Mineralized cementing material and preparation method thereof

Abstract

According to the preparation method, a composite alkaline solution with a specific pH value is adopted as a mineralization liquid phase medium, a silicon-aluminum activating agent, a mineralization accelerant and a crystal nucleus inducer are combined, CO2 gas is introduced into a liquid phase environment to directly trigger a depolymerization reaction of silicon-oxygen bonds and aluminum-oxygen bonds on the surfaces of fly ash particles, and the mineralization cementing material is obtained. The reaction conditions are easy to realize and control, the mineralized cementing material obtained by the preparation method is a non-cement-based material, and large-dosage fly ash gel is realized through mineralization-organic activation excitation. In addition, a gradient mineralization-directional crystallization process is initiated, the ion concentration and the temperature field of a mineralization system are regulated and controlled by stages, the coal ash is guided to dissociate, CO2 gas is introduced, a silicon-aluminum activating agent and a mineralization accelerant are added, and an intermediate is obtained; and generating the mineralized gelling material containing high-activity C-S-H gel and ettringite crystals from the calcium source substance according to a preset crystallization path.

Description

Technical Field

[0001] The 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 amounts of it will occupy land and pollute the environment. Using it in cementitious materials can effectively reduce waste and reduce environmental burden. However, in the related art, cement is required to prepare cementitious materials using fly ash, and there are problems such as low fly ash content and low early strength in the preparation of cementitious materials. Summary of the invention

[0003] The present invention provides a mineralized gelling 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, and a silicon-aluminum activator, a mineralization promoter and a crystal nucleus inducer are combined to introduce CO into a liquid phase environment. 2 The gas directly triggers the depolymerization reaction of the silicon-oxygen bond and aluminum-oxygen bond on the surface of the fly ash particles, making the reaction conditions easy to achieve and control. 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. In addition, the "gradient mineralization-directional crystallization" process is first created. By regulating the ion concentration and temperature field of the mineralization system in stages, the fly ash is guided to dissociate and the CO is introduced. 2 The gas, the intermediate obtained by adding the silica-alumina activator and the mineralization promoter, and the calcium source material generate a mineralized gelling material including a high-activity CSH gel and ettringite crystals 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 solids, and includes NaAlO 2 、[Al(PO 4 ) 2 ] 3- alkaline solution;

[0006] After adding the 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 hours, wherein the mixed gas contains CO 2 gas; the silicon-aluminum activator is a modified chitosan-γ-cyclodextrin derivative;

[0007] A calcium source precursor, a mineralization promoter and a crystal nucleus inducer are added to the material obtained after mineralization, and the pH is adjusted within the range of 10.5-12.5 to achieve the staged advancement of the mineralization treatment; wherein the mineralization promoter is Ca modified by γ-mercaptopropyltrimethoxysilane. 1.5 Si(OH) 6 ·2H 2 O; the crystal nucleus inducing agent is Ca 6 [Al(OH) 6 ] 2 (SO 4 ) 3 ·26H 2 O;

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

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

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

[0011] The solution obtained by the reaction was centrifuged to obtain the Al 3+ Acidic filtrate;

[0012] To the Al-containing 3+ Solid NaOH was slowly added to the acidic filtrate to adjust the pH to 12.5 to generate a composite alkaline solution.

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

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

[0015] Dissolving γ-cyclodextrin in water to prepare a γ-cyclodextrin solution;

[0016] 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 the γ-cyclodextrin solution is added dropwise;

[0017] The pH value of the stirred solution is adjusted to 10-12 to precipitate a product, and the product is filtered, washed and dried to obtain a gamma-cyclodextrin modified chitosan derivative.

[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 method for preparing the mineralization promoter comprises:

[0020] In Ca 1.5 Si(OH) 6 ·2H 2 After adding γ-mercaptopropyltrimethoxysilane to the O powder, the mixture was dried at 45 °C for 2 hours to obtain CaO powder modified with γ-mercaptopropyltrimethoxysilane. 1.5 Si(OH) 6 ·2H 2 O.

[0021] In some embodiments, the method for preparing the crystal nucleation inducing agent comprises:

[0022] Add water to hemihydrate gypsum powder and nano-ettringite seed crystals in a mass ratio of 10:1 and stir to form a slurry;

[0023] The slurry is cured in a 0.5 MPa autoclave at 120° C. for 2 hours to allow the semi-hydrated gypsum powder to fully combine with the nano-ettringite seed crystals to obtain Ca 6 [Al(OH) 6 ] 2 (SO 4 ) 3 ·26H 2 O.

[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 mixed gas contains CO 2 The concentration of the gas is 30%.

[0027] The 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 gelling 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, a silicon-aluminum activator, a mineralization promoter and a crystal nucleus inducer are combined, and CO is introduced into a liquid phase environment. 2 The gas directly triggers the depolymerization reaction of the silicon-oxygen bond and aluminum-oxygen bond on the surface of the fly ash particles, making the reaction conditions easy to achieve and control. 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. In addition, the "gradient mineralization-directional crystallization" process is first created. By regulating the ion concentration and temperature field of the mineralization system in stages, the fly ash is guided to dissociate and the CO is introduced. 2The gas, the intermediate obtained by adding the silica-alumina activator and the mineralization promoter, and the calcium source material generate a mineralized gelling material including a high-activity CSH gel and ettringite 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 the present application is described in detail below through specific implementation methods.

[0031] In order to solve the above technical problems, the present invention provides a mineralized gelling 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, and a silicon-aluminum activator, a mineralization promoter and a crystal nucleus inducer are combined to introduce CO into a liquid phase environment. 2 The gas directly triggers the depolymerization reaction of the silicon-oxygen bond and aluminum-oxygen bond on the surface of the fly ash particles, making the reaction conditions easy to achieve and control. 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. In addition, the "gradient mineralization-directional crystallization" process is first created. By regulating the ion concentration and temperature field of the mineralization system in stages, the fly ash is guided to dissociate and the CO is introduced. 2 The gas, the intermediate obtained by adding the silica-alumina activator and the mineralization promoter, and the calcium source material generate a mineralized gelling material including a high-activity CSH gel and ettringite crystals according to a preset crystallization path.

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

[0033] S100, mixing fly ash and a composite alkaline solution to obtain a mixed solution; wherein the composite alkaline solution is obtained by treating red mud with phosphoric acid and NaOH solids, and includes NaAlO 2 、[Al(PO 4 ) 2 ] 3- of alkaline solution.

[0034] In the embodiment of the present application, the active aluminum source in the red mud is used to react with phosphate to form [Al(PO 4 ) 2 ] 3- Coordinating ions promote the disaggregation of glass in fly ash.

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

[0036] In this embodiment, red mud and phosphoric acid solution are mixed and stirred to react, so that the Al in the red mud is 2 O 3 Partially dissolved as Al 3+ At the same time, the sodium salts in red mud (such as Na 2 O) into free Na + After the reaction is completed, the obtained solution is centrifuged to obtain Al 3+ Then slowly add solid NaOH to the acidic filtrate to adjust the pH to 12.5. 3+ With PO 4 3- , excess OH- complexation generates NaAlO 2 and [Al(PO 4 ) 2 ] 3- of alkaline solution.

[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 the silicon-aluminum activator to the mixed solution, introducing the mixed gas and performing mineralization treatment at 20-60° C. for 1-3 hours, wherein the mixed gas contains CO 2 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 the amino and hydroxyl groups in the molecular structure, and is selectively adsorbed on the surface of fly ash particles, thereby weakening the Si-O-Al bond binding energy in the fly ash.

[0040] In some embodiments, the preparation steps of the silica-alumina activator include: dissolving chitosan in acetic acid solution to form a chitosan solution; dissolving γ-cyclodextrin in water to prepare a γ-cyclodextrin solution; stirring the chitosan solution at 60°C for 20 minutes; wherein, during the stirring process, the γ-cyclodextrin solution is slowly added dropwise to the chitosan solution, and glutaraldehyde is added after the γ-cyclodextrin solution is added dropwise; 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.

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

[0042] In some embodiments, the mixed gas contains CO 2 The concentration of the gas is 15%-30%. In other embodiments, the CO 2 The concentration of the gas is 30%. In this embodiment, the mixed gas includes CO 2 Gas, air or N 2 .

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

[0044] S300, adding a calcium source precursor, a mineralization promoter and a crystal nucleus inducer to the material obtained after mineralization, and adjusting the pH in the range of 10.5-12.5 to achieve the staged advancement of the mineralization treatment; wherein the mineralization promoter is Ca modified by γ-mercaptopropyltrimethoxysilane 1.5 Si(OH) 6 ·2H 2 O; the crystal nucleus inducing agent is Ca 6 [Al(OH) 6 ] 2 (SO 4 ) 3 ·26H 2 O.

[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 present embodiment, the mineralization promoter is Ca2+ modified by γ-mercaptopropyltrimethoxysilane. 1.5 Si(OH) 6 ·2H 2 O, the mineralization promoter can act as a "seed crystal" to reduce the nucleation barrier of the hydration product (i.e., hydrated calcium aluminosilicate) obtained by the depolymerization of the glass in the fly ash. At the same time, the thiol group forms a dynamic coordination bond with the calcium source precursor and the calcium ions in the fly ash to regulate the kinetics of ion release.

[0048] In some embodiments, the method for preparing the mineralization promoter comprises: 1.5 Si(OH) 6 ·2H 2 After adding γ-mercaptopropyltrimethoxysilane to the O powder, the mixture was dried at 45 °C for 2 hours to obtain CaO powder modified with γ-mercaptopropyltrimethoxysilane. 1.5 Si(OH) 6 ·2H 2 O.

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

[0050] In the present embodiment, the nucleus inducing agent is Ca 6 [Al(OH) 6 ] 2 (SO 4 ) 3 ·26H 2 O, the nucleation inducer can serve as a heterogeneous nucleation site for CSH gels, and its surface oxygen vacancies can capture Ca 2+ (The Ca 2+ Mainly the calcium ions in the calcium source precursor) form local high concentration areas, promoting mineralization and gelation reactions.

[0051] In some embodiments, the preparation method of the crystal nucleus inducing agent comprises: adding water to hemihydrate gypsum powder (i.e., hemihydrate calcium sulfate) and nano-ettringite seeds in a mass ratio of 10:1 and stirring to form a slurry; curing the slurry in a 0.5MPa autoclave at 120°C for 2 hours to fully combine the hemihydrate gypsum powder and the nano-ettringite seeds to obtain Ca 6 [Al(OH) 6 ] 2 (SO 4 ) 3 ·26H 2 O.

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

[0053] S400, after adjusting the pH, the mineralized gelling material is obtained by drying at room temperature and micronizing.

[0054] In the embodiment of the present application, after adjusting the pH to achieve the staged advancement of the mineralization treatment, the mineralized cementitious material prepared based on liquid phase direct mineralization of fly ash can be obtained by room 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 preparation method of the mineralized gelling material in the embodiment of the present application, a composite alkaline solution with a specific pH value is used as a mineralized liquid phase medium, combined with a silicon-aluminum activator, a mineralization promoter and a crystal nucleus inducer, and CO is introduced into the liquid phase environment. 2 The gas directly triggers the depolymerization reaction of the silicon-oxygen bonds and aluminum-oxygen bonds on the surface of the fly ash particles, 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 achieved through mineralization-organic activation. In addition, the "gradient mineralization-directional crystallization" process is the first to be created. By controlling the temperature and the orderly addition of silicon-aluminum activators, mineralization promoters and crystal nucleus inducers, the ion concentration and temperature field of the mineralization system are controlled in stages, guiding the dissociation of fly ash and introducing CO 2 The intermediates obtained from the gas, the silica-alumina activator and the mineralization promoter (i.e., aluminosilicate ions), and the calcium source material form a mineralized gelling material including a highly active CSH gel and ettringite crystals according to a preset crystallization path.

[0057] In the embodiments of the present application, a dynamic mineralization environment with synergistic effects of multiple components (i.e., a silicon-aluminum activator, a mineralization promoter, and a crystal nucleus inducer) is constructed to achieve efficient depolymerization of silicon-aluminum components in fly ash at room temperature and orderly assembly of hydration products.

[0058] Compared with the prior art, the present invention realizes the introduction of CO into the fly ash in a liquid environment for the first time. 2 The direct mineralization and gelation conversion of gas avoids the high energy consumption defect of traditional processes and reduces the energy consumption of the production process by at least 60%. In addition, by precisely controlling the mineralization and gelation reaction paths, the CSH gel accounts for a high proportion in the mineralized gelling material and presents a unique nanosheet interlocking structure.

[0059] In an embodiment of the present application, a mineralized gelling material is also provided, which is prepared by the preparation method of the mineralized gelling material.

[0060] The following multiple examples and comparative examples in Table 1 show that the mineralized gelling material prepared by the preparation method of the mineralized gelling material in the examples of the present application has good performance. After the gelling material is added to water with a water-cement ratio of 0.4 to form a hardened slurry, the 28-day compressive strength is measured. The mineralization time in Table 1 is the time of the mineralization treatment. The test materials used in the following examples, unless otherwise specified, are purchased from conventional stores and other channels. The quantitative tests in the following examples are all set up for three repeated experiments, and the data are the average values ​​or average values ​​± standard deviations of the three repeated experiments.

[0061] Table 1

[0062]

[0063]

[0064] Compare the above embodiments and comparative examples:

[0065] Comparison of Example 1 and Example 2 shows that increasing the content of the composite alkaline solution can increase the strength of the mineralized gelling material;

[0066] Comparing Example 1 with Example 3, it is shown that the CO in the mixed gas is increased 2 Concentration can increase the strength of gel materials;

[0067] Comparison of Example 4 and Comparative Example 1 shows that the strength of the mineralized cementitious material can be greatly improved by mineralization and the addition of a calcium source precursor, a mineralization accelerator and a crystal nucleus inducer;

[0068] Comparison of Example 4 and Comparative Example 2 shows that the addition of silicon-aluminum activator can significantly improve the strength of mineralized cementitious materials;

[0069] Comparison of Example 4 and Comparative Example 3 shows that adding a calcium source precursor can significantly increase the strength of the mineralized cementitious material;

[0070] Comparison of Example 4 and Comparative Example 4 shows that adding a mineralization accelerator can significantly improve the strength of the mineralized cementitious material.

[0071] In summary, the present invention provides a mineralized gelling 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, combined with a silicon-aluminum activator, a mineralization promoter and a crystal nucleus inducer, and CO is introduced into a liquid phase environment. 2The gas directly triggers the depolymerization reaction of the silicon-oxygen bond and aluminum-oxygen bond on the surface of the fly ash particles, making the reaction conditions easy to achieve and control. 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. In addition, the "gradient mineralization-directional crystallization" process is first created. By regulating the ion concentration and temperature field of the mineralization system in stages, the fly ash is guided to dissociate and the CO is introduced. 2 The gas, the intermediate obtained by adding the silica-alumina activator and the mineralization promoter, and the calcium source material generate a mineralized gelling material including a high-activity CSH gel and ettringite crystals according to a preset crystallization path.

[0072] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed. The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application. The above are only preferred implementation methods of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present application, and these improvements and variations should also be regarded as the protection scope of the present application.

Claims

1. A method for preparing a mineralized gelling material, characterized in that: include: 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 solids and includes NaAlO2, [Al(PO4)2] 3- alkaline solution; After adding the silicon-aluminum activator to the mixed solution, a mixed gas is introduced and 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; A calcium source precursor, a mineralization promoter and a crystal nucleus inducer are added to the material obtained after mineralization, and the pH is adjusted within the range of 10.5-12.5 to achieve the staged 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; After adjusting the pH, the mineralized gelling material is obtained through room temperature drying and micronization treatment.

2. The method according to claim 1, characterized in that The preparation steps of the composite alkaline solution include: Grind the red mud to 200 mesh, mix it with 20% phosphoric acid solution at a liquid-to-solid ratio of 5:1, and stir and react at 80°C for 2 hours; The solution obtained by the reaction was centrifuged to obtain the Al 3+ Acidic filtrate; To the Al-containing 3+ Solid NaOH was slowly added to the acidic filtrate to adjust the pH to 12.5 to generate a composite alkaline solution.

3. The method according to claim 1, characterized in that 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 prepare 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 the γ-cyclodextrin solution is added dropwise; The pH value of the stirred solution is adjusted to 10-12 to precipitate a 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 accelerator comprises: In Ca 1.5 After adding γ-mercaptopropyltrimethoxysilane to Si(OH)6·2H2O powder, the powder was dried at 45°C for 2 hours to obtain Ca2+ modified with γ-mercaptopropyltrimethoxysilane. 1.5 Si(OH)6·2H2O.

6. The method according to claim 1, characterized in that The preparation method of the crystal nucleus inducing agent comprises: Add water to hemihydrate gypsum powder and nano-ettringite seed crystals in a mass ratio of 10:1 and stir to form a slurry; The slurry is cured in a 0.5 MPa autoclave at 120° C. for 2 hours to allow the semi-hydrated gypsum powder to fully combine with the nano-ettringite seed crystals to obtain Ca6[Al(OH)6]2(SO4)3·26H2O.

7. 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.

8. 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.

9. The method according to claim 1, characterized in that: The concentration of CO2 gas in the mixed gas is 30%.

10. A mineralized cementitious material, characterized in that: The mineralized gelling material is prepared by the preparation method of any one of claims 1 to 9.

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