A recycled concrete, its preparation method and application

Abstract

The present invention discloses a recycled concrete, its preparation method and application, belonging to the technical field of solid resource recycling. By mass parts, the raw materials for preparing the recycled concrete provided by the present invention include: 100 parts of cement; 200 - 300 parts of river sand; 250 - 400 parts of recycled coarse aggregate; 0.2 - 0.4 parts of wood fiber; 1 - 3 parts of steel fiber; 15 - 25 parts of modified fly ash; 1 - 2 parts of water reducer; 45 - 60 parts of water; the modified fly ash contains hydroxyl groups and heavy metal complexing groups. The recycled concrete provided by the present invention can effectively improve the compressive strength, splitting resistance, tensile strength, freeze-thaw resistance and dry-wet cycle resistance of the obtained recycled concrete. The present invention also provides a preparation method and application of the above-mentioned recycled concrete.

Description

Technical Field

[0001] The present invention relates to the technical field of solid resource regeneration, and in particular to a recycled concrete, a preparation method thereof, and an application thereof. Background Art

[0002] Recycled concrete is a new type of concrete made by replacing all or part of natural aggregate with recycled aggregate through artificial treatment of waste concrete. The development and use of recycled concrete not only solves the problem of excessive consumption of natural rocks in the process of urban construction and development, but also solves the problem of recycling and treatment of waste construction waste, enables good utilization of waste building materials, and reduces the pollution problem caused by the exploitation of natural rocks. It realizes the harmonious development of the concrete industry and the environment.

[0003] However, compared with the original concrete, the recycled concrete including recycled aggregate has poor performance, especially problems such as large crushing index, low density, and high water absorption. Thus, it seriously limits the application scope of recycled concrete.

[0004] In order to overcome the above technical problems, related technologies have tried to modify the recycled aggregate or tried to mix the recycled concrete. However, the above methods do not significantly improve the performance of recycled concrete. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a recycled concrete, which can effectively improve the compressive strength, splitting resistance, tensile strength, and freeze-thaw resistance of the obtained recycled concrete.

[0006] The present invention also provides a preparation method of the above-mentioned recycled concrete.

[0007] The present invention also provides an application of the above-mentioned recycled concrete.

[0008] The recycled concrete according to the first aspect embodiment of the present invention, by mass parts, the raw materials for preparing the recycled concrete include:

[0009]

[0010] The modified fly ash contains hydroxyl groups and heavy metal complexing groups.

[0011] The recycled concrete according to the embodiments of the present invention has at least the following beneficial effects:

[0012] Research findings show that the main reason for the poor performance of traditional recycled concrete is the insufficient performance of recycled coarse aggregate compared with traditional coarse aggregate. Specifically, there are certain cracks in the recycled coarse aggregate, and it is prone to shrinkage during subsequent use, hydration, and drying processes. As a result, the compactness of the obtained recycled concrete decreases, and there are more internal cracks, ultimately leading to a decline in the mechanical properties such as compressive strength and crack resistance of the obtained concrete, and relatively low additional properties such as impermeability and freeze-thaw resistance.

[0013] In the recycled concrete provided by the present invention, modified fly ash, wood fiber, and steel fiber are added. These materials can fill the gaps in the recycled coarse aggregate, improving the compactness of the obtained recycled concrete.

[0014] The modified fly ash provided by the present invention has certain hydration activity. Therefore, during the subsequent hydration process, hydration can also occur in the gaps of the recycled coarse aggregate. Compared with traditional simple joint filling, it further improves the mechanical properties such as compressive strength of the recycled coarse aggregate.

[0015] Traditional fly ash contains more or less heavy metal ions. The free state of heavy metal ions may affect the environment and organisms, and may also deteriorate the overall performance of the obtained recycled concrete to a certain extent. The modified fly ash provided by the present invention contains heavy metal complexing groups, which can fix heavy metal ions and prevent their free state, thus well solving the above problems.

[0016] Both the wood fiber and the modified fly ash adopted in the present invention contain hydroxyl groups. When these hydroxyl groups encounter water in the concrete, hydrogen bonds will be formed, thereby tightly adsorbing the water on the surface of the wood fiber or fly ash. For these waters to separate, a relatively large external force is required to overcome the hydrogen bonds. Due to the existence of these hydrogen bonds, the recycled concrete hydrates more fully during the maintenance process than ordinary recycled concrete, and more hydration products accumulate on the surfaces of the wood fiber and fly ash. This further improves the interfacial bonding force between the wood fiber, fly ash, and recycled concrete, thereby enhancing the toughness of the obtained recycled concrete.

[0017] The present invention adopts wood fiber and steel fiber. After mixing, a part (one end) of these fibers exists in the gaps of the recycled coarse aggregate, and the other part exists outside the recycled coarse aggregate (such as the cement matrix). Therefore, these fibers can also be regarded as the connection points and anchor points between the recycled coarse aggregate and the recycled concrete matrix, limiting the shrinkage of the recycled coarse aggregate during the hydration process to a certain extent, and improving the bonding strength between the recycled coarse aggregate and the recycled concrete matrix. Ultimately, it significantly improves the overall performance of the obtained recycled concrete.

[0018] According to some embodiments of the present invention, the diameter of the wood fiber is 10~25μm.

[0019] According to some embodiments of the present invention, the length of the wood fiber is 5 to 20 mm. For example, it can specifically be about 10 mm.

[0020] According to some embodiments of the present invention, the diameter of the steel fiber is 10 to 20 μm.

[0021] According to some embodiments of the present invention, the length of the steel fiber is 10 to 20 mm.

[0022] According to some embodiments of the present invention, the residue on a 45-μm sieve of the modified fly ash is ≤ 12%. For example, it can specifically be about 10% or about 8%.

[0023] According to some embodiments of the present invention, the method for obtaining the modified fly ash includes the following steps:

[0024] D1. Subject the raw fly ash to alkali treatment;

[0025] D2. Mix the treatment product obtained in step D1 with a heavy metal chelating agent.

[0026] According to some embodiments of the present invention, in step D1, the alkali treatment includes mixing the fly ash with an alcoholic solution of alkali. The solid-liquid ratio of the fly ash to the alcoholic solution of alkali is 1 g: 3 to 5 mL; for example, it can specifically be about 1 g: 4 mL. The concentration of the alcoholic solution of alkali is 0.1 to 0.5 mol / L; for example, it can specifically be about 0.2 mol / L or about 0.3 mol / L. In the alcoholic solution of alkali, the solute includes at least one of sodium hydroxide and potassium hydroxide; the solvent includes at least one of methanol, ethanol, and isopropanol.

[0027] According to some embodiments of the present invention, in step D1, the duration of the alkali treatment is 3 to 10 min. For example, it can specifically be about 5 min or about 8 min.

[0028] According to some embodiments of the present invention, in step D1, the temperature of the alkali treatment is 30 to 50 °C. For example, it can specifically be about 40 °C.

[0029] According to some embodiments of the present invention, in step D2, the heavy metal chelating agent includes at least one of EDTA, DTPA, HEDTA, NTA, and CDTA.

[0030] According to some embodiments of the present invention, in step D2, the mixing includes mixing the product obtained in step D1 and an aqueous solution of the heavy metal chelating agent, followed by aging and drying. Among them, the solid-liquid ratio of the product obtained in step D1 and the aqueous solution of the heavy metal chelating agent is 0.1-2 g: 100 mL; for example, it can be specifically about 0.5 g: 100 mL, 1 g: 100 mL or about 1.5 g: 100 mL. The concentration of the aqueous solution of the heavy metal chelating agent is 20-50 wt%; for example, it can be specifically about 30 wt% or about 40 wt%. The aging duration is 7-10 days.

[0031] Research has found that in recycled coarse aggregates, the width of cracks is between 5 and 30 μm. The present invention limits the particle size of the above-mentioned preparation raw materials, which can ensure that the above-mentioned preparation raw materials have a gap-filling effect on the recycled coarse aggregates, further ensuring the improvement of the compactness of the obtained recycled coarse aggregates and the overall performance of the obtained recycled concrete.

[0032] According to some embodiments of the present invention, the recycled coarse aggregate is a crushed product of waste concrete.

[0033] According to some embodiments of the present invention, the particle size of the recycled coarse aggregate is 18-25 mm.

[0034] According to some embodiments of the present invention, the method for obtaining the recycled coarse aggregate includes crushing waste concrete, polishing it in a polishing machine, and then performing particle size screening. Among them, the polishing can smooth the edges and corners of the crushed product and improve its stacking density; and under the action of the polishing machine, the crushed product with large cracks will directly crack, avoiding the use of recycled coarse aggregates with large cracks and also avoiding the crushing of the above-mentioned coarse aggregates with large cracks during the concrete mixing process (affecting the grading), thus improving the strength of the recycled concrete.

[0035] In actual production, an appropriate polishing duration can be selected according to the power of the polishing machine, etc. As long as there are no obvious edges and corners in the obtained recycled coarse aggregate.

[0036] According to some embodiments of the present invention, the particle size of the river sand is between 1 and 2 mm. Specifically, it meets the requirements of Class II natural river sand specified in JGJ52. Thus, a particle size grading can be formed with the recycled coarse aggregate, improving the compactness of the obtained recycled concrete.

[0037] According to some embodiments of the present invention, the water reducing agent includes a polycarboxylate water reducing agent.

[0038] According to some embodiments of the present invention, in the preparation raw materials of the recycled concrete, the water-cement ratio is 0.45-0.55. For example, it can be specifically about 0.5. The water-cement ratio is the mass ratio of the water and cement used.

[0039] According to some embodiments of the present invention, in the preparation raw materials of the recycled concrete, the sand ratio is 0.4 to 0.5. For example, it can be specifically about 0.42, 0.43, 0.44 or about 0.45. The sand ratio is the ratio of the river sand to the sum of the masses of the river sand and the recycled coarse aggregate. Within this range, the grading between the river sand and the recycled coarse aggregate can be maximally exerted.

[0040] According to some embodiments of the present invention, in the preparation raw materials of the recycled concrete, the mass ratio of the wood fiber to the steel fiber is 1:8 to 13. For example, it can be specifically about 1:9 or about 1:10. Within this range, the volume ratio of the wood fiber to the steel fiber is close to 1:1. The synergistic effect of the two can be better exerted. Specifically, the wood fiber improves the degree of hydration around the fiber and enhances the toughness of the recycled concrete, and the steel fiber enhances the strength of the recycled concrete.

[0041] According to some embodiments of the present invention, in the preparation raw materials of the recycled concrete, the mass ratio of the modified fly ash to the recycled coarse aggregate is 1:15 to 20. For example, it can be specifically about 1:16, 1:17 or about 1:18. Thereby, the caulking effect of the modified fly ash can be better exerted, and the excess fly ash can also be used as an ultra-fine aggregate to further form a particle size grading with the river sand and the recycled coarse aggregate.

[0042] According to some embodiments of the present invention, in the preparation raw materials of the recycled concrete, the mass ratio of the steel fiber to the recycled coarse aggregate is 1:100 to 300. For example, it can be specifically about 1:110, 1:120, 1:130, 1:150, 1:200 or about 1:250. Thereby, the caulking effect of the wood fiber and the steel fiber can be better exerted, and the toughness and strength of the recycled concrete are better enhanced.

[0043] According to an embodiment of the second aspect of the present invention, a method for preparing the recycled concrete as described above is provided. The preparation method includes the following steps:

[0044] S1. Mix the recycled coarse aggregate, modified fly ash, river sand, wood fiber and steel fiber to obtain a solid mixture;

[0045] S2. Mix the solid mixture with other preparation raw materials of the recycled concrete.

[0046] The method for preparing the recycled concrete according to the embodiment of the present invention has at least the following beneficial effects:

[0047] First, since the preparation method adopts all the technical solutions of the recycled concrete in the above embodiments, it has at least all the beneficial effects brought by the technical solutions in the above embodiments.

[0048] Furthermore, the present invention first prepares a solid mixture by dry mixing, which solves the problem that it is difficult to mix wood fiber, steel fiber, and fly ash evenly due to their too small particle sizes. That is, through the adjustment of the steps in the preparation method of the present invention, the functions of each raw material for preparation are fully exerted.

[0049] According to some embodiments of the present invention, in step S1, the mixing duration for obtaining the solid mixture is 2 to 15 minutes. For example, it can be specifically about 5 minutes or about 10 minutes.

[0050] According to some embodiments of the present invention, step S2 includes first mixing the water and cement to obtain a binder, mixing the solid mixture and the binder, and mixing the resulting mixture and the water reducing agent.

[0051] According to some embodiments of the present invention, the mixing duration for obtaining the binder is 2 to 5 minutes. For example, it can be specifically about 3 minutes.

[0052] According to some embodiments of the present invention, the mixing duration of the solid mixture and the binder is 2 to 5 minutes. For example, it can be specifically about 3 minutes.

[0053] According to some embodiments of the present invention, the mixing duration after adding the water reducing agent is 30 to 120 seconds. For example, it can be about 50 seconds, 60 seconds, 90 seconds, or about 100 seconds.

[0054] According to the embodiments of the third aspect of the present invention, an application of the recycled concrete in road paving and wall construction is provided.

[0055] Since the application adopts all the technical solutions of the recycled concrete in the above embodiments, it has at least all the beneficial effects brought by the technical solutions in the above embodiments.

[0056] Unless otherwise specified, the "about" in the present invention actually means that the allowable error is within the range of ±2%. For example, about 100 is actually 100 ± 2% × 100.

[0057] Unless otherwise specified, "between... and..." in the present invention includes the numerical values. For example, "between 2 and 3" includes the endpoint values 2 and 3.

[0058] Other features and advantages of the present invention will be described in the subsequent specification, and part of them will become obvious from the specification or be understood by implementing the present invention. Detailed Embodiments

[0059] The concept of the present invention and the technical effects produced will be clearly and completely described below in conjunction with embodiments to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0060] In the description of the present invention, the description of reference terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0061] Example 1

[0062] In this example, a recycled concrete was prepared. The specific ingredients are shown in Table 1, and the preparation process is as follows:

[0063] S0. Raw material preparation:

[0064] Prepare recycled coarse aggregate: Crush the waste concrete to a particle size of 30 - 60 mm, polish it in a polishing machine, and then perform particle size screening to select recycled coarse aggregate with a particle size range of 18 - 25 mm.

[0065] Prepare modified fly ash:

[0066] Perform alkali treatment on the original fly ash (purchased from Guangdong Wanrun Building Materials Co., Ltd., with a 45μm sieve residue rate of 10%);

[0067] The specific conditions for the alkali treatment are: Mix fly ash and 0.2 mol / L sodium hydroxide ethanol solution in a ratio of 1 g:4 mL at 35°C for 5 min, perform solid-liquid separation, wash with clear water, and dry.

[0068] Mix the treatment product obtained from the alkali treatment and 30 wt% EDTA aqueous solution in a ratio of 1 g:100 mL, age for 8 days, then perform solid-liquid separation, do not wash, and directly air dry.

[0069] S1. Referring to the dosages in Table 1, mix the recycled coarse aggregate, modified fly ash, river sand, wood fiber, and steel fiber obtained in step S0 for 5 min to obtain a solid mixture;

[0070] Mix water and cement evenly within 3 min to obtain a binder.

[0071] S2. Mix the solid mixture obtained in step S1 and the sizing material for 3 min, and then add a water reducer and continue to mix for 50 s.

[0072] Example 2

[0073] In this example, a recycled concrete was prepared. The specific difference from Example 1 is as follows:

[0074] In step S0, the prepared recycled coarse aggregate was not polished by a polishing machine, and the directly selected one was the crushed product of 18 - 25 mm.

[0075] Example 3

[0076] In this example, a recycled concrete was prepared. The specific difference from Example 1 is as follows:

[0077] In step S0, the residue on a 45μm sieve of the original fly ash used was 43%, and it was purchased from Guangdong Wanrun Building Materials Co., Ltd.

[0078] Comparative Example 1 [[ID=2,2]]

[0079] In this example, a recycled concrete was prepared. The specific difference from Example 1 is as follows:

[0080] During the preparation of fly ash, alkali treatment was not carried out; that is, in the modified fly ash used, the content of hydroxyl groups was low. ]>

[0081] Comparative Example 2

[0082] In this example, a recycled concrete was prepared. The specific difference from Example 1 is as follows:

[0083] The preparation raw materials were different, as shown in Table 1 specifically.

[0084] Comparative Example 3

[0085] In this example, a recycled concrete was prepared. The specific difference from Example 1 is as follows:

[0086] The preparation raw materials were different, as shown in Table 1 specifically.

[0087] Comparative Example 4

[0088] In this example, a recycled concrete was prepared. The specific difference from Example 1 is as follows:

[0089] In the mixing of step S1, wood fibers and steel fibers were not included;

[0090] In step S2, after mixing the solid mixture and the sizing material and before adding the water reducer, add the above-mentioned wood fibers and steel fibers and stir and mix for 5 min.

[0091] Table 1 Selection of preparation raw materials in some examples and comparative examples by weight

[0092] Example 1 Comparative Example 2 Comparative Example 3 Cement 100 100 100 River sand 250 250 250 Recycled coarse aggregate 320 320 320 Wood fiber 0.3 / 2.8 Steel fiber 2.5 2.8 / Modified fly ash 20 20 20 Water reducing agent 1.5 1.5 1.5 Water 50 50 50

[0093] Unless otherwise specified, in Table 1, the cement is ordinary Portland cement;

[0094] The particle size of the river sand is between 1 - 2 mm, and it is Class II natural river sand meeting the requirements of JGJ52;

[0095] The wood fiber is purchased from Langfang Hexiang Building Materials Co., Ltd., with a diameter distribution of 10 - 25 μm and a length distribution of 10 - 20 mm.

[0096] The steel fiber is purchased from Jiangmen Huasheng New Materials Technology Co., Ltd., with a diameter distribution of 10 - 20 μm and a length distribution of 10 - 20 mm.

[0097] Unless otherwise specified, the determination of the diameter and length of the above wood fiber and steel fiber is carried out under SEM electron microscope testing. Specifically, ≥2 fields of view are selected, and ≥100 samples are selected in each field of view; the diameter and length are measured under the electron microscope, and the size distribution range of the corresponding samples is statistically analyzed.

[0098] The water reducing agent is purchased from Hunan Zhongyan Building Materials Technology Co., Ltd., and it is a self - compacting water reducing agent.

[0099] Test Example

[0100] In this example, the concrete obtained from the examples and comparative examples is poured into molds (Mold A: 100 mm × 100 mm × 100 mm; and Mold B: 100 mm × 100 mm × 400 mm) that have been pre - painted with mold release agent in advance, and then placed on a vibrating table for vibration until the concrete surface shows bleeding, and then the pouring surface is leveled, and the specimens are insulated with plastic wrap. After 24 h, the molds are removed and numbered. Finally, the specimens are moved to a curing room at 20 ± 2 °C with a relative humidity greater than 95% for curing for 28 d.

[0101] The specimens obtained from mold A were used to test the compressive strength, splitting tensile strength, freeze-thaw cycle test and sulfate dry-wet cycle test; the specimens obtained from mold B were used to test the flexural performance. Among them, the compressive strength, splitting tensile strength and flexural performance were all tested by a hydraulic servo universal testing machine. The freeze-thaw test was carried out by a rapid freeze-thaw cycle tester according to the method specified in GB / T 50082—2009; the process of one freeze-thaw cycle: the time was 12h, the freezing time was 8h, and the thawing time was 4h. When freezing, it was required that the time for the temperature to drop to -18℃ did not exceed 2h, and the subsequent freezing temperature was maintained at -20℃~-18℃; when thawing, it was required to add water at 18~20℃, and the water surface exceeded the top of the specimen by 2cm, and it was ensured that the water temperature was not lower than 10℃ within 30min after adding water, and the water temperature was maintained at 18~20℃ after 30min; after every 25 cycles, the specimen should be taken out, the surface moisture should be wiped dry, the transverse fundamental frequency of the specimen should be tested, the mass of the specimen should be weighed, and the damage and crack conditions on the surface of the specimen should be recorded. The compressive strength of the concrete specimen after 300 freeze-thaw cycles was tested and recorded, and the compressive strength loss rate was calculated. The sulfate dry-wet cycle test machine was used for testing. The specific method was that one cycle period was 24h, including 15h soaking time (3.5wt% sodium sulfate aqueous solution), 0.5h solution drainage time, 0.5h air drying time, 6h drying time, and 2h cooling time. The drying temperature was 80℃, the cooling temperature was 28℃, and the solution temperature was controlled at 20-25℃; the compressive strength of the concrete specimens after 15 times (basically the strength peak value) and 20 times of dry-wet cycles was recorded.

[0102] The above test results are shown in Table 2.

[0103] Table 2 Performance of concrete obtained from examples and comparative examples

[0104]

[0105] Comparing Example 1 and Example 2, it can be seen that although the recycled coarse aggregate is polished or not and whether there are edges and corners, the overall performance of the obtained recycled concrete is relatively good. However, the polished recycled coarse aggregate has a higher stacking density, no large cracks, and is not easy to break during the later concrete mixing; therefore, the overall performance of the recycled concrete obtained in Example 1 is relatively good.

[0106] Comparing Example 1 and Example 3, it can be seen that the particle size of the fly ash selected in Example 3 is relatively large, and its gap-filling performance for the recycled coarse aggregate is poor. Therefore, the compactness of the prepared recycled concrete is poor, and the overall mechanical properties, freeze-thaw resistance and dry-wet cycle resistance are slightly inferior to those of Example 1.

[0107] Combined with Examples 1 to 3, it can be seen that although the performance of Example 1 is better than that of Examples 2 to 3, since the examples cannot cover all range point values, Example 1 is not necessarily the optimal performance of the recycled concrete provided by the present invention; in actual production, combinations can be made within the range provided by the present invention, and it is expected to obtain recycled concrete with better effects than those of the examples.

[0108] Comparing Example 1 and Comparative Example 1, it can be seen that if the modified fly ash is not alkali-treated, there are fewer hydroxyl groups in the modified fly ash, and thus there are not enough hydroxyl groups to combine with the carboxyl groups in the heavy metal complexing agent. Therefore, the binding force between the heavy metal complexing agent and the modified fly ash is poor, and it may separate from the fly ash during the later mixing process, and cannot prevent the influence of heavy metal ions on the recycled concrete. Further, without enough hydroxyl groups, there are fewer hydration products around the fly ash, that is, the substances filling the gaps in the recycled coarse aggregate have lower strength, significantly reducing the mechanical properties of the recycled concrete.

[0109] Comparing Example 1 and Comparative Examples 2 to 3, it can be seen that single wood fiber and single steel fiber have a relatively small improvement in the overall performance of the recycled concrete. After the two are combined, the synergistic effect can be fully exerted to obtain recycled concrete with better performance. Comparing Comparative Examples 2 to 3, it can be seen that if wood fiber is added alone, the improvement in the compressive strength of the obtained recycled concrete is relatively small, and the splitting compressive performance is more improved. If steel fiber is added alone, the compressive performance is more improved.

[0110] Comparing Example 1 and Comparative Example 4, it can be seen that if the feeding order of the preparation raw materials is changed, it may lead to uneven dispersion of the preparation raw materials and cannot fully exert the gap-filling effect, thereby resulting in a decrease in the overall performance.

[0111] Regarding the results of the dry-wet cycle, considering that the maintenance period of the specimens is only 28 days, there may still be some raw materials inside that have not been fully hydrated; in the preparation raw materials of the examples, due to the gap-filling effect of the modified fly ash, etc., during the initial dry-wet cycle process, the specimens are further hydrated, the internal pores are filled, and the density increases, which improves its compressive ability to a certain extent; however, in the comparative examples, due to the action of sulfates on heavy metal ions, or due to the lack of a suitable gap-filling structure, the compressive strength generally decreases during the dry-wet cycle process.

[0112] In summary, the recycled concrete provided by the present invention can significantly improve the performance in aspects such as compressive strength, splitting tensile strength, flexural strength, freeze-thaw resistance, and dry-wet cycle by optimizing the feeding order of the preparation raw materials, the types of the preparation raw materials, and parameter selection. Due to the above excellent performance, the recycled concrete provided by the present invention can be used as a weighing building, such as for the preparation of roads or building walls.

[0113] The above has made a detailed description of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the relevant art, various changes can be made without departing from the spirit of the present invention. In addition, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

Claims

1. A recycled concrete, characterized in that: The raw materials for preparing the recycled concrete include, by mass: The modified fly ash contains hydroxyl groups and heavy metal complexing groups; the method for obtaining the modified fly ash comprises the following steps: D1. Alkali treatment of the original fly ash; D2. The treated product obtained in step D1 is mixed with a heavy metal chelating agent; the heavy metal chelating agent comprises at least one of EDTA, DTPA, HEDTA, NTA and CDTA; The recycled coarse aggregate is a crushed product of polished waste concrete.

2. The recycled concrete according to claim 1, characterized in that The diameter of the wood fiber is 10 to 25 μm.

3. The recycled concrete according to claim 1, characterized in that The length of the wood fiber is 5 to 20 mm.

4. The recycled concrete according to claim 1, characterized in that The diameter of the steel fiber is 10 to 20 μm.

5. The recycled concrete according to claim 1, characterized in that The length of the steel fiber is 10 to 20 mm.

6. The recycled concrete according to claim 1, characterized in that The 45 μm sieve residue rate of the modified fly ash is ≤12%.

7. The recycled concrete according to claim 1, characterized in that In step D1, the alkali treatment includes mixing fly ash with an alkali alcohol solution.

8. The recycled concrete according to claim 7, characterized in that The concentration of the alkali alcohol solution is 0.1-0.5 mol / L.

9. The recycled concrete according to claim 1, characterized in that The particle size of the recycled coarse aggregate is 18 to 25 mm.

10. The recycled concrete according to claim 1, characterized in that The method for obtaining the recycled coarse aggregate comprises crushing the waste concrete, polishing it in a polishing machine, and then screening the particle size.

11. A method for preparing recycled concrete according to any one of claims 1 to 10, characterized in that: The preparation method comprises the following steps: S1. The recycled coarse aggregate, modified fly ash, river sand, wood fiber and steel fiber are mixed to obtain a solid mixture; S2. mixing the solid mixture with other raw materials for preparing the recycled concrete.

12. Use of the recycled concrete according to any one of claims 1 to 10 in road paving and wall construction.

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