Method for preparing geopolymer cementitious material by composite solid base activation and synergistic waste incineration fly ash

Abstract

The application discloses a method for preparing geopolymer cementing material by composite solid alkali excitation and synergistic waste incineration fly ash, and the method comprises the following steps: mixing 35-50% of waste incineration fly ash, 10-30% of a composite solid alkali excitation agent, 10-30% of an active silicon-aluminum adjusting component and 10-15% of a functional regulation component, drying, crushing, grinding and screening the above-mentioned raw materials respectively, adding water, stirring to form a uniform slurry, curing the slurry after shaping, and obtaining the geopolymer cementing material. The method replaces the traditional liquid strong alkali excitation agent with the composite solid alkali excitation system, reduces the safety risk in the transportation and use of the alkali excitation material, and realizes the synergistic utilization of waste incineration fly ash, calcium carbide slag, yellow phosphorus slag and other multi-source solid wastes. The obtained material has the characteristics of good coagulation and hardening performance, high structural stability and strong heavy metal solidification capacity, and can be used in the fields of building materials, road engineering materials and solid waste resource utilization.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization and inorganic cementitious material preparation technology, and particularly relates to a method for preparing geopolymer cementitious materials by synergistic activation of composite solid alkali and waste incineration fly ash. Background Technology

[0002] With the accelerating pace of urbanization, the amount of municipal solid waste generated continues to increase. Waste incineration technology, due to its advantages in waste reduction, resource recovery, and energy recycling, has become an important method for urban waste management. However, waste incineration produces a large amount of fly ash, which typically contains high levels of calcium salts, chloride salts, heavy metals, and small amounts of organic pollutants, posing potential environmental risks. Traditional landfill methods not only occupy significant land resources, but the heavy metals and other pollutants may also migrate over long-term environmental processes, impacting soil, water bodies, and the overall ecosystem. Therefore, achieving the safe disposal and resource utilization of waste incineration fly ash has become an urgent problem to be solved in the field of solid waste management.

[0003] Currently, geopolymer materials are considered a promising method for the resource utilization of solid waste due to their low-carbon preparation, high mechanical properties, and good ability to solidify pollutants. These materials primarily utilize industrial solid waste rich in silicon and aluminum as precursors, undergoing dissolution and condensation reactions under alkali activation to form inorganic cementitious materials with a three-dimensional network structure. Waste incineration fly ash contains a certain amount of silicon-aluminum active components, thus possessing the potential to serve as a raw material for geopolymers. However, existing technologies for the resource utilization of waste incineration fly ash still have certain shortcomings. On the one hand, the composition of waste incineration fly ash itself is complex, with high levels of calcium salts, chloride salts, and impurities affecting the dissolution and polymerization process of the silicon-aluminum structure, resulting in insufficient development of the internal gel structure and limiting mechanical properties and long-term stability. On the other hand, existing technologies typically use liquid strong alkalis such as sodium hydroxide and water glass as activators. While these can rapidly increase the alkalinity of the system and promote the reaction, liquid alkali activators suffer from high corrosivity, difficult transportation and storage, high construction safety risks, and high costs, hindering large-scale engineering applications.

[0004] In recent years, the use of the inherent alkalinity and active components of industrial solid waste as solid activation materials has gradually attracted attention. Calcium carbide slag, a major industrial byproduct of acetylene production, is primarily composed of calcium hydroxide and possesses strong alkalinity, providing an alkaline environment for geopolymerization reactions. Yellow phosphorus slag, an industrial byproduct of yellow phosphorus production, contains abundant amorphous silicon-aluminum active components, serving as a source of silicon-aluminum in geopolymerization reactions. Both materials respectively possess alkalinity regulation and active element supply functions, theoretically forming a complementary composite solid alkaline activation system. Existing technologies have utilized single solid wastes as alkaline activation materials, but single activation systems often suffer from insufficient alkalinity regulation, uneven supply of active elements, and insufficient material structural stability. Furthermore, research on the synergistic effect of calcium carbide slag and yellow phosphorus slag in the geopolymerization system of waste incineration fly ash remains limited, lacking a method that can utilize the synergistic effect of multiple solid wastes, reduce the risks of liquid alkali use, and improve the resource utilization efficiency of waste incineration fly ash. In summary, existing technologies are insufficient to simultaneously address the technical requirements of co-utilization of solid waste, substitution of liquid alkali, and improvement of material performance, and the related technical contradictions have not yet been effectively resolved. Summary of the Invention

[0005] This invention provides a method for preparing geopolymer cementitious materials by synergistic activation of composite solid alkali and waste incineration fly ash. This method utilizes multi-source solid waste for synergistic activation, replaces traditional liquid strong alkali, and combines good mechanical properties and environmental stability, thereby realizing the synergistic resource utilization of industrial solid wastes such as waste incineration fly ash, carbide slag, and yellow phosphorus slag.

[0006] The present invention discloses a method for preparing geopolymer cementitious materials using composite solid alkali-activated synergistic waste incineration fly ash. The method involves drying, pulverizing, grinding, and sieving the following raw materials separately, then mixing them, adding water, and stirring to form a uniform slurry. After the slurry is formed, it is cured to obtain the geopolymer cementitious material. The raw materials and their mass percentages are: waste incineration fly ash 35%–50%, composite solid alkali activator 10%–30%, active silica-alumina regulating component 10%–30%, and functional regulating component 10%–15%. The composite solid alkali activator is synergistically compounded from calcium-containing alkaline solid waste and silicon-aluminum-containing active solid waste. The calcium-containing alkaline solid waste provides an alkaline environment and calcium source, while the silicon-aluminum-containing active solid waste provides active silicon and aluminum elements to participate in the geological polymerization reaction. The two work together to regulate the alkalinity release and dissolution behavior of the system, promoting the formation of silicon-aluminum network structure and calcium-silicon-aluminum composite gel system.

[0007] This invention constructs a composite solid-alkali activation system synergistically combining calcium-containing alkaline solid waste and silicon-aluminum-containing active solid waste, achieving a coordinated match between alkaline environment regulation and active element supply during the geological polymerization reaction. Specifically, the calcium-containing alkaline solid waste continuously releases hydroxide ions during hydration, gradually increasing the system's alkalinity and promoting the dissolution of silicon and aluminum components in waste incineration fly ash and silicon-aluminum-containing active solid waste. Simultaneously, the active silicon and aluminum species released by the silicon-aluminum-containing active solid waste directly participate in the condensation reaction, supplementing the active silicon and aluminum source in the system and compensating for the insufficient active components in waste incineration fly ash itself. Clearly, the synergistic effect of the two avoids the problems of excessively rapid reaction and loose structure caused by excessively high alkalinity of a single calcium-containing component, and solves the problems of insufficient alkalinity and incomplete dissolution of a single silicon-aluminum-containing component, creating a dynamic balance between alkalinity release and active element dissolution within the system, laying the foundation for the formation of a high-quality gel structure.

[0008] This invention achieves precise control of material properties through the design of the mass percentage of each raw material component. Waste incineration fly ash is used as the main precursor material at a proportion of 35%–50%. This proportion range ensures the amount of fly ash that can be absorbed while avoiding problems such as insufficient active components and poor gel structure development caused by excessive fly ash content. The composite solid alkali activator plays an activating role at a proportion of 10%–30%. This ratio range provides a suitable alkalinity environment and supplements the active silica-alumina source for the system, preventing insufficient activator leading to incomplete reaction and low mechanical properties, while avoiding excessive activator causing excessive alkalinity and reduced material durability. The active silica-alumina regulating component, at a proportion of 10%–30%, assists in adjusting the silica-alumina ratio of the system and optimizing the gel network structure. The functional regulating component, at an optional proportion of 10%–15%, is used to specifically improve the material's coagulation, mechanical, or durability properties to meet the needs of different application scenarios. It is evident that the proportions of each component are precisely designed to create a synergistic effect that fully absorbs the main precursor, efficiently activates the system, and precisely optimizes the components, thereby ensuring the optimal overall performance of the material.

[0009] The calcium-containing alkaline solid waste is carbide slag, and the silicon-aluminum-containing active solid waste is yellow phosphorus slag; the mass ratio of carbide slag to yellow phosphorus slag is 1:0.5 to 4:3.

[0010] As a major byproduct of the acetylene industry, calcium carbide slag's main component is calcium hydroxide, which exhibits slow-release alkaline characteristics and can gradually release OH- during hydration. -This provides a continuous and stable alkaline environment for the geopolymerization reaction, avoiding the problems of violent reactions and structural inhomogeneity caused by the one-time dissolution of strong liquid alkali. Simultaneously, the calcium ions dissolved from the carbide slag can participate in the formation of calcium-silicon-aluminum hydration gel, forming a composite cementitious system with the silicon-aluminum-oxygen network structure, further improving the mechanical properties and structural density of the material. Yellow phosphorus slag, as an industrial waste from yellow phosphorus production, contains a large amount of amorphous aluminum silicate components. Under alkaline conditions, it easily dissolves active silicon and aluminum species, directly participating in the condensation process of the geopolymerization reaction, effectively supplementing the active silicon and aluminum source in the system. The two are compounded in a mass ratio of 1:0.5 to 4:3. This ratio range achieves an optimal balance between alkaline supply and active element supply: when the proportion of carbide slag is at the lower limit of this range, the alkalinity of the system is sufficient to ensure the full dissolution of silicon and aluminum components; when the proportion of yellow phosphorus slag is at the upper limit of this range, the supply of active silicon and aluminum elements is sufficient to form a complete three-dimensional network structure. It is evident that within this ratio range, the alkalinity regulation effect of carbide slag and the activity supply effect of yellow phosphorus slag form a precise synergy, which not only solves the problems of insufficient silicon and aluminum source and low gel formation in the single carbide slag system, but also avoids the defects of insufficient alkalinity and incomplete dissolution in the single yellow phosphorus slag system, so that the comprehensive efficiency of the composite activation system reaches the optimal level.

[0011] The yellow phosphorus slag is selected from industrial solid waste generated during the production of yellow phosphorus and contains amorphous active silicon-aluminum components.

[0012] Using carbide slag and yellow phosphorus slag, derived from industrial byproducts, as raw materials for the composite activator achieves two key advantages. Firstly, it enables the resource-based disposal of large quantities of industrial solid waste, reducing the environmental pressure from traditional stockpiling or landfilling. Secondly, compared to chemically-based alkaline activating materials, industrial solid waste-derived raw materials are inexpensive and widely available, significantly reducing the preparation cost of geopolymer materials and improving the economic viability of engineering applications. Furthermore, the slow-release alkalinity of carbide slag and the amorphous reactivity of yellow phosphorus slag are naturally well-suited to the kinetic requirements of geopolymerization reactions. Both gradually release active components during the reaction, resulting in uniform gel structure growth and avoiding structural defects caused by rapid reactions under strong liquid alkali activation. This ensures the stability of material performance from the perspective of raw material characteristics.

[0013] The waste incineration fly ash is a solid waste product generated during the incineration of municipal solid waste, with a particle size of less than 100 micrometers. After drying, the fly ash removes surface-adsorbed moisture, preventing moisture from affecting the uniformity of the dry material mixture. This particle size range ensures sufficient reactive surface area for the fly ash particles while avoiding increased energy consumption and particle agglomeration caused by excessive grinding. The suitable particle size allows the fly ash particles to fully contact the activator in an alkaline environment, promoting the dissolution of internal silicon and aluminum components and increasing the degree of reaction. Simultaneously, a uniform particle size distribution improves slurry flowability and molding performance, ensuring the uniformity of the material's internal structure. Clearly, by controlling the particle size of waste incineration fly ash through pretreatment, its reactivity and processing performance as a precursor material can be effectively enhanced, laying the foundation for the full conduct of subsequent geopolymerization reactions.

[0014] The active silicon-aluminum regulating component is selected from fly ash, slag, copper tailings, silica fume, metakaolin, coal gangue, and smelting slag, and is used to adjust the silicon-aluminum element ratio in the system and promote the formation of cementitious structure.

[0015] The performance of geopolymer materials is closely related to the silicon-to-aluminum ratio (Si / A ratio), and a suitable Si / A ratio is key to forming a complete three-dimensional network structure. This invention introduces active Si / A regulating components to flexibly adjust the Si / A ratio of the system, compensating for performance instability caused by fluctuations in the Si / A composition of waste incineration fly ash. Different types of regulating components have different activity characteristics and Si / A ratios, and can be selected and compounded according to the actual conditions of the raw materials: components with potential hydraulic properties, such as fly ash and slag, can both regulate the Si / A ratio and participate in the cementation reaction; highly active components, such as silica fume and metakaolin, can quickly provide an active Si / A source, accelerating the early reaction; and low-activity components, such as copper tailings and coal gangue, mainly improve the pore structure of the material through the micro-aggregate effect. Clearly, the introduction of active Si / A regulating components significantly improves the raw material adaptability of this invention, enabling targeted adjustments based on the compositional characteristics of waste incineration fly ash from different sources, ensuring the stable formation of the gel structure and the consistency of material performance.

[0016] The functional regulating components are selected from blast furnace slag admixtures, water-reducing agents, and gypsum retarder, and are used to improve the material's setting performance, mechanical properties, pore structure, and durability.

[0017] Functional regulating components can optimize material properties according to the specific application requirements. Mineral admixtures and industrial solid waste powders can exert a micro-aggregate effect, filling the internal pores of the material and improving structural density; reinforcing fillers can improve the mechanical strength and flexural strength of the material; setting regulators can adjust the setting and hardening rate of the slurry to meet the time window requirements of different construction processes. By selecting different types and dosages of functional regulating components, flexible control over the material's setting time, strength development, pore structure, and long-term durability can be achieved, enabling the material to adapt to the differentiated needs of various application scenarios such as building engineering, road base courses, and mine filling, further expanding the applicability of the technical solution of this invention.

[0018] Raw material pretreatment involves drying, crushing, grinding, and sieving to ensure that various solid raw materials achieve suitable moisture content and particle size distribution, guaranteeing good reactivity and processing performance of each component. This avoids problems such as uneven mixing and inconsistent reaction degrees caused by uneven particle size and moisture content. A composite solid alkali activator is prepared by mixing carbide slag and yellow phosphorus slag, ensuring that the two activating components are pre-dispersed evenly. This ensures that the alkaline components and active silica-alumina components can function synchronously and evenly when mixed with fly ash, avoiding localized excessive alkalinity or uneven distribution of active components. A dry mixing process is used to pre-mix all solid components evenly. Compared to liquid alkali activation, solid dry powder mixing is safer and more convenient, eliminating the need to handle corrosive liquids. Dry mixes are also easier to store and transport, enabling the supply of pre-prepared dry powder mortar. The geopolymerization reaction is completed through water addition, stirring, molding, and curing. During curing, the composite solid alkali activation system gradually releases alkaline components and active silica-alumina elements, driving the dissolution-condensation reaction to continue, forming a dense composite cementitious structure. It is evident that the entire preparation process is seamlessly integrated with each step and the parameters are matched. From raw material pretreatment to finished product curing, the uniformity and sufficiency of the reaction are ensured throughout the entire process. Moreover, the process is simple and the equipment requirements are low, making it fully suitable for the needs of large-scale industrial production.

[0019] The maintenance method is one or more of the following: natural maintenance, constant temperature maintenance, constant humidity maintenance, and steam maintenance.

[0020] The solid raw materials are ground to a particle size range of 10-200 mesh. This range ensures sufficient specific surface area for optimal reactivity while avoiding the increased energy consumption and secondary agglomeration associated with ultrafine grinding, thus achieving a balance between reactivity and preparation cost. The choice of multiple curing methods allows this invention to adapt to different engineering application conditions: natural curing requires no additional equipment and is suitable for on-site construction scenarios; constant temperature and humidity curing allows for precise control of reaction conditions, ensuring stable performance; steam curing accelerates early strength development and shortens the production cycle. This flexible selection of curing methods further enhances the engineering adaptability of this invention, allowing for the selection of the most economical and suitable curing process based on the specific application scenario.

[0021] The present invention also provides a geopolymer gel material prepared by the above method, wherein the material forms a composite gel structure composed of a three-dimensional network structure of silicon, aluminum, and oxygen and calcium, silicon, and aluminum hydration gel, and reduces the migration ability of heavy metal elements in waste incineration fly ash through structural encapsulation, chemical bonding and adsorption.

[0022] The geopolymer gel material prepared in this invention simultaneously forms two types of gel phases under the action of a composite solid alkali-activated system: one is a three-dimensional network structure of silicon-aluminum-oxygen formed by the condensation reaction of silicon-aluminum components in an alkaline environment, namely the geopolymer gel phase, which has the characteristics of stable chemical bonding and dense structure; the other is a calcium-silicon-aluminum hydrated gel phase formed by the reaction of calcium ions, namely the calcium silicate-like hydrated gel phase, which can fill the pores of the network structure and further improve the material's density. The two intertwine to form a composite gel structure, which has superior mechanical properties and structural stability compared to a single geopolymer system. Furthermore, for heavy metal elements in waste incineration fly ash, this composite gel structure achieves solidification and stabilization through a triple mechanism: first, physical encapsulation, where the dense gel structure encapsulates and seals heavy metal particles inside the matrix, blocking their contact with the external environment; second, chemical bonding, where some heavy metal ions can enter the silicon-aluminum network structure or the hydrated gel lattice, forming a chemically bonded stable state; and third, adsorption and fixation, where active sites on the gel surface can adsorb heavy metal ions, restricting their migration. It is evident that the combination of the composite cementitious structure and multiple curing mechanisms enables the material of this invention to effectively control the environmental risks of heavy metals while disposing of fly ash from waste incineration, thus ensuring the environmental safety of the material.

[0023] The material is used in building materials, road base materials, mine filling materials, and solid waste stabilization treatment.

[0024] The geopolymer gel material prepared by this invention possesses excellent mechanical properties, environmental safety, and low-carbon characteristics, enabling its wide application in multiple engineering fields. As a building material, it can replace some cement-based materials in the preparation of building blocks, panels, and other building products, reducing carbon emissions in the construction industry. As a road base material, it can be used in the construction of highway base and subbase layers, absorbing large quantities of solid waste while meeting the strength requirements of road engineering. As a mine filling material, it can be used for filling mine goaf areas, possessing both filling body strength and heavy metal solidification capabilities. As a solid waste stabilization treatment material, it can be directly used for the solidification and stabilization disposal of various hazardous wastes. This multi-field applicability fully demonstrates the application value and promotion potential of the technical solution of this invention.

[0025] The advantages and technical effects of this invention are as follows: This invention constructs a composite solid alkali activation system that synergistically combines calcium-containing alkaline solid waste with silicon-aluminum-containing active solid waste. Through the slow-release alkalinity regulation of carbide slag and the supply of active silicon-aluminum from yellow phosphorus slag, a precise synergy is achieved, replacing traditional liquid strong alkali activators such as sodium hydroxide and water glass. This fundamentally solves the problems of strong corrosiveness, difficult transportation and storage, and high construction safety risks associated with liquid alkalis, and significantly improves the safety and economy of the preparation and application of geopolymer materials.

[0026] This invention realizes the synergistic resource utilization of multiple sources of industrial solid waste, such as waste incineration fly ash, carbide slag, and yellow phosphorus slag. It uses waste incineration fly ash as the main precursor, carbide slag and yellow phosphorus slag as a composite activation system, and other solid waste adjustment components. Each type of solid waste performs its own function and works synergistically, which not only greatly increases the amount of solid waste disposed of, but also makes full use of the component characteristics of each type of solid waste, and achieves the technical goal of "treating waste with waste and turning waste into treasure".

[0027] This invention utilizes the synergistic effect of a composite solid alkali-activated system to form a composite gel structure in which a three-dimensional silicon-aluminum-oxygen network and a calcium-silicon-aluminum hydration gel intertwine. Compared to a single solid-activated system, this composite structure exhibits superior mechanical properties and structural density. Furthermore, it achieves efficient curing of heavy metals through a triple mechanism of physical encapsulation, chemical bonding, and adsorption fixation, significantly improving the environmental safety performance of the material.

[0028] The preparation process of this invention adopts a full solid dry powder mixing process, which is simple in process flow and low in equipment requirements. It does not require high-energy-consuming processes such as high-temperature calcination. The dry mixture is easy to store and transport, and can be directly mixed with water for use. It has strong engineering adaptability and is easy to realize large-scale industrial production and promotion. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0030] Furthermore, unless otherwise stated, the "%" mentioned in this invention refers to a percentage by mass.

[0031] Example 1: A method for preparing geopolymer cementitious materials by synergistic activation of composite solid alkali and waste incineration fly ash. The raw material composition of this embodiment is 48% waste incineration fly ash, 15% composite solid alkali activator, 25% active silicon-aluminum regulating component, and 12% functional control component. Among them, the composite solid alkali activator is composed of carbide slag and yellow phosphorus slag in a mass ratio of 1:1, that is, carbide slag accounts for 7.5% and yellow phosphorus slag accounts for 7.5%; the active silicon-aluminum regulating component is fly ash; and the functional control component is blast furnace slag.

[0032] S1: Raw material pretreatment: The fly ash from waste incineration, calcium carbide slag, yellow phosphorus slag, fly ash, and blast furnace slag are dried separately, crushed, ground, and then passed through a 100-mesh sieve for later use. S2: Add carbide slag and yellow phosphorus slag to a mixer at a mass ratio of 1:1 and dry mix for 15 minutes until uniform to obtain a composite solid alkali activator. S3: Dry mixing: Add the waste incineration fly ash, composite solid alkali activator, fly ash and blast furnace slag to the mixing equipment and dry mix for 20 minutes to obtain a uniform dry mixture; S4: Molding and curing: Add water to the dry mixture at a water-to-material mass ratio of 0.35:1, stir for 5 minutes to form a uniform slurry, pour the slurry into the mold, vibrate to form the slurry, demold, and place it in a constant temperature and humidity environment of 25℃ and 95% for 28 days to obtain the geopolymer gel material.

[0033] Tests showed that the geopolymer gel material in this embodiment had a 28-day compressive strength of 35.4 MPa, a setting time of 17 minutes for initial setting and 29 minutes for final setting, and the heavy metal leaching concentration met the relevant standard requirements. The material has good mechanical properties and environmental safety performance.

[0034] Example 2: A method for preparing geopolymer cementitious materials by synergistic activation of composite solid alkali and waste incineration fly ash. The raw material composition of this embodiment is 48% waste incineration fly ash, 15% composite solid alkali activator, 25% fly ash, and 12% blast furnace slag. The composite solid alkali activator is composed of carbide slag and yellow phosphorus slag in a mass ratio of 3:2, that is, carbide slag accounts for 9% and yellow phosphorus slag accounts for 6%. S1: Raw material pretreatment: The fly ash from waste incineration, calcium carbide slag, yellow phosphorus slag, fly ash, and blast furnace slag are dried separately, crushed, ground, and then passed through an 80-mesh sieve for later use. S2: Preparation of composite activator: Add carbide slag and yellow phosphorus slag to a mixer at a mass ratio of 3:2, and dry mix for 15 minutes until uniform to obtain composite solid alkali activator; S3: Dry mixing: Weigh out the waste incineration fly ash, composite solid alkali activator, fly ash and blast furnace slag, add them to the mixing equipment and dry mix for 20 minutes to obtain a uniform dry mixture; S4: Molding and curing: Add water to the dry mixture at a water-to-material mass ratio of 0.35:1, stir for 5 minutes to form a uniform slurry, pour the slurry into the mold, vibrate to form the slurry, demold, and place it in a constant temperature and humidity environment of 25℃ and 95% for 28 days to obtain the geopolymer gel material.

[0035] Tests showed that the geopolymer gel material prepared in this embodiment had a 28-day compressive strength of 36.5 MPa, a setting time of 16 min for initial setting and 21 min for final setting, and the heavy metal leaching concentration met the relevant standard requirements.

[0036] Example 3: A method for preparing geopolymer cementitious materials by synergistic activation of composite solid alkali and waste incineration fly ash. The raw material composition of this embodiment is: 48% waste incineration fly ash, 15% composite solid alkali activator, 25% fly ash, and 12% blast furnace slag; wherein, the composite solid alkali activator is composed of carbide slag and yellow phosphorus slag in a mass ratio of 4:3, that is, carbide slag accounts for 8.6% and yellow phosphorus slag accounts for 6.4%; S1: Raw material pretreatment: The fly ash from waste incineration, calcium carbide slag, yellow phosphorus slag, fly ash, and slag powder are dried separately, crushed, ground, and then passed through a 120-mesh sieve for later use. S2: Preparation of composite activator: Add carbide slag and yellow phosphorus slag to a mixer at a mass ratio of 4:3, and dry mix for 15 minutes until uniform to obtain composite solid alkali activator; S3: Dry material mixing: Take the waste incineration fly ash, composite solid alkali activator, fly ash and blast furnace slag, add them to the mixing equipment and dry mix for 20 minutes to obtain a uniform dry mixture; S4: Molding and curing: Add water to the dry mixture at a water-to-material mass ratio of 0.35:1, stir for 5 minutes to form a uniform slurry, pour the slurry into the mold, vibrate to form the slurry, demold, and place it in a constant temperature and humidity environment of 25℃ and 95% for 28 days to obtain the geopolymer gel material.

[0037] Tests showed that the geopolymer gel material prepared in this embodiment had a 28-day compressive strength of 38.2 MPa, a setting time of 15 min for initial setting and 18 min for final setting, and the heavy metal leaching concentration met the relevant standard requirements, achieving optimal overall performance.

[0038] Comparative Example 1: This comparative example does not add composite solid alkali activator, but only uses waste incineration fly ash, fly ash and blast furnace slag to prepare cementitious materials; the raw material composition is 48% waste incineration fly ash, 37% fly ash and 15% blast furnace slag.

[0039] (1) Dry and grind the fly ash, fly ash and blast furnace slag of the waste incineration into 100-mesh sieves respectively; (2) Mix the solid raw materials according to the above proportions and dry mix for 20 minutes until uniform; (3) Add water and stir well. The water-to-material mass ratio is 0.35:1. (4) After being molded by vibration, the mold is demolded and placed under constant temperature and humidity conditions of 25℃ and 95% for 28 days.

[0040] Tests showed that the 28-day compressive strength of the material obtained in this comparative example was only 12.3 MPa, with an initial setting time of 41 min and a final setting time of 52 min. The slow setting and hardening and low mechanical properties indicate that without a composite solid alkali activation system, it is difficult for waste incineration fly ash to undergo an effective geological polymerization reaction.

[0041] Comparative Example 2: This comparative example uses a single calcium carbide slag as a solid alkali activating material, without adding yellow phosphorus slag; the raw material composition is: 48% waste incineration fly ash, 15% calcium carbide slag, 25% fly ash, and 12% blast furnace slag.

[0042] (1) Dry and grind each solid raw material separately and pass it through a 100-mesh sieve; (2) Mix the solid raw materials according to the above proportions and dry mix for 20 minutes until uniform; (3) Add water and stir well. The water-to-material mass ratio is 0.35:1. (4) After being molded by vibration, the mold is demolded and placed under constant temperature and humidity conditions of 25℃ and 95% for 28 days.

[0043] The material obtained in this comparative example had a 28-day compressive strength of 22.7 MPa, an initial setting time of 28 min, and a final setting time of 42 min. The performance was improved compared to comparative example 1, but it was still significantly lower than the composite activation system of example 1. This indicates that although the single carbide slag system can provide an alkaline environment, it lacks the supplementation of active silica-alumina components, resulting in an incomplete gel structure development and limited overall material performance.

[0044] Comparative Example 3: This comparative example uses yellow phosphorus slag as a solid activating material without adding carbide slag. The raw material composition is: 48% waste incineration fly ash, 15% yellow phosphorus slag, 25% fly ash, and 12% blast furnace slag.

[0045] (1) Dry and grind each solid raw material separately and pass it through a 100-mesh sieve; (2) Mix the solid raw materials according to the above proportions and dry mix for 20 minutes until uniform; (3) Add water and stir well. The water-to-material mass ratio is 0.35:1. (4) After being molded by vibration, the mold is demolded and placed under constant temperature and humidity conditions of 25℃ and 95% for 28 days.

[0046] Tests showed that the 28-day compressive strength of the material obtained in this comparative example was 19.5 MPa, the initial setting time was 33 min, and the final setting time was 49 min. The performance was also lower than that of the composite activation system in Example 1, indicating that the alkalinity of the single yellow phosphorus slag system was insufficient, the silicon and aluminum components were not fully dissolved, and it was difficult to form a high-quality gel structure.

[0047] Furthermore, the present invention tested the heavy metal solidification performance of each embodiment and comparative example. Leaching experiments were conducted according to the relevant standards for leaching toxicity of solid waste, and the leaching concentrations of four heavy metal elements, Pb, Cd, Cr, and Cu, were detected. The test results are as follows: the leaching concentrations of Pb, Cd, Cr, and Cu in the original waste incineration fly ash were 1.96 mg / L, 0.48 mg / L, 0.87 mg / L, and 1.35 mg / L, respectively; in Comparative Example 1 (without activation system), the leaching concentrations of each heavy metal decreased to 0. The leaching concentrations of heavy metals in Example 1 (a composite system of calcium carbide slag and yellow phosphorus slag) were 86 mg / L, 0.23 mg / L, 0.46 mg / L, and 0.72 mg / L, respectively. In Comparative Example 2 (a single calcium carbide slag system), the leaching concentrations of each heavy metal decreased to 0.45 mg / L, 0.14 mg / L, 0.31 mg / L, and 0.48 mg / L, respectively. In Example 1 (a composite system of calcium carbide slag and yellow phosphorus slag), the leaching concentrations of each heavy metal further decreased to 0.19 mg / L, 0.05 mg / L, 0.12 mg / L, and 0.21 mg / L, all far below the standard limits. Therefore, the composite solid alkali-activated system of this invention can form a more dense and stable gel structure, and its solidification and stabilization effect on heavy metals is significantly better than that of the single-activated system and the unactivated system, exhibiting excellent environmental safety performance.

[0048] Based on the test results of the above embodiments and comparative examples, it can be seen that the composite solid alkali activation system constructed by the present invention through the synergistic construction of carbide slag and yellow phosphorus slag is significantly superior to the single activation system and the non-activation system in terms of coagulation performance, mechanical strength and heavy metal solidification ability. The synergistic effect of the two achieves a technical effect of 1+1>2, which fully demonstrates the inventiveness and superiority of the technical solution of the present invention.

Claims

1. A method for preparing geopolymer cementitious materials by synergistic activation of composite solid alkali and waste incineration fly ash, characterized in that, The raw materials and their weight percentages are as follows: 35%–50% fly ash from waste incineration, 10%–30% composite solid alkali activator, 10%–30% active silicon-aluminum regulating component, and 10%–15% functional regulating component; The above raw materials are dried, pulverized, ground, and sieved separately, then mixed, water is added, and stirred to form a uniform slurry. After the slurry is formed, it is cured to obtain a geopolymer cementitious material.

2. The method for preparing geopolymer cementitious materials by composite solid alkali activation and synergistic treatment with waste incineration fly ash according to claim 1, characterized in that: The composite solid alkali activator is prepared by mixing calcium-containing alkaline solid waste carbide slag and silicon-aluminum active solid waste yellow phosphorus slag in a mass ratio of 1:0.5 to 4:

3.

3. The method for preparing geopolymer cementitious materials by composite solid alkali activation and synergistic treatment with waste incineration fly ash according to claim 1, characterized in that: Waste incineration fly ash is a solid waste produced during the incineration of municipal solid waste, with a particle size of less than 100 micrometers.

4. The method for preparing geopolymer cementitious materials by composite solid alkali activation and synergistic treatment with waste incineration fly ash according to claim 1, characterized in that: The active silica-alumina regulating components are selected from fly ash, slag, copper tailings, silica fume, metakaolin, coal gangue, and smelting slag.

5. The method for preparing geopolymer cementitious materials by composite solid alkali activation and synergistic treatment with waste incineration fly ash according to claim 1, characterized in that: The functional regulating components are selected from blast furnace slag, water-reducing agent, and gypsum retarder.

6. The geopolymer cementitious material prepared by the method according to any one of claims 1 to 5, characterized in that: The material forms a composite cementitious structure consisting of a three-dimensional network structure of silicon, aluminum, and oxygen and calcium, silicon, and aluminum hydration gel. Through structural encapsulation, chemical bonding, and adsorption, it reduces the migration capacity of heavy metal elements in waste incineration fly ash.

7. The geopolymer cementitious material according to claim 6, characterized in that: Used in building materials, road base materials, mine filling materials, and solid waste stabilization treatment.