Composite fiber doped recycled aggregate concrete and preparation method thereof

Abstract

The invention discloses composite fiber doped recycled aggregate concrete and a preparation method thereof, and belongs to the technical field of building materials. Comprising the following raw materials in parts by mass: 40-60 parts of cement, 20-30 parts of recycled aggregate, 1-6 parts of composite fibers, 22-30 parts of fly ash, 1-5 parts of a water reducing agent and 10-15 parts of water. Wherein the composite fibers are formed by mixing glass fibers, polypropylene fibers and basalt fibers; the mass ratio of the glass fibers to the polypropylene fibers to the basalt fibers is 1: (0.2-0.6): 1. The cement, the recycled aggregate, the composite fiber, the fly ash, the water reducing agent and other raw materials are mixed according to a certain proportion to form the building material with good durability and compressive strength performance. Good application prospects are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a composite fiber-doped recycled aggregate concrete and a preparation method thereof. Background Art

[0002] Concrete is a basic material widely used in construction projects, but traditional concrete is mainly composed of cement, sand and gravel. The mining and processing of these materials cause great pollution to the environment. Therefore, people have been looking for more environmentally friendly and sustainable building materials.

[0003] Composite fiber-doped recycled aggregate concrete is a mixture of cement, recycled aggregate, fiber and water, which has better durability and compressive strength, and is also beneficial to environmental protection. However, since recycled aggregates require a lot of energy and chemicals in the production process, this limits their scope of use.

[0004] Therefore, it is necessary to provide a new type of composite fiber-doped recycled aggregate concrete that can effectively reduce its production cost. Summary of the invention

[0005] In view of the above technical problems, the present invention provides a composite fiber-doped recycled aggregate concrete and a preparation method thereof.

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

[0007] One of the purposes of the present invention is to provide a composite fiber doped recycled aggregate concrete, comprising the following raw materials in parts by weight: 40-60 parts of cement, 20-30 parts of recycled aggregate, 1-6 parts of composite fiber, 22-30 parts of fly ash, 1-5 parts of water reducer and 10-15 parts of water.

[0008] The present invention forms a building material with excellent performance by mixing raw materials such as cement, recycled aggregate, composite fiber, fly ash and water reducing agent in a certain proportion. Among them, cement is used as the main binder to improve the strength and hardness of concrete; the recycled aggregate enhances the compressive strength and durability of concrete; the composite fiber has a good reinforcing effect and improves the tensile strength of concrete; and the fly ash improves the working performance of concrete and reduces the cost of concrete.

[0009] Furthermore, the composite fiber-doped recycled aggregate concrete comprises the following raw materials in parts by weight: 42-55 parts of cement, 20-28 parts of recycled aggregate, 2-4 parts of composite fiber, 25-30 parts of fly ash, 1-3 parts of water reducer and 11-15 parts of water.

[0010] The present invention further improves the raw material ratio of the concrete, so that the performance of the concrete is further optimized. Among them, the content of cement is slightly increased, which enhances the compressive strength of the concrete; and the proportion of fly ash and water reducing agent is reduced, so that the strength and durability of the concrete are balanced.

[0011] Furthermore, the specific processing steps of the recycled aggregate include: crushing the waste concrete or bricks to a particle size of less than 4.75 mm, washing with clean water to remove impurities, and pre-wetting to a saturated surface dry state. This processing method can effectively remove impurities in the aggregate and improve the strength and durability of the concrete.

[0012] Furthermore, the composite fiber is a mixture of glass fiber, polypropylene fiber and basalt fiber, which forms a good bond between the fibers and improves the tensile strength of the concrete.

[0013] Furthermore, the mass ratio of the glass fiber, the polypropylene fiber and the basalt fiber is 1: (0.2-0.6): 1. This specific ratio setting enables the three fibers to play a maximum strengthening role in concrete.

[0014] Furthermore, the fly ash is grade II or above, which ensures the long-term performance of the concrete during use.

[0015] Furthermore, the water reducing agent is a polycarboxylate water reducing agent, which ensures the rapid setting and hardening characteristics of the concrete.

[0016] The second object of the present invention is to provide a method for preparing composite fiber-doped recycled aggregate concrete, comprising the following steps:

[0017] Weigh the raw materials by mass, add the recycled aggregate and fly ash to the composite fiber, stir, and obtain a dry mix;

[0018] Cement, water reducing agent and water are added to the dry-mixed mixture for wet mixing and shearing, and curing to obtain composite fiber-doped recycled aggregate concrete.

[0019] Furthermore, the parameters of the wet mixing shearing are: temperature 40-60° C., and shear rate 110-180 rpm.

[0020] The third object of the present invention is to provide an application of composite fiber-doped recycled aggregate concrete in the field of building materials.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects:

[0022] The present invention discloses a composite fiber doped recycled aggregate concrete and a preparation method thereof. The concrete is composed of raw materials such as cement, recycled aggregate, composite fiber, fly ash, and a water reducer, and has good durability and compressive strength. By controlling the proportion of raw materials, especially the specific proportion of fibers, the strength of concrete can be effectively improved. The preparation method of the present invention comprises mass blending the raw materials, adding recycled aggregate and fly ash, and finally adding water for wet mixing and shearing, and curing under certain conditions. In addition, the present invention also conducts an application experiment of composite fiber doped recycled aggregate concrete in the field of building materials. The results show that the concrete performance of the present invention is better than the prior art and has a good application prospect. DETAILED DESCRIPTION

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0025] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0026] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0027] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0028] The embodiment of the present invention provides a composite fiber-doped recycled aggregate concrete, comprising the following raw materials in parts by weight: 40-60 parts of cement, 20-30 parts of recycled aggregate, 1-6 parts of composite fiber, 22-30 parts of fly ash, 1-5 parts of water reducer and 10-15 parts of water. Preferably, the composite fiber-doped recycled aggregate concrete comprises the following raw materials in parts by weight: 42-55 parts of cement, 20-28 parts of recycled aggregate, 2-4 parts of composite fiber, 25-30 parts of fly ash, 1-3 parts of water reducer and 11-15 parts of water.

[0029] As a typical but non-limiting example, in the following preferred embodiments of the present invention:

[0030] The composite fiber-doped recycled aggregate concrete contains 42 parts, 50 parts, 55 parts or any range or sub-range between the aforementioned proportions of cement;

[0031] The composite fiber-doped recycled aggregate concrete contains 20 parts, 25 parts, 28 parts or any range or sub-range between the aforementioned proportions of recycled aggregate;

[0032] The composite fiber-doped recycled aggregate concrete contains 2 parts, 3 parts, 4 parts or any range or sub-range between the aforementioned proportions of composite fibers;

[0033] The composite fiber-doped recycled aggregate concrete contains 25 parts, 28 parts, 30 parts or any range or sub-range between the aforementioned proportions of fly ash;

[0034] The composite fiber-doped recycled aggregate concrete contains 1 part, 2 parts, 3 parts or any range or sub-range between the aforementioned proportions of water reducer;

[0035] The composite fiber-doped recycled aggregate concrete comprises 11 parts, 13 parts, 15 parts or any range or sub-range therebetween of water.

[0036] In the following preferred embodiments of the present invention, the specific processing steps of the recycled aggregate include: crushing the waste concrete or bricks to a particle size of less than 4.75 mm, washing with clean water to remove impurities, and pre-wetting to a saturated surface dry state.

[0037] In some preferred embodiments of the present invention, the composite fiber is a mixture of glass fiber, polypropylene fiber and basalt fiber, and the mass ratio is 1: (0.2-0.6): 1. Exemplarily, in the following embodiments of the present invention, the mass ratio of the glass fiber, polypropylene fiber and basalt fiber can be selected from 1: 0.2: 1, 1: 0.4: 1, 1: 0.6: 1 or any range between the aforementioned ratios.

[0038] The glass fiber has a diameter of 25 μm and a length of 8-10 mm; the polypropylene fiber has a diameter of 20 μm and is composed of two sizes of 5-8 mm and 10-15 mm in length, with a mass ratio of 1:1; the basalt fiber has a diameter of 15 μm and a length of 2-5 mm. The embodiments of the present invention select fibers of specific sizes for compounding, which can give full play to the characteristics and advantages of various fibers, so that the composite fiber reaches a balanced state, which can not only ensure the strength and rigidity of concrete, but also enhance its toughness and durability. Therefore, this fiber selection method has a positive impact on the performance of concrete and greatly improves the use effect of concrete.

[0039] In the following preferred embodiments of the present invention, the fly ash is grade 2 or above.

[0040] In the following preferred embodiments of the present invention, the water reducer is a polycarboxylate water reducer.

[0041] The embodiment of the present invention also provides a method for preparing composite fiber doped recycled aggregate concrete, comprising the following steps: weighing raw materials by mass, adding recycled aggregate and fly ash to the composite fiber, stirring to obtain a dry-mixed mixture; adding cement, a water reducer and water to the dry-mixed mixture for wet mixing and shearing, and curing to obtain composite fiber doped recycled aggregate concrete.

[0042] In some preferred embodiments of the present invention, the parameters of the wet shearing are: temperature 40-60°C, shear rate 110-180rpm, and time 3-6h. As a typical but non-limiting example, in the following embodiments of the present invention, the temperature of the wet shearing can be selected to be 40°C, 50°C, or 60°C; the shear rate of the wet shearing can be selected to be 110rpm, 150rpm, or 180rpm; and the time of the wet shearing is 3h, 5h, or 6h.

[0043] The embodiment of the present invention also provides an application of composite fiber-doped recycled aggregate concrete in the field of building materials.

[0044] In other optional embodiments, a composite bacterial agent may be further added to the composite fiber doped recycled aggregate concrete to obtain a new formula, namely: a composite fiber doped recycled aggregate concrete, comprising the following raw materials in parts by mass: 40-60 parts of cement, 20-30 parts of recycled aggregate, 1-6 parts of composite fiber, 22-30 parts of fly ash, 1-5 parts of water reducer, 10-15 parts of water and 0.5-1.5 parts of composite bacterial agent.

[0045] In some preferred embodiments of the present invention, the composite bacterial agent is mixed with Bacillus pasteurii and Bacillus siamensis in a mass ratio of 1: (1.5-3). As a typical but non-limiting example, in the following embodiments of the present invention, the mass ratio of Bacillus pasteurii and Bacillus siamensis can be selected as 1: 2. Bacillus pasteurii (Sporosarcina pasteurii, Beijing Biobo Biotechnology Co., Ltd.) can repair concrete cracks by microbial induced calcium carbonate precipitation (MICP), and its metabolite calcium carbonate can fill cracks and micropores, thereby improving the compactness and strength of concrete. Bacillus siamensis (Bacillus siamensis, Shanghai Yushao Biotechnology Co., Ltd.) has good thermal stability and acid-base stability, can adapt to concrete crack repair under different environmental conditions, and its metabolites can promote the mineralization reaction inside the concrete and enhance the durability of the concrete. Through the synergistic effect of multiple strains, defects in recycled concrete aggregates can be more effectively repaired, thereby significantly improving their compressive strength, flexural strength and durability. The most critical thing is that the present invention adds a composite bacterial agent on the basis of the composite fiber. The composite bacterial agent can act on the fiber surface and improve its performance in concrete by changing the chemical properties of the fiber surface. The two have a complementary effect.

[0046] The preparation method of composite fiber doped recycled aggregate concrete with the addition of composite bacterial agent comprises the following steps: weighing raw materials by mass, adding recycled aggregate and fly ash to the composite fiber, stirring to obtain a dry-mixed mixture; adding cement, a water reducer and water to the dry-mixed mixture, and finally adding the composite bacterial agent, wet-mixing shearing, and curing to obtain composite fiber doped recycled aggregate concrete.

[0047] The "room temperature" in the present invention refers to 20-30°C unless otherwise specified.

[0048] The "parts" described in the present invention, unless otherwise specified, refer to parts by mass.

[0049] The raw materials used in the present invention are all purchased from the market.

[0050] The technical solution of the present invention is further illustrated by the following embodiments.

[0051] In the following embodiments, cement is P.O42.5R ordinary Portland cement (Wuhan Meishan Qiaoye Cement Co., Ltd.); the water reducer (Wuhan Huaxuan High-tech Co., Ltd.) is a polycarboxylic acid water reducer with a solid content of 18% and a water reduction rate of 32%; recycled aggregate (Wuhan Tianyicheng Recycling Resources Co., Ltd.); fly ash (Handan Fuxing District Yingqi Fly Ash Sales Co., Ltd.) is Class II fly ash; glass fiber (Hubei Ping'an Electrical Materials Co., Ltd.) has a diameter of 25μm and a length of 8-10mm; polypropylene fiber (Jiangsu Subote New Materials Co., Ltd.) has a diameter of 20μm and consists of two sizes of 5-8mm and 10-15mm in length, with a mass ratio of 1:1; basalt fiber (Zhongding Economic Development Co., Ltd.) has a diameter of 15um and a length of 2-5mm.

[0052] Example 1

[0053] A composite fiber-doped recycled aggregate concrete comprises the following raw materials in parts by mass: 50 parts of cement, 25 parts of recycled aggregate, 3 parts of composite fiber (the mass ratio of glass fiber, polypropylene fiber and basalt fiber is 1:0.4:1), 28 parts of fly ash, 2 parts of water reducer and 13 parts of water.

[0054] A method for preparing composite fiber-doped recycled aggregate concrete comprises the following steps:

[0055] (1) crushing waste concrete or bricks to a particle size of less than 4.75 mm, washing with clean water to remove impurities, pre-wetting to a saturated surface dry state, and obtaining recycled aggregate;

[0056] (2) weighing the raw materials according to the above mass, adding recycled aggregate and fly ash to the composite fiber, stirring, and obtaining a dry mix;

[0057] (3) Cement, a water reducing agent and water were added to the dry-mixed mixture, and then wet-mixed and sheared at a shear rate of 150 rpm at 50° C. for 5 h, and then cured to obtain composite fiber-doped recycled aggregate concrete.

[0058] Example 2

[0059] A composite fiber-doped recycled aggregate concrete comprises the following raw materials in parts by mass: 42 parts of cement, 28 parts of recycled aggregate, 2 parts of composite fiber (the mass ratio of glass fiber, polypropylene fiber and basalt fiber is 1:0.6:1), 30 parts of fly ash, 3 parts of water reducer and 11 parts of water.

[0060] A method for preparing composite fiber-doped recycled aggregate concrete comprises the following steps:

[0061] (1) crushing waste concrete or bricks to a particle size of less than 4.75 mm, washing with clean water to remove impurities, pre-wetting to a saturated surface dry state, and obtaining recycled aggregate;

[0062] (2) weighing the raw materials according to the above mass, adding recycled aggregate and fly ash to the composite fiber, stirring, and obtaining a dry mix;

[0063] (3) Cement, a water reducing agent and water were added to the dry-mixed mixture, and then wet-mixed and sheared at a shear rate of 110 rpm at 60° C. for 3 h, and cured to obtain composite fiber-doped recycled aggregate concrete.

[0064] Example 3

[0065] A composite fiber-doped recycled aggregate concrete comprises the following raw materials in parts by mass: 55 parts of cement, 20 parts of recycled aggregate, 4 parts of composite fiber (the mass ratio of glass fiber, polypropylene fiber and basalt fiber is 1:0.2:1), 25 parts of fly ash, 1 part of water reducing agent and 15 parts of water.

[0066] A method for preparing composite fiber-doped recycled aggregate concrete comprises the following steps:

[0067] (1) crushing waste concrete or bricks to a particle size of less than 4.75 mm, washing with clean water to remove impurities, pre-wetting to a saturated surface dry state, and obtaining recycled aggregate;

[0068] (2) weighing the raw materials according to the above mass, adding recycled aggregate and fly ash to the composite fiber, stirring, and obtaining a dry mix;

[0069] (3) Cement, a water reducing agent and water were added to the dry-mixed mixture, and then wet-mixed and sheared at a shear rate of 80 rpm at 40° C. for 6 h, and cured to obtain composite fiber-doped recycled aggregate concrete.

[0070] Comparative Example 1

[0071] Same as Example 1, except that the mass ratio of glass fiber, polypropylene fiber and basalt fiber is 1:1:0.4.

[0072] Comparative Example 2

[0073] The same as Example 1, except that the amount of composite fiber added remains unchanged, and the composite fiber is composed of glass fiber, polypropylene fiber, basalt fiber, and steel fiber mixed in a mass ratio of 1:0.4:1:1.

[0074] Comparative Example 3

[0075] The same as Example 1, except that the mass of glass fiber is replaced by steel fiber, that is, the mass ratio of steel fiber, polypropylene fiber and basalt fiber is 1:0.4:1.

[0076] Comparative Example 4

[0077] Same as Example 1, except that the diameters of the glass fiber, polypropylene fiber and basalt fiber are all 20 um, and the lengths are all 5-8 mm.

[0078] The composite fiber-doped recycled aggregate concrete prepared in Examples 1-3 and Comparative Examples 1-4 was tested according to the testing standards. The results are shown in Table 1.

[0079] The mechanical properties of the concrete prepared in each embodiment and comparative example were measured according to GB / T50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete"; the frost resistance of the concrete specimens was tested according to the "Test Procedure for Hydraulic Concrete" (DL / T5150-2001). The test specimens were prisms of 150 mm × 150 mm × 400 mm in length × width × height. The freeze-thaw cycles were repeated 300 times, and the durability index was calculated. The formula is as follows: Durability index = p n × freeze-thaw cycles / 300, where p n is the relative dynamic elastic modulus of the specimen, p n =f 2 n / f 2 1×100, f n is the natural frequency of the specimen after freeze-thaw cycles, Hz, f 2 1 is the natural frequency of the specimen before freeze-thaw cycle, Hz.

[0080] Table 1

[0081] 28d compressive strength / MPa 28d flexural strength / MPa Splitting tensile strength / MPa Durability Index Example 1 94.3 31.6 9.27 169 Example 2 93.8 29.7 9.04 166 Example 3 94.1 30.8 9.16 168 Comparative Example 1 86.2 23.7 8.34 143 Comparative Example 2 91.5 28.4 8.89 158 Comparative Example 3 80.1 19.6 7.04 142 Comparative Example 4 82.4 20.7 7.16 144

[0082] As can be seen from Table 1, the composite fiber-doped recycled aggregate concrete prepared by the methods of Examples 1-3 of the present invention has strong durability, is not easy to crack, and has high compressive strength and flexural strength. Compared with Comparative Example 1, Example 1 only changes the dosage ratio of glass fiber, polypropylene fiber and basalt fiber, and the performance of the obtained concrete is also significantly reduced; Compared with Comparative Example 2, it can be found that although a steel fiber is added for compounding, the performance of the obtained concrete is not significantly improved; Compared with Comparative Example 3, Example 1 only replaces a certain fiber in the composite fiber, and the performance of the obtained concrete is significantly reduced. The above results show that in the concrete formula provided by the present invention, the amount of fiber needs to be compounded in a specific ratio, and the more types, the better, but a specific compounding relationship is required. Too many types of compounding will only increase the production cost, and under this ratio, only specific fiber types will improve the performance of concrete. Compared with Comparative Example 4, Example 1 only changes the relationship between the particle size of the fibers, resulting in a decrease in the performance of the concrete, indicating that the present invention is not a simple combination of different fibers, but also needs to consider the influence of fiber diameter and length on performance.

[0083] In summary, the overall performance of Example 1 is the best, so Example 1 is used as the basis for further improvement.

[0084] Example 4

[0085] A composite fiber doped recycled aggregate concrete comprises the following raw materials in parts by mass: 50 parts of cement, 25 parts of recycled aggregate, 3 parts of composite fiber (the mass ratio of glass fiber, polypropylene fiber and basalt fiber is 1:0.4:1), 28 parts of fly ash, 2 parts of water reducer, 13 parts of water and 1 part of composite bacterial agent (the mass ratio of Bacillus pasteurianus and Bacillus siamese is 1:2).

[0086] A method for preparing composite fiber-doped recycled aggregate concrete comprises the following steps:

[0087] (1) Weighing the raw materials according to the above mass, adding recycled aggregate and fly ash to the composite fiber, stirring, and obtaining a dry mix;

[0088] (2) Cement, water reducing agent and water were added to the dry-mixed mixture, and then the composite bacterial agent was added. Finally, the mixture was wet-mixed and sheared at a shear rate of 150 rpm at 50° C. for 5 h, and then cured to obtain composite fiber-doped recycled aggregate concrete.

[0089] Comparative Example 5

[0090] The same as Example 4, except that the mass of Siamese Bacillus is replaced by alkali-resistant Bacillus, that is, the composite bacterial agent is formed by mixing Bacillus pasteurianus and alkali-resistant Bacillus in a mass ratio of 1:2.

[0091] Comparative Example 6

[0092] Same as Example 4, except that the mass ratio of Bacillus pasteurianus to Bacillus siamese is 2:1.

[0093] Comparative Example 7

[0094] Same as Example 4, except that the composite fiber is replaced by cement, that is, no composite fiber is added.

[0095] The composite fiber-doped recycled aggregate concrete prepared in Example 4 and Comparative Examples 5-7 was tested according to the testing standards. The results are shown in Table 2. The testing method is the same as that in Example 1.

[0096] Table 2

[0097] 28d compressive strength / MPa 28d flexural strength / MPa Splitting tensile strength / MPa Durability Index Example 1 94.3 31.6 9.27 169 Example 4 98.4 34.7 11.03 175 Comparative Example 5 95.2 31.9 9.41 171 Comparative Example 6 95.6 32.2 9.47 171 Comparative Example 7 78.9 18.7 6.68 136

[0098] As can be seen from Table 2, the performance of the concrete prepared by the method of Example 4 of the present invention is significantly improved compared with Example 1, while the performance of Comparative Examples 5 and 6 is not significantly improved compared with Example 1 due to the different types and proportions of bacterial species used. In Comparative Example 7, since no composite fiber is added, the effect of the obtained concrete is still reduced even if the composite bacterial agent is added, which further proves that there is an interactive relationship between the fiber and the bacterial agent specified by the present invention.

[0099] 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 composite fiber-doped recycled aggregate concrete, characterized in that: The raw materials include the following parts by weight: 40-60 parts of cement, 20-30 parts of recycled aggregate, 1-6 parts of composite fiber, 22-30 parts of fly ash, 1-5 parts of water reducing agent and 10-15 parts of water; The composite fiber is a mixture of glass fiber, polypropylene fiber and basalt fiber; the mass ratio of the glass fiber, polypropylene fiber and basalt fiber is 1:(0.2-0.6):

1.

2. The composite fiber-doped recycled aggregate concrete according to claim 1, characterized in that: The invention comprises the following raw materials in parts by weight: 42-55 parts of cement, 20-28 parts of recycled aggregate, 2-4 parts of composite fiber, 25-30 parts of fly ash, 1-3 parts of water reducing agent and 11-15 parts of water.

3. The composite fiber-doped recycled aggregate concrete according to claim 1 or 2, characterized in that: The specific processing steps of the recycled aggregate include: crushing the waste concrete or bricks to a particle size of less than 4.75 mm, washing with clean water to remove impurities, and pre-wetting to a saturated surface dry state.

4. The composite fiber-doped recycled aggregate concrete according to claim 1 or 2, characterized in that: The fly ash is grade 2 or above.

5. The composite fiber-doped recycled aggregate concrete according to claim 1 or 2, characterized in that: The water reducer is a polycarboxylate water reducer.

6. A method for preparing composite fiber-doped recycled aggregate concrete according to any one of claims 1 to 5, characterized in that: The following steps are involved: Weigh the raw materials by mass, add the recycled aggregate and fly ash to the composite fiber, stir, and obtain a dry mix; Cement, a water reducing agent and water are added to the dry-mixed mixture for wet mixing and shearing, and curing to obtain composite fiber-doped recycled aggregate concrete.

7. The preparation method according to claim 6, characterized in that: The parameters of the wet mixing shearing are: temperature 40-60° C., and shearing rate 110-180 rpm.

8. Use of the composite fiber-doped recycled aggregate concrete as claimed in any one of claims 1 to 5 in the field of building materials.