Hydrophobic recycled concrete and preparation method thereof

Abstract

The invention discloses hydrophobic recycled concrete and a preparation method thereof, and belongs to the technical field of building materials. The modified recycled aggregate is optimized and modified through the nanometer material, so that the modified recycled aggregate can be filled in aggregate microcracks and pores, interacts with a silane coupling agent, introduces active groups on the surface, reduces the adsorption of water molecules, has a better compatible interface with a cement matrix, and can significantly improve the mechanical strength and hydrophobicity of concrete; by compounding the hydrophobic reinforcing agent and combining the synergistic effect of the hydrophobic thixotropic agent, a uniform and stable hydrophobic network can be formed in the concrete, so that the probability that the concrete is eroded by the environment is reduced, and the service life of the concrete in different environments is prolonged. Besides, reinforced dry particles are added, so that the effect of a micro-aggregate reinforced phase can be achieved, the compactness and strength of the concrete are remarkably improved, the strength and hydrophobic performance are balanced on the whole, and market requirements are met.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and more specifically, to a hydrophobic recycled concrete and its preparation method. Background Technology

[0002] Concrete, as the most widely used building material globally, consumes a large amount of natural sand and gravel resources in its production. Simultaneously, the waste concrete generated from building demolition also poses serious environmental problems. Recycled aggregate, produced by crushing and screening waste concrete, can realize the resource utilization of construction waste. However, compared to natural aggregate, recycled aggregate has a large amount of old cement mortar adhering to its surface, resulting in inherent defects such as high porosity, high water absorption, and low strength. Furthermore, numerous micro-cracks and weak areas exist at the interface between recycled aggregate and the old and new cement mortar, becoming stress concentration points and channels for corrosive media during concrete stress, leading to poor strength in recycled concrete. To improve the performance of recycled concrete, existing technologies often employ methods to modify recycled aggregate. For example, Chinese patent application number CN201210261716.8 discloses a modified recycled aggregate and high-performance recycled aggregate concrete. The modified recycled aggregate in this invention involves immersing the recycled aggregate in a 10-40 wt% nano-silica hydrocolloid solution for at least 5 days. High-performance concrete with recycled aggregates can be obtained by mixing cement, modified recycled aggregates, sand, crushed stone or fine recycled aggregates, and other mineral additives in a certain proportion. However, this method does not introduce active groups that can promote better compatibility between recycled aggregates and cement matrix, leaving room for improvement.

[0003] In addition, to make concrete have a certain degree of hydrophobicity, the water absorption rate can be significantly reduced by introducing hydrophobic components into the concrete. For example, Chinese patent application number CN202410053939.8 discloses a superhydrophobic concrete material and its preparation method. By adding hydrophobic materials to the concrete structure and then spraying a hydrophobic coating on the surface of the precast concrete component, a superhydrophobic concrete material is obtained, giving the concrete material a superhydrophobic effect.

[0004] While existing single or simple composite hydrophobic technologies can reduce water absorption to some extent, they struggle to maintain optimal mechanical properties. Traditional hydrophobic agents, while improving hydrophobicity, may interfere with the cement hydration process, leading to decreased interfacial bond strength and poor compressive strength. Therefore, improving concrete to balance its compressive strength and hydrophobicity is of great significance. Summary of the Invention

[0005] In view of this, in order to solve one of the above-mentioned technical problems, the present invention provides hydrophobic recycled concrete and its preparation method, the specific technical solution of which is as follows:

[0006] A hydrophobic recycled concrete, comprising the following raw materials in parts by weight:

[0007] 100-300 parts cement, 40-100 parts modified recycled aggregate, 150-200 parts fine aggregate, 15-50 parts reinforcing dry aggregate, 40-80 parts hydrophobic reinforcing agent, 25-30 parts silica fume, 45-50 parts fly ash, 1-10 parts thixotropic modifier, 1-7 parts dispersant, 7-10 parts water-reducing agent, 0.01-1 part defoamer, and 70-150 parts water;

[0008] The reinforced dry granules comprise the following components by mass percentage: SiO2: 45%~50%, Al2O3: 12%~35%, CaO: 5%~10%, MgO: 3%~7%, ZrO2: 1%~5%, SiC: 1%~2%.

[0009] Preferably, the cement is at least one of silicate cement, sulfoaluminate cement, and aluminate cement.

[0010] Preferably, the method for preparing the modified recycled aggregate is as follows:

[0011] Add the recycled aggregate to a nitric acid solution with a mass percentage concentration of 3%~4%, soak for 1h~5h, wash until neutral, then add the modifier, stir evenly, let stand for 30min~60min, and dry to obtain the modified recycled aggregate.

[0012] Preferably, the modifier is obtained by mixing and dispersing nano-silica, nano-calcium carbonate, and a silane coupling agent;

[0013] Furthermore, the ratio of nano-silica, nano-calcium carbonate, and silane coupling agent by weight is (1~5):(1~7):(10~30).

[0014] Preferably, the ratio of the recycled aggregate to the modifier in the nitric acid solution is (10~20):(20~50):(1~9) by weight.

[0015] Preferably, the preparation method of the hydrophobic reinforcing agent is as follows: isobutyltriethoxysilane, methacryloxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane are added to a mixing vessel and stirred at a speed of 50 r / min-200 r / min for 20 min to 30 min, then dibutyl dilaurate and cellulose ether are added, and stirring is continued for 30 min to 60 min.

[0016] Preferably, the ratio of isobutyltriethoxysilane, methacryloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, dibutyl dilaurate and cellulose ether by weight is (5~9):(1~7):(3~5):(2~5):(1~3).

[0017] Preferably, the thixotropic modifier is hydrophobic fumed silica.

[0018] Preferably, the dispersant is at least one of sodium dodecylbenzenesulfonate and octylphenol polyoxyethylene ether.

[0019] In addition, the present invention also provides a method for preparing hydrophobic recycled concrete, the method comprising the following steps:

[0020] S1. Add cement, fine aggregate, reinforcing dry particles, silica fume, fly ash and dispersant to a mixer and stir at a speed of 50 r / min to 100 r / min for 5 min to 10 min to obtain mixture A;

[0021] S2. Add water, water-reducing agent, defoamer, modified recycled aggregate, and thixotropic modifier to the mixture A, and continue stirring for 20 min to 60 min to obtain mixture B;

[0022] S3. Add a hydrophobic reinforcing agent to the mixture B, stir evenly, and obtain hydrophobic recycled concrete.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. This invention optimizes and modifies recycled aggregates to reduce their adsorption of water molecules. Furthermore, the modified recycled aggregates, through nanomaterial modification, can fill the microcracks and pores in the aggregates and interact with silane coupling agents to introduce active groups on the surface, resulting in a better compatibility interface with the cement matrix and further increasing the mechanical strength and hydrophobicity of concrete. In addition, the modified recycled aggregates help to close pores, significantly reducing water absorption and also contributing to hydrophobic properties.

[0025] 2. This invention, through the compounding of hydrophobic reinforcing agents and the use of hydrophobic thixotropic agents, works synergistically to form a uniform and stable hydrophobic network inside concrete, thereby reducing its probability of environmental erosion and increasing its service life in different environments.

[0026] 3. This invention adds reinforcing dry particles, which can act as a micro-aggregate reinforcing phase, significantly improving the density and strength of concrete, and balancing strength and hydrophobicity overall to meet market demands. Detailed Implementation

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0028] A hydrophobic recycled concrete according to one embodiment of the present invention comprises the following raw materials in parts by weight:

[0029] 100-300 parts cement, 40-100 parts modified recycled aggregate, 150-200 parts fine aggregate, 15-50 parts reinforcing dry aggregate, 40-80 parts hydrophobic reinforcing agent, 25-30 parts silica fume, 45-50 parts fly ash, 1-10 parts thixotropic modifier, 1-7 parts dispersant, 7-10 parts water-reducing agent, 0.01-1 part defoamer, and 70-150 parts water;

[0030] The reinforced dry granules comprise the following components by mass percentage: SiO2: 45%~50%, Al2O3: 12%~35%, CaO: 5%~10%, MgO: 3%~7%, ZrO2: 1%~5%, SiC: 1%~2%.

[0031] In one embodiment, the cement is at least one of silicate cement, sulfoaluminate cement, and aluminate cement.

[0032] In one embodiment, the method for preparing the modified recycled aggregate is as follows:

[0033] Add the recycled aggregate to a nitric acid solution with a mass percentage concentration of 3%~4%, soak for 1h~5h, wash until neutral, then add the modifier, stir evenly, let stand for 30min~60min, and dry to obtain the modified recycled aggregate.

[0034] In one embodiment, the modifier is obtained by mixing and dispersing nano-silica, nano-calcium carbonate and a silane coupling agent;

[0035] Furthermore, the ratio of nano-silica, nano-calcium carbonate, and silane coupling agent by weight is (1~5):(1~7):(10~30).

[0036] In one embodiment, the silane coupling agent is at least one selected from γ-methacryloyloxypropyltrimethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, and hexadecyltrimethoxysilane.

[0037] In one embodiment, the ratio of the recycled aggregate to the modifier in the nitric acid solution is (10~20):(20~50):(1~9) by weight.

[0038] In one embodiment, the average particle size of the recycled aggregate is 10 mm to 20 mm.

[0039] In one embodiment, the fine aggregate is quartz sand, and the quartz sand has a mud content of 0.5% to 1%.

[0040] In one embodiment, the average particle size of the enhanced dry particles is 10 μm to 80 μm.

[0041] In one embodiment, the hydrophobic reinforcing agent is prepared by adding isobutyltriethoxysilane, methacryloxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane to a mixing vessel and stirring at a speed of 50 r / min-200 r / min for 20 min-30 min. Then, dibutyl dilaurate and cellulose ether are added and stirring is continued for 30 min-60 min.

[0042] In one embodiment, the ratio of isobutyltriethoxysilane, methacryloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, dibutyl dilaurate and cellulose ether by weight is (5~9):(1~7):(3~5):(2~5):(1~3).

[0043] In one embodiment, the thixotropic modifier is hydrophobic fumed silica.

[0044] In one embodiment, the dispersant is at least one of sodium dodecylbenzenesulfonate and octylphenol polyoxyethylene ether.

[0045] In one embodiment, the water-reducing agent is a polycarboxylate water-reducing agent.

[0046] In one embodiment, the defoamer is at least one of an organosilicon defoamer and a polyether defoamer.

[0047] In addition, the present invention also provides a method for preparing hydrophobic recycled concrete, the method comprising the following steps:

[0048] S1. Add cement, fine aggregate, reinforcing dry particles, silica fume, fly ash and dispersant to a mixer and stir at a speed of 50 r / min to 100 r / min for 5 min to 10 min to obtain mixture A;

[0049] S2. Add water, water-reducing agent, defoamer, modified recycled aggregate, and thixotropic modifier to the mixture A, and continue stirring for 20 min to 60 min to obtain mixture B;

[0050] S3. Add a hydrophobic reinforcing agent to the mixture B, stir evenly, and obtain hydrophobic recycled concrete.

[0051] The above scheme optimizes the composition and proportion of concrete, resulting in concrete with excellent strength and hydrophobicity, thus having higher application value.

[0052] The implementation scheme of the present invention will be described in detail below with reference to specific embodiments. The raw materials, reagents, etc. used in the embodiments that are not described in detail are all commercially available.

[0053] Example 1:

[0054] A method for preparing hydrophobic recycled concrete, the method comprising the following steps:

[0055] S1. Add 145 parts of silicate cement, 165 parts of quartz sand, 30 parts of reinforced dry granules, 25 parts of silica fume, 48 parts of fly ash and 6 parts of sodium dodecylbenzene sulfonate to a mixer and stir at 50 r / min for 10 min to obtain mixture A.

[0056] The reinforced dry granules comprise the following components by mass percentage: SiO2: 48%, Al2O3: 34%, CaO: 8%, MgO: 4%, ZrO2: 4%, SiC: 2%;

[0057] S2. Add 110 parts water, 8 parts polycarboxylate superplasticizer, 0.05 parts silicone defoamer, 70 parts modified recycled aggregate, and 9 parts hydrophobic fumed silica to the mixture A, and continue stirring for 40 minutes to obtain mixture B;

[0058] The modified recycled aggregate is prepared as follows: 18 parts of recycled aggregate with an average particle size of 10 mm are added to 50 parts of nitric acid solution with a mass percentage concentration of 4% by weight, soaked for 2 hours, washed until neutral, and then 7 parts of modifier (nano silica, nano calcium carbonate and silane coupling agent mixed and dispersed in a weight ratio of 3:5:10) are added, stirred evenly, allowed to stand for 35 minutes, and dried to obtain modified recycled aggregate.

[0059] S3. Add 45 parts of hydrophobic reinforcing agent to the mixture B, stir evenly, and obtain hydrophobic recycled concrete;

[0060] The preparation method of the hydrophobic reinforcing agent is as follows: 7 parts by weight of isobutyltriethoxysilane, 5 parts by weight of methacryloyloxypropyltrimethoxysilane and 4 parts by weight of γ-aminopropyltriethoxysilane are added to a mixing vessel and stirred at 50 r / min for 25 min. Then, 4 parts by weight of dibutyl dilaurate and 3 parts by weight of cellulose ether are added and stirred for another 30 min.

[0061] Example 2:

[0062] A method for preparing hydrophobic recycled concrete, the method comprising the following steps:

[0063] S1. Add 150 parts of silicate cement, 170 parts of quartz sand, 28 parts of reinforced dry granules, 27 parts of silica fume, 46 parts of fly ash and 7 parts of sodium dodecylbenzene sulfonate to a mixer and stir at 50 r / min for 10 min to obtain mixture A.

[0064] The reinforced dry granules comprise the following components by mass percentage: SiO2: 47%, Al2O3: 33%, CaO: 8%, MgO: 5%, ZrO2: 5%, SiC: 2%;

[0065] S2. Add 120 parts water, 9 parts polycarboxylate superplasticizer, 0.06 parts organosilicon defoamer, 75 parts modified recycled aggregate, and 10 parts hydrophobic fumed silica to the mixture A, and continue stirring for 45 minutes to obtain mixture B;

[0066] The modified recycled aggregate is prepared as follows: 20 parts by weight of recycled aggregate with an average particle size of 10 mm are added to 50 parts by weight of 4% nitric acid solution, soaked for 2 hours, washed until neutral, and then 8 parts by weight of modifier (nano silica, nano calcium carbonate and silane coupling agent mixed and dispersed in a weight ratio of 3:5:15) are added, stirred evenly, allowed to stand for 35 minutes, and dried to obtain modified recycled aggregate.

[0067] S3. Add 47 parts of hydrophobic reinforcing agent to the mixture B, stir evenly, and obtain hydrophobic recycled concrete;

[0068] The preparation method of the hydrophobic reinforcing agent is as follows: 8 parts by weight of isobutyltriethoxysilane, 6 parts by weight of methacryloxypropyltrimethoxysilane and 5 parts by weight of γ-aminopropyltriethoxysilane are added to a mixing vessel and stirred at 50 r / min for 25 min. Then, 4 parts by weight of dibutyl dilaurate and 3 parts by weight of cellulose ether are added and stirred for another 30 min.

[0069] Example 3:

[0070] A method for preparing hydrophobic recycled concrete, the method comprising the following steps:

[0071] S1. Add 145 parts of silicate cement, 165 parts of quartz sand, 27 parts of reinforced dry granules, 28 parts of silica fume, 48 parts of fly ash and 6 parts of sodium dodecylbenzene sulfonate to a mixer and stir at 50 r / min for 10 min to obtain mixture A.

[0072] The reinforced dry granules comprise the following components by mass percentage: SiO2: 46%, Al2O3: 34%, CaO: 7%, MgO: 7%, ZrO2: 4%, SiC: 2%;

[0073] S2. Add 125 parts water, 10 parts polycarboxylate superplasticizer, 0.06 parts organosilicon defoamer, 80 parts modified recycled aggregate, and 10 parts hydrophobic fumed silica to the mixture A, and continue stirring for 40 minutes to obtain mixture B;

[0074] The modified recycled aggregate is prepared as follows: 20 parts by weight of recycled aggregate with an average particle size of 10 mm are added to 50 parts by weight of 4% nitric acid solution, soaked for 1-5 hours, washed until neutral, and then 9 parts by weight of modifier (a mixture of nano-silica, nano-calcium carbonate and silane coupling agent in a weight ratio of 3:5:15) are added, stirred evenly, allowed to stand for 35 minutes, and dried to obtain the modified recycled aggregate.

[0075] S3. Add 45 parts of hydrophobic reinforcing agent to the mixture B, stir evenly, and obtain hydrophobic recycled concrete;

[0076] The preparation method of the hydrophobic reinforcing agent is as follows: 8 parts by weight of isobutyltriethoxysilane, 5 parts by weight of methacryloyloxypropyltrimethoxysilane and 5 parts by weight of γ-aminopropyltriethoxysilane are added to a mixing vessel and stirred at a speed of 50 r / min for 25 min. Then, 5 parts by weight of dibutyl dilaurate and 3 parts by weight of cellulose ether are added and stirred for another 30 min.

[0077] Comparative Example 1:

[0078] The difference between Comparative Example 1 and Example 3 is that conventional calcium powder was used as a reinforcing agent to replace the reinforcing dry granules in Comparative Example 1, while the rest was the same as in Example 3.

[0079] Comparative Example 2:

[0080] The difference between Comparative Example 2 and Example 3 is that no reinforcing dry granules were added in Comparative Example 2, but otherwise the same as in Example 3.

[0081] Comparative Example 3:

[0082] The difference between Comparative Example 3 and Example 3 is that the preparation method of the modified recycled aggregate in Comparative Example 3 is different, while the rest is the same as in Example 3;

[0083] The modified recycled aggregate in Comparative Example 3 was prepared as follows: 20 parts by weight of recycled aggregate with an average particle size of 10 mm were added to 50 parts by weight of 4% nitric acid solution, soaked for 1 h to 5 h, washed until neutral, and then 3 parts by weight of nano silica and 6 parts by weight of nano calcium carbonate were added. The mixture was stirred at 50 r / min for 25 min to obtain the modified recycled aggregate.

[0084] Comparative Example 4:

[0085] The difference between Comparative Example 4 and Example 3 is that the recycled aggregate in Comparative Example 4 was not modified, that is, the recycled aggregate was directly added and used, while the rest was the same as in Example 3.

[0086] Comparative Example 5:

[0087] The difference between Comparative Example 5 and Example 3 is that hydrophobic fumed silica was not added in Comparative Example 5, but otherwise it is the same as Example 3.

[0088] Comparative Example 6:

[0089] The difference between Comparative Example 6 and Example 3 is that no hydrophobic reinforcing agent was added in Comparative Example 6, but otherwise it is the same as Example 3.

[0090] The hydrophobic recycled concrete samples prepared in Examples 1-3 and the concrete comparative samples prepared in Comparative Examples 1-6 were respectively prepared into cubic specimens with dimensions of 150mm×150mm×150mm for compressive strength testing. After curing for 28 days, performance tests were conducted according to GB / T50081-2019. The specimens were placed on a compression testing machine and continuously loaded at a loading rate of 1MPa / s until the specimen failed. The maximum failure load was recorded to obtain the compressive strength. The water absorption rate (%) of the recycled concrete was tested according to ASTM C1585-2013 "Standard Test Method for Determining Water Absorption of Hydraulic Cement Concrete". The water contact angle was tested according to GB / T30693-2014. The results are shown in Table 1 below.

[0091] Table 1: Performance Test Results Group Compressive strength / MPa Water absorption rate / % Contact angle / ° Example 1 48.9 3.2 142.6 Example 2 49.5 2.9 144.5 Example 3 52.3 2.8 145.8 Comparative Example 1 45.6 3.6 137.6 Comparative Example 2 37.1 4.1 129.3 Comparative Example 3 46.8 4.3 127.1 Comparative Example 4 43.5 6.4 102.8 Comparative Example 5 46.9 3.5 138.7 Comparative Example 6 43.7 7.3 68.7

[0092] As can be seen from the data analysis in Table 1, this invention optimizes the composition of concrete, resulting in high density and low absorption rate. This not only ensures the excellent and stable mechanical properties of concrete but also endows it with significant hydrophobicity. Compared to Example 3, Comparative Example 1 used conventional calcium powder as a reinforcing agent to replace the reinforcing dry particles, but the compressive strength of the resulting concrete was lower than that of Example 3. This indicates that the reinforcing dry particles with high hardness and small particle size added in this invention can fill the voids in cement and aggregate, improving the density of the concrete. In contrast, conventional calcium powder reinforcing agent has lower hardness and its filling effect is not as good as the reinforcing dry particles of this invention. Furthermore, it lacks the active SiO2 and Al2O3 in the reinforcing dry particles, which may undergo a weak pozzolanic reaction in an alkaline environment to generate additional hydrated calcium silicate (CSH) gel. It also lacks the high hardness and toughening effect of SiC and ZrO2, resulting in a lower compressive strength of the resulting concrete compared to Example 3, which also affects the water absorption and hydrophobicity. Comparative Example 2 did not add reinforcing dry particles, lacking the filling effect of reinforcing dry particles. The porosity was higher than that of Example 3, resulting in a higher water absorption rate and a significant decrease in compressive strength, which also affected the hydrophobicity. Comparative Example 3 used a different method to prepare the modified recycled aggregate. Although nano-silica and nano-calcium carbonate can physically fill the voids, the results were different. The aggregate surface has pores, but lacks the bridging effect of silane coupling agents, resulting in poorer compatibility with the cement matrix than in Example 3. It is prone to agglomeration, and the water absorption rate of the recycled aggregate is not reduced, affecting the hydration effect of the cement, weakening the strength, and significantly impacting hydrophobicity. In Comparative Example 4, the recycled aggregate was not modified. Unmodified recycled aggregate has many pores and high water absorption rate. During the mixing process, it will absorb a large amount of mixing water, resulting in a reduction of the effective water for cement hydration, a decrease in the degree of cement hydration, and a decrease in overall compressive strength. In Comparative Example 5, without hydrophobic fumed silica (thixotropic modifier), the uniformity and stability of the concrete during the mixing process are not as good as in Example 3, resulting in uneven density and localized lower strength after hardening, which has a certain impact on hydrophobicity. In Comparative Example 6, no hydrophobic reinforcing agent was added, making it easy for water to penetrate and resulting in high water absorption rate, which causes certain erosion, weakens the matrix, and thus affects the compressive strength. In addition, the absence of a hydrophobic reinforcing agent results in the overall hydrophobicity of the concrete being significantly worse than that of Example 3.

[0093] In summary, this invention first modifies the recycled aggregate, filling it with nano-silica and nano-silicon carbide. Then, by combining this with the surface-enhancing effect of a silane coupling agent, the water absorption rate of the recycled aggregate is reduced and its hydrophobicity is increased. At the same time, the dry particles are synergistically reinforced, resulting in concrete with superior compressive strength. Furthermore, a hydrophobic reinforcing agent is used to construct a hydrophobic network, and a hydrophobic thixotropic modifier maintains the uniformity and stability of the system. As a result, the prepared concrete exhibits significant overall compressive strength and hydrophobic properties, thus possessing higher application value.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A hydrophobic recycled concrete, characterized in that, The hydrophobic recycled concrete comprises the following raw materials in parts by weight: 100-300 parts cement, 40-100 parts modified recycled aggregate, 150-200 parts fine aggregate, 15-50 parts reinforcing dry aggregate, 40-80 parts hydrophobic reinforcing agent, 25-30 parts silica fume, 45-50 parts fly ash, 1-10 parts thixotropic modifier, 1-7 parts dispersant, 7-10 parts water-reducing agent, 0.01-1 part defoamer, and 70-150 parts water; The reinforced dry granules comprise the following components by mass percentage: SiO2: 45%~50%, Al2O3: 12%~35%, CaO: 5%~10%, MgO: 3%~7%, ZrO2: 1%~5%, SiC: 1%~2%.

2. The hydrophobic recycled concrete according to claim 1, characterized in that, The cement is at least one of silicate cement, sulfoaluminate cement, and aluminate cement.

3. The hydrophobic recycled concrete according to claim 1, characterized in that, The method for preparing the modified recycled aggregate is as follows: Add the recycled aggregate to a nitric acid solution with a mass percentage concentration of 3%~4%, soak for 1h~5h, wash until neutral, then add the modifier, stir evenly, let stand for 30min~60min, and dry to obtain the modified recycled aggregate.

4. The hydrophobic recycled concrete according to claim 3, characterized in that, The modifier is obtained by mixing and dispersing nano-silica, nano-calcium carbonate and silane coupling agent; Furthermore, the ratio of nano-silica, nano-calcium carbonate, and silane coupling agent by weight is (1~5):(1~7):(10~30).

5. The hydrophobic recycled concrete according to claim 3, characterized in that, The ratio of the recycled aggregate to the modifier in the nitric acid solution by weight is (10~20):(20~50):(1~9).

6. The hydrophobic recycled concrete according to claim 1, characterized in that, The preparation method of the hydrophobic reinforcing agent is as follows: isobutyltriethoxysilane, methacryloxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane are added to a mixing vessel and stirred at a speed of 50r / min-200r / min for 20min-30min. Then, dibutyl dilaurate and cellulose ether are added and stirred for another 30min-60min.

7. The hydrophobic recycled concrete according to claim 6, characterized in that, The proportions of isobutyltriethoxysilane, methacryloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, dibutyl dilaurate and cellulose ether by weight are (5~9):(1~7):(3~5):(2~5):(1~3).

8. The hydrophobic recycled concrete according to claim 1, characterized in that, The thixotropic modifier is hydrophobic fumed silica.

9. The hydrophobic recycled concrete according to claim 1, characterized in that, The dispersant is at least one of sodium dodecylbenzenesulfonate and octylphenol polyoxyethylene ether.

10. A method for preparing hydrophobic recycled concrete, characterized in that, The preparation method includes the following steps: S1. Add cement, fine aggregate, reinforcing dry particles, silica fume, fly ash and dispersant to a mixer and stir at a speed of 50 r / min to 100 r / min for 5 min to 10 min to obtain mixture A; S2. Add water, water-reducing agent, defoamer, modified recycled aggregate, and thixotropic modifier to the mixture A, and continue stirring for 20 min to 60 min to obtain mixture B; S3. Add a hydrophobic reinforcing agent to the mixture B, stir evenly, and obtain hydrophobic recycled concrete.