Aerogel-based core-shell lightweight aggregate and preparation method thereof

Abstract

The invention relates to the technical field of building materials, in particular to aerogel-based core-shell lightweight aggregate and a preparation method thereof. The aerogel-based core-shell lightweight aggregate comprises an inner core and an outer shell layer coating the surface of the inner core, wherein the inner core comprises silica aerogel particles, and the shell layer comprises the following raw materials: an alkaline activator, slag, fly ash and glass powder. According to the aerogel-based core-shell lightweight aggregate, through the combined action of the inner core layer and the outer shell layer, the aerogel-based core-shell lightweight aggregate not only has very good mechanical properties, but also has relatively low density, and is beneficial to stable performance exertion of the silicon dioxide aerogel, so that the practical engineering application range of the aerogel-based core-shell lightweight aggregate is expanded.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to an aerogel-based core-shell lightweight aggregate and a preparation method thereof. BACKGROUND

[0002] Lightweight aggregate concrete refers to concrete using lightweight aggregate, and the apparent density thereof is generally not greater than 1950 kg / m 3 Due to the characteristics of lightweight, high strength, heat preservation and fire resistance, the development of lightweight aggregate concrete has attracted more attention. In addition to the advantages in technology and economy, lightweight aggregate concrete can also incorporate the concept of sustainable development by using artificial aggregate which is lighter than natural aggregate. However, due to the low strength caused by the high porosity of lightweight aggregate, the lightweight aggregate becomes the weakest area in lightweight aggregate concrete, and therefore the quality of lightweight aggregate is an important factor determining the performance of lightweight aggregate concrete. With the increasing demand for lightweight aggregate concrete, it is necessary to develop high-strength lightweight aggregate to meet the application of high-performance lightweight concrete.

[0003] Traditional lightweight aggregate is generally prepared by high-temperature sintering of natural minerals, which consumes a large amount of natural resources and has a negative impact on environmental sustainability. At present, most of the artificial lightweight aggregate is sintered from natural raw materials such as shale, which has high energy consumption, large carbon emissions and high consumption of natural resources. Some use solid waste to sinter lightweight aggregate, which has the problems of unstable quality of solid waste, high sintering temperature, poor product performance and difficulty in preparing high-strength lightweight aggregate concrete. SUMMARY

[0004] The application aims to provide an aerogel-based core-shell lightweight aggregate and a preparation method thereof.

[0005] To achieve the above-mentioned application purposes, the technical solutions adopted by the application are as follows:

[0006] In a first aspect, the application provides an aerogel-based core-shell lightweight aggregate, comprising an inner core and a shell layer coated on the surface of the inner core; wherein the inner core comprises silica aerogel particles, and the raw materials of the shell layer comprise an alkaline activator, a slag, a fly ash and a glass powder.

[0007] In some embodiments, the silica aerogel particles satisfy at least one of the following (1) to (4):

[0008] (1) the particle size of the silica aerogel particles is ≤10 mm;

[0009] (2) the porosity of the silica aerogel particles is greater than 85%;

[0010] (3) the bulk density of the silica aerogel particles is less than 10 kg / m 3 .

[0011] In some embodiments, the core further comprises a binder; and / or,

[0012] The thickness of the shell layer is 1-2 mm.

[0013] In some embodiments, the binder comprises at least one of epoxy resin, polyvinyl alcohol, silica sol, sodium silicate and sodium alginate; and / or,

[0014] The weight ratio of the silica aerogel particles to the binder is 0.5-2:1.

[0015] In some embodiments, the raw materials of the shell layer comprise components in the following weight parts: 25-35 parts of alkaline activator, 60-70 parts of slag, 15-30 parts of fly ash and 10-15 parts of glass powder, and the total weight of the slag, the fly ash and the glass powder is 100 parts.

[0016] In some embodiments, the silica aerogel particles are prepared from first waste glass powder, and the alkaline activator comprises waste liquid with pH of 10-13 generated in the process of preparing the aerogel particles; and / or,

[0017] The glass powder comprises second waste glass powder.

[0018] In a second aspect, the present application provides a preparation method of aerogel-based core-shell lightweight aggregate, comprising:

[0019] Mixing alkaline activator, slag, fly ash and glass powder to obtain shell slurry;

[0020] Mixing silica aerogel particles with the shell slurry and then granulating to obtain aerogel-based lightweight aggregate green body;

[0021] Curing the aerogel-based lightweight aggregate green body to obtain aerogel-based core-shell lightweight aggregate.

[0022] In some embodiments, the preparation step of the silica aerogel particles comprises:

[0023] Mixing first waste glass powder with inorganic alkali solution and then performing heat treatment, and then filtering to obtain sodium silicate filtrate;

[0024] Passing acid gas into the sodium silicate solution to react, to obtain a solution containing silica gel precipitate;

[0025] Filtering the solution containing silica gel precipitate, washing and aging the obtained silica gel, adjusting the pH of the collected waste liquid to 10-13 for use as the alkaline activator, and sequentially performing solvent replacement and drying treatment on the aged silica gel to obtain the silica aerogel particles.

[0026] In some embodiments, the mass percentage of silicon dioxide in the first waste glass powder is > 60%; and / or,

[0027] The concentration of inorganic base in the inorganic base solution is 1-10 mol / L; and / or,

[0028] The mass ratio of the inorganic base solution to the first waste glass powder is 10-50:1.

[0029] In some embodiments, the acid gas comprises at least one of carbon dioxide, sulfur dioxide, hydrogen chloride and nitrogen oxides; and / or,

[0030] The temperature for the acid gas to react with the sodium silicate solution is 0-5℃.

[0031] In some embodiments, the temperature for the heat treatment is 85-95℃, and the time is 12-24h;

[0032] The temperature for the aging treatment is 40-90℃, and the time is 12-24h.

[0033] In some embodiments, the displacement solvent used in the solvent displacement treatment comprises at least one of an alkane solvent, an alcohol solvent and an ether solvent.

[0034] In some embodiments, before mixing the silica aerogel particles with the shell slurry, the silica aerogel particles are further subjected to a mixing and sticking treatment with a binder.

[0035] In some embodiments, the curing treatment comprises: first curing for 1-3 days in an environment with a temperature of 87-93℃ and a relative humidity ≥ 90%, and then curing for 26-30 days in an environment with a temperature of 17-23℃ and a relative humidity ≥ 90%;

[0036] Or first curing for 1-3 days in an environment with a temperature of 87-93℃ and a relative humidity ≥ 90%, and then curing for 1-2 days in an environment with a temperature of 17-23℃, a relative humidity ≥ 90% and a carbon dioxide concentration ≥ 50%.

[0037] The light aggregate provided in the first aspect of the present application is an aerogel-based core-shell light aggregate, the inner core of which comprises silica aerogel particles, and the raw material of the outer shell layer comprises an alkaline activator, slag, fly ash and glass powder. Based on the characteristics of the silica aerogel particles in the inner core, the overall density of the core-shell light aggregate can be reduced, and at the same time, good heat insulation effect is achieved. The outer shell layer can reduce the risk of damage to the silica aerogel particles and improve the stability of the inner core. At the same time, the outer shell layer is an alkali-activated cementitious material made of an alkaline activator, slag, fly ash and glass powder, which can fully encapsulate the silica aerogel particles and enhance the interfacial properties between the inner core and the outer shell layer. Therefore, the aerogel-based core-shell light aggregate of the present application, through the combined action of the inner core and the outer shell layer, not only has good mechanical properties, but also has a low density, which is conducive to the stable performance of the silica aerogel, thereby expanding its actual engineering application range.

[0038] The preparation method of the aerogel-based core-shell light aggregate provided in the second aspect of the present application is to mix the silica aerogel particles with the outer shell slurry containing the alkaline activator, slag, fly ash and glass powder, then granulate, and then cure to obtain the aerogel-based core-shell light aggregate. In this process, the outer shell slurry can form an alkali-activated cementitious material to fully encapsulate the silica aerogel particles, and the interface between the outer shell layer of the alkali-activated cementitious material and the inner core can react to generate calcium-aluminum-silicon gel, thereby enhancing the interfacial properties between the inner core and the outer shell layer. This not only reduces the risk of damage to the silica aerogel particles in the inner shell to improve its stability, but also the obtained aerogel-based core-shell light aggregate still has good mechanical properties, thereby having good application in the field of light aggregate preparation process. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating any creative labor.

[0040] Figure 1 is a schematic diagram of the structure of the aerogel-based core-shell light aggregate provided in an embodiment of the present application;

[0041] Figure 2 is a scanning electron microscope image of the aerogel-based core-shell light aggregate provided in an embodiment of the present application; wherein the left image is the inner core material, and the right image is the outer shell material of the outer shell layer;

[0042] Figure 3 is a schematic diagram of the preparation method of the aerogel-based core-shell light aggregate provided in an embodiment of the present application. DETAILED DESCRIPTION

[0043] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application and not to limit the present application.

[0044] In the present application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can represent the following three cases: A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0045] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one" or similar expressions mean any combination of these items, including any combination of single or multiple items.

[0046] It should be understood that in various embodiments of the present application, the size of the sequence number of the above processes does not mean the order of execution, and part or all of the steps can be executed in parallel or in sequence, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0047] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0048] The weight of the related components mentioned in the specification of the embodiments of the present application can not only refer to the specific content of each component, but also represent the weight ratio relationship between each component, therefore, as long as the content of the related components in the specification of the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass mentioned in the specification of the embodiments of the present application can be μg, mg, g, kg and other mass units commonly known in the chemical field.

[0049] The terms "first", "second" are only used for description purposes, to distinguish objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX can also be referred to as the second XX, and similarly, the second XX can also be referred to as the first XX. Therefore, the features limited by "first" and "second" can explicitly or implicitly include one or more of the features.

[0050] Silica aerogel is a lightweight porous nanomaterial with air as its main component, amorphous SiO2 as its basic framework, and a complex three-dimensional network structure. It possesses properties such as low thermal conductivity, low density, and high porosity. Adding silica aerogel particles as lightweight aggregate to lightweight aggregate concrete can reduce concrete density and further improve its thermal insulation properties. However, silica aerogel particles have very low strength and are prone to deformation or breakage during concrete mixing, thus affecting the concrete's performance.

[0051] Based on this, this application presents an aerogel-based core-shell lightweight aggregate, which not only allows the silica aerogel material to maintain stable performance but also gives the aerogel-based core-shell lightweight aggregate excellent overall mechanical properties. The specific solution is as follows.

[0052] In a first aspect, embodiments of this application provide an aerogel-based core-shell lightweight aggregate. For example... Figure 1 As shown, the aerogel-based core-shell lightweight aggregate of this application embodiment comprises two parts: (1) a core, comprising silica aerogel particles, which has the characteristics of low thermal conductivity, low density, and high porosity; and (2) an outer shell layer, which coats the surface of the core, can improve the stability of the core, and at the same time has good mechanical properties. The raw materials for preparing the outer shell layer include alkaline activator, slag, fly ash, and glass powder.

[0053] Using silica aerogel particles in the core structure can significantly reduce the environmental impact. To fully meet the mechanical performance requirements of lightweight aggregates and reduce the risk of aerogel particle breakage, while also significantly reducing the density of lightweight aggregates, the core-shell design of this application can effectively achieve performance stability of both artificial lightweight aggregates and aerogel particles. Furthermore, this application embodiment effectively combines the core and outer shell materials, improving the mechanical performance stability of the core-shell lightweight aggregate while maintaining the porous structure of the silica aerogel. To this end, the raw materials for the outer shell layer in this application include an alkaline activator, slag, fly ash, and glass powder. The alkali-activated cementitious material formed by these raw materials can fully encapsulate the silica aerogel particles and enhance the interfacial properties between the core and outer shell materials. Therefore, the aerogel-based core-shell lightweight aggregate of this application, through the combined action of the core and outer shell layers, not only possesses excellent mechanical properties but also exhibits low density.

[0054] In some embodiments, the silica aerogel particles have certain characteristics. For example, the silica aerogel particle size is ≤10 mm, or for example, the silica aerogel particle size is 4-10 mm. In some embodiments, the porosity of the silica aerogel particles is greater than 85%, for example, it can be 88-95%. In some embodiments, the bulk density of the silica aerogel particles is less than 10 kg / m³. 3For example, it can be 2-9 kg / m 3 By selecting the above-mentioned particle size, porosity and bulk density of the silica aerogel particles, the silica aerogel particles have good aerogel characteristics, which can not only significantly reduce the density of the core-shell lightweight aggregate as a whole, but also have good thermal insulation effect.

[0055] In some embodiments, the core further comprises a binder; the binder can adhere to the surface of the silica aerogel particles to form a very spherical particle, and can also make the core and the shell layer better bonded and stable.

[0056] In some embodiments, the binder comprises at least one of epoxy resin, polyvinyl alcohol, silica sol, sodium silicate (i.e. water glass) and sodium alginate; the above-mentioned binder has good bonding effect.

[0057] In some embodiments, the weight ratio of the silica aerogel particles to the binder in the core is 0.5-2:1. Specifically, the silica aerogel particles and the binder are mixed and treated according to the above-mentioned weight ratio to form a uniform core; and then the shell layer is coated, so that the core and the shell layer are more stably combined.

[0058] In some embodiments, the size of the core can be the size of the silica aerogel particles or slightly larger than the size of the silica aerogel particles, and the size of the core is ≤10.5 mm, for example, 4-10 mm. The thickness of the shell layer can be 1-2 mm. The shell layer in this thickness range can well coat the core and protect the silica aerogel particles of the core.

[0059] In some embodiments, the silica aerogel particles can be prepared from the first waste glass powder. The silica aerogel particles are prepared by a green and low-cost method. Specifically, the silica content in the first waste glass powder is >60%, and the fineness of the first waste glass powder is <75 μm.

[0060] In some embodiments, the raw material of the shell layer comprises the following components by weight: 25-35 parts of alkaline activator, 60-70 parts of slag, 15-30 parts of fly ash and 10-15 parts of glass powder, and the total weight of the slag, fly ash and glass powder is 100 parts. The alkali-activated cementitious material formed by the above-mentioned weight components can well coat the core to form the shell layer, has good mechanical strength, and has good compactness, which is not easy to make the core absorb water and improve the stability of the core. As shown in Figure 2 The silica aerogel in the core of the aerogel-based core-shell lightweight aggregate prepared in Example 1 has good porosity, and the shell layer has good compactness.

[0061] Specifically, the slag can be one or more of blast furnace slag, steel slag, nickel slag, and copper slag; the fly ash can be one or more of Grade I fly ash and Grade II fly ash; the glass powder includes second waste glass powder, wherein the silica content of the second waste glass powder is >60% and the fineness of the second waste glass powder is <75μm. The second waste glass powder and the first waste glass powder can be the same or different waste glass powders. For ease of material selection and preparation, in the embodiments of this application, the second waste glass powder and the first waste glass powder can be the same waste glass powder.

[0062] In some embodiments, silica aerogel particles can be prepared from first waste glass powder, and the alkaline activator includes waste liquid with a pH of 10-13 generated during the aerogel particle preparation process. Using waste glass as a raw material can significantly reduce the production cost of silica aerogel while ensuring that the product silica aerogel possesses the intrinsic properties of aerogel. Regarding the outer shell material, an alkaline-activated gelling material design is adopted, which reduces the use of high-carbon-emission materials while ensuring good mechanical properties of the outer shell material. Simultaneously, using the alkaline waste liquid generated during silica aerogel production as an alkaline activator not only reduces costs but also further mitigates the adverse environmental impact of silica aerogel production. The specific preparation process will be detailed in the subsequent preparation method of aerogel-based core-shell lightweight aggregate.

[0063] The aerogel-based core-shell lightweight aggregate prepared in this application adopts a core-shell structure design. The core has a large porosity and low density, which makes the lightweight aggregate have low density and high performance. Moreover, the core material and the outer shell material activated by alkali are effectively combined, which not only improves the bonding performance between the core and the outer shell material, but also improves the overall mechanical properties of the aerogel-based core-shell lightweight aggregate.

[0064] Secondly, embodiments of this application provide a method for preparing aerogel-based core-shell lightweight aggregate. The method for preparing aerogel-based core-shell lightweight aggregate provided in this application includes:

[0065] S01: The shell slurry is obtained by mixing alkaline activator, slag, fly ash and glass powder;

[0066] S02: After mixing silica aerogel particles with shell slurry, granulation is carried out to obtain aerogel-based lightweight aggregate blank;

[0067] S03: Aerogel-based lightweight aggregate blanks are cured to obtain aerogel-based core-shell lightweight aggregates.

[0068] This application embodiment involves granulating silica aerogel particles with an outer shell slurry containing an alkaline activator, slag, fly ash, and glass powder, followed by curing to obtain aerogel-based core-shell lightweight aggregate. During this process, the outer shell slurry forms an alkali-activated cementitious material that fully encapsulates the silica aerogel particles. Furthermore, the interface between the outer shell layer and the core layer of this alkali-activated cementitious material reacts to generate calcium aluminum silica gel, thereby enhancing the interfacial properties between the core and outer shell layers. This not only reduces the risk of breakage of the silica aerogel particles in the inner shell, improving its stability, but also ensures that the resulting aerogel-based core-shell lightweight aggregate retains excellent mechanical properties, making it highly applicable in the field of lightweight aggregate preparation.

[0069] For the specific types and weight proportions of raw materials such as alkaline activators, slag, fly ash, and glass powder that can be selected, please refer to the above text.

[0070] In some embodiments, the preparation steps of silica aerogel particles include:

[0071] S11: The first waste glass powder is mixed with an inorganic alkaline solution and then subjected to heat treatment, followed by filtration to obtain sodium silicate filtrate;

[0072] S12: Acidic gas is passed into a sodium silicate solution to react and obtain a solution containing silica gel precipitate;

[0073] S11: Filter the solution containing silica gel precipitate, wash and age the obtained silica gel, adjust the pH of the collected waste liquid to 10-13 and use it as an alkaline activator, and then perform solvent replacement and drying treatment on the aged silica gel to obtain silica aerogel particles.

[0074] The above process prepares silica aerogel particles using a green and low-cost method, enabling the rational use of waste resources without the need for expensive organosilanes or other aerogel precursor materials.

[0075] In some embodiments, the heat treatment of the first waste glass powder mixed with the inorganic alkaline solution can be a water bath treatment, specifically at a temperature of 85-95°C for 12-24 hours.

[0076] In some embodiments, the mass percentage of silica in the first waste glass powder is >60%; the concentration of inorganic alkali in the inorganic alkali solution is 1-10 mol / L, specifically sodium hydroxide solution or potassium hydroxide solution, etc. Further, the mass ratio of the inorganic alkali solution to the first waste glass powder is 10-50:1.

[0077] In some embodiments, the acidic gas includes at least one of carbon dioxide, sulfur dioxide, hydrogen chloride, and nitrogen oxides; specifically, it can be waste gas or tail gas containing the above-mentioned acidic gases, such as acidic industrial waste gas. This not only simplifies the preparation process but also reduces adverse environmental impacts. Making full use of waste materials and tail gas aligns with the concept of sustainable development. The temperature at which the acidic gas is passed into the sodium silicate solution for the reaction is 0-5°C.

[0078] In some embodiments, the aging treatment is carried out at a temperature of 40-90°C for 12-24 hours. Under these conditions, the gel ages more completely and the strength of the gel skeleton is improved.

[0079] In some embodiments, the replacement solvent used in the solvent replacement process includes at least one of alkane solvents, alcohol solvents, and ether solvents. For example, alkane solvents may be cyclohexane, alcohol solvents may be tert-butanol, and ether solvents may be dimethyl ether.

[0080] In some embodiments, after solvent replacement, the drying method may be supercritical drying, atmospheric pressure drying, or a combination of both.

[0081] In some embodiments, before mixing the silica aerogel particles with the shell slurry, the silica aerogel particles are further mixed with a binder. They are then subsequently mixed with the shell slurry and granulated.

[0082] A cold-bonding granulation method is used to fully bond the core material and the outer shell material. This preparation method is more environmentally friendly than the traditional hot sintering method, helps maintain the lightweight properties of the core material, and simultaneously achieves a strengthened bond between the core and outer shell materials, forming a dense, spherical, lightweight, and high-strength core-shell lightweight aggregate. This lightweight aggregate is suitable for the preparation of lightweight aggregate concrete, helping to reduce the density of concrete and improve its thermal insulation properties.

[0083] In some embodiments, the curing treatment includes: first, high-temperature steam curing, such as curing in an environment with a temperature of 87-93°C and a relative humidity of ≥90% for 1-3 days, followed by room temperature curing, such as curing in an environment with a temperature of 17-23°C and a relative humidity of ≥90% for 26-30 days; or first, high-temperature steam curing, such as curing in an environment with a temperature of 87-93°C and a relative humidity of ≥90% for 1-3 days, followed by carbonization curing, such as curing in an environment with a temperature of 17-23°C, a relative humidity of ≥90%, and a carbon dioxide concentration of ≥50% for 1-2 days.

[0084] In some embodiments, such as Figure 3 As shown. The method for preparing aerogel-based core-shell lightweight aggregate according to an embodiment of this application includes the following steps:

[0085] (1) Preparation of aerogel core material: This involves preparing silica aerogel particles using waste glass powder (silica content >60%, fineness <75μm). Specific steps include: mixing finely ground waste glass powder with sodium hydroxide solution (sodium hydroxide solution concentration 1-10mol / L, mass ratio of sodium hydroxide solution to waste glass powder 50:1-10:1), heating and stirring in a water bath at 85-95℃ for 12-24 hours; filtering the reacted solution to obtain sodium silicate filtrate; introducing waste acidic gas (containing one or more of carbon dioxide, sulfur dioxide, hydrogen chloride, and nitrogen oxides) into the sodium silicate solution, keeping the solution in a turbulent state, maintaining the temperature not higher than 5℃, and maintaining the pressure inside the reaction vessel not lower than 0.2MPa, until silica... No more acid gel precipitation occurs, resulting in a solution containing silica gel precipitate (i.e., hydrogel). The solution containing silica gel precipitate is filtered (the precipitate is silica gel), and the precipitated silica gel is washed (using distilled water as the washing solvent, 3-5 times), aged (aging time is 12-24 hours, aging temperature is 40-90℃), and the collected filtrate and washing liquid are mixed. The resulting waste solution is adjusted to pH 10-13 as an alkaline activator. The washed and aged silica gel is then subjected to solvent replacement (the replacement solvent is a low surface tension solvent, including at least one of alkane solvents, olefin solvents, or benzene solvents). The solvent-replaced silica gel is then dried (e.g., supercritical drying, atmospheric pressure drying, or a combination of both) to obtain silica aerogel particles.

[0086] (2) Preparation of alkali-activated shell material: Weigh the raw material components of the shell according to the ratio (25-35 parts of the alkaline activator obtained in the above steps, 60-70 parts of slag, 15-30 parts of fly ash, and 10-15 parts of waste glass powder (silica content >60%, fineness of waste glass powder <75μm), and the total weight of slag, fly ash and glass powder is 100 parts), stir and mix to obtain alkali-activated green and environmentally friendly shell gel material, i.e. shell slurry.

[0087] (3) Assembly of aerogel-based core-shell lightweight aggregate: The silica aerogel particles obtained in step (1) are placed into a lightweight aggregate granulation device (such as a disc lightweight aggregate granulation device), a binder is added and mixed, and then the shell slurry prepared in step (2) is added for granulation to form an aerogel-based lightweight aggregate blank; the obtained aerogel-based lightweight aggregate blank is cured (such as room temperature curing, high temperature steam curing, carbonization curing, or one or more combined methods) to obtain aerogel-based lightweight aggregate.

[0088] In the above preparation method, silica aerogel particles are prepared using waste glass powder and used as the core material. An alkaline waste solution is collected during the silica aerogel preparation process and used as an alkaline activator for the outer shell layer preparation. Slag, fly ash, waste glass powder, and the alkaline activator are mixed in a specific ratio to form an alkaline-activated, environmentally friendly cementitious material. The silica aerogel particles, the core material, are placed into a lightweight aggregate granulation device, surface-treated with a binder, and then the outer shell slurry forming the outer shell layer is added for granulation. Various curing conditions can be used to cure the lightweight aggregate blank, forming aerogel-based core-shell lightweight aggregate. This application's embodiment of a low-energy, low-cost, and simplified process for preparing aerogel-based core-shell lightweight aggregate enables the high-value recycling of waste glass to produce low-density and high-strength aerogel-based core-shell lightweight aggregate.

[0089] The aerogel-based core-shell lightweight aggregate prepared in this application can significantly reduce the density of lightweight concrete when used in concrete, giving it excellent thermal insulation properties. The outer shell material uses an alkali-activated cementitious material, which helps form a robust outer shell structure, improving the mechanical properties and durability of the aerogel-based core-shell lightweight aggregate, and eliminating the use of commonly used high-carbon-emission outer shell materials such as cement. The alkaline activator is a waste liquid generated during the preparation of silica aerogel after pH adjustment; using it as part of the outer shell raw material achieves effective utilization of the waste liquid and reduces the preparation cost of the outer shell.

[0090] In some embodiments of this application, aerogel particles are prepared using inexpensive raw materials such as waste glass, effectively reducing preparation costs and making the embodiments of this application more economically feasible. This fully reflects the sustainable utilization of waste resources and helps to mitigate the excessive consumption of natural resources. The preparation process consumes acidic industrial waste gas, realizing the resource utilization of acidic industrial waste gas. The alkali-activated cementitious material used in the outer shell layer has lower carbon emissions than commonly used cement, reducing negative environmental impacts and meeting environmental protection requirements. This is conducive to achieving a synergistic improvement in economic benefits and practical performance.

[0091] The following description is based on specific embodiments.

[0092] Example 1

[0093] This embodiment provides an aerogel-based core-shell lightweight aggregate and its preparation method.

[0094] This aerogel-based core-shell lightweight aggregate comprises a core and an outer shell covering the core. The core has a diameter of approximately 8.1 mm, and the outer shell has a thickness of approximately 1.7 mm. The raw materials for the outer shell include slag, fly ash, waste glass powder, and an alkaline activator. The raw materials for the core structure include silica aerogel particles prepared from waste glass powder. The average particle size of the slag particles is 15.6 μm; the average particle size of the fly ash particles is 32.5 μm; and the waste glass powder contains 65% SiO2 and has a particle size of 32.9 μm.

[0095] The preparation steps are as follows:

[0096] Step 1: Prepare aerogel core material using waste glass powder;

[0097] S1. Mix the finely ground waste glass powder with sodium hydroxide solution, heat and stir in a water bath at 90°C for 18 hours. The concentration of the sodium hydroxide solution used is 5 mol / L, and the mass ratio of sodium hydroxide solution to waste glass powder is 25:1.

[0098] S2. Filter the solution after the reaction in S1 to obtain sodium silicate filtrate;

[0099] S3. Pass a mixture of carbon dioxide and sulfur dioxide into the sodium silicate solution in S2, keeping the solution in a turbulent state, maintaining the temperature at 0°C, and maintaining the pressure inside the reaction vessel at 0.4 MPa, until no more silica gel precipitate is produced.

[0100] S4. The silica gel obtained in S3 is filtered, washed, aged, and the waste liquid is collected. The washing solvent is distilled water, and the washing is performed 4 times. The aging time is 12 hours and the aging temperature is 60℃.

[0101] S5. Solvent replacement is performed on the aged silica gel (the replacement solvent is tert-butanol);

[0102] S6. The silica gel after solvent replacement is subjected to supercritical drying to obtain silica aerogel particles; wherein the silica aerogel particles have a particle size of approximately 8 mm, a porosity of 90.3%, and a bulk density of 5 kg / m³. 3 .

[0103] Step 2: According to the mass fraction, 63 parts of slag, 25 parts of fly ash, 12 parts of waste glass powder, and 28 parts of alkaline activation solution are stirred and mixed to obtain the shell slurry. The alkaline activation solution is the waste liquid generated in step S4 of the preparation of silica aerogel particles and the pH is adjusted to 12.

[0104] Step 3: Place the silica aerogel particles into the disc lightweight aggregate granulation device, add silica sol binder (weight ratio of 0.5:1), bind them into spheres, and then add the shell slurry prepared in the above steps for granulation to form an aerogel-based lightweight aggregate blank.

[0105] Step 4: The aerogel-based lightweight aggregate blank obtained in the first step is first cured with high-temperature steam (cured for 2 days at a temperature of 90±3℃ and relative humidity ≥90%), and then cured at room temperature (cured for 28 days at a temperature of 20±3℃ and relative humidity ≥90%) to obtain aerogel-based core-shell lightweight aggregate.

[0106] Example 2

[0107] This embodiment provides an aerogel-based core-shell lightweight aggregate and its preparation method.

[0108] The only difference between this embodiment and Embodiment 1 is the size of the core and the outer shell. Specifically, in this embodiment, the core diameter is about 4.5 mm and the outer shell structure thickness is about 1.1 mm.

[0109] The rest is the same as in Example 1.

[0110] Example 3

[0111] This embodiment provides an aerogel-based core-shell lightweight aggregate and its preparation method.

[0112] The only difference between this embodiment and Embodiment 1 is the preparation process of the core silica aerogel particles. Specifically, this embodiment is:

[0113] S1. Mix the finely ground waste glass powder with sodium hydroxide solution, heat and stir in a water bath at 90°C for 24 hours. The concentration of the sodium hydroxide solution used is 8 mol / L, and the mass ratio of sodium hydroxide solution to waste glass is 30:1.

[0114] S2. Filter the solution after the reaction in S1 to obtain sodium silicate filtrate;

[0115] S3. Pass a mixture of carbon dioxide and hydrogen chloride gas into the sodium silicate solution in S2, keeping the solution in a turbulent state, maintaining the temperature at 0°C, and maintaining the pressure inside the reaction vessel at 0.4 MPa, until no more silica gel precipitate is formed.

[0116] S4. The silica gel obtained in S3 is filtered, washed, aged, and the waste liquid is collected. The washing solvent is distilled water, and the washing is performed 5 times. The aging time is 24 hours and the aging temperature is 80℃.

[0117] S5. Solvent replacement is performed on the aged silica gel (the replacement solvent is tert-butanol);

[0118] S6. The solvent-displaced silica gel is subjected to supercritical drying to obtain silica aerogel particles; wherein the silica aerogel particles have a particle size of approximately 8 mm, a porosity of 94.3%, and a bulk density of 2 kg / m³. 3 .

[0119] The rest is the same as in Example 1.

[0120] Example 4

[0121] This embodiment provides an aerogel-based core-shell lightweight aggregate and its preparation method.

[0122] The only difference between this embodiment and Embodiment 1 is the outer shell slurry. Specifically, this embodiment is:

[0123] According to the mass fraction, 69 parts of slag, 19 parts of fly ash, 12 parts of waste glass powder, and 32 parts of alkaline activation solution are stirred and mixed to obtain the shell slurry. The alkaline activation solution is the waste liquid generated in step S4 of the preparation of silica aerogel particles and the pH is adjusted to 12.5.

[0124] The rest is the same as in Example 1.

[0125] Example 5

[0126] This embodiment provides an aerogel-based core-shell lightweight aggregate and its preparation method.

[0127] The only difference between this embodiment and Embodiment 1 is the maintenance process. Specifically, this embodiment is as follows:

[0128] The obtained aerogel-based lightweight aggregate blanks were first subjected to high-temperature steam curing (cured for 2 days at a temperature of 90±3℃ and a relative humidity of ≥90%), followed by carbonization curing (cured for 1 day at a temperature of 20±3℃, a relative humidity of ≥90%, and a carbon dioxide concentration of ≥50%) to obtain aerogel-based core-shell lightweight aggregate.

[0129] The rest is the same as in Example 1.

[0130] Comparative Example 1

[0131] Only the core material prepared in Example 1, namely silica aerogel particles.

[0132] Comparative Example 2

[0133] Only the core material prepared in Example 3, namely silica aerogel particles.

[0134] Performance testing

[0135] According to GB / T17431.2-2010 "Lightweight Aggregates and Test Methods Thereof", the aerogel-based core-shell lightweight aggregates obtained in the examples were tested for compressive strength, bulk density, and water absorption. The test results are shown in Table 1.

[0136] Table 1

[0137]

[0138] As shown in Table 1:

[0139] The aerogel-based core-shell lightweight aggregates prepared in Examples 1-5 exhibit high compressive strength and low bulk density, meeting the strength and density requirements (density grade 800, strength grade 4.0) in standard GB / T17431.2-2010 "Lightweight Aggregates and Their Test Methods". As shown in Examples 1 and 1, and Examples 3 and 2, the aerogel-based core-shell lightweight aggregates of this application, compared to uncoated silica aerogel particles, not only possess excellent mechanical properties but also exhibit low water absorption. In other words, the core-shell lightweight aggregate structure of this application can effectively improve the shortcomings of aerogel materials, such as poor mechanical properties and high water absorption.

[0140] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An aerogel-based core-shell lightweight aggregate, characterized in that, It includes a core and an outer shell covering the surface of the core; wherein the core comprises silica aerogel particles, and the raw materials of the outer shell include an alkaline activator, slag, fly ash, and glass powder.

2. The aerogel-based core-shell lightweight aggregate as described in claim 1, characterized in that, The silica aerogel particles satisfy at least one of the following (1) to (4): (1) The particle size of silica aerogel particles is ≤10mm; (2) The porosity of silica aerogel particles is greater than 85%; (3) The bulk density of silica aerogel particles is less than 10 kg / m³. 3 .

3. The aerogel-based core-shell lightweight aggregate as described in claim 1, characterized in that, The core also includes an adhesive; and / or, The thickness of the outer shell layer is 1-2 mm.

4. The aerogel-based core-shell lightweight aggregate as described in claim 3, characterized in that, The adhesive comprises at least one of epoxy resin, polyvinyl alcohol, silica sol, sodium silicate, and sodium alginate; and / or, The weight ratio of the silica aerogel particles to the binder is 0.5-2:

1.

5. The aerogel-based core-shell lightweight aggregate according to any one of claims 1-4, characterized in that, The raw materials of the outer shell layer include the following components in parts by weight: 25-35 parts of alkaline activator, 60-70 parts of slag, 15-30 parts of fly ash and 10-15 parts of glass powder, and the total weight of the slag, the fly ash and the glass powder is 100 parts.

6. The aerogel-based core-shell lightweight aggregate according to any one of claims 1-4, characterized in that, The silica aerogel particles are prepared from first-stage waste glass powder, and the alkaline activator includes waste liquid with a pH of 10-13 generated during the preparation of the aerogel particles; and / or, The glass powder includes second waste glass powder.

7. A method for preparing an aerogel-based core-shell lightweight aggregate, characterized in that, include: The outer shell slurry is obtained by mixing alkaline activator, slag, fly ash and glass powder; The silica aerogel particles are mixed with the outer shell slurry and then granulated to obtain an aerogel-based lightweight aggregate blank. The aerogel-based lightweight aggregate preform is cured to obtain aerogel-based core-shell lightweight aggregate.

8. The preparation method according to claim 7, characterized in that, The preparation steps of the silica aerogel particles include: The first waste glass powder was mixed with an inorganic alkaline solution and then heat-treated, and then filtered to obtain sodium silicate filtrate. An acidic gas is passed into the sodium silicate solution to react and obtain a solution containing silica gel precipitate; The solution containing the silica gel precipitate is filtered, and the resulting silica gel is washed and aged. The collected waste liquid is adjusted to pH 10-13 and used as the alkaline activator. The aged silica gel is then subjected to solvent replacement and drying treatment to obtain the silica aerogel particles.

9. The preparation method according to claim 8, characterized in that, The mass percentage of silica in the first waste glass powder is >60%; and / or, The concentration of the inorganic alkali in the inorganic alkali solution is 1-10 mol / L; and / or, The mass ratio of the inorganic alkaline solution to the first waste glass powder is 10-50:

1.

10. The preparation method according to claim 8, characterized in that, Acidic gases include at least one of carbon dioxide, sulfur dioxide, hydrogen chloride, and nitrogen oxides; and / or, The acidic gas is introduced into the sodium silicate solution at a temperature of 0-5°C to carry out the reaction.

11. The preparation method according to claim 8, characterized in that, The heat treatment is performed at a temperature of 85-95℃ for 12-24 hours. The aging treatment is performed at a temperature of 40-90℃ for 12-24 hours.

12. The preparation method according to claim 8, characterized in that, The replacement solvent used in the solvent replacement process includes at least one of alkane solvents, alcohol solvents, and ether solvents.

13. The preparation method according to any one of claims 7-12, characterized in that, Before mixing the silica aerogel particles with the shell slurry, the process further includes mixing the silica aerogel particles with a binder.

14. The preparation method according to any one of claims 7-12, characterized in that, The curing treatment includes: first curing in an environment with a temperature of 87-93℃ and a relative humidity of ≥90% for 1-3 days, and then curing in an environment with a temperature of 17-23℃ and a relative humidity of ≥90% for 26-30 days; Alternatively, it can be cured for 1-3 days in an environment with a temperature of 87-93℃ and a relative humidity of ≥90%, and then cured for 1-2 days at a temperature of 17-23℃, a relative humidity of ≥90%, and a carbon dioxide concentration of ≥50%.

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