Graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks and preparation method thereof

Abstract

This invention relates to the field of graphene reinforcing agent technology, specifically disclosing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks and its preparation method. This invention incorporates two types of modified graphene into the reinforcing agent system, constructing a multi-layered complementary reinforcing system. This achieves a dual mechanism of uniform strengthening within the concrete matrix and directional sealing of the internal permeation channels. The addition of slow-release phytic acid microcapsules and sodium alginate-cement microcapsules fundamentally and synergistically improves the mechanical properties and long-term durability of concrete materials.

Description

Technical Field

[0001] This invention relates to the field of graphene reinforcing agent technology, specifically to a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks and its preparation method. Background Technology

[0002] Bricks are a widely used traditional building material in construction projects, characterized by their wide availability of raw materials, low production costs, mature construction techniques, and good thermal insulation properties. They have long played a crucial role in wall construction and landscape design. However, during long-term use, bricks are susceptible to damage from harsh environmental factors such as acid rain, vehicle exhaust, and industrial waste gases. This can lead to problems like powdering, peeling, and cracking on the surface, and the internal pores can gradually enlarge due to the erosion of acid, alkali, and salt media. These factors result in decreased structural durability and even safety hazards. While attempts can be made to improve the corrosion resistance of bricks by adding waterproofing agents and mineral admixtures, these methods have limitations, including limited protective effects, insufficient long-term stability, and difficulty in simultaneously achieving mechanical enhancement and improved weather resistance.

[0003] To improve the durability and acid and alkali resistance of bricks, researching high-performance brick reinforcing agents has become an important direction. Currently, the mechanisms of action of brick reinforcing agents mostly rely on physical filling or surface film formation, making it difficult to block the penetration pathways of corrosive media at the microscopic level. Furthermore, most reinforcing agents have poor compatibility with brick raw materials, easily leading to increased brick brittleness or later strength reduction, failing to meet the modern building requirements for bricks with long lifespan, low maintenance, and multiple functions. In addition, existing brick acid and alkali resistant reinforcing technologies mostly focus on single properties, such as only improving acid resistance or only improving flexural strength, lacking a multi-functional synergistic system that can simultaneously achieve resistance to acid and alkali corrosion, enhanced mechanical properties, and optimized volume stability. Therefore, developing a graphene-based brick acid and alkali resistant reinforcing agent to overcome the limitations of traditional technologies is of great significance for improving the service performance of bricks in harsh environments. Summary of the Invention

[0004] The purpose of this invention is to provide a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks and its preparation method, thereby solving the problems of traditional reinforcing agents having limited performance and poor acid and alkali resistance.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks, specifically comprising: S1. Polyetheramine-organosilicon-modified graphene oxide was prepared using polyetheramine, silane coupling agent KH-560 and graphene oxide as raw materials. S2. Using octadecylamine and graphene oxide as raw materials, prepare octadecylamine-graphene oxide; S3. Prepare sustained-release phytic acid microcapsules using phytic acid, ethyl cellulose and chitosan as raw materials; S4. Sodium alginate-cement microcapsules were prepared using sodium alginate, magnesium phosphate cement, epoxy resin and sulfoaluminate cement as raw materials. S5. A graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks is obtained by mixing polyetheramine-organosilicon modified graphene oxide, octadecylamine-graphene oxide, slow-release phytic acid microcapsules and sodium alginate-cement microcapsules with silica fume, slag powder, polycarboxylate superplasticizer and modified polyether defoamer.

[0006] As a limitation of the present invention, the graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks, by mass fraction, comprises: 0.2-0.3 wt% polyetheramine-organosilicon modified graphene oxide, 0.3-0.4 wt% octadecylamine-graphene oxide, 10-12 wt% slow-release phytic acid microcapsules, 8-9 wt% sodium alginate-cement microcapsules, 0.7-0.8 wt% polycarboxylate superplasticizer, 0.1-0.2 wt% modified polyether defoamer, 35-37 wt% silica fume, and the balance being slag powder.

[0007] As a limitation of this invention, the preparation method of the polyetheramine-organosilicon modified graphene oxide is as follows: Graphene oxide was added to deionized water and stirred at 200-300 rpm for 20-30 min, then ultrasonically dispersed for 20-30 min. 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added, and the mixture was stirred at 25-30℃ and 300-400 rpm for 30-40 min. Polyetheramine was added, and the reaction was continued for 20-24 h. After the reaction was completed, the mixture was ultrafiltered and centrifuged. The product was washed with deionized water and freeze-dried to obtain polyetheramine-modified graphene oxide. Polyetheramine-modified graphene oxide was added to an ethanol aqueous solution, stirred at 200-300 rpm for 20-30 min, ultrasonically dispersed for 20-30 min, and the pH was adjusted to 9-10. Silane coupling agent KH-560 was added, and the reaction was carried out at 60-70℃ and stirred at 300-400 rpm for 6-8 h. After the reaction was completed, the mixture was cooled, the precipitate was collected by centrifugation, washed with ethanol and deionized water, and dried at 60-70℃ for 4-6 h to obtain polyetheramine-organosilicon-modified graphene oxide.

[0008] As a limitation of the present invention, the mass ratio of graphene oxide, polyetheramine, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide is (1-1.2):(2-2.2):(1.5-1.7):(0.9-1.1); the mass ratio of polyetheramine-modified graphene oxide to silane coupling agent KH-560 is (20-22):(2-3).

[0009] In the catalytic system of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), the carboxyl groups on the surface of graphene oxide are activated. The activated carboxyl groups undergo amidation with the amino groups of polyetheramine to form amide bonds. The polyetheramine is then grafted onto the surface of graphene oxide through covalent bonds. Under alkaline heating conditions, the epoxy groups of the silane coupling agent KH-560 undergo ring-opening reactions with the remaining amino groups on the polyetheramine chain, and siloxane groups are grafted onto the polyetheramine chain.

[0010] After grafting hydrophilic polyetheramines onto the surface of graphene oxide, its water dispersibility is improved, ensuring uniform dispersion in water upon contact between the reinforcing agent powder and concrete mixing water. This prevents self-aggregation and provides a medium for the dispersion of other hydrophobic components in the system. Uniformly dispersed graphene oxide effectively inhibits microcrack propagation, and its high strength and strong bond with the matrix enhance compressive and flexural strength. Simultaneously, graphene oxide fills the pores within the concrete and extends the penetration paths of water, chloride ions, and sulfate ions, making the concrete structure denser, reducing chloride ion permeability, and improving the concrete's resistance to acid and alkali corrosion.

[0011] The grafted siloxane groups can hydrolyze into silanols and form strong silicon-oxygen-silicon or silicon-oxygen-calcium covalent bonds with hydroxyl groups in cement hydration products. This greatly enhances the chemical bonding between graphene and the concrete matrix, improves the interfacial transition zone between graphene and the cement paste matrix, and effectively transfers the stress borne by the graphene to the matrix. Furthermore, the flexible polyetheramine segments can absorb and dissipate energy through deformation, bridging microcracks within the concrete, inhibiting microcrack propagation, and improving the toughness and crack resistance of the concrete.

[0012] As a limitation of this invention, the preparation method of the octadecylamine-graphene oxide is as follows: Graphene oxide was added to N,N-dimethylformamide and stirred at 200-300 rpm for 20-30 min, followed by ultrasonic dispersion for 20-30 min to obtain a graphene oxide dispersion. Octadecylamine was added to toluene and stirred at 200-300 rpm for 20-30 min to obtain an octadecylamine solution. Under nitrogen protection, the graphene oxide dispersion was added to the octadecylamine solution, and the mixture was refluxed at 90-100℃ and stirred at 300-400 rpm for 8-12 h. After the reaction was completed, the mixture was cooled, the precipitate was separated by centrifugation, redissolved in toluene, added to acetone to precipitate again, washed with acetone and n-hexane, and vacuum dried at 60-70℃ for 4-6 h to obtain octadecylamine-graphene oxide. The mass ratio of graphene oxide to octadecylamine is (1-1.2):(1-1.2).

[0013] Under heating conditions, the carboxyl groups on the surface of graphene oxide undergo an amidation reaction with the amino groups of octadecylamine to form amide bonds. The long alkyl groups of octadecylamine are then branched onto the surface of graphene oxide, enhancing its hydrophobic properties.

[0014] The grafted hydrophobic long-chain alkyl structure endows graphene oxide with durable hydrophobicity and chemical stability. During concrete mixing and hardening, its hydrophobic properties facilitate its migration and accumulation along water transport pathways such as capillary walls and interfacial transition zones, forming a low-surface-energy hydrophobic surface and a dense two-dimensional barrier network. This reduces capillary pull while significantly extending the diffusion paths of water, chloride ions, and other corrosive media, thereby significantly improving the material's impermeability and resistance to acid and alkali corrosion. Similarly, octadecylamine-graphene oxide can effectively fill the micro- and nano-pores inside concrete, making the concrete structure denser. Furthermore, octadecylamine-graphene oxide physically bonds with the concrete matrix through mechanical interlocking, anchoring itself within the concrete. This causes microcracks to deflect, consuming more energy and inhibiting further expansion of microcracks within the concrete, thus improving the concrete's toughness and crack resistance.

[0015] As a limitation of this invention, the preparation method of the sustained-release phytic acid microcapsules is as follows: Phytic acid was added to deionized water and stirred at 200-300 rpm for 20-30 minutes to obtain an aqueous phytic acid solution. Ethyl cellulose and dispersant Span-80 were added to dichloromethane and stirred at 200-300 rpm for 20-30 minutes to obtain an ethyl cellulose solution. The aqueous phytic acid solution was added dropwise to the ethyl cellulose solution while continuously stirring at 8000-10000 rpm. After the addition was complete, the mixture was homogenized at 8000-10000 rpm for 3-5 minutes to obtain a phytic acid-ethyl cellulose emulsion. Chitosan was added to an aqueous glacial acetic acid solution and stirred at 50-60℃ for 20 minutes. Stir at 0-300 rpm for 20-30 min, add surfactant Tween-80, stir evenly, and adjust pH to 4-5 to obtain chitosan solution; add phytic acid-ethyl cellulose emulsion to chitosan solution while stirring continuously at 500-800 rpm. After addition, react at 25-30℃ and 500-800 rpm for 2-3 h. After reaction, add glutaraldehyde aqueous solution dropwise, maintain pH at 4-5, and continue stirring for 6-8 h. After reaction, collect product by centrifugation, wash with deionized water, and spray dry at 80-100℃ to obtain sustained-release phytic acid microcapsules.

[0016] As a limitation of the present invention, the mass ratio of phytic acid, ethyl cellulose, dispersant Span-80, chitosan and Tween-80 is (2-3):(2-3):(0.1-0.2):(1-2):(0.2-0.3).

[0017] The core material of the sustained-release phytic acid microcapsules is phytic acid, the inner shell is ethyl cellulose, and the outer shell is a glutaraldehyde-crosslinked chitosan network. The inner shell, with ethyl cellulose as the main component, controls the long-term, slow release of phytic acid. Chitosan, a pH-sensitive natural polymer, protonates the amino groups of the microcapsules when exposed to acidic media. The molecular chains extend and swell due to electrostatic repulsion, increasing the porosity of the originally dense chitosan crosslinked network. Partial hydrolysis of the glutaraldehyde crosslinks leads to a significant increase in the permeability of the outer shell or structural damage, thereby triggering the accelerated release of phytic acid from within the microcapsule.

[0018] Slow-release phytic acid microcapsules maintain a low release rate under normal conditions, avoiding ineffective consumption. When acid rain, industrial acidic gas erosion, or other factors lead to the neutralization of concrete, the microcapsules release phytic acid promptly through pH response to slow down concrete corrosion. As a multidentate organic ligand, phytic acid can undergo complexation reactions with metal cations within the concrete, forming insoluble phytate precipitates in capillaries and cracks. These precipitates fill and block the transport channels for moisture and corrosive ions, slowing down the deterioration process of concrete and enhancing the matrix's barrier against the intrusion of media such as moisture, chloride ions, and carbon dioxide, thereby improving the concrete's acid and alkali resistance and permeability. Furthermore, the formed deposits help bridge cracks, inhibiting further crack propagation and promoting microcrack healing, thus improving the long-term acid and alkali resistance and stability of the concrete.

[0019] As a limitation of the present invention, the preparation method of the sodium alginate-cement microcapsules is as follows: Sodium alginate and magnesium phosphate cement were dry-mixed at 35-45℃ and 200-300 rpm for 5-7 minutes to obtain a mixed powder. Under water bath heating at 35-45℃, the mixed powder was added to polyethylene glycol-400 and mixed at low speed of 200-300 rpm for 2-4 minutes, then at high speed of 700-800 rpm for 3-5 minutes. After cooling, the mixture was extruded and granulated, and dried at 35-45℃ for 6-8 hours to obtain the microcapsule core material. Epoxy resin was added to anhydrous ethanol and stirred at 200-300 rpm for 20-30 minutes. After n, add the curing agent polyetheramine and stir evenly to obtain epoxy resin solution. Place the microcapsule core material in a fluidized bed coating machine, spray the epoxy resin solution and dry it to form an epoxy resin layer on the surface of the microcapsule core material. Set the drying temperature to 35-45℃ and the drying time to 20-30min. Then mix it with sulfoaluminate cement powder and stir at 40-50rpm for 30-60s to coat the surface of the epoxy resin layer with sulfoaluminate cement powder to form a cement layer. Cure in a sealed environment at room temperature for 24-36h to obtain sodium alginate-cement microcapsules.

[0020] As a limitation of the present invention, the mass ratio of sodium alginate, magnesium phosphate cement, polyethylene glycol-400 and sulfoaluminate cement powder is (3-4):(3-4):(3.5-4.5):(3-5); the mass ratio of epoxy resin and curing agent polyetheramine is (0.5-1.0):(0.15-0.2); the diameter of the microcapsule core material is 0.8-1.2 mm, the thickness of the epoxy resin layer is 200-300 μm, and the thickness of the cement layer is 200-300 μm.

[0021] The core material of sodium alginate-cement microcapsules is sodium alginate and magnesium phosphate cement, the inner shell is epoxy resin, and the outer shell is sulfoaluminate cement. When concrete develops microcracks due to stress or shrinkage and moisture intrudes, the microcapsule wall material at the crack tip ruptures under stress concentration. The sodium alginate component inside rapidly absorbs the infiltrated moisture and undergoes intense swelling within a very short time, forming a high-water-content hydrogel network structure that blocks the microcrack channels, achieving rapid barrier against moisture and corrosive ions, thus improving the concrete's impermeability. The magnesium phosphate cement, in the medium provided by the infiltrated water, begins a continuous hydration reaction, generating insoluble crystalline products with gelling properties. These products grow and deposit within the three-dimensional network framework provided by the sodium alginate hydrogel, gradually transforming the initial physical soft filler into a chemically solidified body with a certain mechanical strength. This restores the density and continuity of the cracked area, prevents further crack propagation, alleviates stress concentration, and thus improves the material's toughness and extends its fatigue life. Simultaneously, in synergy with other components in the reinforcing agent, a multi-layered composite protection system is constructed.

[0022] A graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks. It is prepared using the preparation method described in any of the above-mentioned methods.

[0023] Compared with the prior art, the beneficial effects of the present invention are: This invention incorporates hydrophilic polyetheramine-organosilicon-modified graphene oxide and hydrophobic octadecylamine-graphene oxide into the reinforcing agent system. The polyetheramine-organosilicon-modified graphene oxide and octadecylamine-graphene oxide work synergistically to construct a multi-layered complementary reinforcing system. The polyetheramine-organosilicon-modified graphene oxide achieves uniform dispersion and strong interfacial bonding of the nano-reinforcing phase within the matrix, forming a reinforcing network. The octadecylamine-graphene oxide forms a directional protective barrier in the pore structure and interfacial region. Together, they achieve a dual mechanism of uniform reinforcement within the concrete matrix and directional sealing of internal permeation channels, fundamentally and synergistically improving the mechanical properties and long-term durability of concrete materials.

[0024] This invention incorporates slow-release phytic acid microcapsules and sodium alginate-cement microcapsules into the reinforcing agent system. Upon acidic attack, the slow-release phytic acid microcapsules respond rapidly, releasing phytic acid to slow the deterioration process of concrete. They also seal microcracks and capillary channels by forming insoluble complexes, inhibiting further crack propagation and promoting microcrack healing, thereby improving the long-term acid and alkali resistance and stability of the concrete. The sodium alginate-cement microcapsules rapidly form a physical barrier in the early stages of moisture intrusion, slowing the penetration rate of corrosive media into the deeper layers of the concrete. Simultaneously, their synergistic effect with other components in the reinforcing agent constructs a multi-layered composite protective system. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The terminology used in the embodiments is for describing specific implementation schemes, not for limiting the scope of protection of the present invention. The dosages in the embodiments are laboratory-scale tests and can be scaled up proportionally. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Graphene oxide (sheet diameter: 2μm, thickness: 1.2nm, specific surface area: 500m²) 2 / g), polyetheramine (brand name: polyetheramine D230, molecular weight: 220), epoxy resin (brand name: E-51 epoxy resin, epoxy value: 0.5eq / 100g, viscosity at 25℃: 5000mPa·s), magnesium phosphate cement (strength grade: 42.5, specific surface area: ≥400m²). 2 / kg), sulfoaluminate cement (strength grade: 42.5, specific surface area: ≥400m²) 2 / kg), silica fume (particle size: 0.3μm, SiO2 content: 85wt%), slag powder (grade: S95, specific surface area: 400m² / kg), 2 / g, Activity Index (7d): ≥75%), Polycarboxylate superplasticizer (brand: R-707, Water Reduction Rate: ≥25%, Moisture Content: ≤5%, Fineness (on 50 mesh sieve): ≤15%), Modified polyether defoamer (brand: FS-202, Bulk Density: 400kg / m³) 3 Moisture content: 3%, chloride ion content: ≤0.05%), sand (ISO standard sand, fineness: modulus 2.3-3.0, apparent density: ≥2500kg / m³) 3 ).

[0027] Example 1: A method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks, specifically as follows: Step 1: Add 100 mg of graphene oxide to 100 mL of deionized water, stir at 200 rpm for 20 min, sonicate for 30 min, add 150 mg of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 90 mg of N-hydroxysuccinimide, stir at 25 °C and 300 rpm for 30 min, add 200 mg of polyetheramine, continue stirring and react for 24 h, after the reaction is complete, ultrafilter and centrifuge at 10 kDa, wash with deionized water, freeze dry to obtain polyetheramine modified graphene oxide; Step 2: Add 200 mg of polyetheramine-modified graphene oxide to 100 mL of ethanol aqueous solution (v 乙醇 :v 水 In a mixture of 4:1, the mixture was stirred at 200 rpm for 20 min, ultrasonically dispersed for 30 min, and the pH was adjusted to 9. 20 mg of silane coupling agent KH-560 was added, and the mixture was stirred at 300 rpm at 60 °C for 8 h. After the reaction was completed, the mixture was cooled, the precipitate was collected by centrifugation, washed with ethanol and deionized water, and dried at 60 °C for 4 h to obtain polyetheramine-organosilicon modified graphene oxide. Step 3: Add 100 mg of graphene oxide to 100 mL of N,N-dimethylformamide, stir at 200 rpm for 20 min, and sonicate for 30 min to obtain a graphene oxide dispersion. Add 100 mg of octadecylamine to 100 mL of toluene, stir at 200 rpm for 20 min to obtain an octadecylamine solution. Under nitrogen protection, add the graphene oxide dispersion to the octadecylamine solution, reflux and stir at 90 °C and 300 rpm for 12 h. After the reaction is complete, cool, centrifuge to separate the precipitate, redissolve it in toluene, add it to acetone to precipitate again, wash with acetone and n-hexane, and vacuum dry at 60 °C for 6 h to obtain octadecylamine-graphene oxide. Step 4: Add 2g of phytic acid to 20mL of deionized water and stir at 200rpm for 20min to obtain an aqueous phytic acid solution; add 2g of ethyl cellulose and 0.1g of dispersant Span-80 to 50mL of dichloromethane and stir at 200rpm for 20min to obtain an ethyl cellulose solution. While stirring continuously at 10000rpm, add 20mL of the aqueous phytic acid solution dropwise to the 50mL ethyl cellulose solution. After the addition is complete, homogenize at 10000rpm for 5min to obtain a phytic acid-ethyl cellulose emulsion; add 1g of chitosan to 100mL of 1% (v / v) glacial acetic acid solution. In the solution, the mixture was stirred at 50℃ and 200 rpm for 20 min, and 0.2 g of surfactant Tween-80 was added. After stirring until homogeneous, the pH was adjusted to 5 to obtain a chitosan solution. Phytic acid-ethyl cellulose emulsion was added to 100 mL of chitosan solution under continuous stirring at 500 rpm. After the addition was completed, the mixture was stirred at 25℃ and 500 rpm for 2 h. After the reaction was completed, 0.5 mL of 25 wt% glutaraldehyde aqueous solution was added dropwise, and the pH was maintained at 4.5. The mixture was stirred for another 6 h. After the reaction was completed, the product was collected by centrifugation, washed with deionized water, and spray-dried at 80℃ to obtain sustained-release phytic acid microcapsules. Step 5: Dry-mix 3g sodium alginate and 3g magnesium phosphate cement at 40℃ and 200rpm for 5min to obtain a mixed powder. Under 40℃ water bath heating conditions, add 6g of the mixed powder to 3.6g polyethylene glycol-400, mix at 300rpm for 2min, then mix at 800rpm for 3min, cool, extrude and granulate, controlling the particle diameter to 1mm, and dry at 40℃ for 6h to obtain the microcapsule core material; add 0.6g epoxy resin to 10mL anhydrous ethanol, stir at 200rpm for 20min, then add 0... 18g of curing agent polyetheramine was stirred evenly to obtain epoxy resin solution. The microcapsule core material was placed in a fluidized bed coating machine, sprayed with epoxy resin solution and dried to form an epoxy resin layer with a thickness of 200μm on the surface of the microcapsule core material. The drying temperature was set at 40℃ and the drying time was 20min. Then it was mixed with 3g of sulfoaluminate cement powder and stirred at 45rpm for 30s to coat the surface of the microcapsule core material with sulfoaluminate cement powder to form a cement layer with a thickness of 200μm. It was then sealed and cured at room temperature for 24h to obtain sodium alginate-cement microcapsules. Step 6: Add 2g of polyetheramine-organosilicon modified graphene oxide, 3g of octadecylamine-graphene oxide, and 50g of silica fume to a mixer and mix at 50 rpm for 30 minutes. Then, add 300g of silica fume, 454.5g of slag powder, 7.5g of polycarboxylate superplasticizer, and 1g of modified polyether defoamer, and continue mixing at 50 rpm for 20 minutes. Finally, add 100g of slow-release phytic acid microcapsules and 82g of sodium alginate-cement microcapsules, and mix at 30 rpm for 10 minutes to obtain a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks.

[0028] Example 2: A method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks, specifically as follows: Step 1: Add 100 mg of graphene oxide to 100 mL of deionized water, stir at 200 rpm for 20 min, sonicate for 30 min, add 150 mg of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 90 mg of N-hydroxysuccinimide, stir at 25 °C and 300 rpm for 30 min, add 210 mg of polyetheramine, continue stirring and react for 24 h, after the reaction is complete, ultrafilter and centrifuge at 10 kDa, wash with deionized water, freeze dry to obtain polyetheramine modified graphene oxide; Step 2: Add 200 mg of polyetheramine-modified graphene oxide to 100 mL of ethanol aqueous solution (v 乙醇 :v 水 In a mixture of 4:1, the mixture was stirred at 200 rpm for 20 min, ultrasonically dispersed for 30 min, and the pH was adjusted to 9. 25 mg of silane coupling agent KH-560 was added, and the mixture was stirred at 300 rpm at 60 °C for 8 h. After the reaction was completed, the mixture was cooled, the precipitate was collected by centrifugation, washed with ethanol and deionized water, and dried at 60 °C for 4 h to obtain polyetheramine-organosilicon modified graphene oxide. Step 3: Add 100 mg of graphene oxide to 100 mL of N,N-dimethylformamide, stir at 200 rpm for 20 min, and sonicate for 30 min to obtain a graphene oxide dispersion. Add 110 mg of octadecylamine to 100 mL of toluene, stir at 200 rpm for 20 min to obtain an octadecylamine solution. Under nitrogen protection, add the graphene oxide dispersion to the octadecylamine solution, reflux and stir at 90 °C and 300 rpm for 12 h. After the reaction is complete, cool, centrifuge to separate the precipitate, redissolve it in toluene, add it to acetone to precipitate again, wash with acetone and n-hexane, and vacuum dry at 60 °C for 6 h to obtain octadecylamine-graphene oxide. Step 4: Add 2.5g of phytic acid to 20mL of deionized water and stir at 200rpm for 20min to obtain an aqueous phytic acid solution; add 2.5g of ethyl cellulose and 0.1g of dispersant Span-80 to 50mL of dichloromethane and stir at 200rpm for 20min to obtain an ethyl cellulose solution. While continuously stirring at 10000rpm, add 20mL of the aqueous phytic acid solution dropwise to the 50mL ethyl cellulose solution. After the addition is complete, homogenize at 10000rpm for 5min to obtain a phytic acid-ethyl cellulose emulsion; add 1.5g of chitosan to 100mL of 1% (v / v) ice water. In an aqueous acetic acid solution, the mixture was stirred at 50°C and 200 rpm for 20 min. 0.2 g of surfactant Tween-80 was added, and the mixture was stirred until homogeneous. The pH was adjusted to 5 to obtain a chitosan solution. Phytic acid-ethyl cellulose emulsion was added to 100 mL of the chitosan solution under continuous stirring at 500 rpm. After the addition was complete, the mixture was stirred continuously at 25°C and 500 rpm for 2 h. After the reaction was complete, 0.5 mL of 25 wt% glutaraldehyde aqueous solution was added dropwise, maintaining the pH at 4.5, and stirring was continued for 6 h. After the reaction was complete, the product was collected by centrifugation, washed with deionized water, and spray-dried at 80°C to obtain sustained-release phytic acid microcapsules. Step 5: Dry-mix 3g sodium alginate and 3g magnesium phosphate cement at 40℃ and 200rpm for 5min to obtain a mixed powder. Under 40℃ water bath heating conditions, add 6g of the mixed powder to 3.6g polyethylene glycol-400, mix at 300rpm for 2min, then mix at 800rpm for 3min, cool, extrude and granulate, controlling the particle diameter to 1mm, and dry at 40℃ for 6h to obtain the microcapsule core material; add 0.6g epoxy resin to 10mL anhydrous ethanol, stir at 200rpm for 20min, then add 0... 18g of curing agent polyetheramine was stirred evenly to obtain epoxy resin solution. The microcapsule core material was placed in a fluidized bed coating machine, sprayed with epoxy resin solution and dried to form an epoxy resin layer with a thickness of 200μm on the surface of the microcapsule core material. The drying temperature was set at 40℃ and the drying time was 20min. Then it was mixed with 3g of sulfoaluminate cement powder and stirred at 45rpm for 30s to coat the surface of the microcapsule core material with sulfoaluminate cement powder to form a cement layer with a thickness of 200μm. It was then sealed and cured at room temperature for 24h to obtain sodium alginate-cement microcapsules. Step 6: Add 3g of polyetheramine-organosilicon modified graphene oxide, 3g of octadecylamine-graphene oxide, and 50g of silica fume to a mixer and mix at 50 rpm for 30 minutes. Then, add 300g of silica fume, 448.5g of slag powder, 7.5g of polycarboxylate superplasticizer, and 1g of modified polyether defoamer, and continue mixing at 50 rpm for 20 minutes. Finally, add 105g of slow-release phytic acid microcapsules and 82g of sodium alginate-cement microcapsules, and mix at 30 rpm for 10 minutes to obtain a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks.

[0029] Example 3: A method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks, specifically as follows: Step 1: Add 100 mg of graphene oxide to 100 mL of deionized water, stir at 200 rpm for 20 min, sonicate for 30 min, add 150 mg of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 90 mg of N-hydroxysuccinimide, stir at 25 °C and 300 rpm for 30 min, add 220 mg of polyetheramine, continue stirring and react for 24 h, after the reaction is complete, ultrafilter and centrifuge at 10 kDa, wash with deionized water, freeze dry to obtain polyetheramine modified graphene oxide; Step 2: Add 200 mg of polyetheramine-modified graphene oxide to 100 mL of ethanol aqueous solution (v 乙醇 :v 水 In a mixture of 4:1, the mixture was stirred at 200 rpm for 20 min, ultrasonically dispersed for 30 min, and the pH was adjusted to 9. 30 mg of silane coupling agent KH-560 was added, and the mixture was stirred at 300 rpm at 60 °C for 8 h. After the reaction was completed, the mixture was cooled, the precipitate was collected by centrifugation, washed with ethanol and deionized water, and dried at 60 °C for 4 h to obtain polyetheramine-organosilicon modified graphene oxide. Step 3: Add 100 mg of graphene oxide to 100 mL of N,N-dimethylformamide, stir at 200 rpm for 20 min, and sonicate for 30 min to obtain a graphene oxide dispersion. Add 120 mg of octadecylamine to 100 mL of toluene, stir at 200 rpm for 20 min to obtain an octadecylamine solution. Under nitrogen protection, add the graphene oxide dispersion to the octadecylamine solution, reflux and stir at 90 °C and 300 rpm for 12 h. After the reaction is complete, cool, centrifuge to separate the precipitate, redissolve it in toluene, add it to acetone to precipitate again, wash with acetone and n-hexane, and vacuum dry at 60 °C for 6 h to obtain octadecylamine-graphene oxide. Step 4: Add 3g of phytic acid to 20mL of deionized water and stir at 200rpm for 20min to obtain an aqueous phytic acid solution; add 3g of ethyl cellulose and 0.1g of dispersant Span-80 to 50mL of dichloromethane and stir at 200rpm for 20min to obtain an ethyl cellulose solution. While continuously stirring at 10000rpm, add 20mL of the aqueous phytic acid solution dropwise to the 50mL ethyl cellulose solution. After the addition is complete, homogenize at 10000rpm for 5min to obtain a phytic acid-ethyl cellulose emulsion; add 2g of chitosan to 100mL of 1% (v / v) glacial acetic acid solution. In the solution, the mixture was stirred at 50℃ and 200 rpm for 20 min, and 0.2 g of surfactant Tween-80 was added. After stirring until homogeneous, the pH was adjusted to 5 to obtain a chitosan solution. Phytic acid-ethyl cellulose emulsion was added to 100 mL of chitosan solution under continuous stirring at 500 rpm. After the addition was completed, the mixture was stirred at 25℃ and 500 rpm for 2 h. After the reaction was completed, 0.5 mL of 25 wt% glutaraldehyde aqueous solution was added dropwise, and the pH was maintained at 4.5. The mixture was stirred for another 6 h. After the reaction was completed, the product was collected by centrifugation, washed with deionized water, and spray-dried at 80℃ to obtain sustained-release phytic acid microcapsules. Step 5: Dry-mix 3g sodium alginate and 3g magnesium phosphate cement at 40℃ and 200rpm for 5min to obtain a mixed powder. Under 40℃ water bath heating conditions, add 6g of the mixed powder to 3.6g polyethylene glycol-400, mix at 300rpm for 2min, then mix at 800rpm for 3min, cool, extrude and granulate, controlling the particle diameter to 1mm, and dry at 40℃ for 6h to obtain the microcapsule core material; add 0.6g epoxy resin to 10mL anhydrous ethanol, stir at 200rpm for 20min, then add 0... 18g of curing agent polyetheramine was stirred evenly to obtain epoxy resin solution. The microcapsule core material was placed in a fluidized bed coating machine, sprayed with epoxy resin solution and dried to form an epoxy resin layer with a thickness of 200μm on the surface of the microcapsule core material. The drying temperature was set at 40℃ and the drying time was 20min. Then it was mixed with 3g of sulfoaluminate cement powder and stirred at 45rpm for 30s to coat the surface of the microcapsule core material with sulfoaluminate cement powder to form a cement layer with a thickness of 200μm. It was then sealed and cured at room temperature for 24h to obtain sodium alginate-cement microcapsules. Step 6: Add 3g of polyetheramine-organosilicon modified graphene oxide, 4g of octadecylamine-graphene oxide, and 50g of silica fume to a mixer and mix at 50 rpm for 30 minutes. Then, add 300g of silica fume, 442.5g of slag powder, 7.5g of polycarboxylate superplasticizer, and 1g of modified polyether defoamer, and continue mixing at 50 rpm for 20 minutes. Finally, add 105g of slow-release phytic acid microcapsules and 87g of sodium alginate-cement microcapsules, and mix at 30 rpm for 10 minutes to obtain a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks.

[0030] Based on Example 1, the following comparative experiments were conducted, specifically Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4, as described below: Comparative Example 1: This comparative example relates to a method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks. The difference from Example 1 is that the reinforcing agent does not include polyetheramine-organosilicon modified graphene. Specifically: Add 3g of octadecylamine-graphene oxide and 50g of silica fume to a mixer and mix at 50 rpm for 30 minutes. Then, add 300g of silica fume, 456.5g of slag powder, 7.5g of polycarboxylate superplasticizer and 1g of modified polyether defoamer, and continue mixing at 50 rpm for 20 minutes. Finally, add 100g of slow-release phytic acid microcapsules and 82g of sodium alginate-cement microcapsules, and mix at 30 rpm for 10 minutes to obtain a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks. The preparation methods for octadecylamine-graphene oxide, sustained-release phytic acid microcapsules, and sodium alginate-cement microcapsules are the same as in Example 1.

[0031] Comparative Example 2: This comparative example relates to a method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks. The difference from Example 1 is that the reinforcing agent does not include octadecylamine-graphene oxide. Specifically: Add 2g of polyetheramine-organosilicon modified graphene oxide and 50g of silica fume to a mixer and mix at 50 rpm for 30 min. Then, add 300g of silica fume, 457.5g of slag powder, 7.5g of polycarboxylate superplasticizer and 1g of modified polyether defoamer, and continue mixing at 50 rpm for 20 min. Finally, add 100g of slow-release phytic acid microcapsules and 82g of sodium alginate-cement microcapsules, and mix at 30 rpm for 10 min to obtain a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks. The preparation methods of polyetheramine-organosilicon modified graphene oxide, slow-release phytic acid microcapsules, and sodium alginate-cement microcapsules are the same as in Example 1.

[0032] Comparative Example 3: This comparative example relates to a method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks. The difference from Example 1 is that the reinforcing agent does not include slow-release phytic acid microcapsules. Specifically: Add 2g of polyetheramine-organosilicon modified graphene oxide, 3g of octadecylamine-graphene oxide, and 50g of silica fume to a mixer and mix at 50 rpm for 30 minutes. Then, add 300g of silica fume, 554.5g of slag powder, 7.5g of polycarboxylate superplasticizer, and 1g of modified polyether defoamer, and continue mixing at 50 rpm for 20 minutes. Finally, add 82g of sodium alginate-cement microcapsules and mix at 30 rpm for 10 minutes to obtain a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks. The preparation methods of polyetheramine-organosilicon modified graphene oxide, octadecylamine-graphene oxide, and sodium alginate-cement microcapsules are the same as in Example 1.

[0033] Comparative Example 4: This comparative example relates to a method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks. The difference from Example 1 is that the reinforcing agent does not include sodium alginate-cement microcapsules. Specifically: Add 2g of polyetheramine-organosilicon modified graphene oxide, 3g of octadecylamine-graphene oxide, and 50g of silica fume to a mixer and mix at 50 rpm for 30 minutes. Then, add 300g of silica fume, 536.5g of slag powder, 7.5g of polycarboxylate superplasticizer, and 1g of modified polyether defoamer, and continue mixing at 50 rpm for 20 minutes. Finally, add 100g of slow-release phytic acid microcapsules and mix at 30 rpm for 10 minutes to obtain a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks. The preparation methods of polyetheramine-organosilicon modified graphene oxide, octadecylamine-graphene oxide and sustained-release phytic acid microcapsules are the same as in Example 1.

[0034] Testing experiment: Graphene-reinforced acid and alkali resistant composite reinforcing agents for bricks were prepared according to the preparation methods in each embodiment and comparative example, and concrete bricks were prepared using the composite reinforcing agents. The specific methods are as follows: Mix 1000g of sulfoaluminate cement and 3000g of sand, stir at 100rpm for 2min, add 20g of graphene-reinforced brick acid and alkali resistant composite reinforcing agent and 500g of deionized water, continue stirring for 5min to obtain mortar matrix, pour the mortar matrix into the mold for casting, vibrate to remove air, let stand at room temperature for 24h to demold, and finally place in a standard curing chamber at 25℃ and 90%RH relative humidity for 28 days to obtain concrete bricks.

[0035] The following tests were conducted using concrete bricks as test samples.

[0036] Compressive strength and flexural strength: The compressive strength and flexural strength of concrete bricks are tested in accordance with the "Test Methods for Concrete Blocks and Bricks" (GB / T 4111-2013). A universal testing machine is used. The concrete brick is placed in the center of the lower platen of the testing machine and continuously and uniformly loaded with a stress increase rate of 0.5 MPa / s until the concrete brick is destroyed. Its compressive strength is then tested. The concrete brick is installed on a flexural testing device and continuously and uniformly loaded with a stress increase rate of 0.05 MPa / s until the concrete brick is destroyed. Its flexural strength is then tested.

[0037] Acid resistance test: The acid resistance test of concrete bricks refers to the "Standard Test Method for Determination of Acid Resistance of Concrete Products" (ASTM C1898-20). A 5% sulfuric acid solution is used as the acid solution. The concrete bricks are immersed in the acid solution, with the acid solution level 20 mm above the top of the bricks. The immersion period is set to 90 days, and the acid solution is changed every 7 days. After 90 days, the bricks are taken out, washed, and dried at 105℃ to constant weight. The compressive strength of the concrete bricks after acid corrosion is measured, and the compressive strength retention rate of the concrete bricks is calculated.

[0038] Chloride ion penetration resistance test: The chloride ion penetration resistance test of concrete bricks was conducted in accordance with the "Standard for Test Methods of Long-term Performance and Durability of Concrete" (GB / T 50082-2024). The concrete bricks were placed in a vacuum container under saturated surface-dry conditions and evacuated to 1 kPa for 3 hours. Then, while maintaining the vacuum, a saturated calcium hydroxide solution was added to immerse the concrete bricks. The vacuum was maintained for another hour, and then restored to normal pressure. The bricks were soaked for another 18 hours before being removed, dried with cold air, and tested using an RCM test apparatus. The cathode solution was a 10 wt% sodium chloride solution, and the anode solution was a 0.3 mol / L sodium hydroxide solution. A 60 V DC voltage was applied for the test, and the energizing time was 24 hours. After 24 hours, the energizing was stopped, and the concrete bricks were radially split open. A 0.1 mol / L silver nitrate solution was sprayed onto the split surface for color development, and the chloride ion migration coefficient was calculated.

[0039]

[0040] Conclusion: The test data shows that, under the same conditions, the concrete with the graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks prepared in Example 1 has higher compressive strength, flexural strength, and compressive strength retention rate after acid corrosion than the concrete with the graphene-reinforced acid and alkali resistant composite reinforcing agent prepared in the comparative example. The chloride ion migration coefficient is the opposite. The graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks provided by this invention can improve the mechanical properties, acid and alkali resistance, and permeability resistance of concrete after being added to concrete. At the same time, the reinforcing agent and concrete have good compatibility.

[0041] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks, characterized in that: Specifically: S1. Polyetheramine-organosilicon-modified graphene oxide was prepared using polyetheramine, silane coupling agent KH-560 and graphene oxide as raw materials. S2. Using octadecylamine and graphene oxide as raw materials, prepare octadecylamine-graphene oxide; S3. Prepare sustained-release phytic acid microcapsules using phytic acid, ethyl cellulose and chitosan as raw materials; S4. Sodium alginate-cement microcapsules were prepared using sodium alginate, magnesium phosphate cement, epoxy resin and sulfoaluminate cement as raw materials. S5. A graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks is obtained by mixing polyetheramine-organosilicon modified graphene oxide, octadecylamine-graphene oxide, slow-release phytic acid microcapsules and sodium alginate-cement microcapsules with silica fume, slag powder, polycarboxylate superplasticizer and modified polyether defoamer.

2. The preparation method of a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks according to claim 1, characterized in that: By mass fraction, the graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks comprises: 0.2-0.3 wt% polyetheramine-organosilicon modified graphene oxide, 0.3-0.4 wt% octadecylamine-graphene oxide, 10-12 wt% slow-release phytic acid microcapsules, 8-9 wt% sodium alginate-cement microcapsules, 0.7-0.8 wt% polycarboxylate superplasticizer, 0.1-0.2 wt% modified polyether defoamer, 35-37 wt% silica fume, and the balance being slag powder.

3. The method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks according to claim 1, characterized in that: The preparation method of polyetheramine-organosilicon modified graphene oxide is as follows: Graphene oxide was added to deionized water and stirred at 200-300 rpm for 20-30 min, then ultrasonically dispersed for 20-30 min. 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added, and the mixture was stirred at 25-30℃ and 300-400 rpm for 30-40 min. Polyetheramine was added, and the reaction was continued for 20-24 h. After the reaction was completed, the mixture was ultrafiltered and centrifuged. The product was washed with deionized water and freeze-dried to obtain polyetheramine-modified graphene oxide. Polyetheramine-modified graphene oxide was added to an ethanol aqueous solution, stirred at 200-300 rpm for 20-30 min, ultrasonically dispersed for 20-30 min, and the pH was adjusted to 9-10. Silane coupling agent KH-560 was added, and the reaction was carried out at 60-70℃ and stirred at 300-400 rpm for 6-8 h. After the reaction was completed, the mixture was cooled, the precipitate was collected by centrifugation, washed with ethanol and deionized water, and dried at 60-70℃ for 4-6 h to obtain polyetheramine-organosilicon-modified graphene oxide.

4. The method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks according to claim 3, characterized in that: The mass ratio of graphene oxide, polyetheramine, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide is (1-1.2):(2-2.2):(1.5-1.7):(0.9-1.1); the mass ratio of polyetheramine-modified graphene oxide to silane coupling agent KH-560 is (20-22):(2-3).

5. The method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks according to claim 1, characterized in that: The preparation method of octadecylamine-graphene oxide is as follows: Graphene oxide was added to N,N-dimethylformamide and stirred at 200-300 rpm for 20-30 min, followed by ultrasonic dispersion for 20-30 min to obtain a graphene oxide dispersion. Octadecylamine was added to toluene and stirred at 200-300 rpm for 20-30 min to obtain an octadecylamine solution. Under nitrogen protection, the graphene oxide dispersion was added to the octadecylamine solution, and the mixture was refluxed at 90-100℃ and stirred at 300-400 rpm for 8-12 h. After the reaction was completed, the mixture was cooled, the precipitate was separated by centrifugation, redissolved in toluene, added to acetone to precipitate again, washed with acetone and n-hexane, and vacuum dried at 60-70℃ for 4-6 h to obtain octadecylamine-graphene oxide. The mass ratio of graphene oxide to octadecylamine is (1-1.2):(1-1.2).

6. The method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks according to claim 1, characterized in that: The preparation method of sustained-release phytic acid microcapsules is as follows: Phytic acid was added to deionized water and stirred at 200-300 rpm for 20-30 minutes to obtain an aqueous phytic acid solution. Ethyl cellulose and dispersant Span-80 were added to dichloromethane and stirred at 200-300 rpm for 20-30 minutes to obtain an ethyl cellulose solution. The aqueous phytic acid solution was added dropwise to the ethyl cellulose solution while continuously stirring at 8000-10000 rpm. After the addition was complete, the mixture was homogenized at 8000-10000 rpm for 3-5 minutes to obtain a phytic acid-ethyl cellulose emulsion. Chitosan was added to an aqueous glacial acetic acid solution and stirred at 50-60℃ for 20 minutes. Stir at 0-300 rpm for 20-30 min, add surfactant Tween-80, stir evenly, and adjust pH to 4-5 to obtain chitosan solution; add phytic acid-ethyl cellulose emulsion to chitosan solution while stirring continuously at 500-800 rpm. After addition, react at 25-30℃ and 500-800 rpm for 2-3 h. After reaction, add glutaraldehyde aqueous solution dropwise, maintain pH at 4-5, and continue stirring for 6-8 h. After reaction, collect product by centrifugation, wash with deionized water, and spray dry at 80-100℃ to obtain sustained-release phytic acid microcapsules.

7. The method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks according to claim 6, characterized in that: The mass ratio of phytic acid, ethyl cellulose, dispersant Span-80, chitosan and Tween-80 is (2-3):(2-3):(0.1-0.2):(1-2):(0.2-0.3).

8. The method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks according to claim 1, characterized in that: The preparation method of sodium alginate-cement microcapsules is as follows: Sodium alginate and magnesium phosphate cement were dry-mixed at 35-45℃ and 200-300 rpm for 5-7 minutes to obtain a mixed powder. Under water bath heating at 35-45℃, the mixed powder was added to polyethylene glycol-400 and mixed at low speed of 200-300 rpm for 2-4 minutes, then at high speed of 700-800 rpm for 3-5 minutes. After cooling, the mixture was extruded and granulated, and dried at 35-45℃ for 6-8 hours to obtain the microcapsule core material. Epoxy resin was added to anhydrous ethanol and stirred at 200-300 rpm for 20-30 minutes. After n, add the curing agent polyetheramine and stir evenly to obtain epoxy resin solution. Place the microcapsule core material in a fluidized bed coating machine, spray the epoxy resin solution and dry it to form an epoxy resin layer on the surface of the microcapsule core material. Set the drying temperature to 35-45℃ and the drying time to 20-30min. Then mix it with sulfoaluminate cement powder and stir at 40-50rpm for 30-60s to coat the surface of the epoxy resin layer with sulfoaluminate cement powder to form a cement layer. Cure in a sealed environment at room temperature for 24-36h to obtain sodium alginate-cement microcapsules.

9. The method for preparing a graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks according to claim 8, characterized in that: The mass ratio of sodium alginate, magnesium phosphate cement, polyethylene glycol-400, and sulfoaluminate cement powder is (3-4):(3-4):(3.5-4.5):(3-5); the mass ratio of epoxy resin and curing agent polyetheramine is (0.5-1.0):(0.15-0.2); the diameter of the microcapsule core material is 0.8-1.2 mm, the thickness of the epoxy resin layer is 200-300 μm, and the thickness of the cement layer is 200-300 μm.

10. A graphene-reinforced acid and alkali resistant composite reinforcing agent for bricks, characterized in that: It is prepared by any one of the preparation methods according to claims 1-9.

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