A recycled mortar concrete, its preparation method and application

Abstract

This invention discloses a recycled mortar concrete, its preparation method, and its application, belonging to the technical field of recycled mortar concrete. The method involves modifying activated hydrophobic aerogel powder with 3-(methacryloyloxy)propyltrimethoxysilane, then incorporating the resulting modified aerogel powder containing double bond segments into a gel system for crosslinking. Water is added for dilution, resulting in a modified liquid with a solid content of 3-4%. Recycled aggregate is impregnated with the modified liquid to obtain modified recycled aggregate. The modified recycled aggregate, silicate cement, fly ash, quartz sand, water-reducing agent, and water are mixed to obtain recycled mortar concrete. The modified recycled aggregate in the recycled mortar concrete exhibits a crosslinked network on its surface, which acts as a thickener and retarder, regulating the fluidity of the concrete. Furthermore, the hydrophobic modified aerogel powder and crosslinked network seal and strengthen the pores of the recycled aggregate, blocking moisture and improving the freeze-thaw resistance and compressive strength of the recycled mortar concrete.

Description

Technical Field

[0001] This invention belongs to the field of recycled mortar concrete technology, specifically a recycled mortar concrete, its preparation method, and its application. Background Technology

[0002] Recycled mortar concrete is a type of green building material made by partially or completely replacing natural sand and gravel with recycled aggregates (recycled sand, recycled coarse aggregates) obtained from the crushing and screening of construction waste (such as waste concrete, bricks and tiles), and by adding cement, mineral admixtures and additives.

[0003] Besides recycled aggregates, recycled mortar concrete generally includes gelling materials, mineral admixtures, and additives. Gelling materials include ordinary Portland cement, while mineral admixtures include fly ash, slag powder, and steel slag powder, used to improve the interfacial transition zone, increase density, and enhance later-stage strength. Additives include water-reducing agents, reinforcing agents, and waterproofing agents. The difference between recycled mortar concrete and ordinary concrete is mainly due to the recycled aggregates. Studies have shown that excessively high water absorption rates, and significant differences in water absorption rates with other materials, can easily lead to defects such as poor fluidity, bleeding, and internal water retention and frost heave within the aggregates. This results in decreased workability of the concrete. Furthermore, the interfacial transition zone strength of recycled aggregates is lower, and numerous cracks are generated during the crushing and recycling process. These cracks preferentially propagate along the aggregate interface, resulting in lower strength compared to conventional quartz sand.

[0004] Therefore, the key to improving the performance and mechanical properties of recycled mortar concrete lies in how to seal the micro-cracks in recycled aggregates and reduce their water absorption rate. Summary of the Invention

[0005] The purpose of this invention is to provide a recycled mortar concrete, its preparation method and application. By impregnating and modifying recycled aggregates with a modifying liquid, micro-cracks on their surface are sealed and moisture is blocked, the interface transition zone of recycled aggregates is enhanced, and the compressive strength and freeze-thaw resistance of recycled mortar concrete are improved.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for preparing recycled mortar concrete includes the following steps:

[0008] Step 1: The silica aerogel powder is hydrophobically modified with heptadecafluorodecyltrimethoxysilane, and then the resulting hydrophobic aerogel powder is activated by oxygen plasma to obtain activated hydrophobic aerogel powder.

[0009] Step 2: The activated hydrophobic aerogel powder is modified with 3-(methacryloyloxy)propyltrimethoxysilane, and then the modified aerogel powder containing double bond segments is incorporated into the gel system to participate in cross-linking. Water is added for dilution to obtain a modified liquid with a solid content of 3-4%.

[0010] Step 3: Impregnate the recycled aggregate with a modifying liquid to obtain modified recycled aggregate. Mix the modified recycled aggregate, silicate cement, fly ash, quartz sand, water-reducing agent and water to obtain recycled mortar concrete.

[0011] This invention also provides an application of recycled mortar concrete in thermal insulation concrete exterior walls.

[0012] Furthermore, the mass ratio of modified recycled aggregate, silicate cement, fly ash, quartz sand, water-reducing agent and water is 260-320:60-90:8-12:50-65:0.8-1.2:40-44.

[0013] Furthermore, the specific preparation method of modified recycled aggregate is as follows:

[0014] Add recycled aggregate with a particle size of 0.15-4.75mm to the modification liquid, stir for 2-3 minutes, vibrate and level it so that the liquid level of the modification liquid is 1-2cm higher than the surface of the recycled aggregate, soak it at 25-30℃ for 12-24 hours, drain it, and you will get the modified recycled aggregate.

[0015] Furthermore, the specific preparation method of the modified liquid is as follows:

[0016] Acrylamide, N,N'-methylenebisacrylamide, and deionized water were added to a reaction vessel and stirred at 200-300 rpm for 20-30 min. Then, activated hydrophobic aerogel powder, 0.05 M ferric chloride solution, and tannic acid were added and ultrasonically dispersed for 20-30 min. Next, gelatin, glycerol, and ammonium persulfate were added and stirred at 25-30 °C and 100-200 rpm for 20-24 h. Water was then added to adjust the solid content to 3-4% to obtain the modified solution.

[0017] Furthermore, the ratio of acrylamide, N,N'-methylenebisacrylamide, deionized water, activated hydrophobic aerogel powder, ferric chloride solution, tannic acid, gelatin, glycerol, and ammonium persulfate is 30-40g: 0.2-0.3g: 300-350mL: 36-50g: 0.5-0.6mL: 6-8g: 30-40g: 15-20mL: 4g.

[0018] Furthermore, the specific preparation method of the modified aerogel powder is as follows:

[0019] Step 1: Add silica aerogel powder and deionized water to a reaction vessel, and add heptadecafluorodecyltrimethoxysilane dropwise at 50-60℃ and 500-800r / min. After the addition is complete, keep the mixture warm and stir for 2-2.5h, centrifuge and filter, wash the precipitate 2-3 times with deionized water, and vacuum dry to constant weight to obtain hydrophobic aerogel powder.

[0020] Step 2: Perform oxygen plasma activation treatment on the fluorinated aerogel powder to re-expose a large number of active groups on its surface, thereby obtaining activated hydrophobic aerogel powder.

[0021] Step 3: Add 3-(methacryloyloxy)propyltrimethoxysilane and a 95% ethanol solution to the reaction vessel and stir at 25-30℃ for 40-60 min. Then add the activated hydrophobic aerogel powder to the reaction vessel and stir at 60-70℃ for 100-120 min. Filter and dry the filter cake to constant weight to obtain the modified aerogel powder.

[0022] Furthermore, in step 1, the ratio of silica aerogel powder, deionized water, and heptadecafluorodecyltrimethoxysilane is 0.2-0.3 g: 10 mL: 1 mL.

[0023] Furthermore, in step 2, the oxygen plasma activation treatment uses a wide-width plasma cleaner to spread the fluorinated aerogel powder on the conveyor belt of the wide-width plasma cleaner. The oxygen flow rate is 80-100 mL / min and the output power is 10 W.

[0024] Furthermore, in step 3, the ratio of 3-(methacryloyloxy)propyltrimethoxysilane, ethanol solution, and activated hydrophobic aerogel powder is 0.5-0.8g:40-50mL:1g.

[0025] The beneficial effects of this invention are:

[0026] 1. The recycled mortar concrete of this invention has good mechanical properties, workability and durability. The recycled aggregate in the recycled mortar concrete is modified, and its surface cross-linked network can play a thickening and retarding role, which regulates the fluidity of the concrete. The hydrophobic modified aerogel powder and cross-linked network can seal and strengthen the pores of the recycled aggregate, block moisture, and improve the freeze-thaw resistance and compressive strength of the recycled mortar concrete.

[0027] 2. Modified aerogel powder increases the amount of recycled aggregate coated by the modifying liquid through its large specific surface area, and reduces the water absorption of recycled aggregate through hydrophobicity. Under the initiation of ammonium persulfate, the double bonds, acrylamide, and N,N'-methylenebisacrylamide on the modified aerogel powder crosslink to form a polyacrylamide chain skeleton. The oxygen-containing functional groups on gelatin and tannic acid can form hydrogen bonds with the amino groups on the polyacrylamide chains. Under the coordination of iron ions, a dense gel network is formed to encapsulate the recycled aggregate. Iron ions can also better penetrate into the microcracks of the recycled aggregate, improving the interfacial bonding between the recycled aggregate and the film-forming material in the modifying liquid, thereby improving the sealing effect on microcracks and bringing the performance of recycled mortar concrete to its optimal state. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1: A method for preparing recycled mortar concrete, comprising the following steps:

[0030] S1: Add 2 kg of silica aerogel powder and 100 L of deionized water to a reaction vessel. Add 10 L of heptadecafluorodecyltrimethoxysilane dropwise at 50 °C and 500 r / min. After the addition is complete, keep the mixture warm and stir for 2 h. Centrifuge and filter the mixture. Wash the precipitate twice with deionized water and vacuum dry it to constant weight to obtain hydrophobic aerogel powder.

[0031] S2: Fluorinated aerogel powder is activated by oxygen plasma to re-expose a large number of active groups on its surface, resulting in activated hydrophobic aerogel powder.

[0032] The oxygen plasma activation treatment uses a wide-width plasma cleaner to spread the fluorinated aerogel powder on the conveyor belt of the wide-width plasma cleaner. The oxygen flow rate is 80 mL / min and the output power is 10 W.

[0033] S3: Add 0.5 kg of 3-(methacryloyloxy)propyltrimethoxysilane and 40 L of 95% ethanol solution to the reactor and stir at 25 °C for 40 min. Then add 1 kg of activated hydrophobic aerogel powder to the reactor and stir at 60 °C for 100 min. Filter and dry the filter cake to constant weight to obtain modified aerogel powder.

[0034] S4: Add 600g acrylamide, 40g N,N'-methylenebisacrylamide and 6L deionized water to a reaction vessel and stir for 20min at 200r / min. Then add 720g activated hydrophobic aerogel powder, 10mL 0.05M ferric chloride solution and 120g tannic acid, and sonicate for 20min. Then add 600g gelatin, 300mL glycerol and 80g ammonium persulfate, and stir for 20h at 25℃ and 100r / min. Then add water to adjust the solid content to 3% to obtain the modified solution.

[0035] S5: Add recycled aggregate with a particle size of 0.15-4.75mm to the modification liquid, stir for 2 minutes, vibrate and level it so that the liquid level of the modification liquid is 1cm higher than the surface of the recycled aggregate, soak it at 25℃ for 12 hours, drain it, and obtain the modified recycled aggregate.

[0036] S6: Mix 0.6kg silicate cement, 0.08kg fly ash, 2.6kg modified recycled aggregate, 0.5kg quartz sand, 8g water-reducing agent, and 0.4kg water for 50s to obtain recycled mortar concrete.

[0037] Example 2: A method for preparing recycled mortar concrete, comprising the following steps:

[0038] S1: Add 2.5 kg of silica aerogel powder and 100 L of deionized water to a reaction vessel. Add 10 L of heptadecafluorodecyltrimethoxysilane dropwise at 55 °C and 650 r / min. After the addition is complete, keep the mixture warm and stir for 2.25 h. Centrifuge and filter the mixture. Wash the precipitate 2.5 times with deionized water and vacuum dry to constant weight to obtain hydrophobic aerogel powder.

[0039] S2: Fluorinated aerogel powder is activated by oxygen plasma to re-expose a large number of active groups on its surface, resulting in activated hydrophobic aerogel powder.

[0040] The oxygen plasma activation treatment uses a wide-width plasma cleaner to spread the fluorinated aerogel powder on the conveyor belt of the wide-width plasma cleaner. The oxygen flow rate is 90 mL / min and the output power is 10 W.

[0041] S3: Add 0.65 kg of 3-(methacryloyloxy)propyltrimethoxysilane and 45 L of 95% ethanol solution to the reactor and stir at 27.5 °C for 50 min. Then add 1 kg of activated hydrophobic aerogel powder to the reactor and stir at 65 °C for 110 min. Filter and dry the filter cake to constant weight to obtain modified aerogel powder.

[0042] S4: Add 700g acrylamide, 50g N,N'-methylenebisacrylamide and 6.5L deionized water to a reaction vessel and stir for 25min at 250r / min. Then add 860g activated hydrophobic aerogel powder, 11mL 0.05M ferric chloride solution and 140g tannic acid, and sonicate for 25min. Then add 700g gelatin, 350mL glycerol and 80g ammonium persulfate, and stir for 22h at 27.5℃ and 150r / min. Then add water to adjust the solid content to 3.5% to obtain the modified solution.

[0043] S5: Add recycled aggregate with a particle size of 0.15-4.75mm to the modification liquid, stir for 2.5min, vibrate and level it so that the liquid level of the modification liquid is 1.5cm higher than the surface of the recycled aggregate, soak it at 27.5℃ for 18h, drain it, and obtain the modified recycled aggregate.

[0044] S6: Mix 0.75kg silicate cement, 0.1kg fly ash, 2.9kg modified recycled aggregate, 0.575kg quartz sand, 10g water-reducing agent, and 0.42kg water for 55s to obtain recycled mortar concrete.

[0045] Example 3: A method for preparing recycled mortar concrete, comprising the following steps:

[0046] S1: Add 3 kg of silica aerogel powder and 100 L of deionized water to a reaction vessel. Add 10 L of heptadecafluorodecyltrimethoxysilane dropwise at 60 °C and 800 r / min. After the addition is complete, keep the mixture warm and stir for 2.5 h. Centrifuge and filter the mixture. Wash the precipitate three times with deionized water and vacuum dry it to constant weight to obtain hydrophobic aerogel powder.

[0047] S2: Fluorinated aerogel powder is activated by oxygen plasma to re-expose a large number of active groups on its surface, resulting in activated hydrophobic aerogel powder.

[0048] The oxygen plasma activation treatment uses a wide-width plasma cleaner to spread the fluorinated aerogel powder on the conveyor belt of the wide-width plasma cleaner. The oxygen flow rate is 100 mL / min and the output power is 10 W.

[0049] S3: Add 0.8 kg of 3-(methacryloyloxy)propyltrimethoxysilane and 50 L of 95% ethanol solution to the reactor and stir at 30 °C for 60 min. Then add 1 kg of activated hydrophobic aerogel powder to the reactor and stir at 70 °C for 120 min. Filter and dry the filter cake to constant weight to obtain modified aerogel powder.

[0050] S4: Add 800g acrylamide, 60g N,N'-methylenebisacrylamide and 7L deionized water to a reaction vessel and stir for 30min at 300r / min. Then add 1000g activated hydrophobic aerogel powder, 12mL 0.05M ferric chloride solution and 160g tannic acid, and sonicate for 30min. Then add 800g gelatin, 400mL glycerol and 80g ammonium persulfate, and stir for 24h at 30℃ and 200r / min. Then add water to adjust the solid content to 4% to obtain the modified solution.

[0051] S5: Add recycled aggregate with a particle size of 0.15-4.75mm to the modification liquid, stir for 3 minutes, vibrate and level it so that the liquid level of the modification liquid is 2cm higher than the upper surface of the recycled aggregate, soak it at 30℃ for 24 hours, drain it, and obtain the modified recycled aggregate.

[0052] S6: Mix 0.9 kg silicate cement, 0.12 kg fly ash, 3.2 kg modified recycled aggregate, 0.65 kg quartz sand, 12 g water-reducing agent, and 0.44 kg water for 60 seconds to obtain recycled mortar concrete.

[0053] Comparative Example 1: The difference from Example 1 is that the silica aerogel powder was directly prepared into a modified liquid through step S3 and subsequent treatments without the treatment of steps S1 and S2. The remaining steps remained unchanged, and recycled mortar concrete was prepared.

[0054] Comparative Example 2: The difference from Example 1 is that ferric chloride solution and tannic acid were not added in step S3, and an equal mass of deionized water was added. The remaining steps remained unchanged, and recycled mortar concrete was prepared.

[0055] Comparative Example 3: The difference from Example 1 is that acrylamide and N,N'-methylenebisacrylamide were not added in step S3, while the other steps remained unchanged, and recycled mortar concrete was prepared.

[0056] Comparative Example 4: The difference from Example 1 is that step S5 was not performed. In step S6, the modified recycled aggregate was replaced with ordinary recycled aggregate to prepare recycled mortar concrete.

[0057] In the examples and comparative examples, the recycled aggregate is a granular material processed from construction waste such as concrete and bricks through crushing and screening processes; the silica aerogel powder was purchased from Suzhou Zhongcui Nanomaterials Technology Co., Ltd., with a particle size of 30-50μm; the fly ash is power plant flue ash, 200 mesh; the quartz sand has a particle size of 0.15-5mm; and the water-reducing agent is polycarboxylate water-reducing agent.

[0058] Performance tests were conducted on Examples 1-3 and Comparative Examples 1-4:

[0059] Mechanical properties of the above concrete were tested in accordance with GB / T 50081-2019; slump was tested in accordance with DB45 / T 1621-2017; freeze-thaw resistance was tested in accordance with GB / T 50082-2009; and water absorption was tested in accordance with GB / T 25177-2010.

[0060] Table 1. Results of various concrete performance tests

[0061] ,

[0062] As can be seen from Table 1, the concrete in Examples 1-3 has better compressive strength, a slump loss rate of less than 20% at 60 min, good fluidity, and high freeze-thaw resistance and low water absorption.

[0063] In Comparative Example 4, the recycled aggregate was not modified by the modified liquid, the natural pores were not sealed, the water absorption was high, and the compressive strength and freeze-thaw resistance were the worst.

[0064] The decrease in compressive strength of concrete in Comparative Example 1 indicates that the microcrack situation in the recycled aggregate has not been improved. The decrease in initial slump may be because the silica aerogel powder was not hydrophobically modified. The recycled aggregate absorbs water rapidly during the mixing process, resulting in decreased fluidity. Furthermore, the microcracks expand during repeated freeze-thaw cycles, leading to a decrease in freeze-thaw resistance.

[0065] In Comparative Example 2, during the modification of recycled aggregate, the modified aerogel powder lacked iron ions and tannic acid. It could not exert the coordination effect of metal ions through the phenolic hydroxyl groups on iron ions and tannic acid, resulting in a decrease in the strength of the cross-linked network. This led to a reduction in the mechanical strength of the outer membrane layer of the recycled aggregate. Furthermore, tannic acid also has a certain degree of adhesion. Without the corresponding components, the polymer alone could not penetrate into the microcracks of the recycled aggregate better, resulting in a decrease in the coating effect on the recycled aggregate and an inability to effectively seal the microcracks. This led to an increase in the water penetration path and a decrease in the corresponding performance of the concrete.

[0066] In Comparative Example 3, the modified liquid failed to form an acrylamide polymer network, and the surface of the modified recycled aggregate failed to form a dense polymer coating. Components such as gelatin absorbed water and swelled, causing water to rapidly penetrate into the microcracks. The bleeding of recycled aggregates increased, resulting in a decrease in the freeze-thaw resistance of the concrete sample. Furthermore, the lack of polymer thickening effect led to an artificially high initial slump of the concrete. After 60 minutes, due to severe bleeding, the volume of the paste shrank significantly, resulting in a rapid decrease in slump.

[0067] Therefore, in this embodiment, the recycled aggregate in the concrete is modified. The modified aerogel powder increases the amount of slurry adhering to the recycled aggregate by the modifying liquid through its large specific surface area, and reduces the water absorption of the recycled aggregate through hydrophobicity. Under the initiation of ammonium persulfate, the double bonds, acrylamide, and N,N'-methylenebisacrylamide on the modified aerogel powder crosslink to form a polyacrylamide chain skeleton. The oxygen-containing functional groups on gelatin and tannic acid can form hydrogen bonds with the amino groups on the polyacrylamide chain. Under the coordination of iron ions, a dense gel network is formed to encapsulate the recycled aggregate. Iron ions can also better penetrate into the microcracks of the recycled aggregate, improving the interfacial bonding force between the recycled aggregate and the film-forming material in the modifying liquid, thereby improving the sealing effect on microcracks and bringing the performance of the recycled mortar concrete to its optimal state.

[0068] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0069] In this document, the description of equipment such as "reaction vessel" is only for illustrative purposes of the reaction site and is not intended to limit its specific structure, material, or operation. Those skilled in the art can obviously make conventional substitutions, modifications, or equivalent changes to the reaction equipment, matching pipes and valves, heating / cooling methods, stirring methods, feeding / discharging methods, and safety interlock settings in the above embodiments without departing from the concept of the present invention; all such changes, modifications, substitutions, and variations should be considered to fall within the protection scope of the present invention.

[0070] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing recycled mortar concrete, characterized in that, Includes the following steps: Step 1: The silica aerogel powder is hydrophobically modified with heptadecafluorodecyltrimethoxysilane, and then the resulting hydrophobic aerogel powder is activated by oxygen plasma to obtain activated hydrophobic aerogel powder. Step 2: The activated hydrophobic aerogel powder is modified with 3-(methacryloyloxy)propyltrimethoxysilane, and then the modified aerogel powder containing double bond segments is incorporated into the gel system to participate in cross-linking. Water is added for dilution to obtain a modified liquid with a solid content of 3-4%. Step 3: Impregnate the recycled aggregate with a modifying liquid to obtain modified recycled aggregate. Mix the modified recycled aggregate, silicate cement, fly ash, quartz sand, water-reducing agent and water to obtain recycled mortar concrete. The specific preparation method of the modified liquid is as follows: Acrylamide, N,N'-methylenebisacrylamide, and deionized water were added to a reaction vessel and stirred at 200-300 rpm for 20-30 min. Then, modified aerogel powder, 0.05 M ferric chloride solution, and tannic acid were added and ultrasonically dispersed for 20-30 min. Next, gelatin, glycerol, and ammonium persulfate were added and stirred at 25-30 °C and 100-200 rpm for 20-24 h. Water was then added to adjust the solid content to 3-4% to obtain the modified solution. The specific preparation method of the modified aerogel powder is as follows: 3-(methacryloyloxy)propyltrimethoxysilane and 95wt% ethanol solution were added to a reaction vessel and stirred at 25-30℃ for 40-60 min. Then, activated hydrophobic aerogel powder was added and stirred at 60-70℃ for 100-120 min. The mixture was filtered and the filter cake was dried to constant weight to obtain modified aerogel powder.

2. The method for preparing recycled mortar concrete according to claim 1, characterized in that, The mass ratio of the modified recycled aggregate, silicate cement, fly ash, quartz sand, water-reducing agent and water is 260-320:60-90:8-12:50-65:0.8-1.2:40-44.

3. The method for preparing recycled mortar concrete according to claim 1, characterized in that, The specific preparation method of the modified recycled aggregate is as follows: Add recycled aggregate with a particle size of 0.15-4.75mm to the modification liquid, stir for 2-3 minutes, vibrate and level it so that the liquid level of the modification liquid is 1-2cm higher than the surface of the recycled aggregate, soak at 25-30℃ for 12-24 hours, drain, and obtain modified recycled aggregate.

4. The method for preparing recycled mortar concrete according to claim 1, characterized in that, The ratio of acrylamide, N,N'-methylenebisacrylamide, deionized water, modified aerogel powder, ferric chloride solution, tannic acid, gelatin, glycerol, and ammonium persulfate is 30-40g: 2-3g: 300-350mL: 36-50g: 0.5-0.6mL: 6-8g: 30-40g: 15-20mL: 4g.

5. The method for preparing recycled mortar concrete according to claim 1, characterized in that, The ratio of 3-(methacryloyloxy)propyltrimethoxysilane, ethanol solution, and activated hydrophobic aerogel powder is 0.5-0.8g: 40-50mL: 1g.

6. The method for preparing recycled mortar concrete according to claim 5, characterized in that, The oxygen plasma activation method for the activated hydrophobic aerogel powder is as follows: Fluorinated aerogel powder was spread out on the conveyor belt of a wide-width plasma cleaner and activated by oxygen plasma with an oxygen flow rate of 80-100 mL / min and an output power of 10 W.

7. The method for preparing recycled mortar concrete according to claim 6, characterized in that, The hydrophobic aerogel powder is prepared by the following steps: Add silica aerogel powder and deionized water to a reaction vessel, add heptadecafluorodecyltrimethoxysilane dropwise at 50-60℃ and 500-800r / min, keep warm and stir for 2-2.5h, centrifuge and filter, wash the precipitate, dry it, and obtain hydrophobic aerogel powder. The ratio of silica aerogel powder, deionized water, and heptadecafluorodecyltrimethoxysilane is 0.2-0.3 g: 10 mL: 1 mL.

8. A recycled mortar concrete, characterized in that, It is prepared by the method for preparing recycled mortar concrete according to any one of claims 1-7.

9. The application of recycled mortar concrete as described in claim 8 in thermal insulation concrete exterior walls.