Geopolymer as well as preparation method and application thereof

Abstract

The invention relates to the technical field of solid waste recycling and building materials, and particularly discloses a geopolymer and a preparation method and application thereof.Iron-rich tailings and metakaolin are mixed according to the mass ratio of 0.25-1.5: 1, an alkali activator solution is added, and the geopolymer is obtained after stirring forming and curing. When the prepared geopolymer is soaked in seawater, Fe < 2 + > / Fe < 3 + > in the geopolymer is converted into an alpha-FeOOH passivation layer to block Cl <-> permeation and refine pores, so that the compressive strength of the geopolymer reaches 76.2 MPa, the porosity is only 10.57%, and seawater erosion can be effectively resisted.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste resource utilization and building materials, and in particular to a geopolymer and a preparation method and application thereof. Background Art

[0002] Iron tailings, the primary solid waste generated during iron ore mining and processing, are stockpiled in enormous quantities, not only occupying significant land resources but also posing a potential threat to the ecological environment. Iron tailings are primarily composed of silicate minerals, oxides, and a small amount of metal sulfides, rich in useful components such as SiO2, Al2O3, and Fe2O3. However, due to their complex composition, uneven particle size, and low activity, their direct utilization faces numerous challenges. Traditional treatment methods often involve stockpiling or landfilling, which not only wastes resources but also can cause environmental problems such as soil and water pollution.

[0003] As a primary building material, concrete's corrosion resistance directly impacts the service life of marine engineering structures. Currently, marine concrete primarily utilizes Portland cement-based binders. Seawater erosion of marine concrete primarily results from the intrusion of various ions in seawater, which react with concrete components, causing varying degrees of structural damage. This results in poor seawater corrosion resistance for Portland cement concrete. Summary of the Invention

[0004] To address the problems of iron tailings accumulation and poor seawater corrosion resistance of marine concrete, the present invention provides a geopolymer, its preparation method, and application. The geopolymer prepared by the present invention has a compressive strength of 76.2 MPa and a porosity of only 10.57%, making it effectively resistant to seawater erosion.

[0005] The present invention provides a geopolymer, characterized in that the geopolymer is prepared by mixing iron-rich tailings, metakaolin and an alkali activator and then undergoing a curing step; The alkaline activator is prepared by mixing sodium hydroxide and water glass; The mass ratio of the iron-rich tailings to the metakaolin is 0.25-1.5:1; The solid-liquid ratio of the total mass of the iron-rich tailings and metakaolin to the alkaline activator solution is 0.6-1.2:1; The curing comprises standing curing at a temperature of 60° C. to 90° C. and a humidity of 90% to 100% for 1 hour to 7 hours, standing curing at room temperature for 4 days to 7 days, and immersing curing in seawater for 28 days to 360 days.

[0006] The geopolymer prepared by the present invention is immersed in seawater, and the Fe 2+ / Fe 3+ Converted into α-FeOOH passivation layer to block Cl -Penetration and pore refinement make the geopolymer compressive strength reach 76.2 MPa and the porosity only 10.57%, which can effectively resist seawater erosion.

[0007] The present invention also provides a method for preparing the above-mentioned geopolymer, which specifically comprises the following steps: After the iron-rich tailings and metakaolin are evenly mixed, an alkaline activator solution is poured in and mixed evenly to form a geopolymer slurry, which is then formed and cured to obtain a geopolymer; The alkaline activator is prepared by mixing sodium hydroxide and water glass, wherein the mass ratio of sodium hydroxide to water glass is 1:5; The mass ratio of the iron-rich tailings to the metakaolin is 0.25-1.5:1; The solid-liquid ratio of the total mass of the iron-rich tailings and metakaolin to the alkaline activator solution is 0.6-1.2:1; The iron-rich tailings and metakaolin are mixed under the conditions of stirring at 300 r / min to 1000 r / min for 1 min to 30 min; The curing comprises standing curing at a temperature of 60° C. to 90° C. and a humidity of 90% to 100% for 1 hour to 7 hours, standing curing at room temperature for 4 days to 7 days, and immersing curing in seawater for 28 days to 360 days.

[0008] Furthermore, the mass ratio of the iron-rich tailings to metakaolin is 0.7:1.

[0009] Furthermore, the liquid-to-solid ratio of the total mass of the iron-rich tailings and metakaolin to the alkaline activator solution is 0.8:1.

[0010] Furthermore, the curing conditions are: curing at 80°C and 95% humidity for 6 hours, curing at room temperature for 4 days, and curing in seawater for 28 days.

[0011] Furthermore, the iron-rich tailings and metakaolin are mixed under the condition of stirring at 600 r / min for 10 min.

[0012] The present invention also provides an application of the geopolymer in resisting seawater erosion.

[0013] Compared with the prior art, the present invention has the following beneficial effects: When the geopolymer prepared by the present invention is exposed to seawater environment, the Fe 2+ / Fe 3+ It will react with oxygen and water molecules in seawater to produce complex chemical reactions, resulting in Fe 2+ / Fe 3+ Gradually transforms into α-FeOOH, forming a dense passivation layer, which can not only effectively block the Cl in seawater -The corrosive ions can further penetrate into the material and reduce the direct contact area between the material surface and seawater, thereby reducing the corrosion rate.

[0014] The fayalite in the geopolymer prepared by the present invention is converted into Na2SiO3 and Fe(OH)2 in a seawater environment, making the pore structure of the geopolymer finer and more uniform, which helps to reduce the penetration channel of seawater inside the material and reduce Cl - The small pores can also increase the surface area of ​​the material, provide more reaction sites, and help form more α-FeOOH passivation layers, further enhancing the corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 XRD spectra of metakaolin and iron-rich tailings.

[0017] Figure 2 The SEM images of the geopolymers prepared in Comparative Example 1 and Example 2 are shown; In the figure, A is the SEM image of the geopolymer prepared in Comparative Example 1; B is the SEM image of the geopolymer prepared in Example 2.

[0018] Figure 3 Raman intensity analysis graphs of geopolymers prepared for Comparative Example 1 and Example 2.

[0019] Figure 4 Microscopic morphology and EDS spectra of Cl of geopolymers prepared for Comparative Example 1 and Example 2; In the figure, A is the microscopic morphology of the geopolymer prepared in Comparative Example 1; B is the microscopic morphology of the geopolymer prepared in Example 2; C is the EDS spectrum of geopolymer Cl prepared in Comparative Example 1; D is the EDS spectrum of geopolymer Cl prepared in Example 2. DETAILED DESCRIPTION

[0020] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited by the specific embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. The experimental methods described in the embodiments of the present invention are conventional methods unless otherwise specified, and the materials, reagents, etc. used in the following embodiments can be obtained from commercial sources unless otherwise specified.

[0021] Example 1: A geopolymer, a preparation method and an application thereof.

[0022] Prepare an alkaline activator solution 6 hours in advance by adding 5 parts water glass and 1 part flaked sodium hydroxide to obtain an alkaline activator solution. The modulus of the alkaline activator solution is 1.2. The mass ratio of the components in the water glass is: 8.35% sodium oxide, 26.54% silicon oxide, and 65.11% water. The purity of the sodium hydroxide is greater than 96%.

[0023] 30 parts of 200 mesh iron-rich tailings and 120 parts of metakaolin were mixed, and 135 parts of alkaline activator solution were added, with a liquid-to-solid ratio of 0.9. The mixture was stirred at a speed of 300 r / min for 30 minutes to make the [SiO4] tetrahedron and [AlO4] tetrahedron in the iron-rich tailings and metakaolin dissolved in the alkaline activator to form [Si(OH)4] and [Al(OH)4] - Monomers, [Si(OH)4] and [Al(OH)4] - Based on the principle of chemical equilibrium, monomers diffuse and penetrate into the solid particles and polymerize to form M X [-(Si-O-) z -Al-O-] n · w The H2O gel phase is the geopolymer slurry. The geopolymer slurry is injected into a 50 mm × 50 mm × 50 mm mold and then cured at 80 ° C and 95% humidity for 6 h, and then continued to cure at room temperature for 7 days. M X [-(Si-O-) z -Al-O-] n · w The H2O gel phase is polymerized to remove water, and a geopolymer is obtained after condensation and solidification. The water-to-binder ratio of the geopolymer is 0.5. Finally, the obtained geopolymer is placed in seawater for curing for 28 days.

[0024] Example 2 A geopolymer, a preparation method and an application thereof.

[0025] Prepare the alkaline activator solution 6 h in advance: the same as in Example 1.

[0026] A geopolymer slurry was prepared by mixing 72 parts of 200-mesh iron-rich tailings and 108 parts of metakaolin. 144 parts of an alkaline activator solution were added, achieving a liquid-to-solid ratio of 0.8. The mixture was thoroughly stirred at 600 r / min for 10 minutes until uniformly mixed. The slurry was then poured into a 50 mm × 50 mm × 50 mm mold and cured at 80°C and 95% humidity for 6 hours. The geopolymer was then cured at room temperature for another 4 days to produce the geopolymer. Finally, the slurry was cured in seawater for 28 days.

[0027] Example 3 A geopolymer, a preparation method and an application thereof.

[0028] Prepare the alkaline activator solution 6 h in advance: the same as in Example 1.

[0029] A geopolymer slurry was prepared by mixing 120 parts of 200-mesh iron-rich tailings and 80 parts of metakaolin. 120 parts of an alkaline activator solution were added, resulting in a liquid-to-solid ratio of 0.6. The mixture was thoroughly stirred at 1000 r / min for 1 minute until uniformly mixed. The slurry was then poured into a 50 mm × 50 mm × 50 mm mold and cured at 80°C and 95% humidity for 6 hours. The geopolymer was then cured at room temperature for 7 days to produce the geopolymer. Finally, the slurry was cured in seawater for 28 days.

[0030] Comparative Example 1 Comparative Example 1 provides a geopolymer and a preparation method thereof, which specifically comprises the following steps: The steps for preparing the alkaline activator solution are the same as those in Example 1.

[0031] A geopolymer slurry was prepared by adding 180 parts of an alkaline activator solution to 150 parts of metakaolin at a liquid-to-solid ratio of 1.2. The mixture was thoroughly stirred at 300 r / min for 3 minutes to achieve a uniform mix. The slurry was then poured into a 50 mm × 50 mm × 50 mm mold and cured at 80°C and 95% humidity for 6 hours. The slurry was then cured at room temperature for 7 days to produce a pure metakaolin-based geopolymer. Finally, the slurry was cured in seawater for 28 days.

[0032] Comparative Example 2 Comparative Example 2 provides a geopolymer and a preparation method thereof, which specifically comprises the following steps: The steps for preparing the alkaline activator solution are the same as those in Example 1.

[0033] A geopolymer slurry was prepared by mixing 72 parts of 200-mesh iron-rich tailings and 108 parts of metakaolin. 216 parts of an alkaline activator solution were added, achieving a liquid-to-solid ratio of 1.2. The mixture was thoroughly stirred at 600 r / min for 10 minutes until uniformly mixed. The slurry was then poured into a 50 mm × 50 mm × 50 mm mold and cured at 80°C and 95% humidity for 6 hours. The geopolymer was then cured at room temperature for 7 days to produce the geopolymer. Finally, the slurry was cured in seawater for 28 days.

[0034] Comparative Example 3 Comparative Example 3 provides a geopolymer and a preparation method thereof, which specifically comprises the following steps: The steps for preparing the alkaline activator solution are the same as those in Example 1.

[0035] A geopolymer slurry was prepared by mixing 72 parts granite and 108 parts metakaolin, adding 150 parts of an alkaline activator solution at a liquid-to-solid ratio of 0.8. The mixture was stirred thoroughly at 500 r / min for 12 minutes until uniformly mixed. The slurry was then poured into a 50 mm × 50 mm × 50 mm mold and cured at 80°C and 95% humidity for 6 hours. The geopolymer was then cured at room temperature for 7 days to produce the geopolymer. Finally, the geopolymer was cured in seawater for 28 days.

[0036] Comparative Example 4 Comparative Example 4 provides a geopolymer and a preparation method thereof, which specifically comprises the following steps: The steps for preparing the alkaline activator solution are the same as those in Example 1.

[0037] A geopolymer slurry was prepared by mixing 72 parts of vanadium tailings and 108 parts of metakaolin with 150 parts of an alkaline activator solution at a liquid-to-solid ratio of 0.8. The mixture was stirred thoroughly at 400 r / min for 15 minutes until uniformly mixed. The slurry was then poured into a 50 mm × 50 mm × 50 mm mold and cured at 60°C and 90% humidity for 1 hour. The geopolymer was then cured at room temperature for 7 days to produce the geopolymer. Finally, the geopolymer was cured in seawater for 360 days.

[0038] Comparative Example 5 Comparative Example 5 provides a geopolymer and a preparation method thereof, which specifically comprises the following steps: The steps for preparing the alkaline activator solution are the same as those in Example 1.

[0039] A geopolymer slurry was prepared by mixing 72 parts red mud and 108 parts metakaolin, adding 150 parts alkaline activator solution at a liquid-to-solid ratio of 0.8. The mixture was stirred thoroughly at 800 r / min for 5 minutes until uniformly mixed. The geopolymer slurry was then poured into a 50 mm × 50 mm × 50 mm mold and cured at 90°C and 100% humidity for 7 hours. The geopolymer was then cured at room temperature for another 7 days to produce the geopolymer. Finally, the geopolymer was cured in seawater for 360 days.

[0040] Application research of geopolymer prepared by the present invention 1. Analysis of the main chemical composition of metakaolin and iron-rich tailings The material composition of the metakaolin and iron-rich tailings raw materials used was analyzed using X-ray diffractometer (XRD) and X-ray fluorescence spectrometer (XRF) to obtain the main chemical compositions of the metakaolin and iron-rich tailings.

[0041] The XRF analysis results (see Table 1) show that the phase composition of metakaolin is mainly amorphous, while the phase composition of iron-rich tailings is mainly crystalline minerals. Figure 1 ) shows that metakaolin contains only two kinds of minerals: anatase (TiO2) and quartz (SiO2); the crystalline phase of the iron-rich tailings is mainly composed of two substances: fayalite (Fe2SiO4) and magnetite (Magnetite, Fe3O4), of which Fe 2+ / Fe 3+ The components will undergo complex chemical reactions with oxygen and water molecules in seawater. These reactions lead to Fe 2+ / Fe 3+ Gradually transforms into α-FeOOH, forming a dense passivation layer, which can not only effectively block the Cl in seawater - The corrosive ions can further penetrate into the material and reduce the direct contact area between the material surface and seawater, thereby reducing the corrosion rate.

[0042] Table 1 Main chemical compositions of metakaolin and iron tailings (wt%) 2. Performance testing of different groups of geopolymers 1. Compressive strength test of different groups of geopolymers The compressive strength of the cured geopolymer product (50 mm × 50 mm × 50 mm) was tested using a universal material testing machine (maximum force range of 100 KN) with load control at a loading speed of 0.55 KN / min.

[0043] Table 2 Compressive strength of different groups of geopolymers The results (see Table 2) show that the compressive strength of the geopolymers of Examples 1-3 is significantly higher than that of the geopolymers of Comparative Examples 1-5, with the geopolymer of Example 3 having the highest compressive strength. Comparative Example 1 is a pure metakaolin geopolymer, while Comparative Examples 3-5 are granite, vanadium tailings, and red mud geopolymers, respectively. Comparison of the compressive strength of the geopolymers of Examples 1-3 with those of Comparative Examples 1 and 3-5 demonstrates that iron-rich tailings can improve the compressive strength of the geopolymers of the present invention. As the amount of iron-rich tailings added in Examples 1-3 increases, the compressive strength of the geopolymers of Examples 1-3 also increases, indicating that the compressive strength of the geopolymers of the present invention increases with increasing iron-rich tailings addition. The same amount of iron-rich tailings was added in Example 2 and Comparative Example 2, but different liquid-to-solid ratios resulted in the compressive strength of the geopolymer of Comparative Example 2 being significantly lower than that of the geopolymer of Example 2, indicating that differences in fluidity caused by different liquid-to-solid ratios can affect the compressive strength of the geopolymers.

[0044] 2. Fluidity test of different groups of geopolymers Four groups of geopolymers, Comparative Example 1 and Examples 1 to 3, which have higher compressive strength, were selected for fluidity testing.

[0045] Prepare a large, smooth, 500 mm × 500 mm glass plate and a standard truncated cone mold with a 36 mm top diameter, 60 mm bottom diameter, and 60 mm height. Place the glass plate on a level surface and clean both the plate and the cone mold with a damp cloth. Use a cement slurry mixer to slowly stir the four geopolymer mixtures for 120 seconds, pause for 15 seconds, and then rapidly stir for 120 seconds. Quickly pour the uniformly stirred geopolymer slurry into the cone mold and smooth the surface with a scraper.

[0046] Table 3 Fluidity test results of different groups of geopolymers Slowly lift the truncated cone mold vertically and start timing with a stopwatch. When the geopolymer slurry has been flowing on the glass plate for 30 seconds, use a ruler to measure the maximum diameter in two mutually perpendicular directions. The average of the two measurements is recorded as the geopolymer slurry fluidity test result. Perform this test twice for each group of neat geopolymer slurry, and the average of the two test results is recorded as the final fluidity result.

[0047] The fluidity test results are shown in Table 3. Fluidity can reflect the consistency of a material's performance. Because iron-rich tailings powder has a larger particle size than metakaolin, absorbs less water, and has lower activity than metakaolin, the fluidity of the geopolymer slurry increases with increasing iron-rich tailings addition. To avoid performance variations caused by the liquid-to-solid ratio, geopolymers with essentially identical fluidity (Example 2 and Comparative Example 1) were selected for subsequent performance testing to ensure consistent performance.

[0048] 3. Microstructure analysis of different groups of geopolymers The micromorphology of the geopolymer samples in Example 2 and Comparative Example 1 was observed using a scanning electron microscope. Figure 2 The results show that compared with Comparative Example 1, the geopolymer prepared in Example 2 has a denser structure, fewer cracks and smaller pores, with an average pore diameter of only 10.64 nm and a total porosity of only 10.57% (see Table 4), indicating that iron-rich tailings can improve the performance of geopolymers.

[0049] Table 4 Average pore size and porosity of different groups of geopolymers 4. Raman strength test of different groups of geopolymers To investigate the phase transformation of the iron-containing phase in geopolymers exposed to marine environments, Raman spectroscopy (Ranisha, UK) was employed using a 532 nm diode laser as the excitation source. The system configuration included a diffraction grating with 1800 lines / mm, which provided a spectral resolution of 3 cm. - ¹, each measurement was preceded by the use of a characteristic 520.7 cm - ¹Silicon Raman bands were used as internal standards to calibrate wavelengths. All spectra were acquired under optimized conditions: 20x objective magnification (numerical aperture 0.40), 50 μm entrance slit width, and 10 s integration time for each spectrum accumulation. The spectral window was from 100 cm - ¹~1200cm - ¹Systematic scanning with peak position repeatability of ±0.2 cm ensured by three-axis stage calibration and automated laser focus maintenance - ¹.

[0050] Test results (see Figure 3 ) showed that the pure metakaolin-based geopolymer of Comparative Example 1 had a -1 、397 cm -1 and 499 cm -1The signal peaks at are attributed to the bending vibration of SiO4 tetrahedron in quartz, the bending modes of Si-O-Al and Si-O-Si in metakaolin raw materials, and the Na + and Ca 2+ The ions will enter the pure metakaolin-based geopolymer network, destroying the stability of the Si-O-Al bond, accelerating the depolymerization of aluminosilicates, and causing the geopolymer to be eroded by seawater. The metakaolin-iron-rich tailings-based geopolymer of Example 2 showed different peaks, at 298 cm -1 and 386 cm -1 The signal at is attributed to Goethite (α-FeOOH), which is caused by Fe 2+ / Fe 3+ It reacts with seawater to form α-FeOOH, which has a needle-like or layered nanostructure and can be tightly packed to form a dense barrier, reducing pores and cracks and reducing Cl - The permeation channel, and the a-FeOOH layer can serve as a passivation film to effectively block CI - Penetration, thereby reducing the erosion of seawater.

[0051] 5. EDS spectrum analysis of Cl in different groups of geopolymers The microscopic morphology of the geopolymer samples in Example 2 and Comparative Example 1 at 1000 times magnification and the EDS spectra of Cl were analyzed using a scanning electron microscope and an EDS spectrometer. The analysis results are as follows: Figure 4 The results show that after long-term seawater immersion, the pure metakaolin geopolymer of Comparative Example 1 exhibited numerous cracks and a large amount of Cl enriched on the surface, while the metakaolin-iron-rich tailings-based geopolymer of Example 2 still had a relatively dense matrix with almost no microcracks and almost no Cl distribution in the matrix, further demonstrating that the incorporation of iron-rich tailings enhanced the geopolymer's resistance to chloride ion penetration, thereby improving its resistance to chloride ion erosion.

[0052] Although preferred embodiments of the present invention have been described, additional changes and modifications to these embodiments may occur to those skilled in the art once the basic inventive concepts become known.

[0053] Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if such modifications and variations fall within the scope of the claims and their equivalents, the present invention is intended to include such modifications and variations.

Claims

1. A geopolymer, characterized in that The geopolymer is prepared by mixing iron-rich tailings, metakaolin and an alkali activator and then undergoing a curing step; The alkaline activator is prepared by mixing sodium hydroxide and water glass; The mass ratio of the iron-rich tailings to the metakaolin is 0.25-1.5:1; The liquid-to-solid ratio of the total mass of the iron-rich tailings and metakaolin to the alkaline activator solution is 0.6-1.2:1; The curing comprises standing curing at a temperature of 60° C. to 90° C. and a humidity of 90% to 100% for 1 hour to 7 hours, standing curing at room temperature for 4 days to 7 days, and immersing curing in seawater for 28 days to 360 days.

2. The geopolymer according to claim 1, characterized in that The iron content of the iron-rich tailings is ≥50%.

3. A method for preparing the geopolymer according to any one of claims 1 to 2, characterized in that: The specific steps include: After the iron-rich tailings and metakaolin are evenly mixed, an alkaline activator solution is poured in and mixed evenly to form a geopolymer slurry, which is then formed and cured to obtain a geopolymer; The alkaline activator is prepared by mixing sodium hydroxide and water glass, wherein the mass ratio of sodium hydroxide to water glass is 1:5; The mass ratio of the iron-rich tailings to the metakaolin is 0.25-1.5:1; The liquid-to-solid ratio of the total mass of the iron-rich tailings and metakaolin to the alkaline activator solution is 0.6-1.2:1; The iron-rich tailings and metakaolin are mixed under the conditions of stirring at 300 r / min to 1000 r / min for 1 min to 30 min; The curing comprises standing curing at a temperature of 60° C. to 90° C. and a humidity of 90% to 100% for 1 hour to 7 hours, standing curing at room temperature for 4 days to 7 days, and immersing curing in seawater for 28 days to 360 days.

4. The method for preparing geopolymer according to claim 3, characterized in that: The mass ratio of the iron-rich tailings to metakaolin is 0.7:

1.

5. The method for preparing geopolymer according to claim 3, characterized in that: The liquid-to-solid ratio of the total mass of the iron-rich tailings and metakaolin to the alkaline activator solution is 0.8:

1.

6. The method for preparing geopolymer according to claim 3, characterized in that: The curing is as follows: curing at a temperature of 80° C. and a humidity of 95% for 6 hours, curing at room temperature for 4 days, and curing by immersing in seawater for 28 days.

7. The method for preparing geopolymer according to claim 3, characterized in that: The iron-rich tailings and metakaolin are mixed under the stirring condition of 600 r / min for 10 min.

8. Use of the geopolymer according to claim 1 in resisting seawater erosion.

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