Process for improving crack resistance of recycled aggregate concrete

Abstract

The invention provides a process for improving the crack resistance of recycled aggregate concrete, and belongs to the technical field of recycled concrete.The process comprises the following steps that 1, recycled fine aggregate is soaked in an organosilicon compound to be soaked and modified, and modified fine aggregate is obtained; (2) soaking the recycled coarse aggregate in a silica sol solution, and then adding quick lime to obtain modified recycled coarse aggregate; and (3) adding water into cement, carbide slag, fly ash and an additive, uniformly stirring, sequentially adding the modified fine aggregate and the modified recycled coarse aggregate, uniformly mixing, and finally performing later maintenance to obtain the recycled aggregate concrete. According to the preparation method provided by the invention, the crack resistance of the recycled aggregate concrete is remarkably improved while the recycled aggregate concrete keeps high strength and good workability, the service life is prolonged, and the preparation method has important significance for promoting green buildings and sustainable development.

Description

Technical Field

[0001] The invention belongs to the technical field of recycled concrete, and in particular relates to a process for improving the crack resistance of recycled aggregate concrete. Background Art

[0002] The crack resistance of concrete refers to its ability to resist cracking, which is an important manifestation of the comprehensive performance of concrete materials. This performance is closely related to multiple factors such as the tensile strength, ultimate tensile deformation capacity, tensile elastic modulus, autogenous volume deformation, creep and thermal properties of concrete. However, in practical applications, there are still many problems and challenges in the crack resistance of concrete. First of all, from the perspective of the concrete material itself, its tensile strength is much lower than its compressive strength, and its ultimate tensile deformation is also very small, which makes it easy for concrete to crack or microcrack under the action of external forces, temperature changes, humidity changes, etc. These cracks or microcracks not only affect the integrity and durability of the building, but may even threaten the safety and stability of the building. Cracks are mainly divided into three categories: stress cracks, shrinkage cracks and temperature cracks. The generation of these cracks is related to the insufficient crack resistance of concrete.

[0003] In the prior art, although a series of measures have been taken to improve the crack resistance of concrete, such as the use of low-calorie cement, various admixtures, and surface insulation measures, there are still some problems. For example, an unreasonable water-cement ratio is an important reason for the poor crack resistance of concrete. A water-cement ratio that is too high will increase the voids inside the concrete and easily cause cracks; a water-cement ratio that is too low may affect the fluidity of the concrete, leading to construction difficulties. At the same time, excessive cement use will also increase the heat generation of the concrete and increase the shrinkage rate, thereby reducing crack resistance. In addition, problems such as uneven batching, insufficient steel density, and insufficient prestress will also affect the crack resistance of concrete. Uneven batching will lead to uneven concrete structure and prone to cracks; insufficient steel density cannot effectively support the tensile force of the concrete and easily cause cracks; insufficient prestress cannot effectively reduce the internal compressive stress of the concrete, thereby reducing the crack resistance of the concrete.

[0004] Therefore, how to provide a method for improving the crack resistance of recycled concrete is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a process for improving the anti-cracking performance of recycled aggregate concrete.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A process for improving the crack resistance of recycled aggregate concrete comprises the following steps:

[0008] (1) soaking the recycled fine aggregate in an organic silicon compound for modification to obtain modified fine aggregate;

[0009] (2) soaking the recycled coarse aggregate in a silica sol solution, and then adding quicklime to obtain modified recycled coarse aggregate;

[0010] (3) After adding water to cement, carbide slag, fly ash and admixtures and stirring evenly, add modified fine aggregate and modified recycled coarse aggregate in turn and mix evenly. Finally, after post-curing, recycled aggregate concrete is obtained.

[0011] Beneficial effects: The present invention soaks the recycled fine aggregate in an organosilicon compound, so that the surface of the fine aggregate is covered with a layer of organosilicon compound film. This film can improve the interfacial bonding between the fine aggregate and the cement paste and reduce the generation of microcracks at the interface. At the same time, the present invention soaks the recycled coarse aggregate in a silica sol solution and then adds quicklime for reaction, so that a dense calcium silicate gel layer can be formed on the surface of the coarse aggregate. This gel layer can enhance the bonding between the coarse aggregate and the cement paste and improve the overall strength of the concrete. In addition, the reaction of silica sol and quicklime can also consume the pores and cracks on the surface of the coarse aggregate, reduce the intrusion of moisture and harmful substances, and thus improve the durability and crack resistance of the coarse aggregate.

[0012] In addition, the present invention adopts the method of secondary stirring in the process of mixing raw materials. First, cement, carbide slag, fly ash and admixture are stirred with water so that various materials can be fully mixed to form a uniform mixture. This uniformity is very important for the later strength and durability of concrete. Then, modified recycled fine aggregate and modified recycled coarse aggregate are added and stirred in sequence so that aggregate can be evenly dispersed in the mixture. This helps to reduce the gap between aggregates and improve the compactness and strength of concrete. In this process, the modified treatment of the surface of modified fine aggregate and modified recycled coarse aggregate can enhance the interfacial bonding between them and cement paste. This strengthening effect helps to reduce the generation of microcracks at the interface and improve the crack resistance of concrete. And the second stirring and mixing can further improve the workability of concrete, such as improving fluidity, reducing segregation and bleeding phenomena, etc., which helps concrete to obtain better compactness and uniformity during pouring and vibrating. Through two stirrings, various materials in concrete can be fully mixed and evenly dispersed, and hydration reaction is fully carried out. At the same time, the application of modified aggregate enhances interfacial bonding and improves the workability of concrete. These factors work together to give the final concrete excellent strength, durability and crack resistance.

[0013] Preferably, the mass ratio of the cement, carbide slag, fly ash, admixture, modified fine aggregate and modified coarse aggregate is 1: (0.1-0.3): (0-0.3): (0.01-0.05): (0.2-0.5): (0.2-0.5).

[0014] The amount of water added is preferably such that the water-cement ratio of the concrete system is controlled within the range of 0.35-0.60W / C.

[0015] Beneficial effects: Under the above raw material addition amount, the mechanical properties and crack resistance of concrete can be effectively improved. In particular, the addition of fly ash can fill the pores and cracks inside the concrete, reduce the shrinkage deformation of the concrete, and thus improve its crack resistance. In addition, the carbide slag in the present invention has high activity and contains substances such as calcium oxide and silicon oxide. These components can react chemically with other components in cement to generate new hydration products, thereby enhancing the strength of concrete. The addition of carbide slag can refine the pore structure of concrete, reduce the number of harmful pores, and improve the compactness and impermeability of concrete. The active ingredients therein can stimulate the potential hydration activity in cement and further improve the durability of concrete.

[0016] Preferably, the recycled fine aggregate is waste brick fine aggregate, and the particle size is 0.2-6 mm.

[0017] Preferably, the SiO2 content in the waste brick fine aggregate is 55-61wt%, and the Al2O3 content is 22-25wt%.

[0018] Beneficial effect: The sum of the SiO2 and Al2O3 contents in the waste brick fine aggregate is at least greater than 70wt%, preferably greater than 80.0wt%. Under this condition, the recycled fine aggregate can achieve good hydration.

[0019] Preferably, the soaking modification in step (1) is carried out at a temperature of 5-20° C. and for a time of 15-20 h.

[0020] Preferably, the organosilicon compound is one or any combination of tetraethyl orthosilicate, a silane coupling agent, tetramethoxysilane, γ-glycidyloxypropyltrimethoxysilane and dimethyl silicone oil.

[0021] Beneficial effects: The above organosilicon compounds can improve the hydrophobicity of fine aggregates, reduce the damage of water to the internal structure of fine aggregates, and thus improve the crack resistance of concrete.

[0022] Preferably, the recycled coarse aggregate in step (2) is obtained by crushing and screening waste concrete and mixing it with sand and / or coarse crushed stone, and has a particle size of 5-25 mm.

[0023] Preferably, the mass ratio of the waste concrete to sand and gravel and / or coarse crushed stone is 1:(1-5).

[0024] Preferably, the mass concentration of the silica sol solution in step (2) is 4-25%;

[0025] The silica sol is neutral silica sol, and the particle size of the silica sol is 20-50 nm.

[0026] Preferably, the soaking temperature in step (2) is 3-20° C. and the soaking time is 5-8 h.

[0027] Preferably, the admixture in step (3) is a polycarboxylic acid high-efficiency water reducer.

[0028] A recycled aggregate concrete prepared by a process for improving the crack resistance of recycled aggregate concrete.

[0029] Compared with the prior art, the present invention has the following advantages and technical effects:

[0030] The process for improving the crack resistance of recycled aggregate concrete provided by the present invention significantly enhances the crack resistance of concrete compared to the prior art. By soaking fine aggregate in organosilicon compound, the interfacial bonding between aggregate and cement paste is improved, and the generation of microcracks is reduced. At the same time, the dense layer formed by the reaction of silica sol and quicklime enhances the durability of coarse aggregate and further enhances the crack resistance of concrete. In addition, the present invention also utilizes industrial wastes such as carbide slag and fly ash, which not only reduces costs but also realizes the recycling of resources. These measures work together to significantly improve the crack resistance of recycled aggregate concrete while maintaining high strength and good workability, and extend its service life, which is of great significance to promoting green buildings and sustainable development. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with specific implementation methods.

[0033] The embodiment of the present invention provides a process for improving the crack resistance of recycled aggregate concrete, comprising the following steps:

[0034] (1) soaking the recycled fine aggregate in an organic silicon compound for modification to obtain modified fine aggregate;

[0035] (2) soaking the recycled coarse aggregate in a silica sol solution, and then adding quicklime to obtain modified recycled coarse aggregate;

[0036] (3) After adding water to cement, carbide slag, fly ash and admixtures and stirring evenly, add modified fine aggregate and modified recycled coarse aggregate in turn and mix evenly. Finally, after post-curing, recycled aggregate concrete is obtained.

[0037] In a preferred embodiment, the mass ratio of the cement, carbide slag, fly ash, admixture, modified fine aggregate and modified coarse aggregate is 1: (0.1-0.3): (0-0.3): (0.01-0.05): (0.2-0.5): (0.2-0.5).

[0038] In a more preferred embodiment, the mass ratio of cement, carbide slag, fly ash, polycarboxylic acid high-efficiency water reducing agent, modified fine aggregate and modified coarse aggregate is 1:0.2:0.2:0.03:0.4:0.3.

[0039] The amount of water added is preferably such that the water-cement ratio of the concrete system is controlled within the range of 0.35-0.60W / C.

[0040] In a preferred embodiment, the recycled fine aggregate is waste brick fine aggregate, and the particle size is 0.2-6 mm.

[0041] In a preferred embodiment, the SiO2 content in the waste brick fine aggregate is 55-61wt%, and the Al2O3 content is 22-25wt%.

[0042] The sum of the SiO2 and Al2O3 contents in the waste brick fine aggregate is at least greater than 70wt%, preferably greater than 80.0wt%. Under this condition, the recycled fine aggregate can achieve good hydration.

[0043] In a preferred embodiment, the soaking modification in step (1) is carried out at a temperature of 5-20° C. and for a time of 15-20 h.

[0044] In a preferred embodiment, the organosilicon compound is selected from one or any of tetraethyl orthosilicate, a silane coupling agent, tetramethoxysilane, γ-glycidyloxypropyl trimethoxysilane and dimethyl silicone oil. In some typical but non-limiting embodiments, the organosilicon compound can be selected from ethyl orthosilicate alone; in other embodiments, the organosilicon compound can also be selected from a composite organosilicon compound obtained by mixing tetramethoxysilane and γ-glycidyloxypropyl trimethoxysilane in a mass ratio of 1:1; in other embodiments, the organosilicon compound can also be selected from a composite organosilicon compound obtained by mixing tetraethyl orthosilicate and a silane coupling agent in a mass ratio of 1:1; in other embodiments, the organosilicon compound is a composite organosilicon compound obtained by mixing tetramethoxysilane, γ-glycidyloxypropyl trimethoxysilane and dimethyl silicone oil in a mass ratio of 1:1:1.

[0045] In a preferred embodiment, the recycled coarse aggregate in step (2) is obtained by crushing and screening waste concrete and mixing it with sand and / or coarse crushed stone, and the particle size is 5-25 mm.

[0046] In a preferred embodiment, the mass ratio of the waste concrete to sand and gravel and / or coarse crushed stone is 1:(1-5).

[0047] In a preferred embodiment, the silica sol in step (2) is a neutral silica sol, and the silica sol particle size is 20-50 nm. A mass concentration of the neutral silica sol in the range of 4 to 25% can achieve a good modification effect; as an example, the mass concentration of the neutral silica sol can be 4%, 10%, 20%, 22% or 25%.

[0048] In a preferred embodiment, the soaking temperature in step (2) is 3-20° C. and the soaking time is 5-8 h.

[0049] In a preferred embodiment, the admixture in step (3) is a polycarboxylic acid high-efficiency water reducer.

[0050] The embodiment of the present invention also provides recycled aggregate concrete prepared by the above process for improving the anti-cracking performance of recycled aggregate concrete.

[0051] Unless otherwise specified, the room temperature or normal temperature in the embodiments of the present invention refers to 25±3°C.

[0052] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0053] Among them, the recycled fine aggregate is waste brick fine aggregate with a particle size of 0.2-6mm;

[0054] The particle size of recycled coarse aggregate is 5-25mm; the specific surface area of ​​carbide slag and fly ash is not less than 300m 2 / kg.

[0055] Waste concrete and waste brick fine aggregates were collected from a construction site and demolition site in Wuhan.

[0056] The "later curing" in the following embodiments refers to curing at room temperature with a relative humidity of more than 90%.

[0057] Example 1

[0058] A process for improving the crack resistance of recycled aggregate concrete comprises the following steps:

[0059] (1) Recycled fine aggregate (SiO2 content of 58.3wt%, Al2O3 content of 22.5wt%) was immersed in an organic silicon compound (tetraethyl orthosilicate) at 10°C for 18h to obtain modified fine aggregate;

[0060] (2) Recycled coarse aggregate (a mixture of waste concrete and sand and / or coarse crushed stone in a mass ratio of 1:2) is immersed in a neutral silica sol solution (particle size of 20-50 nm) with a mass concentration of 20% at 16°C for 7 hours, and then quicklime is added to continue modification for 1.5 hours to obtain modified recycled coarse aggregate;

[0061] (3) After adding water to cement, carbide slag, fly ash and admixtures and stirring evenly, add modified fine aggregate and modified recycled coarse aggregate in turn and mix evenly. The mass ratio of cement, carbide slag, fly ash, polycarboxylic acid high-efficiency water reducing agent, modified fine aggregate and modified coarse aggregate is 1:0.2:0.2:0.03:0.4:0.3, and the amount of water added is 0.4W / C. Finally, after post-curing, recycled aggregate concrete is obtained.

[0062] Example 2

[0063] A process for improving the crack resistance of recycled aggregate concrete comprises the following steps:

[0064] (1) Recycled fine aggregate (SiO2 content of 55.8wt%, Al2O3 content of 24.9wt%) was immersed in an organic silicon compound (tetramethoxysilane and γ-glycidyloxypropyltrimethoxysilane mixed in a mass ratio of 1:1) at 17° C. for 15 h to obtain modified fine aggregate;

[0065] (2) Recycled coarse aggregate (a mixture of waste concrete and sand and / or coarse crushed stone in a mass ratio of 1:3) is immersed in a neutral silica sol solution (particle size of 20-50 nm) with a mass concentration of 22% at 20° C. for 5 h, and then quicklime is added to continue modification for 1 h to obtain modified recycled coarse aggregate;

[0066] (3) After adding water to cement, carbide slag, fly ash and admixtures and stirring evenly, add modified fine aggregate and modified recycled coarse aggregate in turn and mix evenly. The mass ratio of cement, carbide slag, fly ash, polycarboxylic acid high-efficiency water reducing agent, modified fine aggregate and modified coarse aggregate is 1:0.1:0.1:0.05:0.2:0.2, and the amount of water added is 0.35W / C. Finally, after post-curing, recycled aggregate concrete is obtained.

[0067] Example 3

[0068] A process for improving the crack resistance of recycled aggregate concrete comprises the following steps:

[0069] (1) Recycled fine aggregate (SiO2 content of 59.8wt%, Al2O3 content of 22.1wt%) was immersed in an organic silicon compound (tetraethyl orthosilicate and silane coupling agent mixed in a mass ratio of 1:1) at 13°C for 20 hours to obtain modified fine aggregate;

[0070] (2) Recycled coarse aggregate (a mixture of waste concrete and sand and / or coarse crushed stone in a mass ratio of 1:2) is immersed in a neutral silica sol solution (particle size of 20-50 nm) with a mass concentration of 10% at 11°C for 5 hours, and then quicklime is added to continue modification for 1.5 hours to obtain modified recycled coarse aggregate;

[0071] (3) After adding water to cement, carbide slag, fly ash and admixtures and stirring evenly, add modified fine aggregate and modified recycled coarse aggregate in turn and mix evenly. The mass ratio of cement, carbide slag, fly ash, polycarboxylic acid high-efficiency water reducing agent, modified fine aggregate and modified coarse aggregate is 1:0.3:0.3:0.01:0.5:0.5, and the amount of water added is 0.60W / C. Finally, after post-curing, recycled aggregate concrete is obtained.

[0072] Example 4

[0073] A process for improving the crack resistance of recycled aggregate concrete comprises the following steps:

[0074] (1) Recycled fine aggregate (SiO2 content of 60.1wt%, Al2O3 content of 23.7wt%) was immersed in an organic silicon compound (tetraethyl orthosilicate) at 20°C for 17h to obtain modified fine aggregate;

[0075] (2) Recycled coarse aggregate (a mixture of waste concrete and sand and / or coarse crushed stone in a mass ratio of 1:1) is immersed in a neutral silica sol solution (particle size of 20-50 nm) with a mass concentration of 4% at 18°C ​​for 8 hours, and then quicklime is added to continue modification for 2 hours to obtain modified recycled coarse aggregate;

[0076] (3) After cement, carbide slag, fly ash and admixtures are mixed with water and uniformly mixed, modified fine aggregate and modified recycled coarse aggregate are added in sequence and uniformly mixed, wherein the mass ratio of cement, carbide slag, polycarboxylic acid high-efficiency water reducing agent, modified fine aggregate and modified coarse aggregate is 1:0.1:0.02:0.4:0.2. The amount of water added is 0.5W / C, and finally after post-curing, recycled aggregate concrete is obtained.

[0077] Example 5

[0078] A process for improving the crack resistance of recycled aggregate concrete comprises the following steps:

[0079] (1) Recycled fine aggregate (SiO2 content of 55.6wt%, Al2O3 content of 22.9wt%) was immersed in an organic silicon compound (tetramethoxysilane, γ-glycidyloxypropyltrimethoxysilane and dimethyl silicone oil mixed in a mass ratio of 1:1:1) at 5°C for 16 hours to obtain modified fine aggregate;

[0080] (2) Recycled coarse aggregate (a mixture of waste concrete and sand and / or coarse crushed stone in a mass ratio of 1:5) is immersed in a neutral silica sol solution (particle size of 20-50 nm) with a mass concentration of 25% at 3°C ​​for 6 hours, and then quicklime is added to continue modification for 1 hour to obtain modified recycled coarse aggregate;

[0081] (3) After adding water to cement, carbide slag, fly ash and admixtures and stirring evenly, add modified fine aggregate and modified recycled coarse aggregate in turn and mix evenly. The mass ratio of cement, carbide slag, fly ash, polycarboxylic acid high-efficiency water reducing agent, modified fine aggregate and modified coarse aggregate is 1:0.3:0.1:0.04:0.2:0.5, and the amount of water added is 0.4W / C. Finally, after post-curing, recycled aggregate concrete is obtained.

[0082] Comparative Example 1

[0083] A method for preparing recycled aggregate concrete, which differs from Example 1 only in that the modification process in step (1) is not included, and in step (3), the modified recycled fine aggregate is replaced with recycled fine aggregate of equal mass. The remaining process steps and parameters are the same as those in Example 1.

[0084] Comparative Example 2

[0085] A method for preparing recycled aggregate concrete, which differs from Example 1 only in that the modification process in step (2) is not included, and in step (3), the modified recycled coarse aggregate is replaced with recycled coarse aggregate of equal mass. The remaining process steps and parameters are the same as those in Example 1.

[0086] Comparative Example 3

[0087] A method for preparing recycled aggregate concrete, which is different from Example 1 only in that in step (3), all raw materials are directly mixed and stirred uniformly at one time, that is:

[0088] (3) Cement, carbide slag, fly ash, admixtures, modified fine aggregate, modified recycled coarse aggregate and water are mixed and stirred evenly, and finally subjected to post-curing to obtain recycled aggregate concrete.

[0089] The remaining process steps and parameters are the same as those in Example 1.

[0090] Comparative Example 4

[0091] A method for preparing recycled aggregate concrete, which is different from Example 1 only in that the raw material addition ratio in step (3) is: the mass ratio of cement, calcium carbide slag, fly ash, polycarboxylic acid high-efficiency water reducing agent, modified fine aggregate and modified coarse aggregate is 1:0.5:0.5:0.01:0.6:0.1, and the amount of water added is 0.55W / C.

[0092] The remaining process steps and parameters are the same as those in Example 1.

[0093] Comparative Example 5

[0094] A method for preparing recycled aggregate concrete, which is different from Example 1 only in that the raw material in step (3) does not include carbide slag.

[0095] The remaining process steps and parameters are the same as those in Example 1.

[0096] Comparative Example 6

[0097] A method for preparing recycled aggregate concrete, which is different from Example 4 only in that the raw materials in step (3) do not include calcium carbide slag.

[0098] The remaining process steps and parameters are the same as those in Example 4.

[0099] Technical effect:

[0100] The mechanical properties of the recycled aggregate concrete prepared in Examples 1-5 and Comparative Examples 1-6 were tested:

[0101] According to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", standard test blocks were made, and the compressive strength of the standard test blocks after 28 days of curing was measured;

[0102] According to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", the concrete samples were made into cylindrical specimens with a diameter of 150 mm, and then the splitting tensile strength test was carried out according to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", and the splitting tensile strength of the recycled aggregate concrete samples was calculated;

[0103] The obtained concrete was tested for its early crack resistance according to GB / T50082-2009 "Standard for Test Methods for Long-term Performance and Durability of Ordinary Concrete".

[0104] The experimental results are shown in Table 1:

[0105] Table 1

[0106]

[0107] It can be seen from the above results that the modification of recycled coarse aggregate and recycled fine aggregate in the present invention effectively improves the cracking performance of concrete, and the technical effect of adding the two together is greater than the sum of the effects of adding them separately, and has a certain synergistic effect. And the addition of carbide slag effectively improves the splitting tensile performance and compressive strength of the product, and further improves the mechanical properties of concrete. In addition, the secondary mixing process in the present invention can also effectively improve the mechanical properties of concrete, help to reduce the gaps between aggregates, and improve the density and strength of concrete. At the same time, the addition of synergistic modified recycled coarse aggregate and modified recycled fine aggregate helps to reduce the generation of microcracks at the interface and improve the crack resistance of concrete.

[0108] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A process for improving the crack resistance of recycled aggregate concrete, characterized in that: The following steps are involved: (1) soaking the recycled fine aggregate in an organic silicon compound for modification to obtain modified fine aggregate; (2) soaking the recycled coarse aggregate in a silica sol solution, and then adding quicklime to obtain modified recycled coarse aggregate; (3) After adding water to cement, carbide slag, fly ash and admixtures and stirring evenly, add modified fine aggregate and modified recycled coarse aggregate in turn and mix evenly. Finally, after post-curing, recycled aggregate concrete is obtained.

2. A process for improving the crack resistance of recycled aggregate concrete according to claim 1, characterized in that: The recycled fine aggregate in step (1) is waste brick fine aggregate, and the particle size is 0.2-6 mm.

3. A process for improving the crack resistance of recycled aggregate concrete according to claim 2, characterized in that: The SiO2 content of the waste brick fine aggregate is 55-61wt%, and the Al2O3 content is 22-25wt%.

4. A process for improving the crack resistance of recycled aggregate concrete according to claim 1, characterized in that: The soaking modification in step (1) is carried out at a temperature of 5-20° C. and for a time of 15-20 hours.

5. A process for improving the crack resistance of recycled aggregate concrete according to claim 1, characterized in that: The organosilicon compound in step (1) is one or more selected from tetraethyl orthosilicate, silane coupling agent, tetramethoxysilane, γ-glycidyloxypropyltrimethoxysilane and dimethyl silicone oil.

6. A process for improving the crack resistance of recycled aggregate concrete according to claim 1, characterized in that: The recycled coarse aggregate in step (2) is obtained by crushing and screening waste concrete and mixing it with sand and / or coarse crushed stone, and has a particle size of 5-25 mm.

7. A process for improving the crack resistance of recycled aggregate concrete according to claim 6, characterized in that: The mass ratio of the waste concrete to sand and gravel and / or coarse crushed stone is 1:(1-5).

8. A process for improving the crack resistance of recycled aggregate concrete according to claim 1, characterized in that: The silica sol in step (2) is a neutral silica sol, and the particle size of the silica sol is 20-50 nm.

9. A process for improving the crack resistance of recycled aggregate concrete according to claim 1, characterized in that: The soaking temperature in step (2) is 3-20° C. and the soaking time is 5-8 h.

10. The recycled aggregate concrete prepared by the process for improving the crack resistance of recycled aggregate concrete as claimed in claim 1.

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