Fly ash synergistic multi-source solid waste toughened full solid waste cementitious material and preparation method thereof

Abstract

The present application relates to solid waste resource technology field, disclose a kind of fly ash is toughened with multiple source solid waste together with full solid waste cementing material and its preparation method.The present application has carried out optimization to red mud-carbide slag-fly ash-slag gel system, low-temperature degradation fly ash is used by acid leaching, and magnesium nickel iron slag powder, calcined magnesium-aluminum hydrotalcite and silica sol are added, which significantly improves the chloride ion solidification capacity of the gel material, significantly improves the long-term durability of the gel material, and significantly reduces the heavy metal leaching of the gel material.The preparation method uses a step-by-step feeding process of main phase, pre-gel phase and nano-functional phase, combined with anoxic pre-nurturing and toughening carbonization treatment, so that each component plays a leading role at different stages, realizing the unification of early strength, shrinkage compensation, ion solidification and efflorescence inhibition of the gel material.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, and in particular to a fly ash-co-polymerized multi-source solid waste toughening cementitious material and its preparation method. Background Technology

[0002] With the rapid development of the metallurgical, chemical, and urban environmental protection industries, the amount of solid waste such as Bayer process red mud, carbide slag, and incineration fly ash is also increasing. These solid wastes are characterized by high alkalinity, high heavy metal content, and high chloride content, making individual disposal difficult, costly, and requiring large land areas for storage, posing serious environmental safety hazards. To address these hazards, those skilled in the art have proposed technical solutions for the resource-based treatment of Bayer process red mud, carbide slag, and incineration fly ash. For example, CN117285292A discloses a quaternary cementitious mortar material based on red mud-fly ash-carbide slag-fly ash. This technical solution uses the chloride-containing fly ash to generate F salt and hydrated calcium chloroaluminate, which, together with the CSH and CASH gels generated from red mud, carbide slag, and fly ash, fill the particle gaps, enabling the solidified gel material to achieve a compressive strength of 17.6 MPa.

[0003] After in-depth research into the above-mentioned technical solutions, this invention found that the main research direction for gel materials in the prior art is to improve their compressive strength. While gel materials made from red mud, fly ash, carbide slag, and fly ash exhibit excellent compressive strength in practical use, they suffer from the following problems: 1. Weak chloride ion curing ability, leading to corrosion of metals such as reinforcing steel when used together. 2. High risk of heavy metal leaching during practical use due to the presence of large amounts of heavy metals. 3. High drying shrinkage and poor long-term durability. Therefore, solving these technical problems is crucial to obtaining a high-value red mud-carbide slag-fly ash-slag system gel material. Summary of the Invention

[0004] The purpose of this invention is to reduce the leaching of heavy metals from the red mud-carbide slag-fly ash-slag system gel material, and to improve the chloride ion curing ability and long-term durability of the gel material.

[0005] This invention optimizes the red mud-carbide slag-fly ash-slag system. The fly ash used is acid-leached low-temperature pyrolysis fly ash. Under the carbide slag environment, the acid-leached low-temperature pyrolysis fly ash generates a CSH coating layer, providing numerous nucleation sites for subsequent hydration products, significantly shortening the hydration induction period and improving early gel strength. Magnesium-nickel-iron slag powder, nano-silica sol, and calcined magnesium-aluminum hydrotalcite are also added to the system, improving gel strength while solidifying harmful anions such as chloride ions. Furthermore, the combined use of acid-leached low-temperature pyrolysis fly ash, magnesium-nickel-iron slag powder, nano-silica sol, and calcined magnesium-aluminum hydrotalcite can significantly reduce heavy metal leaching from the gel material, significantly improving its environmental performance.

[0006] The specific technical solution of this invention is as follows: A fly ash synergistic multi-source solid waste toughening cementitious material is disclosed, comprising a main phase, a pre-gel phase, and a nano-functional phase. The main phase is composed of red mud, carbide slag, blast furnace slag, and magnesium-nickel-iron slag powder. The pre-gel phase is composed of acid-leached low-temperature pyrolysis fly ash, carbide slag, and water. The nano-functional phase is composed of nano-silica sol, calcined magnesium-aluminum hydrotalcite, and water.

[0007] As preferred, the mass ratio of red mud, carbide slag, blast furnace slag, and magnesium-nickel-iron slag powder is 10–15:15–25:20–30:5–8; the mass ratio of acid leaching low-temperature pyrolysis fly ash, carbide slag, and water is 35–50:1.5–5:5.8–12.9; and the mass ratio of nano-silica sol, calcined magnesium-aluminum hydrotalcite, and water is 0.4–2:0.4–1.3:3.8–9.7.

[0008] A method for preparing the above-mentioned fly ash synergistic multi-source solid waste toughening cementitious material includes the following steps: (1) Nano-functional phases were prepared by ultrasonically dispersing nano-silica sol and calcined magnesium aluminum hydrotalcite in water; (2) A pregel phase is prepared by stirring and dispersing acid-leached low-temperature pyrolysis fly ash and carbide slag in water; (3) Mix red mud, carbide slag, slag and magnesium-nickel-iron slag powder into the main phase, then add the pre-gel phase and mix evenly, then add the nano-functional phase and water and stir to make a slurry; (4) The slurry is injected into the mold for anaerobic pre-curing, toughening carbonization and standard curing to produce fly ash synergistic multi-source solid waste toughening all solid waste cementitious material.

[0009] Preferably, the acid-leached low-temperature pyrolysis fly ash is prepared by acid leaching with hydrochloric acid and pyrolysis in an inert atmosphere at 450~550℃.

[0010] Preferably, the conditions for hydrochloric acid leaching include: a solid-liquid ratio of 5:1, a hydrochloric acid concentration of 0.5~1 mol / L, and a leaching time of 30~60 min.

[0011] Preferably, the fly ash from acid leaching and low-temperature pyrolysis has a specific surface area ≥ 400 m². 2 / kg, residual carbon content 2~5wt%.

[0012] As a preferred option, the conditions for pre-conditioning under anaerobic conditions include: static curing at 18~22℃ for 22~26 hours under sealed conditions.

[0013] As a preferred option, the conditions for toughening and carbonization include: a carbon dioxide volume concentration of 18-22%, a relative humidity of 55-65%, a temperature of 18-22°C, and a time of 10-14 hours.

[0014] As a preferred option, standard maintenance conditions include: temperature 18~22℃ and relative humidity ≥95%.

[0015] Preferably, the molar ratio of magnesium to aluminum in the calcined magnesium-aluminum hydrotalcite is 2~3:1, and the specific surface area of ​​the calcined magnesium-aluminum hydrotalcite is ≥150 m². 2 / g.

[0016] This application addresses the problems of weak chloride ion solidification ability, easy leaching of heavy metals, and poor long-term durability in existing red mud-carbide slag-fly ash-slag gel systems by optimizing the gel system. This invention employs acid leaching and low-temperature degradation of fly ash, and adds magnesium-rich nickel-iron slag powder, calcined magnesium-aluminum hydrotalcite, and silica sol. By optimizing the composition of the gel system, the chloride ion solidification ability of the gel material is significantly improved, the long-term durability of the gel material is significantly enhanced, and the leaching of heavy metals from the gel material is significantly reduced.

[0017] This invention first employs acid leaching and low-temperature degradation of fly ash, a portion of carbide slag, and water to form a pre-gel phase. Low-temperature pyrolysis transforms the silica-alumina phase in the fly ash into a highly defective amorphous phase. The amorphous silica reacts in the calcium hydroxide environment provided by the carbide slag to generate a nano-CSH gel precursor coating layer. These gel nuclei are uniformly dispersed in the slurry, providing numerous nucleation sites for subsequent hydration products. This significantly shortens the hydration induction period, increasing the 1-day compressive strength to over 8.5 MPa. This invention also prepares a nano-functional phase using silica sol, calcined magnesium aluminum hydrotalcite, and water. The nano-silica sol further replenishes early CSH nucleation sites and optimizes particle size distribution, resulting in faster early strength development and better workability. During the anoxic pre-curing stage, residual carbon in the fly ash is consumed during low-temperature pyrolysis via acid leaching to deplete oxygen within the mold, creating a locally anoxic environment and inhibiting the migration of high-valence heavy metal ions. Simultaneously, calcined magnesium aluminum hydrotalcite can rapidly rebuild a layered double hydroxide structure in alkaline porous solutions, and simultaneously adsorb and insert harmful anions such as chloride ions into the interlayer, achieving early chemical solidification. During the toughening stage, the carbide slag on the surface of the gel material carbonizes to form a dense calcium carbonate layer, blocking efflorescence channels and protecting the internal hydrotalcite from damage, achieving long-term stability. Furthermore, the magnesium olivine phase in the magnesium-rich nickel-iron slag powder added in this invention reacts with carbon dioxide during the carbonization stage to generate hydrated magnesia. The growth of needle-like magnesia crystals fills the dense porous structure, giving the gel material a certain initial strength after demolding. This avoids the problems of large drying shrinkage and poor long-term durability in subsequent gel materials. This invention also employs a stepwise feeding process for the main phase, pre-gel phase, and nano-functional phase, avoiding mutual interference between reactions and allowing each component to play a dominant role at different stages, achieving a unified performance of early strength, shrinkage compensation, ion solidification, and efflorescence suppression.

[0018] Compared with the prior art, this application has the following technical effects: (1) The red mud-carbide slag-fly ash-slag gel system was optimized by using acid leaching to degrade fly ash at low temperature and adding magnesium-rich nickel-iron slag powder, calcined magnesium-aluminum hydrotalcite and silica sol, which significantly improved the chloride ion curing ability of the gel material, significantly improved the long-term durability of the gel material, and significantly reduced the heavy metal leaching effect of the gel material. (2) The preparation method adopts a stepwise feeding process of main phase, pregel phase and nano-functional phase, combined with anaerobic pre-curing and toughening carbonization treatment, so that each component plays a dominant role at different stages, realizing the unified function of early strength, shrinkage compensation, ion curing and alkali inhibition of gel material. Detailed Implementation

[0019] The present invention will be further described below with reference to embodiments.

[0020] To better understand the content of this invention, further explanation is provided below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of this invention.

[0021] Example 1:

[0022] A method for preparing a fly ash-co-reinforced multi-source solid waste toughening cementitious material includes the following steps: (1) 20g of nano-silica sol (silica solid content 30%, average particle size 15nm) and 16g of calcined magnesium aluminum hydrotalcite (magnesium to aluminum molar ratio 2.5:1, specific surface area ≥180m²) were mixed. 2 / g) was added to 120g of water and ultrasonically dispersed in a 400W ultrasonic cleaning device for 10min to prepare a nano-functional phase; (2) Treat the waste incineration fly ash with hydrochloric acid (concentration 0.8mol / L) at a solid-liquid ratio of 5:1 for 45 min. After the acid leaching treatment, filter and collect the filter cake. Place the filter cake in a nitrogen atmosphere and pyrolyze at 500℃ for 1 h. After cooling, grind it to produce acid-leached low-temperature pyrolysis fly ash (specific surface area ≥430 m²). 2 / kg, residual carbon content 3.2wt%); mix 800g of acid-leached low-temperature pyrolysis fly ash and 60g of calcium carbide slag (calcium hydroxide content 92%) evenly, then add 160g of water and stir at 500r / min for 5min to prepare a pregel phase; (3) Dry and grind 240g of red mud (Bayer process red mud) to a specific surface area ≥420m². 2 / kg), 500g slag (S95 grade granulated blast furnace slag powder, specific surface area ≥460m²) 2 / kg), 140g nickel-rich iron slag powder (ground to a specific surface area ≥470 m²) 2 / kg, magnesium oxide content 30.5%) and 340g calcium carbide slag (calcium hydroxide content 92%) were added to a stirring device and mixed evenly to form the main phase. Then, the pre-gelled phase was added and dry-mixed for 45 seconds. Then, the nano-functional phase and 629.4g of water were added and stirred (first at 200r / min for 60 seconds, then at 500r / min for 120 seconds) to form a slurry. (4) Pour the slurry into the mold (40mm×40mm×160mm triple mold) and vibrate to remove bubbles for 3 minutes. Seal the mold with plastic film and pre-cur it in the 20℃ anaerobic environment for 24 hours. After the anaerobic pre-curing is completed, demold the material and transfer it to the carbon dioxide oxygen protection device for toughening and carbonization (toughening and carbonization conditions are carbon dioxide volume concentration of 20%, relative humidity of 60%, and temperature of 20℃) for 12 hours. After the toughening and carbonization is completed, transfer the material to the standard curing room and standard cure it at 20℃ and relative humidity ≥95% until the specified age to produce fly ash synergistic multi-source solid waste toughening all solid waste cementitious material.

[0023] Example 2:

[0024] A method for preparing a fly ash-co-reinforced multi-source solid waste toughening cementitious material includes the following steps: (1) 10g of nano-silica sol (silica solid content 30%, average particle size 15nm) and 10g of calcined magnesium aluminum hydrotalcite (magnesium to aluminum molar ratio of 2.5:1, specific surface area ≥180m²) were mixed. 2 / g) was added to 90g of water and ultrasonically dispersed in a 400W ultrasonic cleaning device for 10min to prepare a nano-functional phase; (2) Treat the waste incineration fly ash with hydrochloric acid (concentration 0.8mol / L) at a solid-liquid ratio of 5:1 for 45 min. After the acid leaching treatment, filter and collect the filter cake. Place the filter cake in a nitrogen atmosphere and pyrolyze at 500℃ for 1 h. After cooling, grind it to produce acid-leached low-temperature pyrolysis fly ash (specific surface area ≥430 m²). 2 / kg, residual carbon content 3.2wt%); mix 800g of acid-leached low-temperature pyrolysis fly ash and 60g of calcium carbide slag (calcium hydroxide content 92%) evenly, then add 130g of water and stir at 500r / min for 5min to prepare a pregel phase; (3) Dry and grind 280g of red mud (Bayer process red mud) to a specific surface area ≥420m². 2 / kg), 440g slag (S95 grade granulated blast furnace slag powder, specific surface area ≥460m²) 2 / kg), 120g nickel-rich iron slag powder (ground to a specific surface area ≥470 m²) 2 / kg, magnesium oxide content 30.5%) and 360g calcium carbide slag (calcium hydroxide content 92%) are added to a stirring device and mixed evenly to form the main phase. Then, the pre-gel phase is added and dry-mixed for 45 seconds. Then, the nano-functional phase and 618.6g of water are added and stirred (first stirred at 200r / min speed for 60 seconds, then stirred at 500r / min speed for 120 seconds) to form a slurry. (4) Pour the slurry into the mold (40mm×40mm×160mm triple mold) and vibrate to remove bubbles for 3 minutes. Seal the mold with plastic film and pre-cur it in the 20℃ anaerobic environment for 24 hours. After the anaerobic pre-curing is completed, demold the material and transfer it to the carbon dioxide oxygen protection device for toughening and carbonization (toughening and carbonization conditions are carbon dioxide volume concentration of 20%, relative humidity of 60%, and temperature of 20℃) for 12 hours. After the toughening and carbonization is completed, transfer the material to the standard curing room and standard cure it at 20℃ and relative humidity ≥95% until the specified age to produce fly ash synergistic multi-source solid waste toughening all solid waste cementitious material.

[0025] Example 3:

[0026] A method for preparing a fly ash-co-reinforced multi-source solid waste toughening cementitious material includes the following steps: (1) Mix 30g of nano-silica sol (silica solid content 30%, average particle size 15nm) and 20g of calcined magnesium aluminum hydrotalcite (magnesium to aluminum molar ratio 2.5:1, specific surface area ≥180m²). 2 / g) was added to 120g of water and ultrasonically dispersed in a 400W ultrasonic cleaning device for 10min to prepare a nano-functional phase; (2) Treat the waste incineration fly ash with hydrochloric acid (concentration 0.8mol / L) at a solid-liquid ratio of 5:1 for 45 min. After the acid leaching treatment, filter and collect the filter cake. Place the filter cake in a nitrogen atmosphere and pyrolyze at 500℃ for 1 h. After cooling, grind it to produce acid-leached low-temperature pyrolysis fly ash (specific surface area ≥430 m²). 2 / kg, residual carbon content 3.2wt%); mix 800g of acid-leached low-temperature pyrolysis fly ash and 60g of calcium carbide slag (calcium hydroxide content 92%) evenly, then add 180g of water and stir at 500r / min for 5min to prepare a pregel phase; (3) Dry and grind 200g of red mud (Bayer process red mud) to a specific surface area ≥420m². 2 / kg), 560g slag (S95 grade granulated blast furnace slag powder, specific surface area ≥460m²) 2 / kg), 160g nickel-rich iron slag powder (ground to a specific surface area ≥470 m²) 2 / kg, magnesium oxide content 30.5%) and 440g calcium carbide slag (calcium hydroxide content 92%) are added to a stirring device and mixed evenly to form the main phase. Then, the pre-gel phase is added and dry-mixed for 45 seconds. Then, the nano-functional phase and 770g water are added and stirred (first at 200r / min for 60 seconds, then at 500r / min for 120 seconds) to form a slurry. (4) Pour the slurry into the mold (40mm×40mm×160mm triple mold) and vibrate to remove bubbles for 3 minutes. Seal the mold with plastic film and pre-cur it in the 20℃ anaerobic environment for 24 hours. After the anaerobic pre-curing is completed, demold the material and transfer it to the carbon dioxide oxygen protection device for toughening and carbonization (toughening and carbonization conditions are carbon dioxide volume concentration of 20%, relative humidity of 60%, and temperature of 20℃) for 12 hours. After the toughening and carbonization is completed, transfer the material to the standard curing room and standard cure it at 20℃ and relative humidity ≥95% until the specified age to produce fly ash synergistic multi-source solid waste toughening all solid waste cementitious material.

[0027] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the acid-leached low-temperature pyrolysis fly ash was replaced in equal amounts with waste incineration fly ash that had not undergone acid leaching and low-temperature pyrolysis, including the following steps: (1) 20g of nano-silica sol (silica solid content 30%, average particle size 15nm) and 16g of calcined magnesium aluminum hydrotalcite (magnesium to aluminum molar ratio 2.5:1, specific surface area ≥180m²) were mixed. 2 / g) was added to 120g of water and ultrasonically dispersed in a 400W ultrasonic cleaning device for 10min to prepare a nano-functional phase; (2) Mix 800g of waste incineration fly ash and 60g of calcium carbide slag (calcium hydroxide content 92%) evenly, then add 160g of water and stir at 500r / min for 5min to prepare a pregel phase; (3) Dry and grind 240g of red mud (Bayer process red mud) to a specific surface area ≥420m². 2 / kg), 500g slag (S95 grade granulated blast furnace slag powder, specific surface area ≥460m²) 2 / kg), 140g nickel-rich iron slag powder (ground to a specific surface area ≥470 m²) 2 / kg, magnesium oxide content 30.5%) and 340g calcium carbide slag (calcium hydroxide content 92%) were added to a stirring device and mixed evenly to form the main phase. Then, the pre-gelled phase was added and dry-mixed for 45 seconds. Then, the nano-functional phase and 629.4g of water were added and stirred (first at 200r / min for 60 seconds, then at 500r / min for 120 seconds) to form a slurry. (4) Pour the slurry into the mold (40mm×40mm×160mm triple mold) and vibrate to remove bubbles for 3 minutes. Seal the mold with plastic film and pre-cur it in the 20℃ anaerobic environment for 24 hours. After the anaerobic pre-curing is completed, demold the material and transfer it to the carbon dioxide oxygen protection device for toughening and carbonization (toughening and carbonization conditions are carbon dioxide volume concentration of 20%, relative humidity of 60%, and temperature of 20℃) for 12 hours. After the toughening and carbonization is completed, transfer the material to the standard curing room and standard cure it at 20℃ and relative humidity ≥95% until the specified age to produce fly ash synergistic multi-source solid waste toughening all solid waste cementitious material.

[0028] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 did not include nano-silica sol and calcined magnesium aluminum hydrotalcite, and included the following steps: (1) The fly ash from the waste incineration was treated with hydrochloric acid (concentration 0.8 mol / L) at a solid-liquid ratio of 5:1 for 45 min. After the acid leaching treatment, the filter cake was collected by filtration. The filter cake was then placed in a nitrogen atmosphere and pyrolyzed at 500℃ for 1 h. After cooling, it was ground into acid-leached low-temperature pyrolysis fly ash (specific surface area ≥ 430 m²). 2 / kg, residual carbon content 3.2wt%); mix 800g of acid-leached low-temperature pyrolysis fly ash and 60g of calcium carbide slag (calcium hydroxide content 92%) evenly, then add 160g of water and stir at 500r / min for 5min to prepare a pregel phase; (2) 240g of red mud (Bayer process red mud) was dried and ground to a specific surface area ≥420m². 2 / kg), 500g slag (S95 grade granulated blast furnace slag powder, specific surface area ≥460m²) 2 / kg), 140g nickel-rich iron slag powder (ground to a specific surface area ≥470 m²) 2 / kg, magnesium oxide content 30.5%) and 340g of carbide slag (calcium hydroxide content 92%) were added to a mixing device and mixed evenly to form the main phase. Then, the pregel phase and 629.4g of water were added and stirred (first at 200r / min for 60 seconds, then at 500r / min for 120 seconds) to form a slurry. (3) Pour the slurry into the mold (40mm×40mm×160mm triple mold) and vibrate to remove bubbles for 3 minutes. Seal the mold with plastic film and pre-cur it in the 20℃ anaerobic environment for 24 hours. After the anaerobic pre-curing is completed, demold the material and transfer it to the carbon dioxide oxygen protection device for toughening and carbonization (toughening and carbonization conditions are carbon dioxide volume concentration of 20%, relative humidity of 60%, and temperature of 20℃) for 12 hours. After the toughening and carbonization is completed, transfer the material to the standard curing room and standard cure it at 20℃ and relative humidity ≥95% until the specified age to produce fly ash synergistic multi-source solid waste toughening all solid waste cementitious material.

[0029] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that: no magnesium-nickel-iron slag powder was added; instead, an equal amount of slag was used to replace the magnesium-nickel-iron slag powder, including the following steps: (1) 20g of nano-silica sol (silica solid content 30%, average particle size 15nm) and 16g of calcined magnesium aluminum hydrotalcite (magnesium to aluminum molar ratio 2.5:1, specific surface area ≥180m²) were mixed. 2 / g) was added to 120g of water and ultrasonically dispersed in a 400W ultrasonic cleaning device for 10min to prepare a nano-functional phase; (2) Treat the waste incineration fly ash with hydrochloric acid (concentration 0.8mol / L) at a solid-liquid ratio of 5:1 for 45 min. After the acid leaching treatment, filter and collect the filter cake. Place the filter cake in a nitrogen atmosphere and pyrolyze at 500℃ for 1 h. After cooling, grind it to produce acid-leached low-temperature pyrolysis fly ash (specific surface area ≥430 m²). 2 / kg, residual carbon content 3.2wt%); mix 800g of acid-leached low-temperature pyrolysis fly ash and 60g of calcium carbide slag (calcium hydroxide content 92%) evenly, then add 160g of water and stir at 500r / min for 5min to prepare a pregel phase; (3) Dry and grind 240g of red mud (Bayer process red mud) to a specific surface area ≥420m². 2 / kg), 640g slag (S95 grade granulated blast furnace slag powder, specific surface area ≥460m²) 2 Add 340g of calcium carbide slag (calcium hydroxide content 92%) to a mixing device and mix evenly to form the main phase. Then add the pre-gel phase and dry mix for 45 seconds. Then add the nano-functional phase and 629.4g of water and stir (first stir at 200r / min speed for 60 seconds, then stir at 500r / min speed for 120 seconds) to form a slurry. (4) Pour the slurry into the mold (40mm×40mm×160mm triple mold) and vibrate to remove bubbles for 3 minutes. Seal the mold with plastic film and pre-cur it in the 20℃ anaerobic environment for 24 hours. After the anaerobic pre-curing is completed, demold the material and transfer it to the carbon dioxide oxygen protection device for toughening and carbonization (toughening and carbonization conditions are carbon dioxide volume concentration of 20%, relative humidity of 60%, and temperature of 20℃) for 12 hours. After the toughening and carbonization is completed, transfer the material to the standard curing room and standard cure it at 20℃ and relative humidity ≥95% until the specified age to produce fly ash synergistic multi-source solid waste toughening all solid waste cementitious material.

[0030] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that Comparative Example 4 did not involve stepwise feeding, but included the following steps: (1) The fly ash from the waste incineration was treated with hydrochloric acid (concentration 0.8 mol / L) at a solid-liquid ratio of 5:1 for 45 min. After the acid leaching treatment, the filter cake was collected by filtration. The filter cake was then placed in a nitrogen atmosphere and pyrolyzed at 500℃ for 1 h. After cooling, it was ground into acid-leached low-temperature pyrolysis fly ash (specific surface area ≥ 430 m²). 2 / kg, residual carbon content 3.2wt%). (2) 20g of nano-silica sol (silica solid content 30%, average particle size 15nm) and 16g of calcined magnesium aluminum hydrotalcite (magnesium to aluminum molar ratio 2.5:1, specific surface area ≥180m²) were added. 2 / g), 800g acid-leached low-temperature pyrolysis fly ash, 240g red mud (Bayer process red mud, dried and ground to a specific surface area ≥420m²). 2 / kg), 500g slag (S95 grade granulated blast furnace slag powder, specific surface area ≥460m²) 2 / kg), 140g nickel-rich iron slag powder (ground to a specific surface area ≥470 m²) 2 / kg, magnesium oxide content 30.5%), 400g carbide slag (calcium hydroxide content 92%) and water are added to a mixing device and stirred (first at 200r / min speed for 60 seconds, then at 500r / min speed for 120 seconds) to make a slurry; (3) Pour the slurry into the mold (40mm×40mm×160mm triple mold) and vibrate to remove bubbles for 3 minutes. Seal the mold with plastic film and pre-cur it in the 20℃ anaerobic environment for 24 hours. After the anaerobic pre-curing is completed, demold the material and transfer it to the carbon dioxide oxygen protection device for toughening and carbonization (toughening and carbonization conditions are carbon dioxide volume concentration of 20%, relative humidity of 60%, and temperature of 20℃) for 12 hours. After the toughening and carbonization is completed, transfer the material to the standard curing room and standard cure it at 20℃ and relative humidity ≥95% until the specified age to produce fly ash synergistic multi-source solid waste toughening all solid waste cementitious material.

[0031] Comparative Example 5: Comparative Example 5 is a prior art red mud-carbide slag-acid leaching low-temperature pyrolysis fly ash-slag system, the preparation method of which includes the following steps: (1) The fly ash from the waste incineration was treated with hydrochloric acid (concentration 0.8 mol / L) at a solid-liquid ratio of 5:1 for 45 min. After the acid leaching treatment, the filter cake was collected by filtration. The filter cake was then placed in a nitrogen atmosphere and pyrolyzed at 500℃ for 1 h. After cooling, it was ground into acid-leached low-temperature pyrolysis fly ash (specific surface area ≥ 430 m²). 2 / kg, residual carbon content 3.2wt%). (2) 800g of acid-leached low-temperature pyrolysis fly ash and 240g of red mud (Bayer process red mud) are dried and ground to a specific surface area ≥420m². 2 / kg), 500g slag (S95 grade granulated blast furnace slag powder, specific surface area ≥460m²) 2 / kg), 400g of calcium carbide slag (calcium hydroxide content 92%) and water were added to a mixing device and stirred (first at 200r / min speed for 60 seconds, then at 500r / min speed for 120 seconds) to make a slurry; (3) Pour the slurry into the mold (40mm×40mm×160mm triple mold) and vibrate to remove bubbles for 3 minutes. Seal the mold with plastic film and pre-cur it in the 20℃ anaerobic environment for 24 hours. After the anaerobic pre-curing is completed, demold the material and transfer it to the carbon dioxide oxygen protection device for toughening and carbonization (toughening and carbonization conditions are carbon dioxide volume concentration of 20%, relative humidity of 60%, and temperature of 20℃) for 12 hours. After the toughening and carbonization is completed, transfer the material to the standard curing room and standard cure it at 20℃ and relative humidity ≥95% until the specified age to produce fly ash synergistic multi-source solid waste toughening all solid waste cementitious material.

[0032] Example of detection: The compressive strength and heavy metal leaching of the cementitious materials prepared in Examples 1-3 and Comparative Examples 1-5 were tested. The compressive strength was tested according to the content published in "GB / T 17671-2021 Cement Mortar Strength Test Method"; Heavy metal leaching was tested according to the content disclosed in "HJ 557-2010 Solid Waste Leaching Toxicity Leaching Method - Horizontal Oscillation Method"; The test results are shown in Table 1; Table 1 Compressive strength and heavy metal leaching results

[0033] As shown in Table 1, the fly ash synergistic multi-source solid waste toughening gelling materials prepared in Examples 1-3 of this invention exhibit a compressive strength of 8.5-9.8 MPa after 1 day and a compressive strength of 49.8-56.1 MPa after 28 days. Compared with the existing red mud-carbide slag-acid leaching low-temperature pyrolysis fly ash-slag system (Comparative Example 5), the early strength and long-term durability are significantly increased. Furthermore, the heavy metal leaching of this gelling material meets the general solid waste Class I criteria, and the heavy metal content in the leachate is far below the emission limits of the "GB 8978-1996 Integrated Wastewater Discharge Standard".

[0034] Comparative Example 1 uses fly ash from the original waste incineration process that has not undergone acid leaching and low-temperature pyrolysis. Compared with Example 1, Comparative Example 1 shows significantly reduced early strength and long-term durability, and significantly increased heavy metal leaching. Comparative Example 2 lacks nano-silica sol and calcined magnesium-aluminum hydrotalcite. Compared with Example 1, Comparative Example 2 shows significantly reduced early strength and long-term durability, and significantly increased heavy metal leaching, particularly with cadmium, chromium, lead, and zinc contents significantly exceeding those classified as Class I solid waste. Comparative Example 3 lacks magnesium-nickel-iron slag powder. Compared with Example 1, Comparative Example 3 shows significantly increased heavy metal leaching, and reduced early strength and long-term durability. These results indicate that acid-leached low-temperature pyrolysis fly ash, nano-silica sol, and calcined magnesium-aluminum hydrotalcite play important roles in improving the strength of the gel material, while magnesium-nickel-iron slag powder further enhances the long-term durability of the gel material. In addition, nano-silica sol and calcined magnesium aluminum hydrotalcite can significantly inhibit the leaching of heavy metals, while acid-leached low-temperature pyrolysis fly ash and magnesium-nickel-iron slag powder can further enhance the inhibitory effect of nano-silica sol and calcined magnesium aluminum hydrotalcite on heavy metal leaching. The synergistic effect of the four can significantly improve the heavy metal solidification effect of the gel material.

[0035] Comparative Example 4 is a technical solution without stepwise feeding. Compared with Example 1, Comparative Example 4 shows a significant increase in heavy metal leaching and a decrease in early strength and long-term durability. This indicates that stepwise feeding mixes the materials more evenly, gives different chemical reactions more reaction time, and significantly improves the heavy metal curing effect of the gel material.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A fly ash synergistic multi-source solid waste toughening cementitious material, characterized in that, The raw materials include a main phase, a pregel phase, and a nano-functional phase. The raw materials for the main phase are red mud, carbide slag, slag, and magnesium-nickel-iron slag powder. The raw materials for the pregel phase are acid-leached low-temperature pyrolysis fly ash, carbide slag, and water. The raw materials for the nano-functional phase are nano-silica sol, calcined magnesium-aluminum hydrotalcite, and water.

2. The fly ash synergistic multi-source solid waste toughening cementitious material according to claim 1, characterized in that, The mass ratio of red mud, carbide slag, blast furnace slag, and magnesium-nickel-iron slag powder is 10–15:15–25:20–30:5–8; the mass ratio of acid leaching low-temperature pyrolysis fly ash, carbide slag, and water is 35–50:1.5–5:5.8–12.9; and the mass ratio of nano-silica sol, calcined magnesium-aluminum hydrotalcite, and water is 0.4–2:0.4–1.3:3.8–9.

7.

3. A method for preparing a fly ash-co-reinforced multi-source solid waste toughening cementitious material according to any one of claims 1 to 2, characterized in that, Includes the following steps: (1) Nano-functional phases were prepared by ultrasonically dispersing nano-silica sol and calcined magnesium aluminum hydrotalcite in water; (2) A pregel phase is prepared by stirring and dispersing acid-leached low-temperature pyrolysis fly ash and carbide slag in water; (3) Mix red mud, carbide slag, slag and magnesium-nickel-iron slag powder into the main phase, then add the pre-gel phase and mix evenly, then add the nano-functional phase and water and stir to make a slurry; (4) The slurry is injected into the mold for anaerobic pre-curing, toughening carbonization and standard curing to produce fly ash synergistic multi-source solid waste toughening all solid waste cementitious material.

4. The preparation method according to claim 3, characterized in that, The acid-leached low-temperature pyrolysis fly ash is produced by acid leaching with hydrochloric acid and pyrolysis in an inert atmosphere at 450~550℃.

5. The preparation method according to claim 4, characterized in that, The conditions for hydrochloric acid leaching include: a solid-liquid ratio of 5:1, a hydrochloric acid concentration of 0.5~1 mol / L, and a leaching time of 30~60 min.

6. The preparation method according to claim 3 or 4, characterized in that, Acid-leached low-temperature pyrolysis fly ash with a specific surface area ≥400m² 2 / kg, residual carbon content 2~5wt%.

7. The preparation method according to claim 3, characterized in that, The conditions for pre-conditioning under hypoxic conditions include: static curing at 18~22℃ for 22~26 hours under sealed conditions.

8. The preparation method according to claim 3, characterized in that, The conditions for toughening and carbonization include: carbon dioxide volume concentration of 18-22%, relative humidity of 55-65%, temperature of 18-22℃, and time of 10-14h.

9. The preparation method according to claim 3, characterized in that, Standard maintenance conditions include: temperature 18~22℃, relative humidity ≥95%.

10. The preparation method according to claim 3, characterized in that, The molar ratio of magnesium to aluminum in calcined magnesium-aluminum hydrotalcite is 2~3:1, and the specific surface area of ​​calcined magnesium-aluminum hydrotalcite is ≥150 m². 2 / g.

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