Special low-carbon light material for building outer wall and preparation method thereof

Abstract

The application discloses a kind of special low-carbon light materials for building outer wall and preparation method thereof, and the application relates to the field of advanced inorganic non-metallic technology, in view of the problem that the weak interface bonding of existing hydrophobic modified aerogel and geopolymer matrix leads to the sharp drop of composite material strength, the in-situ construction of aluminium-rich zeolite precursor inorganic shell layer on the surface of aerogel is carried out, the channel size of shell layer is smaller than the effective hydration diameter of hydrated alkali metal ions in strong alkali pore fluid, the dissolution of ions to aerogel framework is blocked by steric hindrance effect, and in-situ polycondensation occurs between shell layer surface metal hydroxyl and geopolymer silicate monomer, forming covalent bond bridging interface, reconstructing physical and mechanical occlusion interface into chemical covalent bonding interface, mixing the core-shell structure modified aerogel particles with slag, fly ash and composite alkali activator, forming, normal temperature curing, to obtain building outer wall material with low carbon emission, light weight, high thermal insulation and A-grade non-combustible fire performance.

Description

Technical Field

[0001] This invention relates to the field of advanced inorganic non-metallic technology, specifically to a special low-carbon lightweight material for building exterior walls and its preparation method. Background Technology

[0002] Under the national dual-carbon strategy, building exterior wall materials are developing towards low-carbon, lightweight, high-insulation, and non-combustible fireproofing. Geopolymer materials, made from industrial solid wastes such as blast furnace slag and fly ash as precursors and cured at room temperature with alkaline activators, have significant low-carbon properties because they do not require silicate cement clinker throughout the process. Furthermore, their inorganic framework naturally possesses Class A non-combustible fireproofing properties, making them considered one of the technological routes to replace traditional cement-based materials. To enable geopolymer wall materials to also possess lightweight and thermal insulation properties, the industry is experimenting with incorporating materials with a thermal conductivity of less than 0.02 watts per meter (Kelvin) into the geopolymer matrix. Aerogel particles as lightweight aggregate;

[0003] The closest prior art to this application is: first, Aerogel particles are surface-treated with organosilane hydrophobic modifiers to change their surface from hydrophilic groups to hydrophobic groups. The hydrophobic modified aerogel particles are then mixed with slag, fly ash and other solid waste precursor powders and alkali activator solution to form a slurry. The slurry is then cast and cured at room temperature to obtain a lightweight thermal insulation polymer composite material.

[0004] The problem with the above-mentioned existing technology is that the interface compatibility between the hydrophobically modified aerogel surface and the highly hydrophilic geopolymer slurry is poor. The two can only achieve physical connection through mechanical interlocking and van der Waals forces, and it is difficult to form effective chemical bonds. This results in the formation of a defect-dense interface transition zone inside the composite material. When the aerogel content reaches the volume ratio required to meet the thermal insulation requirements, the compressive and flexural strength of the composite material decreases significantly, making it difficult to meet the mechanical requirements of wind pressure resistance and durable load-bearing of building exterior walls. Summary of the Invention

[0005] The technical problem this invention aims to solve is: how to stably introduce [a substance] into a strongly alkaline gelling system using industrial solid waste as the main raw material and alkali-activated geopolymer as the matrix. Aerogel, a lightweight aggregate with ultra-low thermal conductivity, overcomes the problem in existing technologies where the weak interface between the hydrophobic modified surface of aerogel and the hydrophilic polymer matrix leads to a sharp drop in the mechanical strength of composite materials. This results in a special building exterior wall material that simultaneously possesses low carbon emissions, lightweight, high thermal insulation, high strength, and Class A non-combustible fire resistance.

[0006] To solve the above-mentioned technical problems, the technical solutions adopted in this invention include a method for preparing core-shell structure modified aerogel particles and a method for preparing special low-carbon lightweight materials for building exterior walls.

[0007] The preparation method of core-shell structure modified aerogel particles includes: dissolving sodium aluminate and sodium silicate in deionized water to prepare an aluminum-rich zeolite precursor sol with a silicon-aluminum molar ratio of 1.0 to 2.5.

[0008] Untreated with hydrophobic modification Aerogel particles were added to the aluminum-rich zeolite precursor sol, and stirring was performed to allow the precursor sol molecules to be adsorbed and spread on the surface. A coating layer is formed on the outer surface of the aerogel particles;

[0009] Adjust the pH of the system to 8 to 10 to initiate the reaction that has been adsorbed onto the [structure / material]. In-situ hydrolysis and condensation reactions occur on the surface of aerogel particles, where precursor sol molecules undergo hydrolysis and polymerization. An aluminum-rich zeolite precursor shell is formed on the outer surface of the aerogel particles.

[0010] The particles with the aforementioned shell layer are sequentially aged, separated, and dried at low temperature to obtain core-shell structured modified aerogel particles. The average diameter of the pores in the shell layer is less than twice the effective hydration diameter of hydrated alkali metal ions in the geopolymer pore liquid, thereby blocking the entry of hydrated alkali metal ions through steric hindrance. The internal framework of aerogel particles prevents the aerogel nanoframework from dissolving and collapsing in strongly alkaline environments. The aforementioned steric hindrance relationship can be expressed mathematically as follows:

[0011] ;

[0012] In the formula, The average pore diameter of the shell layer of the aluminum-rich zeolite precursor is expressed in nanometers.

[0013] The effective hydration radius of hydrated alkali metal ions in the polymer pore liquid is expressed in nanometers. When the diameter of the shell pores is less than twice the effective diameter of the hydrated alkali metal ions, the ions cannot physically pass through the shell pores into the aerogel core framework.

[0014] The preparation method of special low-carbon lightweight materials for building exterior walls includes: preparing core-shell structure modified aerogel particles according to the above method;

[0015] Blast furnace slag and fly ash are mixed to obtain compound solid waste precursor powder;

[0016] Prepare a composite alkali activator solution with a modulus of 0.8 to 1.4;

[0017] The core-shell structure modified aerogel particles were mixed evenly with the compound solid waste precursor powder.

[0018] Add a composite alkali activator solution to the obtained mixture, stir to form a slurry and shape it to obtain a green body;

[0019] The preform is cured in an environment with a temperature of 20°C to 35°C and a relative humidity greater than 90% for 7 to 28 days, allowing the metal hydroxyl functional groups on the outer surface of the shell to undergo in-situ polycondensation with the aluminosilicate monomers in the geopolymer matrix to form a covalently bridged interface, resulting in a special low-carbon lightweight material for building exterior walls. The modulus of the composite alkali activator is calculated as follows:

[0020] ;

[0021] In the formula, Indicates the modulus of the composite alkali activator;

[0022] Indicating the activator solution The molar amount of the component;

[0023] Indicating the activator solution The molar amount of the component.

[0024] This invention does not rely on organic modification methods, but rather... An inorganic mesoporous shell layer is constructed in situ on the surface of the aerogel, which blocks the dissolution channels of the strong alkaline pore liquid on the aerogel skeleton from the perspective of physical spatial steric hindrance, thus fundamentally preserving the original thermal insulation properties of the aerogel.

[0025] Simultaneously, by utilizing the naturally abundant highly active metal hydroxyl groups on the surface of the inorganic shell, an in-situ chemical condensation reaction is carried out with the geopolymer slurry to construct an inorganic covalent bond interface between the aerogel and the matrix. This reconstructs the traditional physical-mechanical interlocking interface into a chemical covalent bond interface, enabling stress to be smoothly transmitted and avoiding a sharp drop in strength caused by high-dosage aerogel.

[0026] Compared with the prior art, the beneficial effects of the present invention by adopting the above technical solution are as follows:

[0027] 1. This invention maintains Under the premise of the original thermal conductivity of aerogel, its structural retention rate in strongly alkaline polymer systems is significantly improved, avoiding the loss of thermal insulation performance during the preparation stage;

[0028] 2. This invention significantly improves the compressive and flexural strength of composite materials through chemical covalent bonding interfaces, enabling the mechanical properties of high-dosage aerogel lightweight insulation systems to meet the requirements of wind pressure resistance and durable load-bearing capacity of building exterior walls;

[0029] 3. This invention uses industrial solid waste to replace silicate cement clinker throughout the process, combined with inorganic aerogel insulating aggregate. The resulting material has low carbon emissions, is lightweight, has high thermal insulation and Class A non-combustible fireproof properties. Furthermore, due to the improved aerogel retention efficiency, the actual amount of aerogel can be effectively reduced while meeting the same thermal insulation standard requirements. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the preparation process of core-shell structure-modified aerogel particles in an embodiment of the present invention.

[0031] Figure 2 This is a complete process flow diagram of the preparation of special low-carbon lightweight building exterior wall materials in the embodiments of the present invention;

[0032] Figure 3 This is a schematic diagram of the covalent bond bridging interface mechanism between aerogel and geopolymer in an embodiment of the present invention. Detailed Implementation

[0033] The following is in conjunction with the appendix Figure 1-3 The specific embodiments of the present invention will be further described below. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0034] The technical solution of the present invention will be further described below with reference to specific embodiments. These embodiments are used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0035] Example 1: Preparation of core-shell structured modified aerogel particles

[0036] First, sodium aluminate and sodium silicate were dissolved in deionized water at a silicon-to-aluminum molar ratio of 1.8 and stirred for 30 minutes at room temperature to form a clear aluminum-rich aluminosilicate composite sol precursor solution. Then, the untreated, unmodified raw material was... Aerogel particles are directly added to the above precursor solution and stirred at low speed for 40 minutes at a temperature of 20 degrees Celsius and a rotation speed of 200 rpm. This allows the precursor sol molecules to be adsorbed by the original surface silanol groups of the aerogel and spread evenly on the outer surface of the aerogel particles, forming a uniform coating layer.

[0037] Next, by adding dilute hydrochloric acid solution, the pH of the system was adjusted to 9, initiating an in-situ hydrolysis and condensation reaction of the precursor sol molecules adsorbed on the aerogel surface. The reaction time was controlled to be 2 hours, forming a dense and continuous aluminum-rich zeolite precursor gel shell. The shell thickness was measured to be approximately 120 nanometers. Finally, the obtained core-shell structured particle suspension was allowed to stand for 4 hours to improve the shell structure. After filtration and multiple washings with deionized water to remove unreacted free ions, the particles were dried at a low temperature of 60 degrees Celsius to obtain core-shell structured modified aerogel particles with a uniform inorganic mesoporous shell coating on the surface.

[0038] Testing revealed that the average pore diameter of the shell layer of the core-shell modified aerogel particles obtained in this embodiment is approximately 0.6 nm, which is smaller than the effective hydration diameter of sodium ions in the strong alkaline pore liquid (approximately 0.72 nm), satisfying the steric hindrance relationship. After immersing the core-shell modified aerogel particles obtained in this embodiment in a strong alkaline solution with a pH of 13.5 for 168 hours, the porosity retention rate of the internal aerogel skeleton was found to be no less than 90%, while the porosity retention rate of the untreated original aerogel particles under the same conditions was less than 40%. This indicates that the shell structure of this embodiment has a significant protective effect on the aerogel skeleton.

[0039] Example 2: Preparation of Special Low-Carbon Lightweight Materials for Building Exterior Walls

[0040] First, blast furnace slag and fly ash powder were weighed at a mass ratio of 7:3 and mixed evenly to obtain a compound solid waste precursor powder. Then, water glass and sodium hydroxide solution were compounded at a modulus ratio of 1.1 to prepare a compound alkali activator solution. The solution was left to stand for 2 hours to allow the silicate ions in the solution to fully polymerize.

[0041] Next, the core-shell modified aerogel particles prepared in Example 1 were mixed with the above-mentioned compound solid waste precursor powder at a volume ratio of 40% in a dry state to make the aerogel particles uniformly dispersed in the powder system. The above-mentioned compound alkali activator solution was slowly added to the mixture, and a low-speed forced stirring method was used to make slurry. The stirring speed and time were controlled to avoid damage to the aerogel core-shell structure under shear force. Then the slurry was poured into a mold to make the outer wall panel blank.

[0042] Finally, the molded preform is placed in a curing environment at 25 degrees Celsius and 95% relative humidity for 14 days to allow the geopolymer matrix to fully react and solidify. At the same time, the in-situ polycondensation reaction between the active hydroxyl groups on the core-shell surface and the aluminosilicate monomers in the matrix is ​​completed, forming a chemical covalent bond interface. After curing, the preform is demolded to obtain the finished product of special low-carbon lightweight building exterior wall material.

[0043] Testing revealed that the material obtained in this embodiment has a dry density of approximately 320 kg / m³, a thermal conductivity of approximately 0.045 W / m Kelvin, a compressive strength of approximately 2.8 MPa, a flexural strength of approximately 1.1 MPa, and a combustion performance rating that meets the Class A non-combustible standard. In comparison, a material prepared using an existing hydrophobic modified aerogel scheme under the same aerogel dosage conditions has a compressive strength of approximately 1.2 MPa and a flexural strength of approximately 0.4 MPa, with significantly lower mechanical properties than the material in this embodiment. This verifies the effect of the interfacial covalent bonding structure of this invention on improving the mechanical properties of the composite material.

[0044] Example 3: Verification of the interfacial bonding between the surface of core-shell modified aerogel particles and the geopolymer matrix

[0045] Cross-sectional microscopic observation of the material obtained in Example 2 showed that there were no obvious gaps between the outer surface of the shell of the core-shell modified aerogel particles and the surrounding geopolymer matrix, and the two were in a continuous transition state. No interface transition zone defects commonly found in existing organic hydrophobic modification technologies were observed. Energy dispersive spectroscopy analysis revealed a continuous distribution of aluminum, silicon, and oxygen elements at the interface between the aerogel particle shell and the geopolymer matrix. This indicates that an in-situ polycondensation reaction occurred between the metal hydroxyl functional groups on the shell surface and the aluminosilicate monomers in the geopolymer matrix, forming a continuous covalent bond interface, which is consistent with the interface bonding mechanism of the present invention.

[0046] Example 4: Explanation of other implementation parameters

[0047] In this invention, the silica-alumina molar ratio of the aluminum-rich zeolite precursor sol can be selected in the range of 1.0 to 2.5, the temperature of the aerogel particle dispersion and precursor adsorption process can be selected in the range of 10 degrees Celsius to 30 degrees Celsius, the rotation speed can be selected in the range of 100 rpm to 300 rpm, and the stirring time can be selected in the range of 20 minutes to 60 minutes.

[0048] The pH value of the in-situ condensation shell formation process can be selected in the range of 8 to 10, the reaction time can be selected in the range of 1 hour to 4 hours, and the shell thickness can be controlled in the range of 50 nanometers to 200 nanometers by controlling the precursor concentration and reaction time.

[0049] The aging time can be selected within the range of 2 to 6 hours, and the low-temperature drying temperature should be controlled within the range of below 80 degrees Celsius;

[0050] The modulus of the composite alkali activator can be selected in the range of 0.8 to 1.4;

[0051] The room temperature curing temperature of the molded preform can be selected from 20 degrees Celsius to 35 degrees Celsius, the relative humidity can be controlled within the range of greater than 90%, and the curing time can be selected from 7 days to 28 days. Those skilled in the art can make adaptive adjustments within the above range according to the actual raw material activity, aerogel content and target performance requirements, and all can achieve the technical effects of the present invention.

[0052] The special low-carbon lightweight material for building exterior walls prepared by this invention has a composite structure in which core-shell modified aerogel particles are uniformly dispersed in a continuous geopolymer matrix phase. The volume content of aerogel particles is determined according to the thermal insulation and strength design requirements. Finally, it is applied to the building exterior wall in the form of exterior wall panels or wall plastering layers.

[0053] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing core-shell structured modified aerogel particles, characterized in that, The process includes the following steps: dissolving sodium aluminate and sodium silicate in deionized water to prepare an aluminum-rich zeolite precursor sol with a silica-alumina molar ratio of 1.0 to 2.

5. Untreated with hydrophobic modification Aerogel particles were added to the aluminum-rich zeolite precursor sol, and stirring was performed to allow the precursor sol molecules to be adsorbed and spread on the surface. A coating layer is formed on the outer surface of the aerogel particles; Adjust the pH of the system to 8 to 10 to initiate the reaction that has been adsorbed onto the [structure / material]. In-situ hydrolysis and condensation reactions occur on the surface of aerogel particles, where precursor sol molecules undergo hydrolysis and polymerization. An aluminum-rich zeolite precursor shell is formed on the outer surface of the aerogel particles. The particles with the aluminous zeolite precursor shell were sequentially aged, separated, and dried at low temperature to obtain core-shell structure modified aerogel particles. The average diameter of the pores in the shell of the alumina-rich zeolite precursor is less than twice the effective hydration diameter of hydrated alkali metal ions in the geopolymer pore liquid, which is used to block the hydrated alkali metal ions from entering the pore liquid through steric hindrance. Internal framework of aerogel particles.

2. The preparation method according to claim 1, characterized in that, The The conditions for stirring the aerogel particles into the aluminum-rich zeolite precursor sol are: temperature 10°C to 30°C, rotation speed 100 rpm to 300 rpm, and stirring time 20 minutes to 60 minutes.

3. The preparation method according to claim 1, characterized in that, The reaction time of the in-situ hydrolysis-condensation reaction is 1 to 4 hours, and the thickness of the resulting aluminum-rich zeolite precursor shell is 50 to 200 nanometers.

4. The preparation method according to claim 1, characterized in that, The aging time is 2 to 6 hours, and the low-temperature drying temperature is below 80 degrees Celsius.

5. A core-shell structured modified aerogel particle, comprising: The aerogel particle core and the aluminum-rich zeolite precursor condensation shell coating the outer surface of the core are characterized in that... The average pore diameter of the shell is less than twice the effective hydration diameter of hydrated alkali metal ions in the geopolymer pore liquid, the thickness of the shell is 50 nanometers to 200 nanometers, and the outer surface of the shell is distributed with metal hydroxyl functional groups.

6. A method for preparing a special low-carbon lightweight material for building exterior walls, characterized in that, The process includes the following steps: preparing core-shell structured modified aerogel particles according to the preparation method of any one of claims 1 to 4; Blast furnace slag and fly ash are mixed to obtain compound solid waste precursor powder; Prepare a composite alkali activator solution with a modulus of 0.8 to 1.4, wherein the modulus is the ratio of the activator solution to the total alkali content. molar amount of components and The ratio of the molar amounts of the components; The core-shell structure modified aerogel particles are mixed evenly with the compound solid waste precursor powder to obtain a mixture; The composite alkali activator solution is added to the mixture, stirred to form a slurry, and then shaped to obtain a green body; The preform is cured for 7 to 28 days in an environment with a temperature of 20 to 35 degrees Celsius and a relative humidity of more than 90%, so that the metal hydroxyl functional groups on the outer surface of the shell of the aluminum-rich zeolite precursor undergo an in-situ polycondensation reaction with the aluminosilicate monomers in the geopolymer matrix to form a covalent bond bridging interface, thereby obtaining a special low-carbon lightweight material for building exterior walls.

7. The preparation method according to claim 6, characterized in that, The composite alkaline activator solution is prepared by combining water glass and sodium hydroxide solution.

8. A special low-carbon lightweight material for building exterior walls, characterized in that, The invention comprises a geopolymer matrix and core-shell modified aerogel particles according to claim 5 dispersed in the geopolymer matrix, wherein the outer surface of the shell layer of the core-shell modified aerogel particles is connected to the geopolymer matrix by covalent bonds, and the geopolymer matrix is ​​formed by solidifying slag and fly ash at room temperature with a composite alkali activator.

9. The special low-carbon lightweight material according to claim 8, characterized in that, The special low-carbon lightweight material has a plate-like structure and is used for building exterior walls.

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