Aerogel foam concrete and method of manufacture

Abstract

The application discloses aerogel foam concrete and a preparation method thereof, and belongs to the field of foam concrete. The modified silica aerogel particles are prepared by a sol-gel method, the low-thermal-conductivity and multi-pore flexible silica aerogel is prepared by 3D printing of the silica aerogel particles, the foam stability is improved by using nano-silica modified foaming agent to prepare high-stability foam concrete slurry, and finally the slurry is poured into the silica aerogel to prepare ultra-light foam concrete with excellent heat preservation and heat insulation performance. The aerogel foam concrete prepared by the application has the advantages of light weight, high strength, heat preservation, heat insulation, sound insulation and the like, and can be widely applied to the field of building energy saving. The application solves the problems of low strength, easy cracking and poor heat preservation performance of traditional foam concrete, and has important application value.

Description

Technical Field

[0001] This invention relates to the field of foamed concrete, and particularly to an aerogel foamed concrete and its preparation method. Background Technology

[0002] Foamed concrete, as a lightweight porous material, has advantages such as light weight, thermal insulation, heat insulation, and sound insulation, and is widely used in the field of building energy conservation. However, traditional foamed concrete has problems such as low strength, easy cracking, and the need to improve its thermal insulation performance, which limits its further application.

[0003] Aerogel is a novel material with a nanoporous structure, exhibiting extremely low density, high specific surface area, and excellent thermal insulation properties. Introducing aerogel into foamed concrete can significantly improve the material's thermal insulation performance, but it can also negatively impact its mechanical properties. Furthermore, the key to preparing foamed concrete lies in the selection of the foaming agent; traditional foaming agents suffer from low foaming efficiency and poor bubble stability, resulting in unsatisfactory performance of the prepared foamed concrete.

[0004] Therefore, developing a low-cost, high-efficiency, and stable foaming agent, and using it in combination with aerogel to prepare ultra-lightweight, low-thermal-conductivity foamed concrete, has significant social value and application prospects. Summary of the Invention

[0005] To address the problems of low strength, easy cracking, and poor thermal insulation performance of existing foamed concrete, this invention provides an aerogel foamed concrete and its preparation method to meet the demand for high-performance thermal insulation materials in the field of building energy conservation.

[0006] In a first aspect, the present invention provides a method for preparing aerogel foam concrete, which is achieved through the following technical solution.

[0007] A method for preparing aerogel foam concrete includes the following steps:

[0008] S1. Preparation of modified silica aerogel particles using the sol-gel method:

[0009] A silicon source, anhydrous ethanol, and deionized water were mixed and stirred evenly in a molar ratio of 1:(5-12):(1-6). The mixture was hydrolyzed under acidic conditions to obtain silica sol. Then, an alkaline catalyst was added dropwise under stirring to adjust the pH to 7.0-8.0. After standing, a preliminarily gelled gel was obtained. The gel was then subjected to aging, solvent replacement, modification, cleaning, and drying to obtain modified silica aerogel particles.

[0010] S2. Preparation of 3D-printed silica aerogel:

[0011] The adhesive and sodium octadecate are mixed, and then the modified silica aerogel particles prepared in step S1 are added and stirred evenly. The mass ratio of modified silica aerogel particles to adhesive is (0.8-1.2):1. 3D printing is performed, and the volume ratio of 3D printing gel is 20%-60%. After freeze drying, 3D printed silica aerogel is obtained.

[0012] S3. Preparation of nano-silica modified foaming agent:

[0013] Cement foaming agent and water are mixed at a mass ratio of 1:30, and then 0.5%-2.0% of nano silica particles by mass of foaming agent are added. The mixture is stirred evenly and then foamed using a foaming machine to obtain nano silica modified foam.

[0014] S4. Preparation of aerogel foam concrete slurry:

[0015] Cement, water, modified silica aerogel particles prepared in step S1, and thickener are thoroughly mixed to form a cement aerogel slurry. Then, nano-silica modified foam prepared in step S3 is added and stirred evenly to obtain aerogel foam concrete slurry. The mass ratio of cement, water, modified silica aerogel particles, and nano-silica modified foam is (14-16):(6-9):(0.8-1.0):(2.2-2.4).

[0016] S5. Pour the slurry prepared in step S4 into the 3D printed silica aerogel prepared in step S2, cover it with plastic wrap, demold it and cure it to obtain aerogel foam concrete.

[0017] By adopting the above technical solution, the modified silica aerogel particles prepared in step S1 of this application are a lightweight, porous material with a network structure and high thermal insulation properties, that is, its thermal conductivity at room temperature can be as low as 0.013 W·m. -1 ·K -1 Specific surface area as high as 500~1000m² 2 ·g -1 The pore size is approximately 10~100nm.

[0018] In step S2 of this application, a 3D printer is used to print suitable mesh structures, including but not limited to three-period minimal surface meshes, pseudo-crystalline structure meshes, eight-fold truss meshes, diamond meshes, and non-periodic meshes, thereby enhancing the thermal insulation performance of the material's macroscopic mechanical properties. The 3D-printed aerogel is white in appearance, has a high porosity structure, and possesses good hydrophobicity.

[0019] In step S3 of this application, nano-silica is used to modify the cement foaming agent. The nano-silica particles can significantly improve the mechanical strength of the foam through irreversible adsorption, and the dense particle film formed at the gas-liquid interface significantly increases the stability of the foam.

[0020] Furthermore, in step S1, the silicon source is tetraethyl orthosilicate, the acidic condition is to add 1 mol / L hydrochloric acid to adjust the pH to 1.0-1.5, and the alkaline catalyst is 0.5 mol / L ammonia.

[0021] Furthermore, in step S1, the aging process is as follows: an aging solution is added to the initially gelled gel, and the mixture is sealed and aged at 40-60°C for 24 hours; the aging solution is a mixture of tetraethyl orthosilicate and anhydrous ethanol in a volume ratio of 1:4.

[0022] Furthermore, in step S1, the solvent exchange step is as follows: the aged gel is placed in n-hexane solvent for solvent exchange at 50°C for 24 hours.

[0023] Furthermore, in step S1, the modification method is as follows: first, trimethylchlorosilane is used to modify the gel to construct a hydrophobic core, and then KH-550 and aminotrimethylphosphonic acid complex are used to modify the hydrophobic core to construct a hydrophilic shell.

[0024] Furthermore, the specific methods for gel modification are as follows:

[0025] a. Add trimethylchlorosilane to the wet gel after solvent exchange, stir and react at 25°C for 5-6 hours. After the reaction is completed, filter and wash to obtain an aerogel with a hydrophobic core; wherein the molar ratio of trimethylchlorosilane to silanol groups on the surface of the aerogel is (1.2-1.5):1.

[0026] b. Add KH-550 and aminotrimethylphosphonic acid to toluene solution in a molar ratio of 1:1, and carry out amidation reaction at 60℃ for 7-8 hours to generate KH-550 and aminotrimethylphosphonic acid complex.

[0027] c. Add the aerogel with a hydrophobic core obtained in step a to the toluene solution of the KH-550 and aminotrimethylphosphonic acid complex prepared in step b, and stir for 4-5 hours to obtain an aerogel with a hydrophilic shell; wherein the amount of the complex is 5%-8% of the mass of the aerogel.

[0028] By employing the above technical solution, convective heat transfer of air in the confined space at the nanoscale is greatly suppressed. The main heat conduction path is the collision between the solid framework and gas molecules. Once water penetrates the nanopores of the aerogel, it replaces the low thermal conductivity of air and, through its higher thermal conductivity and enhanced solid-liquid-gas coupling heat transfer, causes the overall thermal conductivity of the aerogel to increase dramatically, potentially by several times or even an order of magnitude. When water enters the nanopores and evaporates, the resulting capillary stress is sufficient to destroy the fragile silica framework, leading to the aerogel pulverizing or collapsing and permanently losing its nanoporous structure and thermal insulation properties. Hydrophobic modification of the aerogel surface is the most effective means of preventing water intrusion. However, cement hydration products (mainly CSH gel and Ca(OH)2, etc.) are inherently hydrophilic, with surfaces rich in polar groups such as hydroxyl (-OH) and silanol (Si-OH). The hydrophobic aerogel surface is difficult to wet with hydrophilic cement paste. Cement paste tends to "aggregate" around itself rather than spread and tightly encapsulate the aerogel particles or mesh surface. This results in micropores and a weak boundary layer at the interface. Under stress, especially tensile and bending stress, cracks tend to initiate and propagate preferentially at the interface, reducing the overall strength and toughness of the composite material. Furthermore, the hydrophobic surface is not conducive to the adsorption and nucleation of polar water molecules and hydrated ions. Its ability to promote hydration is far lower than that of hydrophilic nano-SiO2 surfaces. Based on the above, this application optimizes the modification of the aerogel by using trimethylchlorosilane (TMCS) to construct a hydrophobic core. The chlorine atoms of TMCS undergo nucleophilic substitution with the silanol groups (Si-OH) on the aerogel surface, forming stable Si-O-Si bonds. The methyl groups (-CH3) are arranged outwards, forming a dense hydrophobic layer that seals the nanopores. This blocks water intrusion, reduces surface energy, and prevents capillary water absorption. The aerogel constructed with the hydrophobic core and KH-550 are reacted with an aminotrimethylphosphonic acid (ATMP) complex. The -Si-OC2H5 in the complex undergoes a hydrolytic condensation reaction with the hydrophobic layer of the aerogel, forming Si-O-Si bonds for anchoring and constructing a hydrophilic outer shell. Meanwhile, the -PO3H2 in the composite reacts with the Ca in the cement. 2+ The reaction produces hydroxyapatite; in the complex, -NH-CO- forms a hydrogen bond network with the CSH gel surface.

[0029] Furthermore, in step S1, drying is carried out under normal pressure, with drying conditions of 80℃ for 3 hours and 120℃ for 6 hours.

[0030] Furthermore, in step S2, the mass ratio of the adhesive to sodium stearate is (20-40):1. The adhesive is polyvinyl alcohol.

[0031] Furthermore, in step S3, the cement foaming agent is a composite foaming agent, model ST300S, whose main components are plant protein and high molecular surfactant composite cement foaming agent.

[0032] Furthermore, in step S4, the cement is PⅡ52.5 cement.

[0033] Furthermore, in step S4, the amount of thickener added is 0.05% to 0.5% of the cement mass. The thickener is selected from at least one of methylcellulose, hydroxypropyl methylcellulose, sodium carboxymethyl cellulose, hydroxyethyl cellulose, starch, and gelatin.

[0034] Furthermore, in step S4, sepiolite fibers, boron nitride nanoribbons, and polyacrylonitrile fibers are added to the aerogel foam concrete slurry. The sepiolite fiber content is 0.18%-0.55% of the cement mass, the boron nitride nanoribbon content is 0.05%-0.15% of the cement mass, and the polyacrylonitrile fiber content is 0.15%-0.27% of the cement mass.

[0035] Specifically, the sepiolite fibers have a diameter of 5-10 μm and a length of 4-6 mm; the boron nitride nanoribbons have a width of 5-10 nm and a length of 1-2 μm; and the polyacrylonitrile fibers have a diameter of 10-15 μm and a length of 3-5 mm.

[0036] By adopting the above technical solution, the three types of fibers exhibit significant multi-scale synergistic effects with modified silica aerogel particles possessing a TMCS hydrophobic core and a KH-550 / ATMP hydrophilic outer shell structure, jointly optimizing the thermal insulation, mechanical, and durability properties of aerogel foam concrete. Specifically, the Si-OH of sepiolite forms Si-OP≡ hydrogen bonds with the PO3H2 of the outer shell, and the B-OH of boron nitride forms Si-OP≡ hydrogen bonds with the PO3 of the outer shell. 2- A BOP electrostatic composite is formed, where the COOH of the polyacrylonitrile reacts with the PO3 of the outer shell. 2- Formation of Ca 2+ Chelating bridges; simultaneously, the hydrophobic core of TMCS, combined with the moisture-absorbing effect of sepiolite, keeps the internal humidity of the aerogel constant at <65% RH; boron nitride can conduct away local heat, and the hydrophobic core prevents vaporization and cracking, allowing the material to withstand 20 thermal cycles without cracking. In summary, the three fibers, together with the modified silica aerogel particles with a TMCS hydrophobic core and a KH550 / ATMP hydrophilic shell structure, achieve a triple synergy through chemical bonding, physical interlocking, and functional complementarity: sepiolite fiber can protect the moisture-proof integrity of the hydrophobic core and amplify the adhesion of the hydrophilic shell; boron nitride nanoribbons can conduct heat in a directional manner to protect the thermal insulation structure and enhance interfacial stability at high temperatures; polyacrylonitrile fiber can suppress cracks across scales and synergistically accelerate hydration with phosphonic acid groups.

[0037] Secondly, the present invention provides an aerogel foam concrete, which is achieved through the following technical solution.

[0038] An aerogel foam concrete prepared by the above preparation method.

[0039] This application has the following beneficial effects.

[0040] (1) The present invention uses nano-silica modified foaming agent to improve the stability and uniformity of foam, thereby preparing ultra-lightweight foamed concrete with excellent pore structure and stable performance.

[0041] (2) In this invention, modified silica aerogel particles and 3D printed aerogel are introduced into foamed concrete. By utilizing the nanoporous structure and high specific surface area of ​​the aerogel, the thermal insulation performance of the material is significantly improved.

[0042] (3) The aerogel foam concrete prepared by the present invention has the advantages of being lightweight, high-strength, heat-insulating, sound-insulating, and can be widely used in the field of building energy conservation. Attached Figure Description

[0043] Figure 1 SEM image (10 μm) of the hydrophobic silica aerogel prepared in Example 1 of this invention.

[0044] Figure 2 SEM image (5 μm) of the hydrophobic silica aerogel prepared in Example 1 of this invention;

[0045] Figure 3 The nitrogen adsorption-desorption isotherm of the hydrophobic silica aerogel prepared in Example 1 of this invention;

[0046] Figure 4 This is a pore size distribution diagram of the hydrophobic silica aerogel prepared in Example 1 of the present invention. Detailed Implementation

[0047] The invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise specified, the experimental methods used in this invention are conventional methods, and the experimental equipment, materials, reagents, etc. used can all be purchased from relevant material sales companies.

[0048] The cement foaming agent used in the following embodiments of this application is ST300S, whose main component is a composite cement foaming agent of plant protein polymer surfactant.

[0049] Example 1

[0050] The preparation of aerogel foam concrete with hydrophobic silica aerogel accounting for 20% by volume includes the following steps:

[0051] (1) Preparation of silica sol: Tetraethyl orthosilicate, anhydrous ethanol and deionized water in a molar ratio of 1:7:3 were added to a container and mixed and stirred for 30 min; then 1 mol / L hydrochloric acid was added to adjust the pH to 1.2 and stirred to hydrolyze and obtain silica sol; under stirring, 0.5 mol / L ammonia water was slowly added dropwise to silica sol to adjust the pH to 7, and the gel was allowed to stand at room temperature until the liquid surface in the container did not tilt when the container was tilted at more than 45°, thus obtaining a pre-gelled gel; the pre-gelled gel was placed in a mixture of tetraethyl orthosilicate and anhydrous ethanol in a volume ratio of 1:4, sealed and aged at 50° for 24 h; the aged gel was placed in n-hexane solvent for solvent exchange at 50° for 24 h to replace the deionized water remaining in the wet gel skeleton;

[0052] (2) Gel modification:

[0053] a. Trimethylchlorosilane was added to the wet gel after solvent exchange, and the mixture was stirred at 25°C for 6 hours. After the reaction was completed, the mixture was filtered and washed to obtain an aerogel with a hydrophobic core. The molar ratio of trimethylchlorosilane to silanol groups on the surface of the aerogel was 1.2:1.

[0054] b. KH-550 and aminotrimethylphosphonic acid were added to toluene solution at a molar ratio of 1:1, and amidation reaction was carried out at 60°C for 8 hours to generate KH-550 and aminotrimethylphosphonic acid complex.

[0055] c. The aerogel with a hydrophobic core prepared in step a is added to a toluene solution of the KH-550 and aminotrimethylphosphonic acid complex prepared in step b, and the mixture is stirred for 4 hours to obtain an aerogel with a hydrophilic outer shell; wherein the amount of the complex is 5% of the mass of the aerogel.

[0056] (3) Drying under normal pressure: The surface of the prepared wet gel is cleaned with hexane and then dried under normal pressure. The drying temperature is 80℃ for 3 hours and 120℃ for 6 hours. After naturally cooling to room temperature, it is ground to obtain nanoporous silica aerogel powder containing a three-dimensional network structure.

[0057] (4) Preparation of flexible silica aerogel for 3D printing: Add 0.2g sodium stearate to 6g of 10% polyvinyl alcohol aqueous solution (containing 0.6g of solid PVA) and stir at 1500r / min for 120s; add 0.6g of modified silica aerogel powder in batches, stir repeatedly, and stir evenly to obtain aerogel ink body that can be used for 3D printing. Use a 3D printing direct writing printer to print a grid of simple cubic structure units, control the size of the connecting rods in the grid, ensure that the volume ratio of 3D printing gel is 20%, and freeze dry;

[0058] (5) Preparation of slurry: Cement, water, modified silica aerogel powder and thickener are thoroughly mixed to form cement aerogel slurry. Cement foaming agent is diluted at a ratio of 30 times, and then 0.5% of nano silica particles by mass of foaming agent are added and stirred evenly. Foaming is performed using a foaming machine to obtain nano silica modified foam, which is added to cement aerogel slurry and stirred evenly to obtain aerogel foam concrete slurry. The mass ratio of cement, water, modified silica aerogel powder and nano silica modified foam is 15:7.5:0.8:2.3. Methylcellulose is selected as the thickener, and the amount of thickener added is 0.1% of the cement mass.

[0059] (6) Mixing and pouring of foamed concrete: After pouring the prepared slurry into the 3D printed aerogel, cover it with plastic wrap, let it stand for 24 hours, demold it, and put it into a standard curing box for curing.

[0060] The thermal conductivity of the 3D-printed aerogel foam concrete prepared in this embodiment, after 28 days of standard curing, was measured by the steady-state method to be 0.065 W / (m·K).

[0061] Tensile strength test: According to GB / T 6344 standard, dumbbell-shaped specimens of foamed concrete were prepared and tensile tests were performed on a universal testing machine. The tensile strength was measured to be 1.40 MPa.

[0062] Example 2

[0063] The preparation of aerogel foam concrete with hydrophobic silica aerogel accounting for 40% by volume includes the following steps:

[0064] (1) Preparation of silica sol: Tetraethyl orthosilicate, anhydrous ethanol and deionized water in a molar ratio of 1:7:3 were added to a container and mixed and stirred for 30 min; then 1 mol / L hydrochloric acid was added to adjust the pH to 1.2 and stirred to hydrolyze and obtain silica sol; under stirring, 0.5 mol / L ammonia water was slowly added dropwise to silica sol to adjust the pH to 7, and the gel was allowed to stand at room temperature until the liquid surface in the container did not tilt when the container was tilted at more than 45°, thus obtaining a pre-gelled gel; the pre-gelled gel was placed in a mixture of tetraethyl orthosilicate and anhydrous ethanol in a volume ratio of 1:4, sealed and aged at 50° for 24 h; the aged gel was placed in n-hexane solvent for solvent exchange at 50° for 24 h to replace the deionized water remaining in the wet gel skeleton;

[0065] (2) Gel modification:

[0066] a. Trimethylchlorosilane was added to the wet gel after solvent exchange, and the mixture was stirred at 25°C for 6 hours. After the reaction was completed, the mixture was filtered and washed to obtain an aerogel with a hydrophobic core. The molar ratio of trimethylchlorosilane to silanol groups on the surface of the aerogel was 1.5:1.

[0067] b. KH-550 and aminotrimethylphosphonic acid were added to toluene solution at a molar ratio of 1:1, and amidation reaction was carried out at 60°C for 8 hours to generate KH-550 and aminotrimethylphosphonic acid complex.

[0068] c. The aerogel with a hydrophobic core prepared in step a is added to a toluene solution of the KH-550 and aminotrimethylphosphonic acid complex prepared in step b, and the mixture is stirred for 4 hours to obtain an aerogel with a hydrophilic outer shell; wherein the amount of the complex is 8% of the mass of the aerogel.

[0069] (3) Drying under normal pressure: The surface of the prepared wet gel is cleaned with hexane and then dried under normal pressure. The drying temperature is 80℃ for 3 hours and 120℃ for 6 hours. After naturally cooling to room temperature, it is ground to obtain nanoporous silica aerogel powder containing a three-dimensional network structure.

[0070] (4) Prepare flexible silica aerogel for 3D printing. Add 0.2g sodium stearate to 6g of 10% polyvinyl alcohol aqueous solution (containing 0.6g of solid PVA) and stir at 1500r / min for 120s. Add 0.6g of modified silica aerogel powder in batches and stir repeatedly until uniformly mixed to obtain aerogel ink body that can be used for 3D printing. Use a 3D printing direct writing printer to print a grid of simple cubic structure units, control the size of the connecting rods in the grid, ensure that the volume ratio of 3D printing gel is 40%, and freeze dry.

[0071] (5) Preparation of slurry: Cement, water, modified silica aerogel powder and thickener are thoroughly mixed to form cement aerogel slurry. Cement foaming agent is diluted at a ratio of 30 times, and then 0.5% of nano silica particles by mass of foaming agent are added and stirred evenly. Foaming is performed using a foaming machine to obtain nano silica modified foam, which is added to cement aerogel slurry and stirred evenly to obtain aerogel foam concrete slurry. The mass ratio of cement, water, modified silica aerogel powder and nano silica modified foam is 15:7.5:0.8:2.3. Methylcellulose is selected as the thickener, and the amount of thickener added is 0.1% of the cement mass.

[0072] (6) Mixing and pouring of foamed concrete: After pouring the prepared slurry into the 3D printed aerogel, cover it with plastic wrap, let it stand for 24 hours, demold it, and put it into a standard curing box for curing.

[0073] The thermal conductivity of the 3D-printed aerogel foam concrete prepared in this embodiment, after 28 days of standard curing, was measured by the steady-state method to be 0.050 W / (m·K).

[0074] Tensile strength test: According to GB / T 6344 standard, dumbbell-shaped specimens of foamed concrete were prepared and tensile tests were performed on a universal testing machine. The tensile strength was measured to be 1.43 MPa.

[0075] Example 3

[0076] The preparation of aerogel foam concrete with hydrophobic silica aerogel accounting for 60% by volume includes the following steps:

[0077] (1) Preparation of silica sol: Tetraethyl orthosilicate, anhydrous ethanol and deionized water in a molar ratio of 1:7:3 were added to a container and mixed and stirred for 30 min; then 1 mol / L hydrochloric acid was added to adjust the pH to 1.2 and stirred to hydrolyze and obtain silica sol; under stirring, 0.5 mol / L ammonia water was slowly added dropwise to silica sol to adjust the pH to 7, and the gel was allowed to stand at room temperature until the liquid surface in the container did not tilt when the container was tilted at more than 45°, thus obtaining a pre-gelled gel; the pre-gelled gel was placed in a mixture of tetraethyl orthosilicate and anhydrous ethanol in a volume ratio of 1:4, sealed and aged at 50° for 24 h; the aged gel was placed in n-hexane solvent for solvent exchange at 50° for 24 h to replace the deionized water remaining in the wet gel skeleton;

[0078] (2) Gel modification:

[0079] a. Trimethylchlorosilane was added to the wet gel after solvent exchange, and the mixture was stirred at 25°C for 6 hours. After the reaction was completed, the mixture was filtered and washed to obtain an aerogel with a hydrophobic core. The molar ratio of trimethylchlorosilane to silanol groups on the surface of the aerogel was 1.5:1.

[0080] b. KH-550 and aminotrimethylphosphonic acid were added to toluene solution at a molar ratio of 1:1, and amidation reaction was carried out at 60°C for 8 hours to generate KH-550 and aminotrimethylphosphonic acid complex.

[0081] c. The aerogel with a hydrophobic core prepared in step a is added to a toluene solution of the KH-550 and aminotrimethylphosphonic acid complex prepared in step b, and the mixture is stirred for 4 hours to obtain an aerogel with a hydrophilic outer shell; wherein the amount of the complex is 8% of the mass of the aerogel.

[0082] (3) Drying under normal pressure: The surface of the prepared wet gel is cleaned with hexane and then dried under normal pressure. The drying temperature is 80℃ for 3 hours and 120℃ for 6 hours. After naturally cooling to room temperature, it is ground to obtain nanoporous silica aerogel powder containing a three-dimensional network structure.

[0083] (4) Prepare flexible silica aerogel for 3D printing. Add 0.2g sodium stearate to 6g of 10% polyvinyl alcohol aqueous solution (containing 0.6g of solid PVA) and stir at 1500r / min for 120s. Add 0.6g of modified silica aerogel powder in batches and stir repeatedly until uniformly mixed to obtain aerogel ink body that can be used for 3D printing. Use a 3D printing direct writing printer to print a grid of simple cubic structure units, control the size of the connecting rods in the grid, ensure that the volume ratio of 3D printing gel is 60%, and freeze dry.

[0084] (5) Preparation of slurry: Cement, water, modified silica aerogel powder and thickener are thoroughly mixed to form cement aerogel slurry. Cement foaming agent is diluted at a ratio of 30 times, and then 0.5% of nano silica particles by mass of foaming agent are added and stirred evenly. Foaming is performed using a foaming machine to obtain nano silica modified foam, which is added to cement aerogel slurry and stirred evenly to obtain aerogel foam concrete slurry. The mass ratio of cement, water, modified silica aerogel powder and nano silica modified foam is 15:7.5:1.0:2.3. Methylcellulose is selected as the thickener, and the amount of thickener added is 0.1% of the cement mass.

[0085] (6) Mixing and pouring of foamed concrete: After pouring the prepared slurry into the 3D printed aerogel, cover it with plastic wrap, let it stand for 24 hours, demold it, and put it into a standard curing box for curing.

[0086] The thermal conductivity of the 3D-printed aerogel foam concrete prepared in this embodiment, after 28 days of standard curing, was measured by the steady-state method to be 0.049 W / (m·K).

[0087] Tensile strength test: According to GB / T 6344 standard, dumbbell-shaped specimens of foamed concrete were prepared and tensile tests were performed on a universal testing machine. The tensile strength was measured to be 1.45 MPa.

[0088] Comparative Example 1

[0089] Preparation of foamed concrete without aerogel printing bodies includes the following steps:

[0090] Mixing and pouring of foamed concrete: Cement, water, and thickener are thoroughly mixed to form a cement paste. The cement foaming agent is diluted 30 times, and then 0.5% of the foaming agent mass of nano-silica particles is added and stirred evenly. Foaming is performed using a foaming machine to obtain nano-silica modified foam, which is then added to the cement paste and stirred evenly to obtain aerogel foamed concrete paste. The mass ratio of cement, water, and nano-silica modified foam is 15:7.5:2.3. Methylcellulose is used as the thickener, and the amount of thickener added is 0.1% of the cement mass.

[0091] The thermal conductivity of the foamed concrete prepared in this comparative example, after 28 days of standard curing, was measured by the steady-state method to be 0.090 W / (m·K).

[0092] Tensile strength test: According to GB / T 6344 standard, dumbbell-shaped specimens of foamed concrete were prepared and tensile tests were performed on a universal testing machine. The tensile strength was measured to be 0.17 MPa.

[0093] according to Figure 1-4 Experimental results show that the modified silica aerogel particles prepared by atmospheric pressure drying in this invention exhibit a highly cross-linked three-dimensional network structure with a specific surface area as high as 751 m². 2 It has an average pore size of 8.92 nm, exhibits good thermal stability at high temperatures, low density, and low thermal conductivity, with a mass loss rate of approximately 13% and a density of 0.13 g / cm³. 3 The thermal conductivity is 0.013 W / m·K. This invention introduces modified silica aerogel particles and 3D-printed silica aerogel into foamed concrete, reducing the thermal conductivity from 0.090 W / (m·K) to 0.049 W / (m·K). Utilizing the nanoporous structure and high specific surface area of ​​the aerogel, the thermal insulation performance of the material is significantly improved, and it can be widely used in building energy conservation, industrial insulation, and other fields.

[0094] Comparative Example 2

[0095] The difference between this comparative example and Example 3 is that the aerogel is not modified using the KH-550 and aminotrimethylphosphonic acid complex.

[0096] Performance Characterization

[0097] Tensile strength test: According to GB / T 6344 standard, dumbbell-shaped specimens of foamed concrete were prepared and tensile tests were performed on a universal testing machine. The tensile strength was measured to be 0.32 MPa, indicating that the KH-550 and aminotrimethylphosphonic acid composite has a certain contribution to the enhancement of the mechanical properties of the material.

[0098] The aerogel in Example 3 of this application possesses a complete KH-550 / ATMP hydrophilic shell, while Comparative Example 2 lacks a hydrophilic shell, retaining only the TMCS hydrophobic methyl layer. The polar functional groups (-PO3H2, -NH-CO-) of the hydrophilic shell transform the aerogel surface from hydrophobic to hydrophilic, solving the wetting problem between hydrophobic aerogels and hydrophilic cement pastes. Specifically, -Si-OC2H5 forms Si-O-Si bonds with the hydrophobic core of the aerogel for anchoring, and -PO3H2 bonds with the cement Ca... 2+ Hydroxyapatite is generated, and the -NH-CO- groups form a hydrogen bond network with the CSH gel, significantly reducing interfacial micropores and weak boundary layers. Therefore, in Comparative Example 2, due to the lack of a hydrophilic shell, the cement paste cannot tightly encapsulate the aerogel, making it easy for crack initiation sites to form at the interface, resulting in reduced mechanical strength.

[0099] Example 4

[0100] The difference between this embodiment and embodiment 3 is that in step (5), sepiolite fiber, boron nitride nanoribbon and polyacrylonitrile fiber are added during the preparation of the slurry, and the mass ratio of cement to sepiolite fiber, boron nitride nanoribbon and polyacrylonitrile fiber is 55:0.2:0.05:0.1.

[0101] Performance Characterization

[0102] Tensile strength test: According to GB / T 6344 standard, dumbbell-shaped specimens of foamed concrete were prepared and tensile tests were conducted on a universal testing machine. The tensile strength was measured to be 1.91 MPa, indicating that the multiple fibers and composite structure enhanced the mechanical properties of the material.

[0103] Thermal conductivity test: The thermal conductivity was tested using a thermal conductivity meter based on the steady-state heat flow method. The obtained thermal conductivity was 0.046 W / (m·K), indicating further improvement in thermal insulation performance.

[0104] Example 5

[0105] The difference between this embodiment and embodiment 3 is that in step (5), sepiolite fiber, boron nitride nanoribbon and polyacrylonitrile fiber are added during the preparation of the slurry, and the mass ratio of cement to sepiolite fiber, boron nitride nanoribbon and polyacrylonitrile fiber is 55:0.3:0.03:0.12.

[0106] Performance Characterization

[0107] Tensile strength test: According to GB / T 6344 standard, dumbbell-shaped specimens of foamed concrete were prepared and tensile tests were conducted on a universal testing machine. The tensile strength was measured to be 1.93 MPa, indicating that the multiple fibers and composite structure enhanced the mechanical properties of the material.

[0108] Thermal conductivity test: The thermal conductivity was tested using a thermal conductivity meter based on the steady-state heat flow method. The obtained thermal conductivity was 0.047 W / (m·K), indicating further improvement in thermal insulation performance.

[0109] Comparative Example 3

[0110] The difference between this comparative example and Example 5 is that sepiolite fiber is not added in step (5) during the preparation of the slurry.

[0111] The tensile strength of Comparative Example 3, measured according to GB / T 6344 standard, was 1.80 MPa. These data indicate that the Si-OH groups on the sepiolite fiber surface form Si-OP hydrogen bonds with the -PO3H2 groups of the hydrophilic shell, further amplifying the adhesion between the hydrophilic shell and the cement matrix, thus improving the overall integrity of the composite material. Without these bonds, the interfacial adhesion weakens, and the interface is more prone to cracking under stress, leading to a decrease in strength. Furthermore, the hygroscopic properties of the sepiolite fiber, in conjunction with the hydrophobic core of the TMCS, maintain a constant internal humidity (<65%RH). Without these bonds, localized humidity fluctuations may cause slight damage to the nanoporous structure, indirectly reducing the material's density.

[0112] Comparative Example 4

[0113] The difference between this comparative example and Example 5 is that boron nitride nanoribbons are not added in step (5) during the preparation of the slurry.

[0114] The tensile strength of Comparative Example 4, measured according to GB / T 6344 standard, is 1.77 MPa. These data indicate that the boron nitride nanoribbons, through the interaction of B-OH and the -PO3 group of the hydrophilic shell... 2- The formation of boron nitride (BOP) electrostatic composites enhances the interface's resistance to damage under stress. Furthermore, the directional thermal conductivity of boron nitride nanoribbons disperses localized heat, reducing interfacial cracking caused by thermal shock, such as microcracks induced by temperature gradients. Without these nanoribbons, uneven heat distribution can easily lead to interfacial micro-damage, resulting in decreased strength.

[0115] Comparative Example 5

[0116] The difference between this comparative example and Example 5 is that polyacrylonitrile fiber is not added in step (5) during the preparation of the slurry.

[0117] The tensile strength of Comparative Example 5, measured according to GB / T 6344 standard, is 1.64 MPa. These data indicate that the polyacrylonitrile fiber, through the interaction of -COOH and the -PO3 group of its hydrophilic outer shell... 2- Formation of Ca 2+Chelating bridges effectively prevent cracks from propagating from the interface into the cement matrix or aerogel skeleton. Furthermore, polyacrylonitrile fibers, in synergy with phosphonic acid groups, accelerate cement hydration, reducing localized structural defects caused by unhydrated particles. Without these bridges, cracks easily propagate and hydration uniformity decreases, leading to reduced strength.

[0118] Examples 4 and 5 of this application achieve high strength through the synergistic effect of the hydrophobic core (TMCS), hydrophilic shell (KH-550 / ATMP), and three types of fibers, via a triple action of chemical bonding, physical interlocking, and functional complementarity. The absence of any component disrupts this synergistic balance: the absence of the hydrophilic shell leads to interfacial bonding failure, and the absence of fibers weakens adhesion or crack inhibition capabilities, ultimately degrading the material's mechanical properties. This demonstrates the irreplaceable role of each component in optimizing the interfacial properties and overall structural stability of aerogel foam concrete.

[0119] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing aerogel foam concrete, characterized in that: Includes the following steps: S1. Preparation of modified silica aerogel particles using the sol-gel method: A silicon source, anhydrous ethanol, and deionized water were mixed and stirred evenly in a molar ratio of 1:(5-12):(1-6). The mixture was hydrolyzed under acidic conditions to obtain a silica sol. Then, an alkaline catalyst was added dropwise under stirring to adjust the pH to 7.0-8.

0. After standing, a pre-gelled gel was obtained. The gel underwent aging, solvent replacement, modification, washing, and drying to obtain modified silica aerogel particles. The modification method was as follows: first, trimethylchlorosilane was used to modify the gel to construct a hydrophobic core; then, a complex of KH-550 and aminotrimethylphosphonic acid was used to modify the hydrophobic core to construct a hydrophilic shell. S2. Preparation of 3D-printed silica aerogel: The adhesive and sodium octadecate were mixed, and then the modified silica aerogel particles prepared in step S1 were added and stirred evenly. The mass ratio of the modified silica aerogel particles to the adhesive was (0.8-1.2):

1. 3D printing was performed, and the 3D printed silica aerogel was obtained after freeze drying. S3. Preparation of nano-silica modified foaming agent: Cement foaming agent and water are mixed at a mass ratio of 1:30, and then 0.5%-2.0% of nano silica particles by mass of foaming agent are added. The mixture is stirred evenly and then foamed using a foaming machine to obtain nano silica modified foam. S4. Preparation of aerogel foam concrete slurry: Cement, water, modified silica aerogel particles prepared in step S1, and thickener are thoroughly mixed to form a cement aerogel slurry. Then, nano-silica modified foam prepared in step S3 is added and stirred evenly to obtain aerogel foam concrete slurry. The mass ratio of cement, water, modified silica aerogel particles, and nano-silica modified foam is (14-16):(6-9):(0.8-1.0):(2.2-2.4). In the preparation of aerogel foam concrete slurry, sepiolite fibers, boron nitride nanoribbons, and polyacrylonitrile fibers are also added. The sepiolite fiber content is 0.18%-0.55% of the cement mass, the boron nitride nanoribbon content is 0.05%-0.15% of the cement mass, and the polyacrylonitrile fiber content is 0.15%-0.27% of the cement mass. S5. Pour the slurry prepared in step S4 into the 3D printed silica aerogel prepared in step S2, cover it with plastic wrap, demold it and cure it to obtain aerogel foam concrete.

2. The method for preparing aerogel foam concrete according to claim 1, characterized in that: In step S1, the aging process is as follows: add aging solution to the initially gelled gel, seal and age at 40-60℃ for 24 hours; the aging solution is a mixture of tetraethyl orthosilicate and anhydrous ethanol in a volume ratio of 1:

4.

3. The method for preparing aerogel foam concrete according to claim 1, characterized in that: In step S1, the solvent exchange step is as follows: the aged gel is placed in n-hexane solvent for solvent exchange at 50°C for 24 hours.

4. The method for preparing aerogel foam concrete according to claim 1, characterized in that: The specific methods for gel modification are as follows: a. Add trimethylchlorosilane to the wet gel after solvent exchange, stir and react at 25°C for 5-6 hours. After the reaction is completed, filter and wash to obtain an aerogel with a hydrophobic core; wherein the molar ratio of trimethylchlorosilane to silanol groups on the surface of the aerogel is (1.2-1.5):

1. b. Add KH-550 and aminotrimethylphosphonic acid to toluene solution in a molar ratio of 1:1, and carry out amidation reaction at 60℃ for 7-8 hours to generate KH-550 and aminotrimethylphosphonic acid complex. c. Add the aerogel with a hydrophobic core obtained in step a to the toluene solution of the KH-550 and aminotrimethylphosphonic acid complex prepared in step b, and stir for 4-5 hours to obtain an aerogel with a hydrophilic shell; wherein the amount of the complex is 5%-8% of the mass of the aerogel.

5. The method for preparing aerogel foam concrete according to claim 1, characterized in that: In step S2, the mass ratio of adhesive to sodium stearate is (20-40):

1.

6. An aerogel foam concrete prepared by any one of the preparation methods described in claims 1-5.

Images