Nano-diamond-bamboo fiber-graphite tailing geopolymer rapid repairing material and preparation method thereof

Abstract

The invention discloses a nano diamond-bamboo fiber-graphite tailing-based geopolymer rapid repairing material and a preparation method of the nano diamond-bamboo fiber-graphite tailing-based geopolymer rapid repairing material. The nano-diamond-bamboo fiber-graphite tailing-based geopolymer rapid repairing material comprises the following components in percentage by weight: 20%-30% of slag, 40%-60% of graphite tailings, 10%-15% of an alkaline activator, 0.05%-0.3% of nano-diamond, 0.8%-1.5% of bamboo fibers, 2%-4% of polyurethane microcapsules and the balance of water. By implementing the method, the mechanical property and the crack self-repairing rate of the geopolymer material can be remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a rapid repair material of nanodiamond-bamboo fiber-graphite tailings geopolymer and its preparation method. Background Technology

[0002] Geopolymers, due to their unique three-dimensional network structure, low cost, good mechanical properties, resistance to chemical erosion, thermal stability, and environmental friendliness, have shown broad application prospects in functional materials and building materials. Commonly used geopolymer raw materials include industrial wastes such as fly ash, slag, metakaolin, and tailings. Among these, the preparation of geopolymer materials using activated tailings has become an important research area in this field in recent years. Tailings-based geopolymers have the following advantages: First, the chemical composition of some tailings is similar to that of natural volcanic ash, possessing potential volcanic ash activity; second, tailings particles after physical activation can undergo lattice distortion, providing favorable conditions for further chemical activation; third, composite geopolymer materials prepared from tailings and fly ash, silica fume, metakaolin, etc., have a relatively uniform particle size distribution and high activity index, effectively improving the mechanical properties and erosion resistance of cement-based materials.

[0003] Graphite tailings possess superior comprehensive properties, making them promising candidates for the preparation of novel tailings-based geopolymers. Graphite tailings exhibit good material stability, a high Si / Al ratio, and a reasonable CaO content, which can mitigate issues such as large shrinkage and easy cracking in geopolymers. Their favorable particle size distribution and lamellar structure provide the prerequisites for mechanical activation, enabling the aggregation and dissolution of alkaline activators, thereby controlling the polymerization rate, optimizing the degree of crosslinking, and reducing alkaline activator residue and corrosion. Furthermore, the natural volcanic ash reactivity and good thermal stability of graphite tailings offer the possibility of preparing tailings-based geopolymers under low-alkali activation conditions during room-temperature curing.

[0004] While existing technologies can achieve solid waste resource utilization through graphite tailings and slag compound systems, they suffer from the following key problems: First, brittleness, with the flexural strength of the materials generally below 15 MPa and insufficient fracture toughness; second, microcrack propagation, where early shrinkage stress leads to the initiation of microcracks within the material, reducing durability; third, lack of repair capability, as traditional fiber-reinforced geopolymers (such as PP / steel fiber) only provide physical toughening and lack self-healing function; and fourth, the traditional microencapsulation method has low repair efficiency in geopolymers (crack width repair limit < 100 μm) and poor compatibility with the alkaline environment of geopolymers. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a rapid repair material of nanodiamond-bamboo fiber-graphite tailings geopolymer and its preparation method, which can significantly improve the mechanical properties and crack self-healing rate of geopolymer materials.

[0006] To address the aforementioned problems, this invention discloses a nanodiamond-bamboo fiber-graphite tailings base polymer rapid repair material, comprising the following components by weight percentage: slag 20%–30%, graphite tailings 40%–60%, alkaline activator 10%–15%, nanodiamond 0.05%–0.3%, bamboo fiber 0.8%–1.5%, polyurethane 2%–4%, with the balance being water.

[0007] As an improvement to the above technical solution, the particle size of the nanodiamond is 15nm to 45nm;

[0008] The polyurethane microcapsules have a particle size of 50 μm to 80 μm.

[0009] The particle size of the graphite tailings is ≤50μm.

[0010] As an improvement to the above technical solution, the length of the bamboo fiber is 2mm to 5mm and the aspect ratio is >100;

[0011] The bamboo fiber is alkali-pretreated bamboo fiber, the treatment solution is 5wt% to 8wt% sodium hydroxide, and the treatment time is 5min to 10min.

[0012] As an improvement to the above technical solution, the alkaline activator includes sodium hydroxide and water glass, wherein the modulus of the water glass is 2 to 2.5.

[0013] As an improvement to the above technical solution, the polyurethane microcapsule includes a core material and a wall material, wherein the core material is a polyurethane prepolymer containing terminal isocyanate groups, and the wall material is a polyurea-silica hybrid wall material.

[0014] Accordingly, this invention also discloses a method for preparing the above-mentioned nanodiamond-bamboo fiber-graphite tailings geopolymer rapid repair material, comprising the following steps:

[0015] The slag and graphite tailings are mixed and stirred to obtain the first component;

[0016] The nanodiamond, polyurethane, first alkaline activator and water are mixed and stirred to obtain the second component;

[0017] Bamboo fiber and a second alkaline activator are mixed and subjected to high-speed shearing to obtain a third component;

[0018] The first, second, and third components are stirred and mixed to obtain the nanodiamond-bamboo fiber-graphite tailings geopolymer rapid repair material.

[0019] As an improvement to the above technical solution, the mass ratio of the first alkaline activator to the second alkaline activator is 1:(4-7.5).

[0020] As an improvement to the above technical solution, the second component obtained by mixing and stirring nanodiamond, polyurethane, a first alkaline activator, and water includes:

[0021] Nanodiamonds and a first alkaline activator were premixed and ultrasonically treated to obtain a mixture; the ultrasonic treatment frequency was 30kHz to 50kHz and the ultrasonic treatment time was 20min to 40min.

[0022] Polyurethane and water are added to the mixture, and the mixture is stirred until homogeneous to obtain the second component.

[0023] As an improvement to the above technical solution, the shearing speed of the high-speed shearing process is 1800 rpm to 2200 rpm, and the shearing time is 4 min to 8 min;

[0024] The first, second, and third components were stirred evenly under vacuum conditions, with a vacuum degree of -0.08 MPa to -0.06 MPa.

[0025] As an improvement to the above technical solution, the graphite tailings are pretreated before stirring and mixing. The pretreatment includes:

[0026] The graphite tailings were screened to a particle size of 0.6 mm to 0.65 mm.

[0027] The sieved graphite tailings were ball-milled to a powder with a particle size ≤50μm; the ball milling speed was 200r / min~250r / min, and the ball milling time was 15min~20min.

[0028] Implementing this invention has the following beneficial effects:

[0029] The geopolymer rapid repair material provided by this invention uses slag and graphite tailings as cementing materials, combined with an alkaline activator to achieve polymerization; bamboo fiber, as a long fiber, provides bridging and inhibits the propagation of micron- to millimeter-scale cracks; nanodiamond sheets enhance the density of the matrix through chemical bonding, treating micron- to submicron-scale microcracks and stress concentration points, causing crack paths to deflect, branch, or pin; polyurethane microcapsules rupture during crack propagation, releasing a repair agent to the crack surface, achieving molecular-level bonding repair through polymerization. Simultaneously, the alkaline activator and polyurethane microcapsules also promote the bonding of carboxyl groups on the nanodiamond surface with Ca in the cementing material. 2+ The reaction generates healing products, further enabling self-repair.

[0030] The geopolymer rapid repair material provided by this invention can achieve a three-level synergy of macroscopic crack bridging of bamboo fiber, microscopic crack deflection of nanodiamond, and microscopic self-repair of polyurethane microcapsules, thus constructing a comprehensive defense and recovery network that is cross-scale, multifunctional, and time-series. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below.

[0032] This invention provides a nanodiamond-bamboo fiber-graphite tailings base polymer rapid repair material, comprising the following components by weight percentage: slag 20%–30%, graphite tailings 40%–60%, alkaline activator 10%–15%, nanodiamond 0.05%–0.3%, bamboo fiber 0.8%–1.5%, polyurethane microcapsules 2%–4%, and the balance being water.

[0033] This invention provides a rapid repair material based on nanodiamond-bamboo fiber-graphite tailings polymer. Slag and graphite tailings serve as cementing materials, polymerized with an alkaline activator. Bamboo fiber, as a long fiber, provides bridging, inhibiting crack propagation from micrometer to millimeter scale. Nanodiamond sheets enhance matrix density through chemical bonding, addressing micro- to submicrometer scale microcracks and stress concentration points, causing crack paths to deflect, branch, or pin. The synergistic effect of nanodiamond and bamboo fiber is further enhanced by the interface strengthening effect of nanodiamond, which strengthens the bridging and pull-out effect of bamboo fiber. The inhibition of macro-cracks by bamboo fiber allows nanodiamond to better handle micro-damage, forming a comprehensive anti-crack network from micro to macro, reducing the probability of crack occurrence. Furthermore, polyurethane microcapsules rupture during crack propagation, releasing a repair agent to the crack surface, achieving molecular-level bonding repair through polymerization. Simultaneously, the alkaline activator and polyurethane microcapsules promote the bonding of carboxyl groups on the nanodiamond surface with Ca in the cementing material. 2+ The reaction generates healing products, further enabling self-repair.

[0034] In one embodiment, the nanodiamond particles have a diameter of 15 nm to 45 nm, exemplarily 20 nm, 25 nm, 30 nm, 35 nm, or 40 nm, but are not limited thereto. Nanodiamond sheets enhance the density of the matrix through chemical bonding, addressing micro- to submicron-level microcracks and stress concentration points. Within the matrix or at interfaces, they deflect, branch, or pin the main crack path, consuming more energy. If the nanodiamond particle size is too large, the larger particles easily become internal defects in the material. Under external force, stress will highly concentrate around the large particles, initiating microcracks first, leading to decreased material strength and increased brittleness. If the nanodiamond particle size is too small, it will produce hard agglomerates that are difficult to break down. The large specific surface area of ​​nanodiamonds will also cause excessively high viscosity of the system, resulting in a severe decrease in processing performance. Furthermore, nanodiamonds with extremely small and uniform particle size are difficult and costly to process.

[0035] The polyurethane microcapsules have a particle size of 50μm to 80μm, with exemplary values ​​of 55μm, 60μm, 65μm, 70μm, or 75μm, but are not limited thereto. When cracks or damage occur in the geopolymer system, the repair reaction of the polyurethane microcapsules is automatically triggered. The polyurethane microcapsules release polyurethane, which undergoes a chemical reaction in the microcracks to repair the damaged structure, thus realizing the self-healing function of the geopolymer. If the particle size of the polyurethane microcapsules is too large, it will affect the mechanical properties of the concrete and become a source of defects; if the particle size of the polyurethane microcapsules is too small, they are easily encapsulated by the cementitious material or agglomerate during the mixing process, making it difficult to disperse evenly and limiting the repair capacity.

[0036] The graphite tailings have a particle size ≤50μm. In a preferred embodiment, the D of the graphite tailings is... 50 Its diameter is 10μm to 15μm, and its specific surface area is 485m². 2 / kg~495m 2 / kg, effectively activating the pozzolanic activity of graphite tailings.

[0037] The length of the bamboo fiber is 2mm to 5mm, with exemplary lengths of 2.5mm, 3mm, 3.5mm, 4mm, or 4.5mm, but not limited to these. If the bamboo fiber is too short, the toughening effect is poor; if the bamboo fiber is too long, it is difficult to disperse and easily agglomerates, becoming a defect. Controlling the aspect ratio of the bamboo fiber to >100 effectively utilizes its reinforcing effect. As a long fiber, bamboo fiber can handle cracks that are visible to the naked eye or of a larger size, bearing tensile stress through bridging and preventing cracks from opening, thus achieving crack bridging on a macroscopic scale.

[0038] In a preferred embodiment, the bamboo fiber is alkali-pretreated bamboo fiber, the treatment solution is 5wt% to 8wt% sodium hydroxide, and the treatment time is 5 min to 10 min. The low-concentration sodium hydroxide solution can dissolve pectin, wax, some hemicellulose and lignin on the surface of the bamboo fiber, exposing more cellulose and increasing the number of hydroxyl groups, thereby improving the mechanical and chemical bonding between the bamboo fiber and the cementitious material.

[0039] The alkaline activator comprises sodium hydroxide and water glass, wherein the modulus of the water glass is 2–2.5. The alkaline activator creates a strongly alkaline environment, with OH- ions acting as a catalyst to accelerate the condensation reaction of dissolved silicate and aluminate ions, resulting in the removal of water molecules and the formation of a Si-O-Al-O gel with a three-dimensional network structure. The modulus of the water glass directly affects the free OH- ions within it. - By selecting a higher modulus and a higher concentration of soluble silica species, the final material will have better strength and durability, and lower shrinkage.

[0040] The polyurethane microcapsules comprise a core material and a wall material. The core material is a polyurethane prepolymer containing isocyanate-terminated groups, and the wall material is a polyurea-silica hybrid wall material. When cracks propagate into the polyurethane microcapsules, the released core material (containing the isocyanate-terminated polyurethane prepolymer) reacts with free Ca in the geopolymer. 2+ The reaction generates a cross-linked network, enabling self-healing. Polyurea-silica hybrid wall materials exhibit good stability in environments with a pH of 12–13, showing more than three times the stability of conventional urea-formaldehyde resin wall materials.

[0041] In a preferred embodiment, the slag is S95 grade slag, and by weight percentage, the slag comprises the following components: CaO 25%–40%, SiO2 25%–40%, Al2O3 12%–25%, MgO 8%–18%, SO3 1%–5%, Fe2O3 0.5%–1.5%, K2O 0.1%–1%, Na2O 0.5%–1.5%, TiO2 1%–5%, MnO 0.1%–1%, with the balance being loss on ignition.

[0042] In a preferred embodiment, the graphite tailings, by weight percentage, comprises the following components: 58%–65% SiO2, 3%–8% Fe3O4, 1%–5% FeS, 8%–15% Al2O3, 0.5%–5% K2O, 0.1%–0.5% Na2O, 2%–10% CaO, 0.1%–1% MgO, 0.1%–1% TiO2, 1%–5% C, with the balance being loss on ignition.

[0043] Accordingly, the present invention provides a method for preparing the above-mentioned nanodiamond-bamboo fiber-graphite tailings geopolymer rapid repair material, comprising the following steps:

[0044] S1. Mix and stir the slag and graphite tailings to obtain the first component.

[0045] In one embodiment, the graphite tailings are pretreated before stirring and mixing, the pretreatment including:

[0046] S11. Screen the graphite tailings to a particle size of 0.6mm to 0.65mm.

[0047] S12. Ball mill the sieved graphite tailings to a powder with a particle size ≤50μm. The ball mill speed is 200r / min~250r / min, and the ball milling time is 15min~20min. Ball milling the graphite tailings further activates the pozzolanic activity of the graphite tailings.

[0048] S2. Mix and stir the nanodiamond, polyurethane, first alkaline activator and water to obtain the second component.

[0049] In one implementation, S2 specifically includes the following steps:

[0050] S21. Premix nanodiamonds and the first alkaline activator and sonicate to obtain a mixture; the frequency of sonication is 30kHz to 50kHz and the time of sonication is 20min to 40min.

[0051] S22. Add polyurethane and water to the mixture, mix and stir until homogeneous to obtain the second component.

[0052] S3. Bamboo fiber and the second alkaline activator are mixed and subjected to high-speed shearing to obtain the third component.

[0053] The alkaline activator is divided into a first alkaline activator and a second alkaline activator. The first alkaline activator is mixed with nanodiamond, and the second alkaline activator is mixed with bamboo fiber. The mass ratio of the first alkaline activator to the second alkaline activator is 1:(4 to 7.5), with examples of 1:4.5, 1:5, 1:5.5, 1:6, and 1:7, but not limited to these.

[0054] Specifically, the high-speed shearing treatment involves a shearing speed of 1800 rpm to 2200 rpm and a shearing time of 4 min to 8 min. The bamboo fiber undergoes high-speed shearing with the second alkaline activator to achieve hydroxyl activation.

[0055] S4. Stir and mix the first component, the second component and the third component to obtain the nanodiamond-bamboo fiber-graphite tailings polymer rapid repair material.

[0056] In one embodiment, the first component, the second component, and the third component are stirred uniformly under vacuum conditions, with a vacuum degree of -0.08 MPa to -0.06 MPa.

[0057] Through a three-stage dispersion process, components are added in stages to ultimately obtain a high-performance and uniformly dispersed nanodiamond-bamboo fiber-graphite tailings polymer rapid repair material.

[0058] The present invention will be further described below with reference to specific embodiments:

[0059] Example 1

[0060] This embodiment provides a nanodiamond-bamboo fiber-graphite tailings base polymer rapid repair material, comprising the following components by weight: 28% slag, 52% graphite tailings, 12% alkaline activator, 0.15% nanodiamond, 1.2% bamboo fiber, 3% polyurethane microcapsules, and the balance being water.

[0061] A method for preparing a rapid repair material of nanodiamond-bamboo fiber-graphite tailings polymer includes the following steps:

[0062] S1. Mix and stir the slag and graphite tailings to obtain the first component.

[0063] S2. Mix and stir the nanodiamond, polyurethane, first alkaline activator and water to obtain the second component.

[0064] S2 specifically includes the following steps:

[0065] S21. Premix nanodiamonds and the first alkaline activator and sonicate to obtain a mixture; the sonication frequency is 40kHz and the sonication time is 30min.

[0066] S22. Add polyurethane and water to the mixture, mix and stir until homogeneous to obtain the second component.

[0067] S3. Bamboo fiber and the second alkaline activator are mixed and subjected to high-speed shearing to obtain the third component.

[0068] The mass ratio of the first alkaline activator to the second alkaline activator is 1:4. The shearing speed of the high-speed shearing treatment is 2000 rpm, and the shearing time is 5 min.

[0069] S4. Mix the first, second, and third components in a vacuum environment of -0.08 MPa to obtain the nano-diamond-bamboo fiber-graphite tailings base polymer rapid repair material.

[0070] Example 2

[0071] This embodiment provides a nanodiamond-bamboo fiber-graphite tailings base polymer rapid repair material, comprising the following components by weight: 23% slag, 42% graphite tailings, 10% alkaline activator, 0.05% nanodiamond, 0.8% bamboo fiber, 2% polyurethane microcapsules, and the balance being water.

[0072] Everything else is the same as in Example 1.

[0073] Example 3

[0074] This embodiment provides a nanodiamond-bamboo fiber-graphite tailings base polymer rapid repair material, comprising the following components by weight: 26% slag, 50% graphite tailings, 12% alkaline activator, 0.3% nanodiamond, 1.5% bamboo fiber, 4% polyurethane microcapsules, and the balance being water.

[0075] Everything else is the same as in Example 1.

[0076] Comparative Example 1

[0077] This comparative example provides a geopolymer rapid repair material, which differs from Example 1 in that it does not include bamboo fiber in its components.

[0078] Everything else is the same as in Example 1.

[0079] Comparative Example 2

[0080] This comparative example provides a geopolymer rapid repair material, which differs from Example 1 in that it does not include nanodiamonds in its composition.

[0081] Everything else is the same as in Example 1.

[0082] Comparative Example 3

[0083] This comparative example provides a geopolymer rapid repair material, which differs from Example 1 in that it does not include polyurethane microcapsules in its components.

[0084] Everything else is the same as in Example 1.

[0085] The geopolymer rapid repair materials prepared in Examples 1-3 and Comparative Examples 1-3 were cured using the following steps: The prepared geopolymer rapid repair materials were poured into a 40mm×40mm×160mm mold and vibrated evenly on a vibration table. After standing for 3-5 minutes, the mold was sealed with plastic wrap. The resulting sample was steam-cured at 60℃ for 24 hours, then sealed and cured at room temperature for 7 days, and finally naturally cured for 28 days to obtain the finished geopolymer sample. The performance of the finished geopolymer samples obtained in Examples 1-3 and Comparative Examples 1-3 was tested, and the specific results are as follows:

[0086]

[0087] The above description is a preferred embodiment of the invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the invention, and these improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A rapid repair material for nanodiamond-bamboo fiber-graphite tailings polymer, characterized in that, It comprises the following components by weight percentage: 20%–30% slag, 40%–60% graphite tailings, 10%–15% alkaline activator, 0.05%–0.3% nanodiamond, 0.8%–1.5% bamboo fiber, 2%–4% polyurethane microcapsules, and the balance being water.

2. The rapid repair material of nanodiamond-bamboo fiber-graphite tailings polymer as described in claim 1, characterized in that, The nanodiamond has a particle size of 15nm to 45nm; The polyurethane microcapsules have a particle size of 50 μm to 80 μm. The particle size of the graphite tailings is ≤50μm.

3. The rapid repair material of nanodiamond-bamboo fiber-graphite tailings polymer as described in claim 1, characterized in that, The bamboo fiber has a length of 2mm to 5mm and a diameter-to-width ratio of >100; The bamboo fiber is alkali-pretreated bamboo fiber, the treatment solution is 5wt% to 8wt% sodium hydroxide, and the treatment time is 5min to 10min.

4. The rapid repair material of nanodiamond-bamboo fiber-graphite tailings polymer as described in claim 1, characterized in that, The alkaline activator includes sodium hydroxide and water glass, wherein the modulus of the water glass is 2 to 2.

5.

5. The rapid repair material of nanodiamond-bamboo fiber-graphite tailings polymer as described in claim 1, characterized in that, The polyurethane microcapsule comprises a core material and a wall material, wherein the core material is a polyurethane prepolymer containing terminal isocyanate groups, and the wall material is a polyurea-silica hybrid wall material.

6. A method for preparing a rapid repair material of nanodiamond-bamboo fiber-graphite tailings polymer as described in any one of claims 1 to 5, characterized in that, Includes the following steps: The slag and graphite tailings are mixed and stirred to obtain the first component; The nanodiamond, polyurethane, first alkaline activator and water are mixed and stirred to obtain the second component; Bamboo fiber and a second alkaline activator are mixed and subjected to high-speed shearing to obtain a third component; The first, second, and third components are stirred and mixed to obtain the nanodiamond-bamboo fiber-graphite tailings geopolymer rapid repair material.

7. The preparation method of the nanodiamond-bamboo fiber-graphite tailings polymer rapid repair material as described in claim 6, characterized in that, The mass ratio of the first alkaline activator to the second alkaline activator is 1:(4 to 7.5).

8. The preparation method of the nanodiamond-bamboo fiber-graphite tailings geopolymer rapid repair material as described in claim 6, characterized in that, The second component, obtained by mixing and stirring nanodiamonds, polyurethane, a first alkaline activator, and water, comprises: Nanodiamonds and a first alkaline activator were premixed and ultrasonically treated to obtain a mixture; the ultrasonic treatment frequency was 30kHz to 50kHz and the ultrasonic treatment time was 20min to 40min. Polyurethane and water are added to the mixture, and the mixture is stirred until homogeneous to obtain the second component.

9. The preparation method of the nanodiamond-bamboo fiber-graphite tailings polymer rapid repair material as described in claim 6, characterized in that, The high-speed shearing process has a shearing speed of 1800 rpm to 2200 rpm and a shearing time of 4 min to 8 min. The first, second, and third components were stirred evenly under vacuum conditions, with a vacuum degree of -0.08 MPa to -0.06 MPa.

10. The preparation method of the nanodiamond-bamboo fiber-graphite tailings geopolymer rapid repair material as described in claim 6, characterized in that, Before mixing, the graphite tailings are pretreated, the pretreatment including: The graphite tailings were screened to a particle size of 0.6 mm to 0.65 mm. The sieved graphite tailings were ball-milled to a powder with a particle size ≤50μm; the ball milling speed was 200r / min~250r / min, and the ball milling time was 15min~20min.

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