture content of ≤10%, and is pulverized and passed through a 100-mesh sieve. The residue contains 15%-25% SiO2, 5%-15% Al2O3, 30%-45% CaO, 2%-8% MgO, and ≤5% easily soluble salts (NaCl, CaCl2). The metakaolin has a calcination temperature of 700-800℃, a specific surface area of ​​10000-15000cm² / g, a SiO2 content of ≥50%, and an Al2O3 content of ≥30%. The fly ash is Grade I fly ash with a specific surface area of ​​5000-8000 cm² / g, SiO2 content ≥40%, and Al2O3 content ≥20%. The degree of polymerization of the polyvinyl alcohol is 1700-2000, and the degree of alcoholysis is 88%-90%. The basalt fibers have a length of 3-6 mm, a diameter of 10-20 μm, and a tensile strength ≥3000 MPa.

7. The method for preparing the alkaline residue-based polymer according to claim 5 or 6, characterized in that, Includes the following steps: Step 1: Raw material pretreatment 1.1 Pretreatment of alkali residue: The alkali residue from the ammonia-soda process is placed in an open-air storage yard for natural drying for 24-48 hours to remove surface free moisture. Then it is sent to a dryer and dried at 105±5℃ for 6-8 hours. After drying, it is sent to a pulverizer for pulverization. After pulverization, it is passed through a 100-mesh sieve. The residue is returned to the pulverizer for re-pulverization. The pulverized alkali residue is placed in a sealed container for later use. The moisture content of the alkali residue after pretreatment is controlled to be ≤8%. 1.2 Pretreatment of silica-alumina admixture: Mix metakaolin and fly ash evenly in proportion, send to a dryer, dry at 110±5℃ for 3-4 hours to remove moisture, then send to a high-speed mixer, adjust the speed to 200-300 r / min, mix for 10-15 minutes to obtain a uniform silica-alumina admixture for later use. 1.3 Modifier pretreatment: Add polyvinyl alcohol to deionized water, heat to 80-90℃, stir until completely dissolved to obtain a polyvinyl alcohol solution; cut basalt fibers to the specified length, immerse them in the polyvinyl alcohol solution for 20-30 minutes, remove them and air dry to obtain the pretreated modifier for later use; 1.4 Pretreatment of special composite activator: Place the special composite activator according to claim 1 or 2 in a dryer and dry it at 100±5℃ for 1-2 hours to remove moisture and set aside for later use; Step 2: Ingredient Preparation and Mixing 2.1 Dry material mixing: The pretreated alkali residue and silica-alumina admixture are fed into a forced mixer, the speed is adjusted to 300-400 r / min, and the mixture is mixed for 20-30 min to obtain a uniform dry material mixture; 2.2 Activator Mixing: Slowly add the pretreated special composite activator to the dry material mixture and continue stirring for 15-20 minutes to ensure that the activator is evenly dispersed in the dry material; 2.3 Wet Mixing: Add the pretreated modifier to the dry material-activator mixture, then slowly add deionized water, adjust the stirring speed to 200-300 r / min, and continue stirring for 25-35 min to obtain a uniform geopolymer slurry; during the stirring process, check the slurry flowability every 10 min, and control the slurry flowability to 180-220 mm. If the flowability is too low, add a small amount of deionized water; if the flowability is too high, add a small amount of dry material mixture to adjust. Step 3: Molding Pour the geopolymer slurry obtained in step two into a mold pre-coated with a release agent. The mold size is selected according to actual needs (such as a standard test mold of 40mm×40mm×160mm). After pouring, place the mold on a vibration table, adjust the vibration frequency to 50-60Hz, and the vibration time to 2-3 minutes to remove air bubbles in the slurry and ensure that the slurry is densely filled. After vibration, use a scraper to smooth the excess slurry on the surface of the mold and place it in a room temperature (20±5℃) environment for 1-2 hours for pre-curing. Step 4: Maintenance 4.1 Primary curing: Place the pre-cured mold into the curing chamber, control the curing temperature at 25±3℃ and the relative humidity at 85%-95%, and cure for 24-48 hours. During this period, check the temperature and humidity of the curing environment every 8 hours to ensure that they meet the requirements. 4.2 Intermediate curing: After the primary curing is completed, the mold is removed to obtain the geopolymer green body. The green body is then placed in the curing chamber, and the curing temperature is adjusted to 35±3℃ and the relative humidity to 80%-90%. The curing is carried out for 3-5 days to promote the further geopolymerization reaction. 4.3 Final Curing: After intermediate curing, the geopolymer green body is transferred to a standard curing room, where the curing temperature is controlled at 20±2℃ and the relative humidity at 90%-95% for 20-22 days until the specified strength is reached. During the curing process, a small amount of deionized water is sprayed on the surface of the green body every day to prevent surface cracking. Step 5: Finished Product Inspection and Packaging 5.1 Performance Testing: The finished geopolymer product after final curing will undergo performance testing. Testing indicators include compressive strength, flexural strength, water resistance, corrosion resistance, freeze-thaw resistance, density, and porosity. Specifically, the following parameters must be met: 28-day compressive strength ≥ 40 MPa, 28-day flexural strength ≥ 5 MPa, softening coefficient ≥ 0.85, hydrochloric acid corrosion resistance (immersion in 5% HCl solution for 7 days) with strength loss ≤ 10%, freeze-thaw resistance (25 freeze-thaw cycles at -20℃) with strength loss ≤ 8%, density 1.8-2.2 g / cm³, and porosity ≤ 20%. 5.2 Packaging and Storage: Qualified finished products are cut and polished according to specifications, then packaged with waterproof packaging materials and stored in a dry, ventilated, and cool warehouse. During storage, they should be protected from moisture and pressure. The shelf life is 6 months. Qualified finished products are returned to the raw material pretreatment step for reprocessing.

8. The preparation method according to claim 7, characterized in that, In step 1.1, during the drying of the alkali residue, it is turned over regularly to ensure that the moisture evaporates evenly; in step 1.3, during the soaking of basalt fiber, it is stirred once every 5 minutes to ensure that the fiber absorbs the polyvinyl alcohol solution evenly; in step 2.3, constant temperature stirring is used during the stirring process, and the stirring environment temperature is controlled at 20±3℃ to prevent the slurry from solidifying too quickly or too slowly.

9. The preparation method according to claim 7, characterized in that, The mold release agent in step three is a mixture of engine oil and diesel oil with a weight ratio of 1:1; in step four, 4.1, an automatic temperature and humidity control system is set up in the curing box to monitor and adjust the temperature and humidity in real time; in step five, 5.1, during the performance test, three parallel samples are selected for each test index, and the average value of the test results is taken. If the test result of a single sample deviates from the average value by more than 10%, a new sample is selected for testing.

10. The alkaline residue-based polymer according to claim 5, characterized in that, Depending on the actual application requirements, 0.1-0.5 parts of pigment or 0.3-1 parts of defoamer can be added to the raw materials. The defoamer is an organosilicon defoamer, which is added during the wet material mixing process in step 2.3, and is added at the same time as deionized water.

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