Fibrous tobermorite-zeolite composite mineral admixture and preparation method thereof

Abstract

The invention relates to the technical field of mineral admixtures, in particular to a fibrous tobermorite-zeolite composite mineral admixture and a preparation method thereof.The preparation method comprises the following steps that A, steel slag, fly ash and mineral powder are evenly mixed and dried to obtain a solid mixture; wherein the chemical components of the steel slag, the coal ash and the mineral powder all comprise SiO2, Al2O3 and CaO. B, adding a sodium silicate aqueous solution into the solid mixture, and stirring to obtain a solid-liquid mixture; and C, carrying out a hydrothermal reaction on the solid-liquid mixture at 140-150 DEG C for 144-192 h, taking out the solid-liquid mixture, and sequentially cleaning, centrifuging and drying the solid-liquid mixture to obtain the fibrous tobermorite-zeolite composite mineral admixture. According to the fibrous tobermorite-zeolite composite mineral admixture and the preparation method thereof provided by the invention, the performance synergistic effect of the fibrous tobermorite-zeolite composite mineral admixture is improved on the premise of simplifying the preparation method and reducing the production cost, so that the defects in the prior art are overcome.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mineral admixtures, and particularly relates to a fibrous tobermorite-zeolite composite mineral admixture and a preparation method thereof. BACKGROUND

[0002] Mineral admixtures refer to mineral materials processed by physical or chemical methods, which are widely used in the fields of green building materials such as cement-based materials, ceramics and concrete due to their excellent performance in aspects of reinforcement, adsorption and promotion of hydration reaction.

[0003] Among numerous mineral admixtures, fibrous tobermorite and zeolite have become research hotspots due to their unique structural characteristics. Fibrous tobermorite not only can effectively promote the cement hydration process as a crystal seed due to its similar crystal structure to hydrated calcium silicate (C-S-H), but also can significantly improve the toughness and strength of building materials such as permeable bricks and ecological stones through bridge effect and crack deflection mechanism. Zeolite exhibits unique advantages in pollutant adsorption due to its porous structure and ion exchange capacity. Meanwhile, the polyhedral morphology of zeolite and fibrous tobermorite form complementary distribution, which can effectively improve the rheological properties of the slurry and inhibit the particle agglomeration phenomenon. In addition, zeolite can generate hydrated calcium silicate gel and ettringite through pozzolanic reaction, further refining the pore structure of building materials such as permeable bricks and ecological stones. What is particularly important is that there is a synergistic effect between fibrous tobermorite and zeolite, which not only strengthens the interface transition zone, but also realizes internal curing through the nanopores of zeolite, so that the building materials with both of the two minerals have high toughness, high strength and excellent adsorption performance.

[0004] However, in practical applications, fibrous tobermorite and zeolite have the following defects:

[0005] (1) Synthesis cost and large-scale application problem: Although the synthesis methods of fibrous tobermorite and zeolite are relatively mature, the synthesis processes of the two materials mainly rely on hydrothermal method. This method needs to use high-purity silicon source (such as silica sol) and aluminum source (such as aluminum isopropylate), which is difficult to realize industrial production due to high cost of raw materials.

[0006] (2) Functional limitation of single mineral admixture: The existing technology can only prepare fibrous tobermorite or zeolite. Single mineral admixture, i.e. fibrous tobermorite only with reinforcement performance or zeolite only with adsorption performance, is difficult to meet the demand of multifunctional building materials (such as high-strength and high-toughness permeable bricks with adsorption performance) for multiple performances.

[0007] (3) The performance of simple physical mixing is restricted: in theory, if the reinforcing effect of fibrous tobermorite and the adsorption function of zeolite are combined, a multifunctional building material with high strength, high toughness and environmental purification ability can be prepared. However, simple physical mixing cannot realize uniform dispersion and good interface combination of the two, which seriously restricts the synergistic optimization of material performance.

[0008] In view of the above problems, it is imperative to develop a low-cost preparation method that can generate a composite product with fibrous tobermorite and zeolite in one step, realize the in-situ compounding of the two minerals, and solve the problems in the prior art that the two minerals can only be synthesized separately, the production cost is high, and the performance synergistic effect is limited. SUMMARY

[0009] The purpose of the present application is to provide a fibrous tobermorite-zeolite composite mineral admixture and a preparation method thereof, which can improve the performance synergistic effect under the premise of simplifying the preparation method and reducing the production cost, and overcome the shortcomings of the prior art.

[0010] To achieve this purpose, the present application adopts the following technical solutions:

[0011] A preparation method of a fibrous tobermorite-zeolite composite mineral admixture, comprising the following steps:

[0012] A. uniformly mix steel slag, fly ash and mineral powder, and obtain a solid mixture after drying; wherein the chemical composition of the steel slag, the fly ash and the mineral powder each comprises SiO2, Al2O3 and CaO;

[0013] B. add a sodium silicate aqueous solution to the solid mixture, and obtain a solid-liquid mixture after stirring;

[0014] C. hydrothermally react the solid-liquid mixture at a temperature of 140-150°C for 144-192h, and then sequentially perform cleaning, centrifugation and drying after taking out, to obtain a fibrous tobermorite-zeolite composite mineral admixture; wherein the hydrothermal reaction in the 144-192h is subjected to stirring treatment for the first 24-48h, and is subjected to static treatment for the remaining time.

[0015] Further, in step A, the chemical composition of the steel slag comprises Al2O3 7.5-8%, SiO2 15-16%, Na2O 0.4-0.6%, MgO 4.1-4.3%, CaO 40-41%, TiO2 0.5-1%, MnO 3-4% and Fe2O3 20-22%, and the rest is loss on ignition, in terms of mass percentage;

[0016] The chemical composition of the fly ash includes, in percentage by mass, Al2O3 32-33%, SiO2 45-47%, Na2O 0.1-0.3%, MgO 1-1.1%, CaO 6.5-7%, TiO2 1.5-2%, MnO 0.1-0.2%, and Fe2O3 6.5-7%, and the rest is loss on ignition;

[0017] The chemical composition of the mineral powder includes, in percentage by mass, Al2O3 13-13.5%, SiO2 30-32%, Na2O 0.4-0.6%, MgO 7-8%, CaO 40-41%, TiO2 1-1.2%, MnO 0.2-0.4%, and Fe2O3 0.5-0.6%, and the rest is loss on ignition;

[0018] The mixing ratio of the steel slag, the fly ash and the mineral powder is 1:(1.4-1.6):(2.4-2.6) by mass.

[0019] Further, in step A, the steel slag includes, in percentage by mass, 8-12% of a first type of steel slag powder having a particle size of <6.47 μm, 35-45% of a second type of steel slag powder having a particle size of ≥6.47 μm and <37.61 μm, 35-45% of a third type of steel slag powder having a particle size of ≥37.61 μm and <80.24 μm, and 8-12% of a fourth type of steel slag powder having a particle size of ≥80.24 μm.

[0020] The fly ash includes, in percentage by mass, 8-12% of a first type of fly ash powder having a particle size of <3.37 μm, 35-45% of a second type of fly ash powder having a particle size of ≥3.37 μm and <17.61 μm, 35-45% of a third type of fly ash powder having a particle size of ≥17.61 μm and <70.24 μm, and 8-12% of a fourth type of fly ash powder having a particle size of ≥70.24 μm.

[0021] The mineral powder includes, in percentage by mass, 8-12% of a first type of mineral powder having a particle size of <4.07 μm, 35-45% of a second type of mineral powder having a particle size of ≥4.07 μm and <27.61 μm, 35-45% of a third type of mineral powder having a particle size of ≥27.61 μm and <60.24 μm, and 8-12% of a fourth type of mineral powder having a particle size of ≥60.24 μm.

[0022] Further, in step B, the modulus of the sodium silicate in the sodium silicate aqueous solution is 1.0-1.2.

[0023] Further, in step B, the content of the sodium silicate in the sodium silicate aqueous solution is 40-45% by mass.

[0024] Further, in step B, the mixing ratio of the sodium silicate aqueous solution to the solid mixture is (9-10):1 by mass ratio.

[0025] Further, in step C, the stirring speed of the stirring treatment is 250-350 r / min.

[0026] Further, in step C, the specific method of the centrifugation is: the solid-liquid mixture is loaded into a centrifuge tube, centrifuged at a centrifugal speed of 4000-6000 r / min for 0.1-0.2 h, the supernatant is removed, and a white precipitate is obtained.

[0027] The specific method of the washing is: the white precipitate is washed with clean water until the liquid after washing is colorless and transparent, and a white solid is obtained.

[0028] The specific method of the drying is: the white solid is dried at a temperature of 50-60℃ for 20-24 h, and a fibrous tobermorite-zeolite composite mineral admixture is obtained.

[0029] Further, in step A, the drying temperature of the drying is 100-120℃, and the drying time is 20-24 h.

[0030] A fibrous tobermorite-zeolite composite mineral admixture is prepared by using the preparation method of the fibrous tobermorite-zeolite composite mineral admixture.

[0031] The technical solution provided by the present application can include the following beneficial effects:

[0032] 1、The present technical solution forms a hybrid gel system composed of calcium silicate gel (C-S-H), calcium aluminum silicate gel (C-A-S-H) and sodium aluminum silicate gel (N-A-S-H) through the interaction of the solid mixture composed of steel slag, fly ash and mineral powder and the sodium silicate aqueous solution. In the hydrothermal reaction process at 140-150℃, through the stirring treatment in the first 24-48 h of the hydrothermal reaction to promote nucleation and the static treatment in the remaining time of the hydrothermal reaction to guide growth, the segmented dynamic-static hydrothermal control technology makes the hybrid gel system undergo directional phase change: the calcium silicate gel and the calcium aluminum silicate gel are converted into fibrous tobermorite (5CaO·6SiO2·5H2O), the sodium aluminum silicate gel is restructured into Na-X type zeolite framework, the fiber network of the tobermorite provides spatial confinement for the growth of the zeolite, the zeolite epitaxially grows on the surface of the fibrous tobermorite, the two are in-situ composite growth and chemically bonded through Si-O-Al bond, thereby forming a fibrous tobermorite-zeolite composite mineral admixture, and the fibrous tobermorite and the zeolite in the formed composite mineral admixture are uniformly dispersed.

[0033] 2、The fibrous tobermorite and the zeolite are chemically bonded through Si-O-Al bonds in the technical solution, and the fibrous tobermorite and the zeolite are uniformly dispersed in the composite mineral admixture formed, the mechanical reinforcing effect (fiber bridging effect) of the tobermorite is retained, the adsorption function (nanopore channel characteristic) of the zeolite is fully exerted, the problems of poor interface bonding and uneven dispersion in the traditional physical mixing method are solved, and the performance synergy effect of the composite mineral admixture is significantly improved. Meanwhile, the preparation method of the technical solution is simple and easy to operate, industrial solid wastes such as steel slag and fly ash are used as main raw materials, the solid waste resource utilization is realized, and the raw material cost is greatly reduced, which is beneficial to simplify the preparation method and reduce the production cost. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 and Figure 2 are SEM images of the fibrous tobermorite-zeolite composite mineral admixture obtained in Embodiment 1 of the present application. DETAILED DESCRIPTION

[0035] The technical solution provides a preparation method of a fibrous tobermorite-zeolite composite mineral admixture, including the following steps:

[0036] A. uniformly mixing steel slag, fly ash and mineral powder, and obtaining a solid mixture after drying; wherein the chemical compositions of the steel slag, the fly ash and the mineral powder all include SiO2, Al2O3 and CaO;

[0037] B. adding a sodium silicate aqueous solution into the solid mixture, and obtaining a solid-liquid mixture after stirring;

[0038] C. hydrothermally reacting the solid-liquid mixture at a temperature of 140-150 DEG C for 144-192 h, sequentially performing cleaning, centrifugation and drying after taking out, and obtaining the fibrous tobermorite-zeolite composite mineral admixture; wherein the hydrothermal reaction in the 144-192 h is subjected to stirring treatment for the first 24-48 h, and is subjected to static treatment for the remaining time.

[0039] In order to solve the problems of the mineral admixture in the prior art, such as only being able to be synthesized separately, high production cost and limited performance synergy effect, the technical solution provides a preparation method of a fibrous tobermorite-zeolite composite mineral admixture, and through the multi-solid waste synergy of the steel slag, the fly ash and the mineral powder, a segmented dynamic-static hydrothermal control technology is combined to realize in-situ composite crystallization of the fibrous tobermorite and the zeolite, and the fibrous tobermorite-zeolite composite mineral admixture is obtained, which is beneficial to improve the performance synergy effect of the fibrous tobermorite-zeolite composite mineral admixture under the premise of simplifying the preparation method and reducing the production cost.

[0040] Specifically, when the aqueous sodium silicate solution is added to the solid mixture composed of the steel slag, the fly ash and the mineral powder, the OH - activates the CaO in the steel slag, the fly ash and the mineral powder and also generates OH - , increasing the alkalinity of the system; in addition, the SiO2 in the steel slag, the fly ash and the mineral powder all exist in the form of a silicon-oxygen network structure, and the Al2O3 in the steel slag, the fly ash and the mineral powder all exist in the form of an aluminum-oxygen network structure. In the alkaline environment, the silicon-oxygen chains in the silicon-oxygen network structure and the aluminum-oxygen chains in the aluminum-oxygen network structure are depolymerized to generate silicate and aluminate, respectively. + (coming from the sodium silicate) directly condensate to generate sodium aluminosilicate gel (N-A-S-H) having a three-dimensional network structure. At the same time, the silicate can react with the product Ca(OH)2 generated after the activation of the CaO in the steel slag, the fly ash and the mineral powder in the system, to form calcium silicate gel (C-S-H) mainly in the form of a layered structure, and the aluminate can replace part of the silicate into the calcium silicate gel to form calcium alumino-silicate gel (C-A-S-H) in this system. That is, the present technical solution forms a hybrid gel system composed of calcium silicate gel (C-S-H), calcium alumino-silicate gel (C-A-S-H) and sodium aluminosilicate gel (N-A-S-H) through the interaction of the solid mixture composed of the steel slag, the fly ash and the mineral powder and the aqueous sodium silicate solution.

[0041] Further, in the hydrothermal reaction process at 140-150°C, the segmented dynamic-static hydrothermal control technology of stirring treatment for the first 24-48h to promote nucleation and static treatment for the remaining time to guide growth makes the hybrid gel system undergo directional phase transition: the calcium silicate gel and the calcium alumino-silicate gel are converted into fibrous tobermorite (5CaO·6SiO2·5H2O), the sodium aluminosilicate gel is restructured into Na-X type zeolite framework, and the fibrous network of the tobermorite provides spatial confinement for the growth of the zeolite, the zeolite epitaxially grows on the surface of the fibrous tobermorite, the two are in-situ composite growth and chemically bonded through Si-O-Al bonds, thereby forming fibrous tobermorite-zeolite composite mineral admixture, and the fibrous tobermorite and the zeolite are uniformly dispersed in the formed composite mineral admixture.

[0042] Further, the fibrous tobermorite and the zeolite are chemically bonded through Si-O-Al bonds in the technical solution, and the fibrous tobermorite and the zeolite are uniformly dispersed in the composite mineral admixture, the mechanical reinforcing effect (fiber bridging effect) of the tobermorite is retained, the adsorption function (nanopore channel characteristics) of the zeolite is fully exerted, the problems of poor interface bonding and uneven dispersion in the traditional physical mixing method are solved, and the performance synergy of the composite mineral admixture is significantly improved. Meanwhile, the preparation method of the technical solution is simple and easy to operate, industrial solid wastes such as steel slag and fly ash are used as main raw materials, the solid waste resource utilization is realized, and the raw material cost is greatly reduced, which is beneficial to simplify the preparation method and reduce the production cost.

[0043] Preferably, in step B, the stirring speed of the stirring is 400-600 r / min.

[0044] The stirring speed is adjusted to make the silicate, aluminate, Na + and Ca 2+ ions in the system exchange rapidly to form calcium silicate gel, calcium aluminum silicate gel and sodium aluminum silicate gel (i.e. precursor gel), and the stirring speed of 400-600 r / min can accelerate the mass transfer and ion exchange process, which is beneficial to the formation of the precursor gel of the tobermorite and the zeolite; meanwhile, if the stirring speed is too high, the formed gel microstructure can be damaged due to excessive shearing, so as to be beneficial to ensure the formation of the fibrous tobermorite-zeolite composite mineral admixture.

[0045] Further, in step A, the chemical composition of the steel slag includes Al2O3 7.5-8%, SiO2 15-16%, Na2O 0.4-0.6%, MgO 4.1-4.3%, CaO 40-41%, TiO2 0.5-1%, MnO 3-4% and Fe2O3 20-22% by mass percentage, and the rest is loss on ignition;

[0046] The chemical composition of the fly ash includes Al2O3 32-33%, SiO2 45-47%, Na2O 0.1-0.3%, MgO 1-1.1%, CaO 6.5-7%, TiO2 1.5-2%, MnO 0.1-0.2% and Fe2O3 6.5-7% by mass percentage, and the rest is loss on ignition;

[0047] The chemical composition of the mineral powder, calculated in percentage by mass, comprises Al2O3 13-13.5%, SiO2 30-32%, Na2O 0.4-0.6%, MgO 7-8%, CaO 40-41%, TiO2 1-1.2%, MnO 0.2-0.4%, and Fe2O3 0.5-0.6%, and the rest is loss on ignition;

[0048] The mixing ratio of the steel slag, the fly ash and the mineral powder, calculated in mass ratio, is 1:(1.4-1.6):(2.4-2.6).

[0049] The technical scheme optimizes the composition and mixing ratio of the steel slag, the fly ash and the mineral powder, uses the steel slag to provide abundant calcium source and promote the formation of tobermorite, uses the high silicon-aluminum ratio of the fly ash to accelerate the reaction of the amorphous active components, and uses the mineral powder to balance the calcium and aluminum content in the system and prevent the instability of the phase structure caused by the excessive single component. That is, the technical scheme optimizes the composition and mixing ratio of the steel slag, the fly ash and the mineral powder to make the CaO / SiO2 ratio in the system be in the range suitable for forming tobermorite and the Al2O3 / SiO2 ratio be in the range suitable for forming zeolite, thereby facilitating the formation of the fibrous tobermorite-zeolite composite mineral admixture.

[0050] Preferably, the chemical composition of the steel slag, calculated in percentage by mass, comprises Al2O3 7.96%, SiO2 15.36%, Na2O 0.51%, MgO 4.19%, CaO 40.97%, TiO2 0.95%, MnO 3.36%, Fe2O3 21.75%, and the rest is loss on ignition;

[0051] The chemical composition of the fly ash, calculated in percentage by mass, comprises Al2O3 32.7%, SiO2 46.45%, Na2O 0.20%, MgO 1.04%, CaO 6.92%, TiO2 1.98%, MnO 0.13%, and Fe2O3 6.73%, and the rest is loss on ignition.

[0052] The chemical composition of the mineral powder, calculated in percentage by mass, comprises Al2O3 13.08%, SiO2 31.78%, Na2O 0.58%, MgO 7.74%, CaO 40.82%, TiO2 1.14%, MnO 0.31%, and Fe2O3 0.57%, and the rest is loss on ignition.

[0053] Further, in step A, the steel slag includes, in percentage by mass, 8-12% of a first steel slag powder having a particle size of <6.47 μm, 35-45% of a second steel slag powder having a particle size of ≥6.47 μm and <37.61 μm, 35-45% of a third steel slag powder having a particle size of ≥37.61 μm and <80.24 μm, and 8-12% of a fourth steel slag powder having a particle size of ≥80.24 μm;

[0054] The fly ash includes, in percentage by mass, 8-12% of a first fly ash having a particle size of <3.37 μm, 35-45% of a second fly ash having a particle size of ≥3.37 μm and <17.61 μm, 35-45% of a third fly ash having a particle size of ≥17.61 μm and <70.24 μm, and 8-12% of a fourth fly ash having a particle size of ≥70.24 μm;

[0055] The mineral powder includes, in percentage by mass, 8-12% of a first mineral powder having a particle size of <4.07 μm, 35-45% of a second mineral powder having a particle size of ≥4.07 μm and <27.61 μm, 35-45% of a third mineral powder having a particle size of ≥27.61 μm and <60.24 μm, and 8-12% of a fourth mineral powder having a particle size of ≥60.24 μm.

[0056] The present technical solution optimizes the mesh number and the ratio of each type of steel slag powder in the steel slag, the mesh number and the ratio of each type of fly ash in the fly ash, and the mesh number and the ratio of each type of mineral powder in the mineral powder, so that the steel slag, the fly ash and the mineral powder all have a large specific surface area, thereby fully exposing the active components such as Al2O3 and SiO2 in the system, facilitating the improvement of the efficiency of the hydrothermal reaction and the yield of the product.

[0057] Further, in step B, the modulus of the sodium silicate in the sodium silicate aqueous solution is 1.0-1.2.

[0058] The modulus of the sodium silicate refers to the molar ratio of SiO2 to Na2O in the molecule of the sodium silicate, and when the modulus of the sodium silicate is 1.0-1.2, the free OH - is more, which promotes the complete depolymerization of Al2O3 and SiO2 in the steel slag, the fly ash and the mineral powder, thereby promoting the generation of calcium silicate gel (C-S-H), calcium aluminum silicate gel (C-A-S-H) and sodium aluminum silicate gel (N-A-S-H), and further facilitating the formation of fibrous tobermorite-zeolite composite mineral admixture.

[0059] Further, the hydrolysis of sodium silicate (Na2O·nSiO2+H2O→2Na + +n[SiO4] 4- +OH -) also produce sodium ions and silicate. When the modulus of sodium silicate is less than 1.0, it will cause an excess of sodium ions in the system, destroy the zeolite structure and increase the amorphous phase; when the modulus of sodium silicate is 1.2, it will cause an excess of silicate in the system, and the excess silicate will preferentially promote the formation of sheet-shaped zeolite, while inhibiting the participation of calcium ions in the reaction, resulting in a sharp decrease in tobermorite content.

[0060] Therefore, by limiting the modulus of sodium silicate to 1.0-1.2, the present technical solution promotes the complete depolymerization of Al2O3 and SiO2 in steel slag, fly ash and mineral powder, and optimizes the nucleation kinetics, realizing the synergistic growth of tobermorite fibers and zeolites, avoiding the generation of impurities and amorphous phases, and being conducive to the preparation of high-performance composite mineral admixtures.

[0061] Further, in step B, the content of sodium silicate in the aqueous sodium silicate solution is 40-45% by mass.

[0062] Controlling the concentration of the aqueous sodium silicate solution in the range of 40-45% can ensure that the hydrothermal reaction system has an ideal ion migration rate, which not only maintains sufficient reaction driving force to accelerate mineral phase formation, but also does not cause local component imbalance due to excessive consumption of calcium and aluminum ions caused by too high concentration; at the same time, the pH value (about 12-13) of the solution corresponding to this concentration range can effectively dissolve the silicon and aluminum components in the raw materials without causing excessive gelation, creating an optimal liquid phase environment for the symbiotic growth of fibrous tobermorite and analcime, thereby realizing the structure regulation and performance optimization of the composite material.

[0063] Further, in step B, the mixing ratio of the aqueous sodium silicate solution to the solid mixture is (9-10):1 by mass.

[0064] By limiting the mixing ratio of the aqueous sodium silicate solution to the solid mixture (i.e. liquid-solid ratio), the following effects are achieved: (1) the solid-liquid mixture obtained after mixing the aqueous sodium silicate solution with the solid mixture has a certain liquid phase proportion, thereby ensuring that Ca 2+ , Al 3+ and [SiO4] 4-(2) The liquid-solid ratio can produce a moderate space limitation effect, which promotes the preferential growth of tobermorite in one-dimensional direction to form a fiber morphology, while inhibiting the isotropic growth of zeolite crystals; (3) The slurry viscosity formed by the liquid-solid ratio can not only prevent composition segregation caused by particle sedimentation, but also will not hinder bubble discharge due to excessively high viscosity, ensuring that the product obtains a uniform dispersion state; (4) The amount of calcium silicate gel, calcium aluminum silicate gel and sodium aluminum silicate gel generated in the system reaches a suitable ratio. The above-mentioned gels control the ratio of the generated fibrous tobermorite and zeolite to be (0.9-1.1):1 through the subsection dynamic-static hydrothermal control technology, so that not only the mechanical enhancement effect (fiber bridging effect) of fibrous tobermorite can be fully utilized, but also the adsorption function of zeolite can be effectively utilized, ensuring that the obtained fibrous tobermorite-zeolite composite mineral admixture has excellent performance.

[0065] Therefore, by limiting the mixing ratio of the aqueous acid-sodium solution and the solid mixture, a limited space reaction environment can be constructed. On the premise of ensuring a sufficient proportion of liquid medium such as water, not only can the hydrodynamic conditions required for ion transport be maintained, but also a physical constraint conducive to crystal directional growth is created, ensuring the uniform compounding and compounding ratio of mullite fibers and zeolite nanoparticles.

[0066] Further, in step C, the stirring speed of the stirring treatment is 250-350 r / min.

[0067] By limiting the stirring speed, not only can the agglomeration and hardening of the mixed gel system composed of calcium silicate gel, calcium aluminum silicate gel and sodium aluminum silicate gel be prevented, but also the calcium silicate gel, calcium aluminum silicate gel and sodium aluminum silicate gel can be promoted to nucleate and crystallize smoothly in the hydrothermal reaction, which is conducive to obtaining the target product.

[0068] Further, in step C, the specific method of centrifugation is as follows: the solid-liquid mixture is loaded into a centrifuge tube, centrifuged at a centrifugal speed of 4000-6000 r / min for 0.1-0.2 h, the supernatant is removed, and a white precipitate is obtained.

[0069] The specific method of washing is as follows: the white precipitate is washed with water until the liquid after washing is colorless and transparent, and a white solid is obtained.

[0070] The specific method of drying is as follows: the white solid is dried at a temperature of 50-60℃ for 20-24 h, and a fibrous tobermorite-zeolite composite mineral admixture is obtained.

[0071] By optimizing the specific methods of centrifugation, washing and drying, the purity of the product can be ensured, thereby facilitating the performance of the fibrous tobermorite-zeolite composite mineral admixture.

[0072] Further illustrate, in step A, the drying temperature is 100-120℃, and the drying time is 20-24h.

[0073] The limitation of drying temperature and drying time has the following effects: (1) fully remove moisture to avoid caking: if the solid mixture composed of steel slag, fly ash and mineral powder has too high moisture content, it is easy to clog when mixed with sodium silicate solution later, affecting uniformity. Low temperature drying at 100-110℃ can slowly evaporate free water, avoiding high temperature (such as >120℃) leading to early hydration or structural changes of some active ingredients (such as CaO); (2) retain raw material activity: SiO2 and Al2O3 in steel slag, fly ash and mineral powder are key active ingredients for hydrothermal reaction, low temperature drying can avoid crystallization (such as quartz phase generation), ensuring subsequent reaction with sodium silicate; (3) energy saving and efficiency balance: 20-24h can ensure that the solid mixture is completely dried, while avoiding long drying time leading to increased energy consumption or oxidation of raw materials.

[0074] A fibrous tobermorite-zeolite composite mineral admixture is prepared by using the preparation method of the fibrous tobermorite-zeolite composite mineral admixture.

[0075] The technical scheme further provides a fibrous tobermorite-zeolite composite mineral admixture prepared by using the preparation method of the fibrous tobermorite-zeolite composite mineral admixture, which improves the performance synergy effect under the premise of simplifying the preparation method and reducing production costs, to meet the actual use requirements.

[0076] The technical scheme of the present application will be further described below through specific embodiments.

[0077] In the embodiments and comparative examples of the present application, the chemical composition of steel slag includes Al2O3 7.96%, SiO2 15.36%, Na2O 0.51%, MgO 4.19%, CaO 40.97%, TiO2 0.95%, MnO 3.36%, Fe2O3 21.75%, and the rest is loss on ignition, calculated by mass percentage.

[0078] The chemical composition of fly ash includes Al2O3 32.7%, SiO2 46.45%, Na2O 0.20%, MgO 1.04%, CaO 6.92%, TiO2 1.98%, MnO 0.13%, and Fe2O3 6.73%, calculated by mass percentage.

[0079] The chemical composition of the ore powder, calculated in terms of mass percentage, comprises Al2O3 13.08%, SiO2 31.78%, Na2O 0.58%, MgO 7.74%, CaO 40.82%, TiO2 1.14%, MnO 0.31%, and Fe2O3 0.57%, and the rest is loss on ignition.

[0080] The steel slag, calculated in terms of mass percentage, comprises 10% of a first type of steel slag powder with a particle size of <6.47 μm, 40% of a second type of steel slag powder with a particle size of ≥6.47 μm and <37.61 μm, 40% of a third type of steel slag powder with a particle size of ≥37.61 μm and <80.24 μm, and 10% of a fourth type of steel slag powder with a particle size of ≥80.24 μm.

[0081] The fly ash, calculated in terms of mass percentage, comprises 10% of a first type of fly ash with a particle size of <3.37 μm, 40% of a second type of fly ash with a particle size of ≥3.37 μm and <17.61 μm, 40% of a third type of fly ash with a particle size of ≥17.61 μm and <70.24 μm, and 10% of a fourth type of fly ash with a particle size of ≥70.24 μm.

[0082] The ore powder, calculated in terms of mass percentage, comprises 10% of a first type of ore powder with a particle size of <4.07 μm, 40% of a second type of ore powder with a particle size of ≥4.07 μm and <27.61 μm, 40% of a third type of ore powder with a particle size of ≥27.61 μm and <60.24 μm, and 10% of a fourth type of ore powder with a particle size of ≥60.24 μm.

[0083] Example 1

[0084] A. The steel slag, the fly ash, and the ore powder are mixed uniformly, and a solid mixture is obtained after drying at a temperature of 120°C for 20 h; wherein the mixing ratio of the steel slag, the fly ash, and the ore powder, calculated in terms of mass ratio, is 1:1.5:2.5;

[0085] B. The sodium silicate aqueous solution is added to the solid mixture, and a solid-liquid mixture is obtained after stirring at a stirring speed of 400 r / min for 0.3 h; wherein the modulus of sodium silicate in the sodium silicate aqueous solution is 1.2; the content of sodium silicate in the sodium silicate aqueous solution, calculated in terms of mass percentage, is 45%; and the mixing ratio of the sodium silicate aqueous solution and the solid mixture, calculated in terms of mass ratio, is 10:1;

[0086] C, the solid-liquid mixture is hydrothermally reacted at a temperature of 150 DEG C for 168 h, after being taken out, the solid-liquid mixture is loaded into a centrifuge tube, centrifuged at a centrifugal speed of 5000 r / min for 0.2 h, the supernatant is removed, and a white precipitate is obtained; the white precipitate is washed with clean water until the liquid after washing is colorless and transparent, and a white solid is obtained; the white solid is dried at a temperature of 60 DEG C for 24 h, and a fibrous tobermorite-zeolite composite mineral admixture is obtained; wherein, the hydrothermal reaction in the first 24 h of the 168 h is treated by stirring at a stirring speed of 300 r / min, and the hydrothermal reaction in the remaining time is treated by standing.

[0087] The SEM diagram of the fibrous tobermorite-zeolite composite mineral admixture obtained in Example 1 is shown in Figure 1 and Figure 2 , Figure 1 and Figure 2 , wherein the circles are zeolites and the irregular needles are fibrous tobermorites. It can be seen from Figure 1 and Figure 2 that the present technical solution can synthesize fibrous tobermorites and zeolites, the ratio of the fibrous tobermorites and the zeolites is close to 1:1, the fibrous tobermorites and the zeolites are combined to form a composite mineral admixture, and the fibrous tobermorites and the zeolites are uniformly dispersed in the composite mineral admixture.

[0088] Example 2

[0089] A, the steel slag, the fly ash and the mineral powder are uniformly mixed, and a solid mixture is obtained after being dried at a temperature of 100 DEG C for 24 h; wherein, the mixing ratio of the steel slag, the fly ash and the mineral powder is 1:1.4:2.4 according to the mass ratio;

[0090] B, a sodium silicate aqueous solution is added to the solid mixture, and a solid-liquid mixture is obtained after being stirred at a stirring speed of 500 r / min for 0.3 h; wherein, the modulus of sodium silicate in the sodium silicate aqueous solution is 1.1; the content of sodium silicate in the sodium silicate aqueous solution is 40% according to the mass percentage; and the mixing ratio of the sodium silicate aqueous solution and the solid mixture is 9:1 according to the mass ratio;

[0091] C, the solid-liquid mixture is hydrothermally reacted at a temperature of 140 DEG C for 144 h, after being taken out, the solid-liquid mixture is loaded into a centrifuge tube, centrifuged at a centrifugal speed of 4000 r / min for 0.2 h, the supernatant is removed, and a white precipitate is obtained; the white precipitate is washed with clean water until the liquid after washing is colorless and transparent, and a white solid is obtained; the white solid is dried at a temperature of 50 DEG C for 20 h, and a fibrous tobermorite-zeolite composite mineral admixture is obtained; wherein, the hydrothermal reaction in the first 24 h of the 144 h is treated by stirring at a stirring speed of 250 r / min, and the hydrothermal reaction in the remaining time is treated by standing.

[0092] Example 3

[0093] A, the steel slag, fly ash and slag powder were mixed uniformly, and a solid mixture was obtained after drying at a temperature of 110℃ for 22h; wherein, according to the mass ratio, the mixing ratio of the steel slag, fly ash and slag powder was 1:1.6:2.6;

[0094] B, the sodium silicate aqueous solution was added to the solid mixture, and a solid-liquid mixture was obtained after stirring at a stirring speed of 600r / min for 0.1h; wherein, the modulus of sodium silicate in the sodium silicate aqueous solution was 1.0; according to the mass percentage, the content of sodium silicate in the sodium silicate aqueous solution was 43%; according to the mass ratio, the mixing ratio of the sodium silicate aqueous solution and the solid mixture was 10:1;

[0095] C, the solid-liquid mixture was hydrothermally reacted at a temperature of 145℃ for 192h, and after taking out, the solid-liquid mixture was loaded into a centrifuge tube and centrifuged at a centrifugal speed of 6000r / min for 0.1h, the supernatant was removed, and a white precipitate was obtained; the white precipitate was washed with water until the liquid after washing was colorless and transparent, and a white solid was obtained; the white solid was dried at a temperature of 50℃ for 22h, and a fibrous tobermorite-zeolite composite mineral admixture was obtained; wherein, the hydrothermal reaction for the first 48h of the 192h was treated by stirring at a stirring speed of 250r / min, and the hydrothermal reaction for the remaining time was treated by standing.

[0096] Comparative Example 1

[0097] Comparative Example 1 and Example 1 had the same preparation method and raw materials, except that the fibrous tobermorite-zeolite composite mineral admixture in Comparative Example 1 was obtained by physically mixing the fibrous tobermorite and the zeolite composite mineral admixture.

[0098] The fibrous tobermorite-zeolite composite mineral admixture obtained in the examples and comparative examples is used to prepare high-strength and high-toughness water-permeable bricks with adsorption performance. The specific preparation method is as follows: 60 parts of quartz sand, 15 parts of cement, 20 parts of fibrous tobermorite-zeolite composite mineral admixture, 8 parts of water, and 0.1 part of polycarboxylic acid water reducer are uniformly stirred to obtain a slurry; the slurry is poured into a mold to obtain an intermediate blank; the intermediate blank is sealed and then steam-cured to obtain high-strength and high-toughness water-permeable bricks with adsorption performance. The bending strength and compressive strength of the high-strength and high-toughness water-permeable bricks with adsorption performance are tested according to the test standard of “GB / T 25993-2010 Water-permeable pavement bricks and water-permeable pavement panels”. At the same time, 25 water-permeable bricks prepared in the examples and comparative examples are taken and laid into rectangular areas, and a non-permeable film is laid under each rectangular area. 20L of sewage containing aluminum ions, zinc ions and copper ions is sprayed on each rectangular area, so that the sewage flows through the rectangular area paved with water-permeable bricks, and the effluent sewage is collected. The content of metal ions in the original sewage and the effluent sewage is tested according to the test method in “GB3838-2022 Environmental Quality Standards for Surface Water”, and the removal percentage of metal ions is calculated. The test results are shown in Table 1 below:

[0099] Table 1 Test results of the properties of water-permeable bricks

[0100]

[0101] The bending strength and compressive strength are related to the strength and toughness of the water-permeable bricks, and the higher the bending strength and compressive strength, the higher the strength and toughness of the water-permeable bricks. The removal rate of aluminum ions, zinc ions and copper ions is related to the adsorption performance of the water-permeable bricks, and the higher the removal rate of aluminum ions, zinc ions and copper ions, the higher the adsorption performance. From the performance test results in Table 1, it can be seen that the high-strength and high-toughness water-permeable bricks with adsorption performance prepared from the fibrous tobermorite-zeolite composite mineral admixture obtained in the examples of the present technical solution have a compressive strength of ≥40MPa, a bending strength of ≥8MPa, a removal rate of aluminum ions and zinc ions of ≥90%, and a removal rate of copper ions of ≥75%. Through comparative experiments, it is found that the high-strength and high-toughness water-permeable bricks with adsorption performance prepared from the fibrous tobermorite-zeolite composite mineral admixture obtained in the examples of the present technical solution have better performance test indexes than the high-strength and high-toughness water-permeable bricks with adsorption performance prepared from the fibrous tobermorite-zeolite composite mineral admixture obtained by pure physical mixing of the fibrous tobermorite and zeolite composite mineral admixture in Comparative Example 1. Therefore, according to the test results, it can be concluded that the fibrous tobermorite-zeolite composite mineral admixture of the present technical solution is beneficial to improving the performance synergistic effect under the premise of simplifying the preparation method and reducing the production cost.

[0102] The technical principles of the present application are described above in combination with specific embodiments. These descriptions are only for explaining the principles of the present application, and cannot be interpreted as limiting the protection scope of the present application in any way. Based on the explanations herein, other specific embodiments of the present application can be conceived by those skilled in the art without any creative effort, and these embodiments will all fall within the protection scope of the present application.

Claims

1. A method for preparing a fibrous tobermorite-zeolite composite mineral admixture, characterized in that: The following steps are involved: A. uniformly mixing steel slag, fly ash, and mineral powder, and drying to obtain a solid mixture; wherein the chemical components of the steel slag, the fly ash, and the mineral powder all include SiO2, Al2O3, and CaO; B. adding an aqueous sodium silicate solution to the solid mixture and stirring to obtain a solid-liquid mixture; C. hydrothermally reacting the solid-liquid mixture at a temperature of 140-150° C. for 144-192 hours, taking it out and washing, centrifuging and drying it in sequence to obtain a fibrous tobermorite-zeolite composite mineral admixture; wherein, the hydrothermal reaction of the first 24-48 hours of the 144-192 hours is stirred, and the hydrothermal reaction of the remaining time is allowed to stand.

2. The method for preparing a fibrous tobermorite-zeolite composite mineral admixture according to claim 1, characterized in that: In step A, the chemical composition of the steel slag, calculated by mass percentage, includes Al2O3 7.5-8%, SiO2 15-16%, Na2O 0.4-0.6%, MgO 4.1-4.3%, CaO 40-41%, TiO2 0.5-1%, MnO 3-4% and Fe2O3 20-22%, with the remainder being loss on ignition; Calculated by mass percentage, the chemical composition of the fly ash includes Al2O3 32-33%, SiO2 45-47%, Na2O 0.1-0.3%, MgO 1-1.1%, CaO 6.5-7%, TiO2 1.5-2%, MnO 0.1-0.2% and Fe2O3 6.5-7%, with the remainder being loss on ignition; Calculated by mass percentage, the chemical composition of the mineral powder includes Al2O3 13-13.5%, SiO2 30-32%, Na2O 0.4-0.6%, MgO 7-8%, CaO 40-41%, TiO2 1-1.2%, MnO 0.2-0.4% and Fe2O3 0.5-0.6%, with the remainder being loss on ignition; Calculated by mass ratio, the mixing ratio of the steel slag, the fly ash and the mineral powder is 1:(1.4-1.6):(2.4-2.6).

3. The method for preparing a fibrous tobermorite-zeolite composite mineral admixture according to claim 1, characterized in that: In step A, the steel slag includes, calculated by mass percentage, 8-12% of Class I steel slag powder with a particle size of less than 6.47 μm, 35-45% of Class II steel slag powder with a particle size of ≥6.47 μm and less than 37.61 μm, 35-45% of Class III steel slag powder with a particle size of ≥37.61 μm and less than 80.24 μm, and 8-12% of Class IV steel slag powder with a particle size of ≥80.24 μm; Calculated by mass percentage, the fly ash includes 8-12% of Class I fly ash with a particle size of less than 3.37 μm, 35-45% of Class II fly ash with a particle size of ≥3.37 μm and less than 17.61 μm, 35-45% of Class III fly ash with a particle size of ≥17.61 μm and less than 70.24 μm, and 8-12% of Class IV fly ash with a particle size of ≥70.24 μm. Calculated by mass percentage, the mineral powder includes 8-12% of Class I mineral powder with a particle size of <4.07μm, 35-45% of Class II mineral powder with a particle size of ≥4.07μm and <27.61μm, 35-45% of Class III mineral powder with a particle size of ≥27.61μm and <60.24μm, and 8-12% of Class IV mineral powder with a particle size of ≥60.24μm.

4. The method for preparing a fibrous tobermorite-zeolite composite mineral admixture according to claim 1, characterized in that: In step B, the modulus of sodium silicate in the sodium silicate aqueous solution is 1.0 to 1.

2.

5. The method for preparing a fibrous tobermorite-zeolite composite mineral admixture according to claim 1, characterized in that: In step B, the content of sodium silicate in the sodium silicate aqueous solution is 40-45% calculated by mass percentage.

6. The method for preparing a fibrous tobermorite-zeolite composite mineral admixture according to claim 1, characterized in that: In step B, the mixing ratio of the sodium silicate aqueous solution to the solid mixture is (9-10):1, calculated by mass ratio.

7. The method for preparing a fibrous tobermorite-zeolite composite mineral admixture according to claim 1, characterized in that: In step C, the stirring speed of the stirring treatment is 250 to 350 r / min.

8. The method for preparing a fibrous tobermorite-zeolite composite mineral admixture according to claim 1, characterized in that: In step C, the specific method of the centrifugation is: placing the solid-liquid mixture into a centrifuge tube, centrifuging it at a centrifugal speed of 4000-6000 r / min for 0.1-0.2 h, removing the supernatant to obtain a white precipitate; The specific method of washing is: washing the white precipitate with clean water until the washed liquid is colorless and transparent to obtain a white solid; The specific drying method is: drying the white solid at a temperature of 50 to 60° C. for 20 to 24 hours to obtain a fibrous tobermorite-zeolite composite mineral admixture.

9. The method for preparing a fibrous tobermorite-zeolite composite mineral admixture according to claim 1, characterized in that: In step A, the drying temperature is 100-120° C., and the drying time is 20-24 hours.

10. A fibrous tobermorite-zeolite composite mineral admixture, characterized in that: The fibrous tobermorite-zeolite composite mineral admixture is prepared using the preparation method of any one of claims 1 to 9.

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