Durable recycled aggregate concrete and method of making same

Abstract

The application relates to the field of concrete, and particularly discloses a durable recycled aggregate concrete and a preparation method thereof. The concrete comprises the following raw materials: modified recycled coarse aggregate, modified recycled fine aggregate, recycled micro powder, cement, fly ash, mineral powder, reinforcing fiber, water reducing agent, water and epoxy resin emulsion; wherein the modified recycled coarse aggregate and the modified recycled fine aggregate are obtained by soaking in a modified liquid for 5-6 hours and then drying; the modified liquid is prepared from the following raw materials in parts by weight: 8-10 parts of chitosan, 6-8 parts of acetic acid, 100-120 parts of water, 20-30 parts of nano zirconium oxide, 20-30 parts of nano silicon dioxide and 10-20 parts of bentonite; the recycled aggregate concrete prepared by the application has the advantages of good crack resistance, good mechanical properties and good durability.

Description

Technical Field

[0001] This application relates to the field of concrete, and more specifically, to a durable recycled aggregate concrete and a method for its preparation. Background Technology

[0002] With the development of urbanization, a large amount of construction waste has accumulated, and natural aggregate resources have decreased. Construction waste refers to the excavated soil, waste materials, slag, silt, and other waste left over from the laying, construction, or demolition of various buildings and structures by individuals, construction units, or contractors. Waste concrete is usually the largest component of construction waste. After being crushed, screened, and processed through other methods, waste concrete can be used to replace natural aggregates in concrete. Aggregates prepared from waste concrete are called recycled aggregates.

[0003] Recycled aggregate concrete, or simply recycled concrete, is a new type of concrete made by partially or completely replacing natural aggregates with recycled aggregates (mainly recycled coarse aggregates) processed from crushed waste concrete. Recycled concrete technology enables the recycling of waste concrete, partially or completely restoring its original properties to form new building materials. This not only solves some environmental problems but also maximizes resource utilization, aligning with the sustainable development strategy of the construction industry and representing a crucial measure for developing green and eco-friendly concrete.

[0004] However, the damage accumulated inside recycled aggregates during the crushing process causes numerous microcracks. Therefore, compared to natural aggregates, recycled aggregates have many problems, such as high porosity, high water absorption, low bulk density, high crushing index, and weak bonding properties. Consequently, concrete made from recycled aggregates has poorer durability and a shorter lifespan than ordinary concrete. It cannot withstand sun and rain, is prone to water seepage, and its compressive strength decreases. It can only be used for simple foundations and wall fillings, and cannot be used for building surfaces or load-bearing materials. Summary of the Invention

[0005] To improve the durability of recycled aggregate concrete, this application provides a durable recycled aggregate concrete and a method for preparing the same.

[0006] In a first aspect, this application provides a durable recycled aggregate concrete, which adopts the following technical solution:

[0007] A durable recycled aggregate concrete is made from the following raw materials in parts by weight: 80-100 parts modified recycled coarse aggregate, 30-40 parts modified recycled fine aggregate, 20-30 parts recycled micro powder, 30-40 parts cement, 10-15 parts fly ash, 10-15 parts mineral powder, 60-70 parts reinforcing fiber, 1-2 parts water-reducing agent, 20-25 parts water and 15-20 parts epoxy resin emulsion;

[0008] Both the modified recycled coarse aggregate and the modified recycled fine aggregate are obtained by soaking in the modifying solution for 5-6 hours and then drying. The modifying solution is made from the following raw materials in parts by weight: 8-10 parts chitosan, 6-8 parts acetic acid, 100-120 parts water, 20-30 parts nano zirconium oxide, 20-30 parts nano silica and 10-20 parts bentonite.

[0009] By adopting the above technical solutions, the addition of mineral powder can reduce water consumption, reduce cement consumption, and lower the heat of hydration of cement. Furthermore, mineral powder can fill the gaps between cement and aggregate in concrete, improving its density and strength. Fly ash has a similar effect to mineral powder, containing volcanic active components, which can reduce cement consumption and lower the heat of hydration of cement. Fly ash can not only fill the gaps in concrete to improve its density but also improve the fluidity and workability of the concrete mix.

[0010] Epoxy resin, as a cementing material, can significantly improve the compressive strength and impermeability of recycled aggregate permeable concrete. It can also effectively isolate recycled aggregate from water, reducing its permeability. In addition, chitosan forms an impermeable film on the surface of recycled coarse aggregate, which can further reduce the permeability of recycled aggregate. Moreover, the surface of chitosan has abundant functional groups, which can improve cross-linking with epoxy resin, further improving the compressive strength and durability of recycled aggregate concrete. Acetic acid provides an acidic environment for the dissolution of chitosan and can also alleviate the alkali-aggregate reaction, thereby reducing the formation of cracks in recycled aggregate concrete and improving the durability of concrete.

[0011] Adding bentonite to the modifying solution acts as a lubricant. Bentonite facilitates the rapid penetration of nano-silica and nano-zirconia into the broken voids of the recycled aggregate, and enables chitosan to quickly form a film on the surface of the recycled aggregate. Furthermore, bentonite's adhesive properties allow it to work with chitosan, improving the adhesion of nano-silica and nano-zirconia within the voids of the recycled aggregate, thereby enhancing its compressive strength and impermeability. Nano-silica particles, with their ultrafine texture, high specific surface area, and high activity, form a nano-silica sol in the slurry, exhibiting a filling effect. This fills micro-cracks in the recycled coarse aggregate, reducing the number of internal pores and improving its density. Nano-silica can also react chemically with calcium hydroxide in the recycled aggregate to form CSH gel, which fills the voids, making the recycled coarse aggregate denser, reducing porosity, and increasing strength. Nano-zirconia, with its high hardness, effectively improves the compressive strength of the recycled aggregate when incorporated into it.

[0012] Therefore, in this application, bentonite, nano-silica and nano-zirconia are used together to fill recycled aggregate to improve the viscosity and density of recycled aggregate. They are further combined with chitosan and epoxy resin to further improve the viscosity of recycled aggregate and reduce its permeability, thereby improving the compressive strength and durability of recycled aggregate concrete.

[0013] Preferably, the mass ratio of the nano-zirconia, bentonite, and nano-silica is 6:5:3.

[0014] By adopting the above technical solution, when the mass ratio of nano-zirconia, bentonite and nano-silica is 6:5:3, the synergistic effect between them can be better exerted, and the compressive strength of recycled aggregate can be further improved.

[0015] Preferably, the modified recycled coarse aggregate has a particle size of 20-40 mm, and the modified recycled fine aggregate has a particle size of 5-20 mm.

[0016] By adopting the above technical solution, the particle size distribution of the modified recycled coarse aggregate and modified recycled fine aggregate can significantly improve the compressive strength of recycled aggregate concrete.

[0017] Preferably, the reinforcing fibers include glass fibers, lignin fibers, and polypropylene fibers.

[0018] By adopting the above technical solution, the three types of reinforcing fibers with different elasticity and roughness are mixed together and incorporated into concrete, which can form a multi-directional three-dimensional network support system in the concrete, increase the toughness and density of the concrete, improve the compressive strength of the concrete, reduce the generation of cracks, and improve the durability of recycled aggregate concrete.

[0019] Preferably, the mass ratio of the glass fiber, lignin fiber and polypropylene fiber is (2-3):(1-2):1.

[0020] By adopting the above technical solution, the mass ratio of glass fiber, lignin fiber and polypropylene fiber is (2-3):(1-2):1, which can significantly enhance the compressive strength and durability of concrete.

[0021] Preferably, the reinforcing fiber further undergoes the following modification steps:

[0022] The modified reinforcing fiber was obtained by immersing the reinforcing fiber in a solution of silane coupling agent KH550 and allowing it to stand and dry.

[0023] By adopting the above technical solution, the reinforcing fiber is modified with silane coupling agent KH550, so that the surface of the reinforcing fiber has amino groups. The amino groups can react with the epoxy groups of epoxy resin, thereby improving the interfacial bonding force between the reinforcing fiber and concrete, and further improving the compressive strength and durability of concrete.

[0024] Preferably, it also contains 10-20 parts of hollow glass microspheres.

[0025] By adopting the above technical solutions, hollow glass microspheres can improve the workability of concrete and reduce the impact of hydration heat on concrete, thereby reducing crack formation and improving the durability of concrete.

[0026] Secondly, this application provides a method for preparing durable recycled aggregate concrete, employing the following technical solution:

[0027] Includes the following steps:

[0028] S1: After uniformly mixing recycled micro powder, cement, fly ash, and mineral powder, add water-reducing agent, water, and epoxy resin emulsion, and stir thoroughly to obtain precast concrete;

[0029] S2: After uniformly mixing modified recycled coarse aggregate, modified recycled fine aggregate and reinforced fiber aggregate, a blend is obtained; then the blend is added to precast concrete and stirred evenly to obtain recycled aggregate concrete.

[0030] In summary, this application has the following beneficial effects:

[0031] 1. Epoxy resin, as a cementing material, can significantly improve the compressive strength and impermeability of recycled aggregate permeable concrete. It can also effectively isolate recycled aggregate from water, reducing its permeability. In addition, chitosan forms an impermeable film on the surface of recycled coarse aggregate, which can further reduce the permeability of recycled aggregate. Moreover, the surface of chitosan has abundant functional groups, which can improve cross-linking with epoxy resin, further improving the compressive strength and durability of recycled aggregate concrete. Acetic acid provides an acidic environment for the dissolution of chitosan and can also alleviate the alkali-aggregate reaction, thereby reducing the formation of cracks in recycled aggregate concrete and improving the durability of concrete.

[0032] 2. Adding bentonite to the modifying solution acts as a lubricant. Bentonite allows the nano-silica and nano-zirconia in the modifying solution to quickly penetrate into the broken voids of the recycled aggregate, and enables chitosan to quickly form a film on the surface of the recycled aggregate. In addition, bentonite has a certain degree of viscosity, which can cooperate with chitosan to improve the adhesion of nano-silica and nano-zirconia in the voids of the recycled aggregate, thereby improving the compressive strength and impermeability of the recycled aggregate. Nano-silica particles have the advantages of being ultrafine, having a high specific surface area, and being highly active. They form nano-silica sol in the slurry, which has a filling effect. It can fill the micro-cracks in the recycled coarse aggregate, reduce the number of internal pores, and improve the density of the recycled coarse aggregate. Nano-silica can react chemically with calcium hydroxide in the recycled aggregate to generate CSH gel, which fills the voids in the recycled coarse aggregate, making the recycled coarse aggregate denser, reducing the porosity, and increasing the strength. Nano-zirconia has high hardness, and when filled in the recycled aggregate, it can effectively improve the compressive strength of the recycled aggregate.

[0033] 3. The reinforcing fibers are modified with silane coupling agent KH550, which gives the surface of the reinforcing fibers amino groups. The amino groups can react with the epoxy groups of the epoxy resin, thereby improving the interfacial bonding between the reinforcing fibers and the concrete and further improving the compressive strength and durability of the concrete. Detailed Implementation

[0034] Raw material source:

[0035] Chitosan is from Qingdao Yuekang Biotechnology Co., Ltd.;

[0036] Nano-zirconia comes from Shandong Haoshun Chemical Co., Ltd.;

[0037] Nano-silica comes from Shandong Wanhua Tianhe New Materials Co., Ltd.;

[0038] The bentonite comes from Tianjin Yandong Mineral Products Co., Ltd.

[0039] Recycled coarse aggregate, recycled fine aggregate, and recycled micro powder are made from the following raw materials in parts by weight: 35% silicate cement, 25% mineral powder, 27% fly ash, 1% water-reducing agent, and the remainder is water.

[0040] The cement came from Wenshui County Sunshine Cement Co., Ltd.

[0041] Lingshou County Haibin Mineral Products Trading Co., Ltd. (Fly Ash)

[0042] The mineral powder came from Lingshou County Jingjia Mineral Products Processing Plant;

[0043] The epoxy resin emulsion comes from Shandong Changyao New Materials Co., Ltd.

[0044] The present application will be further described in detail below with reference to preparation examples and embodiments.

[0045] Preparation Example

[0046] Preparation Example 1

[0047] Both modified recycled coarse aggregate and modified recycled fine aggregate were obtained by soaking in a modifying solution for 5 hours and then drying. The modifying solution was made by mixing the following raw materials: 8 kg chitosan, 6 kg acetic acid, 100 kg water, 20 kg nano zirconium oxide, 20 kg nano silica and 10 kg bentonite.

[0048] Preparation Example 2

[0049] Both modified recycled coarse aggregate and modified recycled fine aggregate were obtained by soaking in a modifying solution for 5.5 hours and then drying. The modifying solution was made by mixing the following raw materials: 9 kg chitosan, 7 kg acetic acid, 110 kg water, 25 kg nano zirconium oxide, 25 kg nano silica and 15 kg bentonite.

[0050] Preparation Example 3

[0051] Both modified recycled coarse aggregate and modified recycled fine aggregate were obtained by soaking in a modifying solution for 6 hours and then drying. The modifying solution was made by mixing the following raw materials: 10 kg chitosan, 8 kg acetic acid, 120 kg water, 30 kg nano zirconium oxide, 30 kg nano silica and 20 kg bentonite.

[0052] Preparation Example 4

[0053] The difference between Preparation Example 4 and Preparation Example 3 is that chitosan was not added, but the rest of the steps were the same as those in Preparation Example 3.

[0054] Preparation Example 5

[0055] The difference between Preparation Example 5 and Preparation Example 3 is that chitosan was replaced with carboxymethyl cellulose, while the rest of the steps were the same as those in Preparation Example 3.

[0056] Preparation Example 6

[0057] The difference between Preparation Example 6 and Preparation Example 3 is that acetic acid was not added, but the rest of the steps were the same as those in Preparation Example 3.

[0058] Preparation Example 7

[0059] The difference between Preparation Example 7 and Preparation Example 3 is that nano-zirconia was replaced with an equal amount of nano-silica, while the rest of the steps were the same as those in Preparation Example 3.

[0060] Preparation Example 8

[0061] The difference between Preparation Example 8 and Preparation Example 3 is that nano-silica was replaced with an equal amount of zirconium oxide, while the rest of the steps were the same as those in Preparation Example 3.

[0062] Preparation Example 9

[0063] The difference between Preparation Example 9 and Preparation Example 3 is that bentonite was replaced with an equal amount of nano-silica, while the rest of the steps were the same as those in Preparation Example 3.

[0064] Preparation Examples 10-14

[0065] The difference between Preparation Examples 10-14 and Preparation Example 3 lies in the mass and mass ratio of nano-zirconia, nano-silica, and bentonite, as shown in the table below:

[0066] Table 1. Mass and mass ratio of nano-zirconia, nano-silica, and bentonite in Preparation Examples 10-14

[0067]

[0068]

[0069] Preparation Example 15

[0070] The modified reinforcing fibers (glass fiber, lignin fiber and polypropylene fiber) were immersed in a 5% KH550 silane coupling agent solution for 10 minutes and then allowed to stand and dry to obtain the modified reinforcing fibers.

[0071] Preparation Example 16

[0072] The modified reinforcing fibers (glass fiber, lignin fiber and polypropylene fiber) were immersed in a 5% polymethyltriethoxysilane solution for 10 minutes and then allowed to stand and dry to obtain the modified reinforcing fibers.

[0073] Example

[0074] Example 1

[0075] A method for preparing durable recycled aggregate concrete includes the following steps:

[0076] S1: Mix 20kg recycled micro powder, 30kg cement, 10kg fly ash, and 10kg mineral powder evenly, then add 1kg polycarboxylate superplasticizer, 20kg water, 10kg hollow glass microspheres, and 15kg epoxy resin emulsion. Stir thoroughly to obtain precast concrete.

[0077] S2: 80 kg of modified recycled coarse aggregate with a particle size of 20-40 mm, 30 kg of modified recycled fine aggregate with a particle size of 5-20 mm, and 60 kg of reinforcing fiber (30 kg of glass fiber, 15 kg of lignin fiber, and 15 kg of polypropylene fiber) aggregate are mixed evenly to obtain a blend; then the blend is added to precast concrete and stirred evenly to obtain recycled aggregate concrete; wherein the modified recycled coarse aggregate and modified recycled fine aggregate are from preparation example 1.

[0078] Example 2

[0079] A method for preparing durable recycled aggregate concrete includes the following steps:

[0080] S1: Mix 25kg recycled micro powder, 35kg cement, 12kg fly ash, and 13kg mineral powder evenly, then add 1.5kg polycarboxylate superplasticizer, 22kg water, 15kg hollow glass microspheres, and 18kg epoxy resin emulsion, and stir thoroughly to obtain precast concrete.

[0081] S2: 90 kg of modified recycled coarse aggregate with a particle size of 20-40 mm, 35 kg of modified recycled fine aggregate with a particle size of 5-20 mm, and 65 kg of reinforcing fiber (35 kg of glass fiber, 15 kg of lignin fiber, and 15 kg of polypropylene fiber) aggregate are mixed evenly to obtain a blend; then the blend is added to precast concrete and stirred evenly to obtain recycled aggregate concrete; wherein the modified recycled coarse aggregate and modified recycled fine aggregate are from preparation example 1.

[0082] Example 3

[0083] A method for preparing durable recycled aggregate concrete includes the following steps:

[0084] S1: Mix 30kg recycled micro powder, 40kg cement, 15kg fly ash, and 15kg mineral powder evenly, then add 2kg polycarboxylate superplasticizer, 25kg water, 20kg hollow glass microspheres, and 20kg epoxy resin emulsion, and stir thoroughly to obtain precast concrete.

[0085] S2: 100 kg of modified recycled coarse aggregate with a particle size of 20-40 mm, 40 kg of modified recycled fine aggregate with a particle size of 5-20 mm, and 70 kg of reinforcing fiber (30 kg of glass fiber, 20 kg of lignin fiber, and 20 kg of polypropylene fiber) aggregate are mixed evenly to obtain a blend; then the blend is added to precast concrete and stirred evenly to obtain recycled aggregate concrete; wherein the modified recycled coarse aggregate and modified recycled fine aggregate are from preparation example 1.

[0086] Examples 4-5

[0087] The difference between Examples 4-5 and Example 3 is that the modified recycled coarse aggregate and the modified recycled fine aggregate are respectively derived from Preparation Examples 2-3, while the remaining steps are the same as in Example 3.

[0088] Examples 6-16

[0089] The difference between Examples 6-16 and Example 5 is that the modified recycled coarse aggregate and the modified recycled fine aggregate are respectively derived from Preparation Examples 4-14, while the remaining steps are the same as in Example 5.

[0090] Example 17

[0091] The difference between Example 17 and Example 15 is that the modified recycled coarse aggregate has a particle size of 30-50 mm and the modified recycled fine aggregate has a particle size of 5-10 mm. The remaining steps are the same as in Example 15.

[0092] Example 18

[0093] The difference between Example 18 and Example 15 is that no glass fiber was added, while the rest of the steps are the same as in Example 15.

[0094] Example 19

[0095] The difference between Example 19 and Example 15 is that no lignin fiber was added, while the rest of the steps were the same as in Example 15.

[0096] Example 20

[0097] The difference between Example 20 and Example 15 is that no polypropylene fiber was added, while the rest of the steps were the same as in Example 15.

[0098] Examples 21-25

[0099] The difference between Examples 21-25 and Example 15 lies in the different masses and mass ratios of the glass fiber, lignin fiber, and polypropylene fiber. Specific masses are shown in the table below:

[0100] Table 2. Mass and mass ratio of glass fiber, lignin fiber, and polypropylene fiber in Examples 21-25

[0101] glass fiber / kg Lignin fiber / kg Polypropylene fiber / kg The quality ratio of the three Example 21 35 17.5 17.5 2:1:1 Example 22 35 21 14 2.5:1.5:1 Example 23 35 23.3 11.7 3:2:1 Example 24 21 35 14 1.5:2.5:1 Example 25 49 7 14 3.5:0.5:1

[0102] Examples 26-27

[0103] The difference between Examples 26-27 and Example 22 is that the reinforcing fibers were modified, and the modification methods were derived from Preparation Examples 15-16, respectively. The remaining steps were the same as in Example 22.

[0104] Example 28

[0105] The difference between Example 28 and Example 26 is that hollow glass microspheres were not added, while the rest of the steps are the same as in Example 26.

[0106] Comparative Example

[0107] Comparative Example 1

[0108] The difference between Comparative Example 1 and Example 5 is that the recycled coarse aggregate and recycled fine aggregate were not modified by the modified liquid, while the remaining steps were the same as in Example 5.

[0109] Comparative Example 2

[0110] The difference between Comparative Example 2 and Example 5 is that no epoxy resin emulsion was added, while the rest of the steps were the same as in Example 5.

[0111] Performance testing

[0112] Detection methods

[0113] Referring to GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete", concrete products were made into several standard cubic test blocks with a side length of 150mm, cured at room temperature, and tested for crack resistance, compressive strength and splitting tensile strength.

[0114] The crack resistance was tested according to the following method: The crack resistance of recycled aggregate concrete was tested according to GB / T50082-2009, and the total crack area per unit area (mm²) of the recycled aggregate concrete after 28 days was measured. 2 / ㎡), the test results are shown in Table 3.

[0115] Compressive strength test: The 28-day compressive strength of the concrete provided in Example 128 and Comparative Example 12 was tested in accordance with the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete GB / T50081-2002". The test results are shown in Table 3.

[0116] Splitting strength: The 28-day splitting strength of the concrete provided in Example 128 and Comparative Example 12 was tested in accordance with GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete".

[0117] After aging tests on the concrete prepared in Examples 1-28 and Comparative Examples 1-2, the total crack area, splitting tensile strength, and compressive strength were measured after 28 days. The aging conditions were as follows: the concrete specimens were placed in an ultraviolet aging chamber with an ultraviolet intensity of 210 W / m². 2 The aging temperature was 60℃, the UV aging time was 1 day, then it was immersed in water and frozen at -20℃ for 1 day, and the cycle was repeated 14 times.

[0118] Table 3 Performance tests of concrete in Example 128 and Comparative Example 12

[0119]

[0120]

[0121]

[0122] Based on the data from Examples 1-3 and Table 3, it can be seen that the recycled aggregate concrete prepared in Examples 1-3 has high compressive strength and splitting strength. The 28-day compressive strength reaches above 44.3 MPa and the 28-day splitting strength reaches above 7.3 MPa. Compared with recycled aggregate concrete that has not undergone aging tests, the total crack area of ​​the recycled aggregate concrete that has undergone aging tests is slightly increased, and the compressive strength and splitting strength are slightly decreased, which proves that the recycled aggregate concrete prepared in this application has good durability.

[0123] Based on the data from Examples 3-5 and Table 1, it can be seen that the recycled aggregate concrete prepared in Example 5 has better crack resistance, compressive strength, and splitting strength, indicating that the modified recycled coarse aggregate and modified recycled fine aggregate prepared in Example 3 have better performance.

[0124] Based on the data from Examples 5-7 and Table 3, it can be seen that chitosan-modified recycled aggregate, when combined with epoxy resin, can significantly improve the crack resistance, compressive strength, and splitting strength of concrete. Furthermore, the durability of concrete made from recycled aggregate that has not been modified with chitosan or has been modified with carboxymethyl cellulose is significantly reduced.

[0125] Combining the data from Examples 5 and 8 and Table 3, it can be seen that adding acetic acid during the modification of recycled aggregate can improve the performance of recycled aggregate, thereby improving the crack resistance of concrete. This is mainly because acetic acid provides a certain dissolution environment for chitosan and can also alleviate the alkali-aggregate reaction.

[0126] Based on the data from Examples 5, 9-11, and Table 3, it can be seen that when bentonite, nano-silica, and nano-zirconia are combined and filled into recycled aggregate, and when combined with chitosan and epoxy resin, they can improve the crack resistance, compressive strength, splitting resistance, and durability of concrete.

[0127] Based on the data from Examples 5, Examples 12-16, and Table 3, it can be seen that Example 15 exhibits better crack resistance, mechanical properties, and durability. Specifically, when the mass ratio of nano-zirconia, bentonite, and nano-silica is 6:5:3, they can effectively exert their synergistic effect, resulting in better performance of concrete made from the modified recycled aggregate.

[0128] Based on the data from Examples 15 and 17 and Table 3, it can be seen that when the particle size of the modified recycled coarse aggregate is 20-40 mm and the particle size of the modified recycled fine aggregate is 5-20 mm, the mechanical properties of the prepared concrete are better.

[0129] Based on the data from Examples 15, 18-20, and Table 3, it can be seen that when glass fiber, lignin fiber, and polypropylene fiber, three types of reinforcing fibers with different elasticities and roughnesses, are mixed together and incorporated into concrete, they can work together to form a multi-directional three-dimensional network support system in the concrete, thereby increasing the crack resistance, mechanical properties, and durability of the concrete.

[0130] Based on the data from Examples 15, 21-25, and Table 3, it can be seen that when the mass ratio of glass fiber, lignin fiber, and polypropylene fiber is (2-3):(1-2):1, they can fully exert their synergistic effect and significantly enhance the compressive strength and durability of concrete.

[0131] Based on the data from Examples 22, 26-27, and Table 3, it can be seen that the reinforcing fibers modified with silane coupling agent KH550 can significantly improve the compressive strength and durability of concrete.

[0132] Based on the data from Examples 22 and 28 and Table 3, it can be seen that hollow glass microspheres can improve the compressive strength and durability of concrete.

[0133] Based on the data from Examples 5, 6-7, Comparative Examples 1-2, and Table 1, it can be seen that the modified liquid prepared in this application can significantly improve the performance of recycled aggregate. In this application, bentonite, nano-silica, and nano-zirconia are filled into the recycled aggregate in combination to improve its viscosity and density. Chitosan and epoxy resin are then added to further improve the viscosity of the recycled aggregate and reduce its permeability, thereby improving the crack resistance, mechanical properties, and durability of the recycled aggregate concrete.

[0134] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A durable recycled aggregate concrete, characterized in that: It is made from the following raw materials in parts by weight: 80-100 parts modified recycled coarse aggregate, 30-40 parts modified recycled fine aggregate, 20-30 parts recycled micro powder, 30-40 parts cement, 10-15 parts fly ash, 10-15 parts mineral powder, 60-70 parts reinforcing fiber, 1-2 parts water-reducing agent, 20-25 parts water and 15-20 parts epoxy resin emulsion; Both the modified recycled coarse aggregate and the modified recycled fine aggregate are obtained by soaking in the modifying solution for 5-6 hours and then drying. The modifying solution is made from the following raw materials in parts by weight: 8-10 parts chitosan, 6-8 parts acetic acid, 100-120 parts water, 20-30 parts nano zirconium oxide, 20-30 parts nano silica and 10-20 parts bentonite.

2. The durable recycled aggregate concrete according to claim 1, characterized in that: The mass ratio of nano-zirconia, bentonite, and nano-silica is 6:5:

3.

3. The durable recycled aggregate concrete according to claim 1, characterized in that: The modified recycled coarse aggregate has a particle size of 20-40 mm, and the modified recycled fine aggregate has a particle size of 5-20 mm.

4. The durable recycled aggregate concrete according to claim 1, characterized in that: The reinforcing fibers include glass fibers, lignin fibers, and polypropylene fibers.

5. The durable recycled aggregate concrete according to claim 4, characterized in that: The mass ratio of the glass fiber, lignin fiber and polypropylene fiber is (2-3):(1-2):

1.

6. The durable recycled aggregate concrete according to claim 5, characterized in that: The reinforcing fibers also undergo the following modification steps: The modified reinforcing fiber was obtained by immersing the reinforcing fiber in a solution of silane coupling agent KH550 and allowing it to stand and dry.

7. The durable recycled aggregate concrete according to claim 1, characterized in that: It also contains 10-20 parts of hollow glass microspheres.

8. A method for preparing durable recycled aggregate concrete as described in any one of claims 1-7, characterized in that: Includes the following steps: S1: After uniformly mixing recycled micro powder, cement, fly ash, and mineral powder, add water-reducing agent, water, and epoxy resin emulsion, and stir thoroughly to obtain precast concrete; S2: After uniformly mixing modified recycled coarse aggregate, modified recycled fine aggregate and reinforcing fiber, a blend is obtained; then the blend is added to precast concrete and stirred evenly to obtain recycled aggregate concrete.

Images