Recycled concrete ash-based composite aerogel as well as preparation method and application thereof

Abstract

The invention discloses recycled concrete ash-based composite aerogel as well as a preparation method and application thereof, and belongs to the field of solid waste resource utilization and aerogel materials. The method comprises the following steps: preparing a one-dimensional clay nanofiber dispersion liquid, dispersing recycled concrete ash to prepare a clay-recycled concrete ash dispersion liquid, promoting gelling of the clay-recycled concrete ash dispersion liquid through crosslinking to form clay-recycled concrete ash hydrogel, and freeze-drying to form the recycled concrete ash-based composite aerogel. According to the preparation method provided by the invention, high-added-value conversion of the recycled concrete ash is realized, and chemical modification is not needed. The production process is simple and efficient, and large-scale expansion is easy. The raw materials used for production are inorganic materials and have the excellent characteristics of low cost, easiness in obtaining, environment friendliness, flame retardance, heat insulation and the like. The obtained composite aerogel has the characteristics of high mechanical strength, excellent heat-insulating and flame-retardant properties and the like, is high in practicability, opens up a reliable way for efficient resource utilization of recycled concrete ash and other building solid wastes, and provides a new scheme for reducing the production cost of the aerogel.

Description

Technical Field

[0001] The present invention belongs to the fields of solid waste resource utilization and aerogel materials, and particularly relates to a recycled concrete ash-based composite aerogel, a preparation method thereof, and an application thereof. Background Art

[0002] Concrete has extensive demands and applications in the construction industry. With the highly developed urbanization construction, along with the production of concrete and the renovation of old buildings, more than 6,000,000 m 3 of waste concrete is generated every year. The random stacking of waste concrete will bring ecological problems such as environmental deterioration. To solve these problems, industrially, waste concrete is usually processed through processes such as crushing and screening to form recycled concrete ash. Recycled concrete ash is mainly used in the production of building materials such as concrete, cement, mortar, and blocks. Although its comprehensive utilization rate is relatively high, there are problems such as a single utilization path, an environmentally unfriendly utilization process, and the generation of new construction waste such as waste concrete. Therefore, it is urgent to develop high-value-added applications of recycled concrete and prepare high-value-added recycled concrete composites.

[0003] An aerogel is a solid material with a nano-porous structure, and has excellent physical and chemical properties such as a high porosity (>92%), a high specific surface area (600 - 1200 m 2 / g), a low density close to that of air, and a low thermal conductivity. In recent years, in order to reduce the secondary pollution caused by recycled concrete ash and increase its added value, many domestic enterprises and universities have mixed aerogel particles with recycled concrete ash particles to prepare high-temperature-resistant concrete. For example, Wang Xinjie et al. from Changzhou University used recycled concrete ash, fly ash, and SiO 2 aerogel particles to be compounded by an integral molding method in "A High-Temperature-Resistant Aerogel Mortar Composite Recycled Concrete and a Preparation Method Thereof" (CN 118619607A) to fully utilize waste building materials and prepare high-temperature-resistant concrete. Wang Leiliang from Wuxi Southern Concrete Co., Ltd. used SiO 2 aerogel and an organic solvent to modify recycled concrete ash to prepare a compressive and carbonation-resistant recycled concrete in "A Compressive and Carbonation-Resistant Recycled Concrete and a Preparation Method Thereof" (CN 117263603A). However, existing resource utilization methods mostly use expensive SiO 2 aerogel to be compounded with recycled concrete ash to produce high-value-added recycled concrete. The adhesives used are mostly expensive organic materials, and secondary construction waste will also be generated during the production of recycled concrete. By using recycled concrete ash as a raw material to produce an aerogel material with a wider range of uses than recycled concrete, it is possible to 100% utilize recycled concrete ash without generating secondary construction waste and significantly increase its added value. However, there are few reports on the method of directly preparing aerogel using recycled concrete ash as the main raw material. Summary of the Invention

[0004] The object of the present invention is to overcome the defects in the prior art and provide a recycled concrete ash-based composite aerogel, a preparation method thereof and an application thereof. The recycled concrete ash-based composite aerogel prepared by the present invention has a stable structure, good mechanical properties, excellent heat insulation and flame retardant properties. The preparation method has low production cost, simple preparation process and is easy to scale up, which has positive production significance for the high-value utilization of recycled concrete ash.

[0005] The specific technical solutions adopted by the present invention are as follows:

[0006] In a first aspect, the present invention provides a preparation method of a recycled concrete ash-based composite aerogel, which is specifically as follows:

[0007] S1. Mix the one-dimensional clay material with water evenly, and obtain a stable and controllable concentration of one-dimensional clay nanofiber dispersion after ultrasonic dispersion treatment;

[0008] S2. Mix the recycled concrete ash with the one-dimensional clay nanofiber dispersion evenly, and obtain a clay-recycled concrete ash dispersion after ultrasonic dispersion treatment;

[0009] S3. Mix the sodium silicate aqueous solution with the clay-recycled concrete ash dispersion and carry out a crosslinking reaction to obtain a clay-recycled concrete ash hydrogel;

[0010] S4. After freeze-drying the clay-recycled concrete ash hydrogel, obtain a recycled concrete ash-based composite aerogel.

[0011] Preferably, in S1, in the one-dimensional clay suspension obtained by mixing the one-dimensional clay material with water, the concentration of the one-dimensional clay material is 10-30 g / L.

[0012] Preferably, the one-dimensional clay material is one of sepiolite, palygorskite or halloysite.

[0013] Preferably, the ultrasonic treatment adopts tip ultrasonic treatment, the ultrasonic treatment time in S1 is 30-65 min, and the ultrasonic treatment time in S2 is 20-60 min.

[0014] Preferably, in S2, the mass ratio of the recycled concrete ash to the one-dimensional clay nanofiber dispersion is 1:(1-4).

[0015] Preferably, in S3, the mass fraction of the sodium silicate aqueous solution is 10 wt%-30 wt%, the sodium silicate aqueous solution and the clay-recycled concrete ash dispersion are mixed according to a solid content mass ratio of 1:10, and the crosslinking reaction time is 1.5 h-3 h.

[0016] Preferably, in S4, the clay-recycled concrete ash hydrogel is frozen at -196°C to -20°C for 0.1 to 3 h, and then freeze-dried at -65°C to -45°C and a vacuum degree of 4 to 16 Pa for 24 to 48 h to obtain the recycled concrete ash-based composite aerogel.

[0017] In a second aspect, the present invention provides a recycled concrete ash-based composite aerogel obtained by using the preparation method according to any one of the first aspect.

[0018] In a third aspect, the present invention provides an application of the recycled concrete ash-based composite aerogel according to the second aspect in heat insulation and flame retardancy.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) The present invention uses recycled concrete ash as a raw material. By introducing an inorganic dispersant (i.e., a clay nanofiber dispersion liquid with a one-dimensional structure), the recycled concrete ash is assisted in dispersion by the steric effect to obtain a clay-recycled concrete ash dispersion liquid; by adding an inorganic cross-linking agent Na 2 SiO 3 solution, the recycled concrete ash composite dispersion liquid is gelled to obtain a hydrogel; finally, the hydrogel is freeze-dried to obtain a recycled concrete ash-based aerogel without any chemical pretreatment modification.

[0021] 2) The present invention directly prepares an aerogel using recycled concrete ash as a raw material, abandoning expensive and highly dangerous materials in the traditional method, and at the same time simplifying the complex preparation process. This method has the characteristics of simple preparation process and high reaction efficiency, realizing 100% utilization of recycled concrete ash, and no secondary waste residue is generated in the whole process. For the dispersion method of recycled concrete ash in water, the present invention uses a one-dimensional clay nanofiber dispersion liquid prepared from inexpensive natural clay fibers to assist the recycled concrete ash, and the dispersion effect is excellent. The present invention uses inexpensive and easily available Na 2 SiO 3The solution, used as a binder and cross-linking agent instead of organic solvents, significantly enhances the structural stability and mechanical strength of the aerogel and reduces the production cost. The regenerated concrete ash composite dispersion prepared by the present invention has high tunability and stability. By simply adjusting the material ratio of the slurry, properties such as the composition, density, pore structure, mechanical strength, and thermal conductivity of the aerogel can be finely controlled. The preparation method proposed by the present invention realizes the high-value conversion of 100% of the regenerated concrete ash. Its process flow is simple and easy to scale up the preparation. The production raw materials are cheap and easily available and are environmentally friendly. The regenerated concrete ash-based aerogel proposed by the present invention has both excellent mechanical properties and heat insulation and flame retardant characteristics, with significant practical value, providing a simple, low-cost, and environmentally friendly new way for the resource utilization of regenerated concrete ash and a new solution for reducing the production cost of aerogels. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a graph showing the relationship between the density and thermal conductivity of the composite aerogel prepared by dispersing different mass fractions of regenerated concrete ash in the 20 g / L sepiolite dispersion prepared in the embodiment of the present invention.

[0023] Figure 2 It is a graph showing the relationship between the density and thermal conductivity of the composite aerogel prepared by dispersing 50% of the regenerated concrete ash in sepiolite dispersions with different concentrations prepared in the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will be further described and explained below in conjunction with the drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly without conflict.

[0025] The present invention provides a method for preparing a regenerated concrete ash-based composite aerogel. The preparation method uses regenerated concrete ash as a raw material. By introducing an inorganic dispersant (i.e., one-dimensional clay nanofiber dispersion), the regenerated concrete ash is assisted in dispersion by the steric effect to obtain a clay-regenerated concrete ash dispersion; by adding an inorganic cross-linking agent Na 2 SiO 3 solution to gel the regenerated concrete ash composite dispersion to obtain a clay-regenerated concrete ash hydrogel; finally, the hydrogel is freeze-dried to obtain a regenerated concrete ash-based aerogel, and no chemical modification is required during the preparation process. The preparation method of the present invention specifically includes the following steps:

[0026] S1. Prepare a one-dimensional clay nanofiber dispersion:

[0027] Mix the one-dimensional clay material with water evenly, and obtain a stable and concentration-controllable one-dimensional clay nanofiber dispersion after ultrasonic dispersion treatment.

[0028] As a preferred embodiment of the present invention, the steps are specifically as follows:

[0029] Mix the one-dimensional clay material with deionized water to prepare a mixed aqueous solution with a concentration of 10 - 30 g / L to obtain a one-dimensional clay suspension; then, after subjecting the one-dimensional clay suspension to ultrasonic dispersion treatment for 30 min, a stable and concentration-controllable one-dimensional clay nanofiber dispersion is obtained.

[0030] As a preferred embodiment of the present invention, the one-dimensional clay material can be one of sepiolite, palygorskite, or halloysite.

[0031] As a preferred embodiment of the present invention, ultrasonic dispersion can be carried out by tip sonication, and the ultrasonic treatment time in this step can be 30 - 65 min.

[0032] S2. Prepare a clay-recycled concrete ash dispersion:

[0033] Mix the recycled concrete ash with the one-dimensional clay nanofiber dispersion evenly, and after ultrasonic dispersion treatment, a clay-recycled concrete ash dispersion is obtained.

[0034] As a preferred embodiment of the present invention, the steps are specifically as follows:

[0035] Mix the recycled concrete ash with the one-dimensional clay nanofiber dispersion prepared in S1, and control the mass ratio of the recycled concrete ash to the one-dimensional clay nanofiber dispersion to be 1:(1 - 4). Subsequently, subject the obtained suspension to ultrasonic dispersion treatment to obtain a uniformly dispersed clay-recycled concrete ash dispersion.

[0036] As a preferred embodiment of the present invention, ultrasonic dispersion can be carried out by tip sonication, and the ultrasonic treatment time in this step can be 20 - 60 min.

[0037] S3. Promote the gelation of the clay-recycled concrete ash dispersion to form a clay-recycled concrete ash hydrogel through crosslinking:

[0038] Mix the sodium silicate aqueous solution with the clay-recycled concrete ash dispersion prepared in S2, and carry out a crosslinking reaction to obtain a clay-recycled concrete ash hydrogel.

[0039] As a preferred embodiment of the present invention, the steps are specifically as follows:

[0040] Mix the Na 2 SiO 3 solution with a mass fraction of 10 wt% - 30 wt% and the clay-recycled concrete ash dispersion prepared in S2 according to a solid content mass ratio of 1:10, and after crosslinking reaction for 1.5 h - 3 h, a clay-recycled concrete ash hydrogel is obtained.

[0041] S4. Freeze-dry to form a recycled concrete ash-based composite aerogel:

[0042] The clay-recycled concrete ash hydrogel prepared in S3 is freeze-dried to obtain a recycled concrete ash-based composite aerogel.

[0043] As a preferred embodiment of the present invention, the specific steps are as follows:

[0044] The clay-recycled concrete ash hydrogel is frozen at a temperature of -196°C to -20°C for 0.1 to 3 hours, and then freeze-dried at a temperature of -65°C to -45°C and a vacuum degree of 4 to 16 Pa for 24 to 48 hours to obtain a recycled concrete ash-based composite aerogel.

[0045] In the present invention, the recycled concrete ash-based composite aerogel prepared through the above steps has the following characteristics: the thermal conductivity of the recycled concrete ash-based composite aerogel is 31 to 45 mW / (m·K), and the density is 31 to 0.043 g / cm 3 ; when bearing a load 1000 times its own weight, the overall porous structure of the recycled concrete ash-based composite aerogel does not change.

[0046] The following further elaborates on the present invention with specific embodiments, but is not limited to the following embodiments.

[0047] In the embodiments, the one-dimensional clay material is taken as sepiolite as an example, but is not limited thereto.

[0048] Example 1

[0049] In this example, a recycled concrete ash-based composite aerogel was prepared, and the preparation method specifically included the following steps:

[0050] S1. Mix sepiolite with deionized water to form a mixed aqueous solution with a concentration of 20 g / L to obtain a one-dimensional clay suspension; after the one-dimensional clay suspension is ultrasonically dispersed for 30 minutes, a stable and concentration-controllable one-dimensional clay nanofiber dispersion is obtained;

[0051] S2. Mix the recycled concrete ash with the one-dimensional clay nanofiber dispersion, control the mass ratio of the recycled concrete ash to the one-dimensional clay nanofiber dispersion to be 1:4, and ultrasonically disperse the obtained suspension for 20 minutes to obtain a uniformly dispersed clay-recycled concrete ash dispersion.

[0052] S3. Add 10 wt% of Na 2 SiO 3The solution is mixed with the clay-recycled concrete ash dispersion liquid according to a solid content mass ratio of 1:10, and after crosslinking reaction for 1.5 h, a clay-recycled concrete ash hydrogel is obtained.

[0053] S4. Freeze the clay-recycled concrete ash hydrogel at -20 °C for 1 h, and then perform freeze-drying for 24 h under the conditions of a temperature of -65 °C and a vacuum degree of 4 Pa to obtain a recycled concrete ash-based composite aerogel.

[0054] It is measured that the thermal conductivity of the recycled concrete ash-based composite aerogel prepared in this example is 41.42 mW / (m·K), and the density is 0.039 g / cm 3 , and it maintains its complete volume when bearing a weight more than 1000 times its own weight. The results are as Figure 1 shown.

[0055] Example 2

[0056] A recycled concrete ash-based composite aerogel is prepared in this example. The preparation method specifically includes the following steps:

[0057] S1. Mix sepiolite with deionized water to prepare a mixed aqueous solution with a concentration of 20 g / L to obtain a one-dimensional clay suspension; after subjecting the one-dimensional clay suspension to ultrasonic dispersion treatment for 30 min, a stable and controllable-concentration one-dimensional clay nanofiber dispersion liquid is obtained;

[0058] S2. Mix the recycled concrete ash with the one-dimensional clay nanofiber dispersion liquid, control the mass ratio of the recycled concrete ash to the one-dimensional clay nanofiber dispersion liquid to be 3:7, and subject the obtained suspension to ultrasonic dispersion treatment for 30 min to obtain a uniformly dispersed clay-recycled concrete ash dispersion liquid.

[0059] S3. Mix the Na 2 SiO 3 solution with a mass fraction of 20 wt% and the clay-recycled concrete ash dispersion liquid according to a solid content mass ratio of 1:10, and after crosslinking reaction for 2 h, a clay-recycled concrete ash hydrogel is obtained.

[0060] S4. Freeze the clay-recycled concrete ash hydrogel at -30 °C for 1 h, and then perform freeze-drying for 36 h under the conditions of a temperature of -45 °C and a vacuum degree of 16 Pa to obtain a recycled concrete ash-based composite aerogel.

[0061] It is measured that the thermal conductivity of the recycled concrete ash-based composite aerogel prepared in this example is 37.35 mW / (m·K), and the density is 0.036 g / cm 3 , and it maintains its complete volume when bearing a weight more than 1000 times its own weight. The results are as Figure 1 shown.

[0062] Example 3

[0063] In this example, a regenerated concrete ash-based composite aerogel was prepared. The preparation method specifically includes the following steps:

[0064] S1. Mix sepiolite with deionized water to form a mixed aqueous solution with a concentration of 20 g / L to obtain a one-dimensional clay suspension; after subjecting the one-dimensional clay suspension to ultrasonic dispersion treatment for 40 min, a stable and controllable-concentration one-dimensional clay nanofiber dispersion is obtained;

[0065] S2. Mix the regenerated concrete ash with the one-dimensional clay nanofiber dispersion, control the mass ratio of the regenerated concrete ash to the one-dimensional clay nanofiber dispersion to be 2:3, and subject the obtained suspension to ultrasonic dispersion treatment for 30 min to obtain a uniformly dispersed clay-regenerated concrete ash dispersion.

[0066] S3. Mix a Na 2 SiO 3 solution with a mass fraction of 10 wt% and the clay-regenerated concrete ash dispersion according to a solid content mass ratio of 1:10, and carry out a cross-linking reaction for 3 h to obtain a clay-regenerated concrete ash hydrogel.

[0067] S4. Freeze the clay-regenerated concrete ash hydrogel at -25 °C for 1 h, and then carry out freeze-drying for 48 h under the conditions of a temperature of -50 °C and a vacuum degree of 10 Pa to obtain a regenerated concrete ash-based composite aerogel.

[0068] It was measured that the thermal conductivity of the regenerated concrete ash-based composite aerogel prepared in this example is 35.44 mW / (m·K), and the density is 0.034 g / cm 3 , and it maintains its volume integrity when bearing a weight more than 1000 times its own weight. The results are as Figure 1 shown.

[0069] Example 4

[0070] In this example, a regenerated concrete ash-based composite aerogel was prepared. The preparation method specifically includes the following steps:

[0071] S1. Mix sepiolite with deionized water to form a mixed aqueous solution with a concentration of 20 g / L to obtain a one-dimensional clay suspension; after subjecting the one-dimensional clay suspension to ultrasonic dispersion treatment for 30 min, a stable and controllable-concentration one-dimensional clay nanofiber dispersion is obtained;

[0072] S2. Mix the recycled concrete ash with the one-dimensional clay nanofiber dispersion liquid, control the mass ratio of the recycled concrete ash to the one-dimensional clay nanofiber dispersion liquid to be 1:1, and subject the obtained suspension to ultrasonic dispersion treatment for 30 min to obtain a uniformly dispersed clay-recycled concrete ash dispersion liquid.

[0073] S3. Mix the Na 2 SiO 3 solution with the clay-recycled concrete ash dispersion liquid according to the solid content mass ratio of 1:10, and carry out cross-linking reaction for 3 h to obtain a clay-recycled concrete ash hydrogel.

[0074] S4. Freeze the clay-recycled concrete ash hydrogel at -20 °C for 1 h, and then carry out freeze-drying for 36 h under the conditions of a temperature of -55 °C and a vacuum degree of 6 Pa to obtain a recycled concrete ash-based composite aerogel.

[0075] It is measured that the thermal conductivity of the recycled concrete ash-based composite aerogel prepared in this example is 33.52 mW / (m·K), and the density is 0.032 g / cm 3 , and it maintains the volume integrity when bearing a weight exceeding 1000 times its own weight, and the results are as Figure 1 shown.

[0076] In the above Examples 1 to 4, the relationship diagram of the density and thermal conductivity of the composite aerogels (i.e., recycled concrete ash-based composite aerogels) prepared by dispersing different mass fractions of recycled concrete ash in the prepared 20 g / L sepiolite nanofiber dispersion liquid is as Figure 1 shown. It can be seen from the figure that the density of the recycled concrete ash-based composite aerogel increases linearly with the increase of the mass fraction of the recycled concrete ash, and at the same time, the thermal conductivity increases with the increase of the mass fraction of the recycled concrete ash, which proves that the present invention can regulate the density of the composite aerogel by changing the mass fraction of the recycled concrete to obtain an aerogel with low thermal conductivity.

[0077] Example 5

[0078] In this example, a recycled concrete ash-based composite aerogel is prepared, and the preparation method specifically includes the following steps:

[0079] S1. Mix sepiolite with deionized water to form a mixed aqueous solution with a concentration of 10 g / L to obtain a one-dimensional clay suspension; after subjecting the one-dimensional clay suspension to ultrasonic dispersion treatment for 30 min, a stable and controllable concentration of one-dimensional clay nanofiber dispersion liquid is obtained;

[0080] S2. Mix the recycled concrete ash with the one-dimensional clay nanofiber dispersion liquid, control the mass ratio of the recycled concrete ash to the one-dimensional clay nanofiber dispersion liquid to be 1:1, and subject the obtained suspension to ultrasonic dispersion treatment for 30 min to obtain a uniformly dispersed clay-recycled concrete ash dispersion liquid.

[0081] S3. Mix the Na 2 SiO 3 solution with a mass fraction of 20 wt% and the clay-recycled concrete ash dispersion liquid according to the solid content mass ratio of 1:10, and obtain a clay-recycled concrete ash hydrogel after crosslinking reaction for 2 h.

[0082] S4. Freeze the clay-recycled concrete ash hydrogel at -30 °C for 1 h, and then perform freeze-drying for 36 h under the conditions of a temperature of -45 °C and a vacuum degree of 16 Pa to obtain a recycled concrete ash-based composite aerogel.

[0083] It is measured that the thermal conductivity of the recycled concrete ash-based composite aerogel prepared in this example is 43.57 mW / (m·K), and the density is 0.045 g / cm 3 , and it maintains its volume integrity when bearing a weight more than 1000 times its own weight. The results are as Figure 2 shown.

[0084] Example 6

[0085] A recycled concrete ash-based composite aerogel is prepared in this example. The preparation method specifically includes the following steps:

[0086] S1. Mix sepiolite with deionized water to prepare a mixed aqueous solution with a concentration of 30 g / L to obtain a one-dimensional clay suspension; after subjecting the one-dimensional clay suspension to ultrasonic dispersion treatment for 30 min, obtain a stable and controllable concentration of one-dimensional clay nanofiber dispersion liquid;

[0087] S2. Mix the recycled concrete ash with the one-dimensional clay nanofiber dispersion liquid, control the mass ratio of the recycled concrete ash to the one-dimensional clay nanofiber dispersion liquid to be 1:1, and subject the obtained suspension to ultrasonic dispersion treatment for 30 min to obtain a uniformly dispersed clay-recycled concrete ash dispersion liquid.

[0088] S3. Mix the Na 2 SiO 3 solution with a mass fraction of 20 wt% and the clay-recycled concrete ash dispersion liquid according to the solid content mass ratio of 1:10, and obtain a clay-recycled concrete ash hydrogel after crosslinking reaction for 2 h.

[0089] S4. Freeze the clay-recycled concrete ash hydrogel at -30°C for 1 h, and then perform freeze-drying for 36 h at a temperature of -45°C and a vacuum degree of 16 Pa to obtain the recycled concrete ash-based composite aerogel.

[0090] It is measured that the thermal conductivity of the recycled concrete ash-based composite aerogel prepared in this example is 31.31 mW / (m·K), and the density is 0.031 g / cm 3 , and it maintains its volume integrity when bearing a weight more than 1000 times its own weight. The results are as Figure 2 shown.

[0091] In the above Examples 4 to 6, the relationship diagram of the density and thermal conductivity of the composite aerogel (i.e., the recycled concrete ash-based composite aerogel) prepared by dispersing 50% of the recycled concrete ash with different concentrations of sepiolite dispersions is as Figure 2 shown. It can be seen from the figure that the density of the recycled concrete ash-based composite aerogel increases with the increase in the concentration of the clay (sepiolite) dispersion liquid, and at the same time, the thermal conductivity increases with the increase in the concentration of the clay dispersion liquid. This proves that the present invention can regulate the density of the composite aerogel by changing the concentration of the clay dispersion liquid to obtain an aerogel with low thermal conductivity.

[0092] The preparation method proposed by the present invention realizes the high-value conversion of recycled concrete ash without chemical modification. The production process is simple and efficient, and is easy to scale up. The raw materials used in the production are all inorganic materials, and they all have excellent properties such as being cheap and easily available, green and environmentally friendly, flame-retardant and heat-insulating. The prepared recycled concrete ash-based composite aerogel has high mechanical strength, excellent heat-insulating and flame-retardant properties, and strong practicability. It opens up a reliable way for the efficient resource utilization of construction solid wastes such as recycled concrete ash, and provides a new solution for reducing the production cost of aerogels.

[0093] The above-described embodiments are only a preferred solution of the present invention, but they are not intended to limit the present invention. Those of ordinary skill in the relevant technical field can still make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by adopting equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A method for preparing recycled concrete ash-based composite aerogel, characterized in that: The details are as follows: S1, mixing the one-dimensional clay material and water uniformly, and obtaining a stable one-dimensional clay nanofiber dispersion with controllable concentration after ultrasonic dispersion treatment; S2, uniformly mixing the recycled concrete ash and the one-dimensional clay nanofiber dispersion, and obtaining a clay-recycled concrete ash dispersion after ultrasonic dispersion treatment; S3, mixing the sodium silicate aqueous solution with the clay-recycled concrete ash dispersion and performing a cross-linking reaction to obtain a clay-recycled concrete ash hydrogel; S4. Freeze-drying the clay-recycled concrete ash hydrogel to obtain a recycled concrete ash-based composite aerogel.

2. The method for preparing a recycled concrete ash-based composite aerogel according to claim 1, characterized in that: In the above S1, in the one-dimensional clay suspension obtained by mixing the one-dimensional clay material with water, the concentration of the one-dimensional clay material is 10-30 g / L.

3. The method for preparing a recycled concrete ash-based composite aerogel according to claim 1, characterized in that: The one-dimensional clay material is one of sepiolite, palygorskite or halloysite.

4. The method for preparing a recycled concrete ash-based composite aerogel according to claim 1, characterized in that: The ultrasonic treatment adopts tip ultrasonic treatment, the ultrasonic treatment time in S1 is 30 to 65 minutes, and the ultrasonic treatment time in S2 is 20 to 60 minutes.

5. The method for preparing a recycled concrete ash-based composite aerogel according to claim 1, characterized in that: In the S2, the mass ratio of recycled concrete ash to one-dimensional clay nanofiber dispersion is 1:(1-4).

6. The method for preparing a recycled concrete ash-based composite aerogel according to claim 1, characterized in that: In S3, the mass fraction of the sodium silicate aqueous solution is 10wt% to 30wt%, the sodium silicate aqueous solution is mixed with the clay-recycled concrete ash dispersion at a solid content mass ratio of 1:10, and the cross-linking reaction time is 1.5h to 3h.

7. The method for preparing a recycled concrete ash-based composite aerogel according to claim 1, characterized in that: In S4, the clay-recycled concrete ash hydrogel is frozen at -196°C to -20°C for 0.1 to 3 hours, and then freeze-dried at -65°C to -45°C and a vacuum degree of 4 to 16 Pa for 24 to 48 hours to obtain a recycled concrete ash-based composite aerogel.

8. A recycled concrete ash-based composite aerogel obtained by the preparation method according to any one of claims 1 to 7.

9. An application of the recycled concrete ash-based composite aerogel according to claim 8 in thermal insulation and flame retardancy.

Images