A mineralized cementitious material and its preparation method

Abstract

The present invention discloses a mineralized cementitious material and a preparation method thereof. In the preparation method, a composite alkaline solution with a specific pH value is used as a mineralized liquid phase medium. In combination with a silicon-aluminum activator, a mineralization promoter, and a crystal nucleation inducer, CO2 gas is introduced into a liquid phase environment to directly trigger the depolymerization reaction of silicon-oxygen bonds and aluminum-oxygen bonds on the surface of fly ash particles, making the reaction conditions easy to achieve and control. The mineralized cementitious material obtained by the preparation method is a non-cement-based material, and a large amount of fly ash gel is achieved through mineralization-organic activation. In addition, the "gradient mineralization-directional crystallization" process is pioneered. By regulating the ion concentration and temperature field of the mineralization system in stages, the fly ash is guided to dissociate and the intermediate obtained by introducing CO2 gas, adding a silicon-aluminum activator and a mineralization promoter, and a calcium source substance are used to generate a mineralized cementitious material including high-activity C-S-H gel and ettringite crystals according to a preset crystallization path.

Description

Technical Field

[0001] The present invention relates to the technical field of mineralized gelling materials, and in particular to a mineralized gelling material and a preparation method thereof. Background Art

[0002] Fly ash is a byproduct of coal-fired power plants. Large accumulations of fly ash can occupy land and pollute the environment. Using it in cementitious materials can effectively reduce waste and lower the environmental burden. However, the related art of using fly ash to prepare cementitious materials requires cement, and the preparation of cementitious materials suffers from problems such as low fly ash content and low early strength. Summary of the Invention

[0003] The embodiment of the present application provides a mineralized cementitious material and a preparation method thereof, wherein the preparation method uses a composite alkaline solution of a specific pH value as a mineralized liquid phase medium, combines a silicon-aluminum activator, a mineralization promoter, and a crystal nucleation inducer, and introduces CO2 gas into a liquid phase environment to directly trigger the depolymerization reaction of the silicon-oxygen bonds and aluminum-oxygen bonds on the surface of the fly ash particles, making the reaction conditions easy to achieve and control, and the mineralized cementitious material obtained by the preparation method is a non-cement-based material, and a large amount of fly ash gel is achieved through mineralization-organic activation excitation. In addition, the "gradient mineralization-directional crystallization" process is pioneered, which guides the dissociation of fly ash by regulating the ion concentration and temperature field of the mineralization system in stages, and generates a mineralized cementitious material including high-activity CSH gel and calcium aluminite crystals by introducing CO2 gas, adding an intermediate obtained by a silicon-aluminum activator and a mineralization promoter, and a calcium source substance according to a preset crystallization path.

[0004] The present invention provides a method for preparing a mineralized gelling material, comprising:

[0005] The fly ash and the composite alkaline solution are mixed to obtain a mixed solution; wherein the composite alkaline solution is obtained by treating red mud with phosphoric acid and NaOH solid, and includes NaAlO2, [Al(PO4)2] 3- alkaline solution;

[0006] After adding a silicon-aluminum activator to the mixed solution, a mixed gas is introduced and a mineralization treatment is performed at 20-60° C. for 1-3 hours, wherein the mixed gas contains CO2 gas; the silicon-aluminum activator is a modified chitosan-γ-cyclodextrin derivative;

[0007] A calcium source precursor, a mineralization promoter and a crystal nucleation inducer are added to the material obtained after mineralization, and the pH is adjusted within the range of 10.5-12.5 to achieve a phased advancement of the mineralization treatment; wherein the mineralization promoter is Ca modified by γ-mercaptopropyltrimethoxysilane. 1.5 Si(OH)6·2H2O; the crystal nucleus inducing agent is Ca6[Al(OH)6]2(SO4)3·26H2O;

[0008] After adjusting the pH, the mineralized cementitious material is obtained through normal temperature drying and micronization treatment.

[0009] In some embodiments, the preparation steps of the composite alkaline solution include:

[0010] Grind the red mud to 200 mesh, mix it with 20% phosphoric acid solution according to a liquid-solid ratio of 5:1, and stir and react at 80 °C for 2 hours;

[0011] Centrifuge the solution obtained from the reaction to obtain an acidic filtrate containing Al 3+ ;

[0012] Slowly add NaOH solid to the acidic filtrate containing Al 3+ to adjust the pH to 12.5 to generate a composite alkaline solution.

[0013] In some embodiments, the preparation steps of the silicon-aluminum activator include:

[0014] Dissolve chitosan in an acetic acid solution to form a chitosan solution;

[0015] Dissolve γ-cyclodextrin in water to make a γ-cyclodextrin solution;

[0016] Stir the chitosan solution at 60 °C for 20 min; wherein, during the stirring process, slowly drop the γ-cyclodextrin solution into the chitosan solution, and add glutaraldehyde after dropping the γ-cyclodextrin solution;

[0017] Adjust the pH value of the stirred solution to 10-12 to precipitate the product, and filter, wash and dry the product to obtain γ-cyclodextrin modified chitosan derivatives.

[0018] In some embodiments, the calcium source precursor includes at least one of mineral powder, steel slag and carbide slag.

[0019] In some embodiments, the preparation method of the mineralization promoter includes:

[0020] After adding γ-mercaptopropyltrimethoxysilane to Ca 1.5 Si(OH)6·2H2O powder, dry it at 45 °C for 2 hours to obtain γ-mercaptopropyltrimethoxysilane modified Ca 1.5 Si(OH)6·2H2O.

[0021] In some embodiments, the preparation method of the crystal nucleus inducer includes:

[0022] Add water to hemihydrate gypsum powder and nano-calcium aluminate hydrate crystal seeds with a mass ratio of 10:1 and stir to make a slurry;

[0023] The slurry was cured in a 0.5 MPa autoclave at 120° C. for 2 hours to fully combine the semi-hydrated gypsum powder with the nano-ettringite seed crystals to obtain Ca6[Al(OH)6]2(SO4)3·26H2O.

[0024] In some embodiments, the calcium source precursor includes at least one of mineral powder, steel slag, and carbide slag.

[0025] In some embodiments, the mass ratio of the fly ash to the composite alkaline solution is 1:3-5.

[0026] In some embodiments, the concentration of CO 2 gas in the mixed gas is 30%.

[0027] The present invention also provides a mineralized gelling material, which is prepared by adopting the preparation method of the mineralized gelling material.

[0028] The present invention provides a mineralized cementitious material and a preparation method thereof. In the preparation method, a composite alkaline solution with a specific pH value is used as a mineralized liquid phase medium. In combination with a silicon-aluminum activator, a mineralization promoter, and a crystal nucleation inducer, CO2 gas is introduced into a liquid phase environment to directly trigger the depolymerization reaction of the silicon-oxygen bonds and aluminum-oxygen bonds on the surface of the fly ash particles, making the reaction conditions easy to achieve and control. The mineralized cementitious material obtained by the preparation method is a non-cement-based material, and a large amount of fly ash gel is achieved through mineralization-organic activation. In addition, the "gradient mineralization-directional crystallization" process is pioneered. By regulating the ion concentration and temperature field of the mineralization system in stages, the fly ash is guided to dissociate and the intermediate obtained by introducing CO2 gas, adding a silicon-aluminum activator and a mineralization promoter, and a calcium source substance are used to generate a mineralized cementitious material including high-activity CSH gel and calcium aluminite crystals according to a preset crystallization path. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A flow chart of a method for preparing a mineralized cementitious material according to some embodiments is exemplified. DETAILED DESCRIPTION

[0030] In order to better understand the above technical solution, the technical solution of this application is described in detail below through specific implementation methods.

[0031] To solve the above technical problems, an embodiment of the present application provides a mineralized cementitious material and a preparation method thereof. In this preparation method, a composite alkaline solution with a specific pH value is used as the mineralized liquid phase medium, combined with a silicon-aluminum activator, a mineralization promoter, and a crystal nucleus inducer. By introducing CO2 gas into the liquid phase environment, the depolymerization reaction of the silicon-oxygen bond and aluminum-oxygen bond on the surface of fly ash particles is directly triggered, making the reaction conditions easy to achieve and control. Moreover, the mineralized cementitious material obtained by this preparation method is a non-cement-based material, and a large amount of fly ash gel is achieved through mineralization-organic activation excitation. In addition, the "gradient mineralization-oriented crystallization" process is pioneered. By regulating the ion concentration and temperature field of the mineralization system in stages, the dissociation of fly ash is guided, and the intermediate obtained by introducing CO2 gas, adding a silicon-aluminum activator and a mineralization promoter, and a calcium source material generate a mineralized cementitious material including high-activity C-S-H gel and ettringite crystals according to a preset crystallization path.

[0032] Figure 1 A flowchart of a preparation method of a mineralized cementitious material according to some embodiments is exemplarily shown, and the preparation method includes S100-S400.

[0033] S100. Mix fly ash and a composite alkaline solution to obtain a mixed solution; wherein, the composite alkaline solution is an alkaline solution including NaAlO2 and [Al(PO4)2] obtained by treating red mud with phosphoric acid and NaOH solid. 3-

[0034] In the embodiment of the present application, the active aluminum source in red mud is used to form [Al(PO4)2] 3- coordination ions with phosphate radicals to promote the depolymerization of the vitreous body in fly ash.

[0035] In some embodiments, the preparation steps of the composite alkaline solution include: grinding red mud to 200 mesh, mixing it with a 20% phosphoric acid solution according to a liquid-solid ratio of 5:1, stirring and reacting at 80 °C for 2 hours; centrifuging the reaction solution to obtain an acidic filtrate containing Al 3+ ; slowly adding NaOH solid to the acidic filtrate containing Al 3+ to adjust the pH to 12.5 to generate a composite alkaline solution.

[0036] In this embodiment, after mixing and stirring red mud with a phosphoric acid solution for reaction, part of the Al2O3 in red mud is dissolved into Al 3+ under acidic conditions (pH≈1.5), and at the same time, the sodium salt (such as Na2O) in red mud is converted into free Na + . After the reaction, the reaction solution is centrifuged to obtain an acidic filtrate containing Al 3+ , and then NaOH solid is slowly added to the acidic filtrate to adjust the pH to 12.5. At this time, Al3+ with PO4 3- and excessive OH - to form a complex to generate an alkaline solution containing NaAlO2 and [Al(PO4)2] 3- .

[0037] In some embodiments, the mass ratio of the fly ash to the composite alkaline solution is 1:3 - 5. In some embodiments, the mass ratio of the fly ash to the composite alkaline solution is 1:5.

[0038] S200. After adding a silicon-aluminum activator to the mixed solution, a mixed gas is introduced and mineralization treatment is carried out at 20 - 60 °C for 1 - 3 h, wherein the mixed gas contains CO2 gas; the silicon-aluminum activator is a modified chitosan-γ-cyclodextrin derivative.

[0039] In the embodiments of the present application, the modified chitosan-γ-cyclodextrin derivative forms a hydrogen bond network through amino groups and hydroxyl groups in the molecular structure, selectively adsorbs on the surface of fly ash particles, and weakens the binding energy of the Si-O-Al bond in the fly ash.

[0040] In some embodiments, the preparation steps of the silicon-aluminum activator include: dissolving chitosan in an acetic acid solution to form a chitosan solution; dissolving γ-cyclodextrin in water to make a γ-cyclodextrin solution; stirring the chitosan solution at 60 °C for 20 min; wherein, during the stirring process, the γ-cyclodextrin solution is slowly added dropwise to the chitosan solution, and glutaraldehyde is added after adding the γ-cyclodextrin solution; adjusting the pH value of the stirred solution to 10 - 12 to precipitate the product, and filtering, washing, and drying the product to obtain a γ-cyclodextrin modified chitosan derivative.

[0041] In this embodiment, a γ-cyclodextrin solution and glutaraldehyde are added to the chitosan solution to initiate a cross-linking reaction between γ-cyclodextrin and glutaraldehyde. By adjusting the pH to 10 - 12, the product obtained from the cross-linking reaction is precipitated, and the product is filtered, washed, and dried to obtain a γ-cyclodextrin modified chitosan derivative.

[0042] In some embodiments, the concentration of CO2 gas in the mixed gas is 15% - 30%. In some other embodiments, the concentration of CO2 gas in the mixed gas is 30%. In this embodiment, in addition to CO2 gas, the mixed gas may also contain air or N2.

[0043] In some embodiments, the mass fraction of the silicon-aluminum activator in the fly ash is 0.5% - 2%.

[0044] S300. Add a calcium source precursor, a mineralization promoter, and a crystal nucleus inducer to the material obtained after mineralization, and adjust the pH within the range of 10.5 - 12.5 to achieve a phased advancement of the mineralization treatment; wherein, the mineralization promoter is Ca 1.5 Si(OH)6·2H2O modified by γ-mercaptopropyltrimethoxysilane; the crystal nucleus inducer is Ca6[Al(OH)6]2(SO4)3·26H2O.

[0045] In the embodiments of the present application, the role of the calcium source precursor is to provide a calcium source. In some embodiments, the calcium source precursor includes at least one of mineral powder, steel slag, and carbide slag.

[0046] In some embodiments, the mass fraction of the calcium source precursor in the fly ash is 5% - 20%.

[0047] In the embodiments of the present application, the mineralization promoter is Ca 1.5 Si(OH)6·2H2O modified by γ-mercaptopropyltrimethoxysilane. This mineralization promoter can act as a "seed crystal" to reduce the nucleation barrier of the hydration product (i.e., calcium silicoaluminate hydrate) obtained by depolymerizing the vitreous body in fly ash. At the same time, the thiol group forms dynamic coordination bonds with the calcium ions in the calcium source precursor and fly ash, regulating the ion release kinetics.

[0048] In some embodiments, the preparation method of the mineralization promoter includes: adding γ-mercaptopropyltrimethoxysilane to the Ca 1.5 Si(OH)6·2H2O powder, and drying it at 45°C for 2 hours to obtain Ca 1.5 Si(OH)6·2H2O modified by γ-mercaptopropyltrimethoxysilane.

[0049] In some embodiments, the mass fraction of the mineralization promoter in the fly ash is 0.5% - 2%. In some embodiments, the mass fraction of the mineralization promoter in the fly ash is 1%.

[0050] In the embodiments of the present application, the crystal nucleus inducer is Ca6[Al(OH)6]2(SO4)3·26H2O. This crystal nucleus inducer can serve as a heterogeneous nucleation site for C-S-H gel, and its surface oxygen vacancies can capture Ca 2+ (This Ca 2+ is mainly the calcium ions in the calcium source precursor) to form a locally high-concentration region, promoting the mineralization cementation reaction.

[0051] In some embodiments, the preparation method of the crystal nucleus inducer includes: adding water to hemihydrate gypsum powder (i.e., hemihydrate calcium sulfate) and nano-calcium aluminate seed crystals with a mass ratio of 10:1 and stirring to form a slurry; curing the slurry in an autoclave at 0.5 MPa and 120 °C for 2 hours to fully combine the hemihydrate gypsum powder and the nano-calcium aluminate seed crystals, obtaining Ca6[Al(OH)6]2(SO4)3·26H2O.

[0052] In some embodiments, the mass fraction of the crystal nucleus inducer in the fly ash is 0.5%-2%. In some embodiments, the mass fraction of the crystal nucleus inducer in the fly ash is 1%.

[0053] S400. After adjusting the pH, through normal temperature drying and micronization treatment, a mineralized cementitious material is obtained.

[0054] In the embodiments of the present application, after adjusting the pH to achieve the phased advancement of mineralization treatment, a mineralized cementitious material prepared based on direct liquid-phase mineralization of fly ash can be obtained through normal temperature drying and micronization treatment.

[0055] In practical applications, water with a water-cement ratio of 0.3-0.5 can be added to the mineralized cementitious material to obtain a hardened slurry with a 28-day compressive strength of 10-60 MPa.

[0056] In the embodiments of the present application, a composite alkaline solution with a specific pH value is used as the mineralization liquid phase medium in the preparation method of the mineralized cementitious material. Combining a silicon-aluminum activator, a mineralization promoter, and a crystal nucleus inducer, the depolymerization reaction of silicon-oxygen bonds and aluminum-oxygen bonds on the surface of fly ash particles is directly triggered by introducing CO2 gas in a liquid phase environment, breaking through the energy barriers of traditional high-temperature calcination and mechanical activation, making the reaction conditions easy to achieve and control. And the mineralized cementitious material obtained by this preparation method is a non-cement-based material, and a large amount of fly ash gel is excited through mineralization-organic activation. In addition, the "gradient mineralization-oriented crystallization" process is pioneered. By controlling the temperature and the orderly addition of a silicon-aluminum activator, a mineralization promoter, and a crystal nucleus inducer, the ionic concentration and temperature field of the mineralization system are regulated in stages, guiding the dissociation of fly ash and obtaining intermediates (i.e., silicate-aluminate ions) through introducing CO2 gas, a silicon-aluminum activator, and a mineralization promoter, and generating a mineralized cementitious material including highly active C-S-H gel and ettringite crystals with a calcium source substance according to a preset crystallization path.

[0057] In the embodiments of the present application, by constructing a dynamic mineralization environment with the synergistic action of multiple components (i.e., a silicon-aluminum activator, a mineralization promoter, and a crystal nucleus inducer), the room-temperature and high-efficiency depolymerization of silicon-aluminum components in fly ash and the orderly assembly of hydration products are realized.

[0058] Compared with the prior art, in the embodiments of the present application, the direct mineralization and cementitious conversion of fly ash by introducing CO2 gas in a liquid phase environment is realized for the first time, avoiding the high energy consumption defect of the traditional process, and the energy consumption during the generation process is reduced by at least 60%; in addition, by precisely regulating the mineralization and cementitious reaction paths, the proportion of C-S-H gel in the mineralized cementitious material is relatively high, and it presents a unique nano-sheet interlocking structure.

[0059] In the embodiments of the present application, a mineralized cementitious material is also provided, which is prepared by using the preparation method of the mineralized cementitious material.

[0060] The following shows through multiple examples and comparative examples in Table 1 that the mineralized cementitious material prepared by the preparation method of the mineralized cementitious material in the embodiments of the present application has good performance. After adding water with a water-cement ratio of 0.4 to the gel material to form a hardened paste, the 28-day compressive strength is measured. The mineralization time in Table 1 is the time of mineralization treatment. The test materials used in the following examples are all obtained from conventional stores and other channels without special instructions. For the quantitative tests in the following examples, three repeated experiments are set, and the data are the average or average ± standard deviation of the three repeated experiments.

[0061] Table 1

[0062]

[0063]

[0064] Compare the above examples and comparative examples:

[0065] Comparing Example 1 and Example 2, it shows that increasing the content of the composite alkaline solution can improve the strength of the mineralized cementitious material;

[0066] Comparing Example 1 and Example 3, it shows that increasing the CO2 concentration in the mixed gas can improve the strength of the gel material;

[0067] Comparing Example 4 and Comparative Example 1, it shows that through mineralization and adding calcium source precursors, mineralization promoters and crystal nucleus inducing agents can greatly improve the strength of the mineralized cementitious material;

[0068] Comparing Example 4 and Comparative Example 2, it shows that adding a silicon-aluminum activator can greatly improve the strength of the mineralized cementitious material;

[0069] Comparing Example 4 and Comparative Example 3, it shows that adding a calcium source precursor can greatly improve the strength of the mineralized cementitious material;

[0070] Comparing Example 4 and Comparative Example 4, it shows that adding a mineralization promoter can greatly improve the strength of the mineralized cementitious material.

[0071] In summary, the present invention provides a mineralized cementitious material and a preparation method thereof. In the preparation method, a composite alkaline solution with a specific pH value is used as the mineralized liquid phase medium, combined with a silicon-aluminum activator, a mineralization promoter, and a crystal nucleus inducer. CO2 gas is introduced into the liquid phase environment to directly trigger the depolymerization reaction of silicon-oxygen bonds and aluminum-oxygen bonds on the surface of fly ash particles, making the reaction conditions easy to achieve and control. Moreover, the mineralized cementitious material obtained by this preparation method is a non-cement-based material, and a large amount of fly ash gel is achieved through mineralization-organic activation excitation. In addition, the "gradient mineralization-oriented crystallization" process is pioneered. By regulating the ion concentration and temperature field of the mineralization system in stages, the dissociation of fly ash is guided, and the intermediate obtained by introducing CO2 gas, adding a silicon-aluminum activator and a mineralization promoter, and the calcium source material generate a mineralized cementitious material including high-activity C-S-H gel and ettringite crystals according to the preset crystallization path.

[0072] It is easy for those skilled in the art to understand that, on the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed. The above is only the preferred embodiment of the present application, and it is not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application. The above is only the preferred implementation manner of the present application. It should be pointed out that for those of ordinary skill in the art in the technical field, without departing from the technical principle of the present application, several improvements and modifications can still be made, and these improvements and modifications should also be regarded as the protection scope of the present application.

Claims

1. A preparation method of a mineralized cementitious material, characterized in that, Comprising: Mix fly ash and a composite alkaline solution to obtain a mixed solution; wherein, the composite alkaline solution is an alkaline solution obtained by treating red mud with phosphoric acid and NaOH solid, including NaAlO2, [[Al(PO4)2]] 3- and having a pH of 12.5; After adding a silicon-aluminum activator to the mixture, a mixed gas is introduced and mineralization treatment is carried out at 20 - 60 °C for 1 - 3 h, wherein the mixed gas contains CO2 gas; the silicon-aluminum activator is a modified chitosan-γ-cyclodextrin derivative; Add a calcium source precursor, a mineralization promoter, and a crystal nucleus inducer to the material obtained after mineralization, and regulate the pH within the range of 10.5 - 12.5 to achieve the staged advancement of the mineralization treatment; among them, the mineralization promoter is Ca 1.5 Si(OH)6·2H2O modified by γ-mercaptopropyltrimethoxysilane; the crystal nucleus inducer is Ca6[Al(OH)6]2(SO4)3·26H2O; After adjusting the pH, mineralized cementitious material is obtained through normal temperature drying and micronization treatment.

2. The method according to claim 1, wherein The preparation steps of the composite alkaline solution include: The red mud is ground to 200 meshes, mixed with 20% phosphoric acid solution at a liquid-solid ratio of 5:1, and stirred and reacted at 80 °C for 2 hours; Centrifuge the solution obtained from the reaction to obtain an acidic filtrate containing Al 3+ ; Slowly add solid NaOH to the acidic filtrate containing Al 3+ to adjust the pH to 12.5 to form a composite alkaline solution.

3. The method according to claim 1, characterized in that, The preparation steps of the silicon-aluminum activator include: Chitosan is dissolved in an acetic acid solution to form a chitosan solution; γ-cyclodextrin is dissolved in water to make a γ-cyclodextrin solution; The chitosan solution is stirred at 60 °C for 20 min; wherein, during the stirring process, the γ-cyclodextrin solution is slowly added dropwise to the chitosan solution, and glutaraldehyde is added after adding the γ-cyclodextrin solution; The pH value of the stirred solution is adjusted to 10 - 12 to precipitate the product, and the product is filtered, washed and dried to obtain a γ-cyclodextrin modified chitosan derivative.

4. The method according to claim 1, characterized in that, The calcium source precursor includes at least one of mineral powder, steel slag and carbide slag.

5. The method according to claim 1, characterized in that, The preparation method of the mineralization promoter includes: After adding γ-mercaptopropyltrimethoxysilane to Ca 1.5 Si(OH)6·2H2O powder and drying it at 45 °C for 2 hours, Ca 1.5 Si(OH)6·2H2O modified with γ-mercaptopropyltrimethoxysilane is obtained.

6. The method according to claim 1, characterized in that The preparation method of the crystal nucleus inducer includes: Water is added to hemihydrate gypsum powder and nano-calcium aluminate crystal seeds with a mass ratio of 10:1 and stirred to form a slurry; The slurry is cured at 120 °C in an autoclave at 0.5 MPa for 2 hours to fully combine the hemihydrate gypsum powder and the nano-calcium aluminate crystal seeds to obtain Ca6[Al(OH)6]2(SO4)3·26H2O.

7. The method according to claim 1, characterized in that, The mass ratio of the fly ash to the composite alkaline solution is 1:3 - 5.

8. The method according to claim 1, wherein The concentration of CO2 gas in the mixed gas is 30%.

9. A mineralized cementitious material, characterized in that, Prepared by using the preparation method of the mineralized cementitious material according to any one of claims 1 - 8.

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