Quick-setting recycled concrete for emergency repair and construction and preparation method thereof

Abstract

The present invention discloses a quick-setting recycled concrete for emergency repair and construction and a preparation method thereof. The method comprises weighing water, cement, fly ash, natural river sand, recycled coarse aggregate, a water reducer, a liquid alkali-free quick-setting agent, and copper-plated steel fiber, uniformly mixing the cement and fly ash to obtain a cementitious material, reserving a portion of the water, mixing the natural river sand and the cementitious material and dry-mixing them, then adding the remaining water and the water reducer and stirring, then adding the copper-plated steel fiber and recycled coarse aggregate and stirring, adding the liquid alkali-free quick-setting agent and the reserved water to the obtained mixture and stirring to obtain a gel-state concrete mixture, placing the gel-state concrete mixture into a mold, vibrating it, letting it stand, demoulding it, and curing it to obtain a quick-setting recycled concrete for emergency repair and construction. The quick-setting recycled concrete of the present invention has the advantages of short setting time, high mechanical strength, stable chemical properties, etc., and has good economy and environmental protection.

Description

Technical Field

[0001] The invention belongs to the technical field of building engineering materials, and particularly relates to a quick-setting recycled concrete used for emergency repair and construction and a preparation method thereof. Background Art

[0002] my country's emergency repair sector faces dual challenges: First, achieving rapid concrete formation within 3 hours within the 72-hour post-disaster rescue window; second, addressing key bottlenecks such as the inefficient transportation of traditional building materials (aggregate transportation accounts for over 60% of transport costs) and high environmental impact in areas with traffic disruption. In particular, for emergency scenarios like clearing collapsed roads and plugging dam pipe bursts, the existing material setting control system (initial setting 4-12 hours, final setting 12-24 hours) lags significantly behind the time-sensitive requirements of emergency projects.

[0003] Recycled concrete is a concrete material made by recycling crushed concrete waste, then screening and processing it to replace a portion of natural aggregate. It is environmentally friendly, but its curing time and strength still fall short of the requirements for applications in special environments where construction is urgently needed. Traditional quick-setting concrete, commonly used for shotcreting, has extremely poor fluidity. After the use of an accelerating setting agent, it instantly loses its fluidity and can solidify on the bottom of some steep slopes or walls. If this concrete is poured into a mold, it will solidify instantly at the pouring point and will not flow on its own to fill the mold. Therefore, traditional quick-setting concrete cannot be used in conventional projects to cast concrete according to mold patterns.

[0004] In summary, the development of a quick-setting recycled concrete suitable for emergency repair and construction has important practical significance for improving construction efficiency, reducing resource waste and making full use of waste concrete resources. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a quick-setting recycled concrete for emergency repair and construction, which has short setting time, high mechanical strength, stable chemical properties, excellent economy and environmental protection, and a preparation method thereof.

[0006] In order to solve the above technical problems, the present invention proposes the following technical solutions.

[0007] A method for preparing quick-setting recycled concrete for emergency repair and construction comprises the following steps:

[0008] (1) Weigh the raw materials according to the following mass parts: 192 to 195 parts of water, 642 to 643 parts of cement, 98 to 99 parts of fly ash, 723 to 724 parts of natural river sand, 523 to 524 parts of recycled coarse aggregate, 3.1 to 3.2 parts of water reducer, 44.4 to 44.5 parts of liquid alkali-free quick-setting agent, and 77.8 to 78.1 parts of copper-coated steel fiber;

[0009] (2) Mix cement and fly ash evenly to obtain cementitious material; reserve a portion of water, which is recorded as ,but Satisfies the following formula (I):

[0010] Formula (I)

[0011] Where: The reserved water, unit is kg / m 3 concrete, C Cement consumption, unit is kg / m 3 concrete, T The construction temperature is in °C, 0 °C ≤ T ≤45℃ (preferably 5℃≤ T ≤45℃) t is the stirring time, in seconds, t ≤3600s;

[0012] The natural river sand and the cementitious material are mixed and dry-mixed, and then the remaining water and the water reducing agent are added, wherein the remaining water is the total water minus the reserved water, and the mixture is stirred once, and then the copper-coated steel fiber and the recycled coarse aggregate are added and stirred twice to obtain a mixture; wherein the total time of the first and second stirring is t in formula (I);

[0013] (3) Add liquid alkali-free quick-setting agent and the reserved water to the mixture , stirring for 20s to 45s to obtain a concrete mixture in a gel state;

[0014] (4) The gel-state concrete mixture is placed in a mold and vibrated, and after standing, demoulding, and curing, a quick-setting recycled concrete for emergency repair and construction is obtained.

[0015] In the above-mentioned method for preparing quick-setting recycled concrete for emergency repair and construction, preferably, in step (1), the liquid alkali-free quick-setting agent meets the implementation standard GB / T 35159-2017, and the liquid alkali-free quick-setting agent includes an FSA-AF type liquid alkali-free quick-setting agent. The liquid alkali-free quick-setting agent has an appearance of a white to light yellow liquid.

[0016] In the above-mentioned method for preparing quick-setting recycled concrete for emergency repair and construction, preferably, in step (1), the copper-plated steel fiber meets the implementation standard JT / T 524-2019, the length of the copper-plated steel fiber is 12 mm to 15 mm, the diameter of the copper-plated steel fiber is 0.18 mm to 0.3 mm, and the tensile strength of the copper-plated steel fiber is greater than 3000 MPa. The copper-plated steel fiber has a smooth surface and a brass-colored appearance.

[0017] In the above-mentioned method for preparing quick-setting recycled concrete for emergency repair and construction, preferably, in step (1), the recycled coarse aggregate is obtained by crushing, screening, washing and drying discarded ordinary natural aggregate concrete, and the recycled coarse aggregate has the following characteristics: 0<moisture content ≤0.5%, 9.7%≤water absorption ≤11.3%, 0<particle size ≤31.5mm;

[0018] The characteristics of the discarded ordinary natural aggregate concrete are: the standard curing strength after 28 days reaches more than 50 MPa; if the components are calculated by mass, they include 402 to 403 parts of ordinary Portland cement, 100 to 101 parts of pulverized coal, 729 to 730 parts of natural river sand, 1048.5 to 1050.5 parts of natural crushed stone, 1.0 to 1.2 parts of water reducer, 161 to 162 parts of water, and a water-cement ratio of 0.32.

[0019] In the above-mentioned method for preparing quick-setting recycled concrete for emergency repair and construction, preferably, in step (1), the natural river sand has the following characteristics: 0.08mm < particle size ≤ 0.16mm accounts for 13% ± 5%, 0.16mm < particle size ≤ 0.5mm accounts for 20% ± 5%, 0.5mm < particle size ≤ 1.00mm accounts for 23% ± 5%, 1mm < particle size ≤ 1.6mm accounts for 33% ± 5%, and 1.6mm < particle size ≤ 2mm accounts for 11% ± 5%.

[0020] In the above-mentioned method for preparing quick-setting recycled concrete for emergency repair and construction, preferably, in step (1), the water reducer is a polycarboxylate water reducer, the water reduction rate of the polycarboxylate water reducer is 25% to 29%, the cement is ordinary Portland cement, the ordinary Portland cement includes PO42.5 ordinary Portland cement, and the fly ash is Class I fly ash. The polycarboxylate water reducer is a white powdery particle with a solid content of 99%. Class I fly ash is in the form of spherical particles (fly ash microbeads) with a specific surface area of ​​1280m 2 / kg, water requirement is 98%, and sphere density is 2.25g / cm 3 The content of spherical particles is 90%, the fineness is 12%, the loss on ignition is 2.34%, and the strength activity index is 86%.

[0021] In the above-mentioned method for preparing quick-setting recycled concrete for emergency repair and construction, preferably, in step (2), the dry mixing time is 2 minutes to 4 minutes, the primary mixing time is 2 minutes to 4 minutes, and the secondary mixing time is 3 minutes to 5 minutes.

[0022] In the above-mentioned method for preparing quick-setting recycled concrete for emergency repair and construction, preferably, in step (4), the vibration time is 30s to 45s, the standing time is 23h to 24h, and the curing time is 1 day to 3 days.

[0023] As a general technical concept, the present invention also provides a quick-setting recycled concrete for emergency repair and construction prepared by the above-mentioned method for preparing the quick-setting recycled concrete for emergency repair and construction.

[0024] In the present invention, the recycled coarse aggregate can be prepared by, but is not limited to, manually screening discarded ordinary natural aggregate concrete (with a strength of 50 MPa or above) to select solid blocks of good quality, removing impurities such as needle-like flakes, wood chips, cement mortar blocks, and other components, crushing them into aggregates of different particle sizes using a jaw crusher, sieving the aggregates using standard square hole sieves of different particle sizes, and repeatedly washing to remove surface dust, impurities and other surface attachments, and then airing and drying them to obtain recycled coarse aggregate.

[0025] Glossary:

[0026] Sand ratio: mass percentage of natural river sand / (natural river sand + recycled coarse aggregate).

[0027] Rapid setting: Ordinary concrete may take several hours from pouring to hardening, but rapid setting concrete shortens this time. Rapid setting represents the performance of setting time. Compared with ordinary concrete, if it has a faster setting time, it is said to have rapid setting.

[0028] Compared with the prior art, the advantages of the present invention are:

[0029] (1) The present invention provides a method for preparing quick-setting recycled concrete for emergency repair and construction. The method adopts a staged quantitative water control process, which enables the concrete to not only set quickly but also obtain high fluidity in a short period of time. This solves the problem of extremely poor fluidity of traditional quick-setting concrete, making the recycled concrete of the present invention more conducive to the construction and pouring of ordinary projects compared to ordinary concrete or quick-setting concrete. Compared with existing conventional concrete, the recycled concrete prepared by the present invention significantly reduces the setting time and is more resource-saving and has higher strength. The initial setting time of the recycled concrete of the present invention is only within 25 minutes, the final setting time is within 35 minutes, and the strength after standard curing for 3 days can reach more than 44MPa, making it more suitable for the requirements of rapid emergency repair and construction of damaged buildings required by engineering construction.

[0030] Traditional quick-setting concrete is generally used for spraying concrete due to its poor fluidity. After using the quick-setting agent, it loses its fluidity instantly and solidifies on the bottom surface of some large slopes or walls. If this concrete is poured into a mold, it will solidify instantly at the pouring point and cannot flow on its own to fill the mold to complete the casting. Therefore, it cannot be used in conventional projects to cast concrete according to the mold style. The quick-setting recycled concrete of the present invention adopts a staged quantitative water control process to enable the concrete to obtain great fluidity in a short time. By the method shown in formula (I), V 1 The reserved water volume formula accurately controls the fluidity and comprehensively considers the variable construction temperature of the on-site construction environment. T (℃), stirring time t (s) and cement dosage C Compared with ordinary concrete or quick-setting concrete, the recycled concrete of the present invention has better construction performance and workability than conventional quick-setting concrete, making it more suitable for construction.

[0031] The recycled concrete prepared by the present invention is different from the low-strength recycled concrete of the past. The recycled concrete of the present invention has excellent mechanical properties while being quick-setting. Due to the natural disadvantage of recycled concrete, namely the relatively weak bonding area between the recycled aggregate and the new and old mortar, the strength of recycled concrete is inferior to that of natural aggregate concrete. However, the present invention uses copper-plated steel fibers and a staged water control process to increase crack resistance while greatly improving the tensile strength, toughness and early strength of the concrete. In the preparation process of the present invention, cement and fly ash are evenly mixed to obtain a cementitious material. The subsequent addition of water allows the hydration products (calcium aluminate, calcium hydroxide, calcium silicate, etc.) formed by the cementitious material to effectively fill the rough holes on the recycled aggregate, so that the cement matrix is ​​tightly combined with the recycled coarse aggregate, the strength is significantly improved, and better mechanical properties are obtained.

[0032] Conventional concrete failure is characterized by severe brittle failure, and fragments shattered upon impact can cause secondary harm to people inside the building. However, the present invention offers a superior failure morphology. Instead of shattering upon failure, the concrete cracks like bulletproof glass, significantly reducing fragmentation. Furthermore, the fluidity provided by the phased, quantitative water control process makes the concrete more compact, significantly improving its impact resistance. This ensures optimal morphology even under high-strain-rate impact loads, significantly minimizing injury and protecting people and equipment within the building.

[0033] (2) To ensure the rational use of the reserved water formula (I), the present invention controls the mixing time to no more than 3600s, which can ensure that the water consumption in the first stage can fully stimulate the cement hydration activity without destroying the designed water-cement ratio of the concrete.

[0034] (3) After adding the liquid alkali-free quick-setting agent and the reserved water to the mixture, the present invention controls the stirring time to 20s to 45s. A stirring time of not less than 20s can ensure that the concrete mixture forms a uniform gelled state. If it exceeds 45 seconds, the fluidity will be greatly reduced under the action of the quick-setting agent.

[0035] (4) The preparation technology process of the present invention can be used for the repair concrete that will appear in the future, which has the characteristics of short setting time, fast strength growth, easy to obtain local materials, and environmentally friendly and low-carbon preparation and construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a SEM image of the quick-setting recycled concrete prepared in Example 1 of the present invention for emergency repair and construction.

[0037] Figure 2 This is the SEM image of the ordinary concrete prepared in Comparative Example 1. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby. The materials and instruments used in the following examples are all commercially available.

[0039] Example 1

[0040] A method for preparing quick-setting recycled concrete for emergency repair and construction of the present invention comprises the following steps:

[0041] (1) Weigh the following raw materials in parts by mass: 192 parts of water, 642.3 parts of cement, 98.46 parts of fly ash, 723 parts of natural river sand, 523.0 parts of recycled coarse aggregate, 3.1 parts of water reducer, 44.5 parts of liquid alkali-free quick-setting agent, and 77.8 parts of copper-coated steel fiber; 1 part by mass is 1 kg, and 1 m³ of concrete is obtained;

[0042] (2) The cement and fly ash weighed in step (1) are mixed evenly to obtain a cementitious material; a portion of water is reserved, and the reserved water is recorded as ,but Satisfies the following formula (I):

[0043] Formula (I)

[0044] Where: The reserved water, unit is kg / m 3 concrete, C Cement consumption, unit is kg / m 3 concrete, T The construction temperature is in °C, 5 °C ≤ T ≤45℃( T It can also be as low as 0℃). t is the stirring time, in seconds, t ≤3600s; In this embodiment, the construction temperature T The temperature is 25℃ and the stirring time is 300s. =48.173kg / m 3 concrete, i.e. 48.173 parts;

[0045] Add natural river sand and cementitious materials into HJW-60 mixing equipment and dry mix for 3 minutes, then add the remaining water and water reducing agent. The remaining water is the total water ( ) minus the reserved water , stirring for 2 minutes, then adding copper-coated steel fiber and recycled coarse aggregate, stirring for 3 minutes to obtain a mixture;

[0046] (3) Add liquid alkali-free accelerator and reserved water to the mixture , stirring for 30 seconds until the concrete mixture is completely in a uniform gel state, thereby obtaining a gel-state concrete mixture;

[0047] (4) The gel-state concrete mixture was placed into a 100mm×100mm×100mm cubic mold and vibrated for 30 seconds. After standing for 24 hours, it was demoulded and placed in a standard curing box for curing to obtain a quick-setting recycled concrete for emergency repair and construction. The microstructure is as follows: Figure 1 shown.

[0048] In step (1) of this embodiment:

[0049] The liquid alkali-free accelerator meets the implementation standard GB / T 35159-2017. The liquid alkali-free accelerator is FSA-AF type liquid alkali-free accelerator, which is commercially available under the brand name Ni I Technology. The liquid alkali-free accelerator appears as a white to pale yellow liquid. In this embodiment, the dosage of the liquid alkali-free accelerator (hereinafter referred to as accelerator) is 6%.

[0050] The calculation formula of the dosage is shown in formula (II):

[0051] Formula (II)

[0052] Among them, A is the amount of liquid alkali-free quick-setting agent, the unit is kg / m³ concrete, C is the amount of cement, the unit is kg / m³ concrete, and F is the amount of fly ash, the unit is kg / m³ concrete.

[0053] Copper-coated steel fiber meets the implementation standard JT / T 524-2019. The length of the copper-coated steel fiber is 12mm~15mm, the diameter of the copper-coated steel fiber is 0.18mm~0.3mm, the surface is smooth, the appearance is brass-colored, and the tensile strength is greater than 3000MPa.

[0054] The water is tap water that meets national standards;

[0055] Recycled coarse aggregate is made from discarded ordinary natural aggregate concrete through crushing, screening, cleaning and drying. The recycled coarse aggregate has the following characteristics: 0<moisture content≤0.5%, 9.7%≤water absorption≤11.3%, 0<particle size≤31.5mm.

[0056] The characteristics of the discarded ordinary natural aggregate concrete are: a 28-day standard curing strength of 50 to 55 MPa; or, its composition, by weight, includes 402.3 parts of ordinary Portland cement, 100.58 parts of fly ash, 723 parts of natural river sand, 1049 parts of natural crushed stone, 1.1 parts of water reducing agent, 161.3 parts of water, and a water-binder ratio of 0.32, but is not limited thereto;

[0057] Natural river sand is naturally salvaged river sand, and natural river sand has the following characteristics: particle size 0.08mm<≤2mm, of which natural river sand with a particle size of 0.08mm~0.16mm accounts for 13%±5%, 0.16mm~0.5mm accounts for 20%±5%, 0.5mm~1.00mm accounts for 23%±5%, 1mm~1.6mm accounts for 33%±5%, and 1.6mm~2mm accounts for 11%±5%.

[0058] The water reducer is polycarboxylate water reducer, which is a white powdery granule with a solid content of 99%. The water reduction rate of polycarboxylate water reducer is 25% to 28%;

[0059] Cement is ordinary Portland cement, and ordinary Portland cement is PO42.5 ordinary Portland cement;

[0060] The fly ash is Class I fly ash.

[0061] In step (4) of this embodiment, a portion of the specimens were taken for compressive strength tests at 3 days, 7 days, and the standard age of 28 days. The results are shown in Table 1.

[0062] Comparative Example 1

[0063] A common concrete, the preparation process of which differs from that of Example 1 in that: 1. the recycled coarse aggregate is replaced by natural gravel coarse aggregate; 2. all the water is added in step (2) instead of being added twice; 3. no liquid alkali-free quick-setting agent and copper-coated steel fiber are added; 4. the mix ratio is different from that of Example 1, namely, 161 parts of water, 402 parts of ordinary Portland cement, 100 parts of pulverized coal, 729 parts of natural river sand, 1049.0 parts of natural gravel coarse aggregate, 1.0 part of water-reducing agent, and the water-cement ratio is 0.32. The microscopic morphology of the common concrete is as follows: Figure 2 shown.

[0064] Depend on Figure 1 and Figure 2 It can be seen that from a microscopic perspective, there is a clear transition zone between the cement mortar matrix and the aggregate of ordinary concrete, while the recycled aggregate concrete of the present invention can tightly combine the cement mortar matrix and aggregate, showing more excellent macroscopic performance. Compared with ordinary concrete, the recycled aggregate concrete of the present invention has better impact mechanical properties. This is because the incorporation of copper-plated steel fibers and the use of a staged quantitative water control process increase its setting time while ensuring its compaction performance. After the cement solidifies, it forms a mechanical bite force with the copper-plated steel fibers, making the copper-plated steel fibers tightly embedded in the cement mortar, which increases the concrete's ductility and tensile strength.

[0065] Comparative Example 2

[0066] A method for preparing recycled aggregate concrete, the preparation process is basically the same as that of Example 1, except that: a staged quantitative water control process is not adopted, and all the water is added in step (2). Due to the lack of this process, after the addition of the accelerator, the mixture instantly loses fluidity, completely loses fluidity, loses the ability to be cast into a mold, and has many internal cavities, exposed aggregates, and the like. The 28d standard compressive strength is only 81.2% of that of Example 1.

[0067] Comparative Example 3

[0068] A method for preparing rapid-setting recycled aggregate concrete is described. The preparation process is essentially the same as in Example 1, except that copper-coated steel fibers are not added. When the copper-coated steel fiber content is reduced by 100% relative to that in Example 1, the 3-day, 7-day, and 28-day strengths decrease by 20%, 12.4%, and 5.3%, respectively. The copper-coated steel fibers in Example 1 exert mechanical interlocking forces, tightly embedding them in the cement mortar and improving the concrete's ductility and tensile strength.

[0069] Example 2

[0070] A method for preparing quick-setting recycled concrete for emergency repair and construction of the present invention is basically the same as that of Example 1, except that the dosage of the quick-setting agent is 7%. Example 3

[0071] A method for preparing quick-setting recycled concrete for emergency repair and construction of the present invention is basically the same as that of Example 1, except that the dosage of the quick-setting agent is 8%.

[0072]

[0073] As shown in Table 1, the 3-day strength of the quick-setting recycled concrete of the present invention can reach 71% of the 28-day compressive strength, demonstrating a certain degree of early strength. As shown in Tables 1 and 2, the quick-setting recycled concrete of the present invention exhibits good early strength and excellent setting properties, making it suitable for practical applications in emergency repair and construction projects.

[0074] The quick-setting recycled concrete prepared in this embodiment for emergency repair and construction also has good workability and meets the technical requirements of the project for concrete. Combined with Table 1 and Table 2, under the premise of meeting the setting time of minutes, it can reach a strength grade of 60 MPa, which is significantly reduced compared to the setting time of several hours of ordinary concrete. In addition, the construction process is simple and easy, which can meet the demand for high-strength concrete in civil concrete projects.

[0075] The above description is only a preferred embodiment of the present invention and does not constitute any formal limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the spirit and technical solution of the present invention, use the methods and technical contents disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing quick-setting recycled concrete for emergency repair and construction, characterized in that: The following steps are involved: (1) Weigh the raw materials according to the following mass parts: 192 to 195 parts of water, 642 to 643 parts of cement, 98 to 99 parts of fly ash, 723 to 724 parts of natural river sand, 523 to 524 parts of recycled coarse aggregate, 3.1 to 3.2 parts of water reducer, 44.4 to 44.5 parts of liquid alkali-free quick-setting agent, and 77.8 to 78.1 parts of copper-coated steel fiber; (2) Mix cement and fly ash evenly to obtain cementitious material; reserve a portion of water, which is recorded as ,but Satisfies the following formula (I): Formula (I) Where: The reserved water, unit is kg / m 3 concrete, C Cement consumption, unit is kg / m 3 concrete, T The construction temperature is in °C, 0 °C ≤ T ≤45℃, t is the stirring time, in seconds, t ≤3600s; The natural river sand and the cementitious material are mixed and dry-mixed, and then the remaining water and the water reducing agent are added, and the remaining water is the total water minus the reserved water, and the mixture is stirred once, and then the copper-plated steel fiber and the recycled coarse aggregate are added and stirred twice to obtain a mixture; wherein the total time of the first and second stirring is the time of the formula (I) t ; (3) Add liquid alkali-free quick-setting agent and the reserved water to the mixture , stirring for 20s to 45s to obtain a concrete mixture in a gel state; (4) The gel-state concrete mixture is placed in a mold and vibrated, and after standing, demoulding, and curing, a quick-setting recycled concrete for emergency repair and construction is obtained.

2. The method for preparing quick-setting recycled concrete for emergency repair and construction according to claim 1, characterized in that: In step (1), the liquid alkali-free quick-setting agent meets the implementation standard GB / T 35159-2017, and the liquid alkali-free quick-setting agent includes FSA-AF type liquid alkali-free quick-setting agent.

3. The method for preparing quick-setting recycled concrete for emergency repair and construction according to claim 1, characterized in that: In step (1), the copper-plated steel fiber meets the implementation standard JT / T 524-2019, the length of the copper-plated steel fiber is 12 mm to 15 mm, the diameter of the copper-plated steel fiber is 0.18 mm to 0.3 mm, and the tensile strength of the copper-plated steel fiber is greater than 3000 MPa.

4. The method for preparing quick-setting recycled concrete for emergency repair and construction according to any one of claims 1 to 3, characterized in that: In step (1), the recycled coarse aggregate is obtained by crushing, screening, washing and drying discarded ordinary natural aggregate concrete. The recycled coarse aggregate has the following characteristics: 0<moisture content≤0.5%,9.7%≤water absorption≤11.3%,0<particle size≤31.5mm; The characteristics of the discarded ordinary natural aggregate concrete are: the standard curing strength after 28 days reaches above 50 MPa.

5. The method for preparing quick-setting recycled concrete for emergency repair and construction according to any one of claims 1 to 3, characterized in that: In step (1), the natural river sand has the following characteristics: Particle size of 0.08mm<≤0.16mm accounts for 13%±5%, particle size of 0.16mm<≤0.5mm accounts for 20%±5%, particle size of 0.5mm<≤1.00mm accounts for 23%±5%, particle size of 1mm<≤1.6mm accounts for 33%±5%, and particle size of 1.6mm<≤2mm accounts for 11%±5%.

6. The method for preparing quick-setting recycled concrete for emergency repair and construction according to any one of claims 1 to 3, characterized in that: In step (1), the water reducer is a polycarboxylate water reducer, the water reduction rate of the polycarboxylate water reducer is 25% to 29%, the cement is ordinary Portland cement, the ordinary Portland cement includes PO42.5 ordinary Portland cement, and the fly ash is Class I fly ash.

7. The method for preparing quick-setting recycled concrete for emergency repair and construction according to any one of claims 1 to 3, characterized in that: In step (2), the dry stirring time is 2 min to 4 min, the first stirring time is 2 min to 4 min, and the second stirring time is 3 min to 5 min.

8. The method for preparing quick-setting recycled concrete for emergency repair and construction according to any one of claims 1 to 3, characterized in that: In step (4), the vibration time is 30s to 45s, the standing time is 23h to 24h, and the curing time is 1 day to 3 days.

9. A quick-setting recycled concrete for emergency repair and construction prepared by the method for preparing quick-setting recycled concrete for emergency repair and construction according to any one of claims 1 to 8.

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