Waste-doped ultra-high performance concrete

Abstract

The invention relates to the field of concrete, and particularly discloses waste-doped ultra-high performance concrete. The concrete is mainly prepared from cement, silica fume, microbeads, fly ash, limestone, regenerated fibers I, regenerated fibers II, a modified water reducer and an expanding agent, the regenerated fibers are prepared from the waste wind driven generator blade shells in the concrete, the regenerated fibers are modified in two different modes, one mode serves as an outer curing agent, and the other mode serves as an inner curing agent. The other one is used as an internal curing agent, and the two regenerated fibers replace steel fibers, so that the compressive strength, bending strength, tensile strength and other mechanical properties are not reduced after the ultra-high performance concrete is cured for 28 days; meanwhile, the self-shrinkage amount of the ultra-high performance concrete is reduced, and the ultra-high performance concrete has good anti-cracking performance.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and more particularly to an ultra-high performance concrete mixed with waste. Background Art

[0002] Concrete is one of the most widely used engineering materials at present. Concrete can be applied to different scenarios according to its strength. Ultra-high performance concrete has high strength, high toughness and low porosity. It uses ordinary Portland cement, fine aggregate, admixtures and steel fiber as main materials, and its compressive strength can reach more than 150MPa. Ultra-high performance concrete can be applied to super high-rise buildings, tunnels and other scenarios.

[0003] While ultra-high performance concrete has significant advantages, it also has the following defects: the addition amount of steel fiber is generally 0.5-2.5%, and the high cost of steel fiber leads to high overall cost of ultra-high performance concrete. At the same time, after ultra-high performance concrete exceeds its service life, steel fiber cannot be recycled, resulting in a waste of resources. Second, the self-shrinkage of ultra-high performance concrete limits its development. Although the addition of steel fiber helps to improve the shrinkage rate of ultra-high performance concrete, due to the limited addition amount of steel fiber, the shrinkage of ultra-high performance concrete increases when it exceeds the established addition amount, which leads to the fact that ultra-high performance concrete is still prone to large shrinkage in the early stage. The serious self-shrinkage problem of ultra-high performance concrete needs to be further improved. Summary of the invention

[0004] The present application provides an ultra-high performance concrete doped with waste, which uses waste to replace ultra-high performance concrete steel fibers while ensuring that the compressive strength and flexural strength of the ultra-high performance concrete are not reduced, so as to reduce the cost of the ultra-high performance concrete; at the same time, the shrinkage rate of the ultra-high performance concrete is greatly improved.

[0005] The present application provides an ultra-high performance concrete doped with waste, which adopts the following technical solution: An ultra-high performance concrete mixed with waste, comprising the following raw materials in parts by weight: 370-430 parts of cement, 200-300 parts of microsilica powder, 100-150 parts of microspheres, 70-80 parts of fly ash, 100-200 parts of limestone, 5-10 parts of recycled fiber 1, 5-20 parts of recycled fiber 2, 1-5 parts of modified water reducing agent and 5-10 parts of expansion agent; Control the water-binder ratio to 0.135-0.165; The preparation methods of the regenerated fiber 1 and the regenerated fiber 2 are as follows: Use discarded wind turbine blade shells, crush and grind them to millimeter level to obtain recycled fibers; Take a part of the regenerated fiber and immerse it in the dopamine solution, keep it warm and stir it at room temperature until the polydopamine layer adheres to the surface of the regenerated fiber, take it out and put it in micron-sized montmorillonite powder, mix it and take it out to obtain regenerated fiber 1; Taking part of the regenerated fiber and immersing it in the oxidant solution, the immersion temperature of the regenerated fiber in the oxidant solution is 50-70°C, the immersion time is 2-6 hours, washing and drying after the immersion is completed, and then placing it in a mixed solution of silane coupling agent and water, heating and stirring, filtering the product, washing with alcohol, and drying to obtain regenerated fiber II; The modified water-reducing agent is a sodium alginate modified polycarboxylic acid water-reducing agent.

[0006] Furthermore, the weight ratio of the regenerated fiber 1 to the regenerated fiber 2 is 1:(1.15-1.5).

[0007] Furthermore, the size of the regenerated fiber 1 is (0.15-0.20) mm×(10-15) mm.

[0008] Furthermore, the size of the regenerated fiber 2 is (0.08-0.12) mm×(6-8) mm.

[0009] Furthermore, the particle size of the montmorillonite powder is 1 to 50 μm.

[0010] Furthermore, in the regenerated fiber preparation step, the regenerated fiber is immersed in the dopamine solution at a temperature of 20 to 25° C., for a time of 24 to 48 hours, and the weight ratio of the regenerated fiber to dopamine is 1:(0.35 to 0.45).

[0011] Furthermore, in the second step of preparing the regenerated fiber, the silane coupling agent is a hydroxy silane coupling agent.

[0012] Furthermore, in the second regenerated fiber preparation step, the weight ratio of the regenerated fiber to the silane coupling agent is 1:(0.3-1), and the mixture is heated to 55-65° C. and kept warm for 6-8 hours.

[0013] Furthermore, the preparation steps of the modified water reducing agent are as follows: Sodium alginate is dissolved in water, the pH value of the sodium alginate solution is adjusted, and then formaldehyde, acrylamide and cyclohexyl isonitrile are added to react at room temperature to obtain modified sodium alginate; The modified sodium alginate and the polyether monomer of the polycarboxylate water reducer are dissolved in water, and an initiator solution, an acrylic acid solution and a sodium methacrylate sulfonate solution are added dropwise, and the mixture is kept warm at 60 to 75° C. for 2 to 4 hours, and the pH value of the reaction system is adjusted to 7 to obtain a sodium alginate-polycarboxylate water reducer.

[0014] Furthermore, the water-to-binder ratio is 0.15.

[0015] Furthermore, the cement is P.O52.5, and the 28d mortar strength is 61.7MPa.

[0016] Furthermore, the weight ratio of the cement, microsilica powder, microbeads, fly ash, limestone, recycled fiber 1, recycled fiber 2, modified water reducing agent and expansion agent is 400:200:150:75:150:8:12:5:10.

[0017] Based on the above scheme, this application has at least the following advantages: First, the present application uses discarded wind turbine blade shells as recycled fibers, and the recycled fibers replace steel fibers. The recycled fibers are modified in two different ways and then added to concrete. This can reduce the cost of ultra-high performance concrete and ensure that the 28d compressive strength of ultra-high performance concrete reaches more than 150MPa, and the autogenous shrinkage rate is reduced, which is convenient for later maintenance. The reasons are as follows: the shell of the discarded wind turbine blade is mainly composed of epoxy resin and glass fiber; the regenerated fiber is crushed to millimeter-level specifications, and the surface of part of the regenerated fiber is treated with polydopamine and montmorillonite in turn to obtain regenerated fiber 1, and the surface of another part of the regenerated fiber is treated with aminosilane coupling agent after excessive oxidation etching to obtain regenerated fiber 2; Recycled fiber 1 and recycled fiber 2 form a staggered three-dimensional network structure inside the concrete, which can serve as a skeleton during the shrinkage process of the concrete. Both recycled fiber 1 and recycled fiber 2 can effectively absorb and disperse the stress inside the concrete. At the same time, they can bridge the cracks and share part of the tensile stress, limit the aggregation and expansion of micro cracks inside the concrete, and improve the tensile strength of the concrete. The density of the regenerated fiber is high, close to the density of materials such as fly ash and silica fume, and it is not easy to have the problem of sedimentation and agglomeration during the hydration process; the surface of the regenerated fiber is impregnated with a dopamine solution to form a polydopamine layer. The hydroxyl groups rich in the polydopamine layer can react with montmorillonite through hydrogen bonds, so that the montmorillonite adheres to the surface of the regenerated fiber; montmorillonite can react with calcium ions in concrete to form a stable calcium-montmorillonite complex, which improves the bonding strength between the surface of the regenerated fiber and the interface of the cement gel material; the flaky structure of montmorillonite can hinder the heat transfer between cement particles to reduce the evaporation of water in the early hydration process of concrete, thereby reducing the possibility of early self-shrinkage and cracking of concrete; at the same time, the regenerated fiber can also be used as an internal curing agent. The polydopamine layer and montmorillonite of the regenerated fiber can absorb free water. When the concrete is in a low water-cement ratio environment, the water stored in the regenerated fiber is released, which provides sufficient power for the complete hydration of the cementitious material during the cement hydration process, reducing the possibility of early self-shrinkage of the concrete; The surface of the regenerated fiber 2 is oxidatively etched. On the one hand, the weight of the regenerated fiber can be reduced after oxidative etching, and the regenerated fiber 2 can easily float on the surface of the ultra-high performance concrete. Since a polysilane film layer is attached to the surface of the regenerated fiber 2, and the silane chain segments in the polysilane film layer have a certain hydrophobicity, the regenerated fiber 2 can be used as an external curing agent to hinder the large-scale evaporation of water in the late hydration period of the ultra-high performance concrete, increase the possibility of reducing the self-shrinkage of the concrete in the late period, and reduce the difficulty of curing the ultra-high performance concrete. On the other hand, there are active groups such as grooves and hydroxyl groups on the surface of the regenerated fiber 2, which can connect with the concrete gel material through hydrogen bonds, thereby improving the bonding strength between the interface of the regenerated fiber and the gel material; a slight meshing structure is formed between the regenerated fiber 2 and the concrete gel material, thereby improving the compressive strength of the ultra-high performance concrete. Recycled fiber 1 / 2, cement and fly ash, microsilica powder, limestone and microspheres and other fine aggregates of different grades are compounded. Based on the principle of closest packing, the compressive strength of ultra-high performance concrete can reach 175MPa.

[0018] Second, the size and ratio of the regenerated fiber 1 / 2 are optimized in the present application. Since the regenerated fiber 1 / 2 adopts two different sizes, the size of the regenerated fiber 1 is larger than that of the regenerated fiber 2, and the size ratio of the two is adjusted. The size of the regenerated fiber 1 is large, and the content of montmorillonite that can be adsorbed on the surface is increased. Under the premise of not affecting the internal fluidity of the concrete, it helps to improve the completeness of the hydration of the later gel material and reduce the content of incompletely hydrated cement in the concrete; while the size of the regenerated fiber 2 is small, the fluidity of the external material of the concrete is excellent, and the regenerated fiber 2 can be fully dispersed on the outside of the concrete, which helps to fill the external pores of the concrete, thereby improving the overall compressive strength of the concrete.

[0019] Third, the water-cement ratio and the selection of the water-reducing agent are optimized in this application. At a lower water-cement ratio, the sodium alginate-polycarboxylate water-reducing agent has a larger conformation size in the aqueous solution compared with the ordinary polycarboxylate water-reducing agent, which hinders the adsorption of the water-reducing agent between the montmorillonite layers. The water-reducing agent can still play a viscosity-reducing role, and the concrete maintains excellent fluidity. DETAILED DESCRIPTION

[0020] Unless otherwise specified, the sources of the raw materials used in the examples and comparative examples of this application are as follows: Cement: PO 52.5, origin: Hebei, specific surface area (Blaine method) 362m 2 / kg; Microsilica fume: Origin: Qinghai, silica content 93%, specific surface area (BET method) 18.4m 2 / g; Microbeads: Origin: Jiangsu, specific surface area (BET method) 5.7m 2 / g; Fly ash: Origin: Hebei, specific surface area: 899m 2 / kg; Limestone: Origin: Hebei, specific surface area 440m 2 / kg; Montmorillonite: Origin: Hebei; Expansion agent: Model II, magnesium oxide expansion agent, sourced from Wuhan Sanyuan; Discarded wind turbine blade shell: recycled material, the main material is epoxy resin impregnated glass fiber.

[0021] A sodium alginate-polycarboxylate water reducer is prepared according to the following method: Take 400g of sodium alginate and dissolve it in 16kg of water, and continue stirring until the sodium alginate is completely dissolved; use a 0.5mol / L hydrochloric acid solution to adjust the pH value of the sodium alginate solution to 3.6, then add 11g of formaldehyde, 26g of acrylamide and 400g of cyclohexyl isonitrile in sequence, and stir and react at 25°C for 24h to obtain modified sodium alginate; Take 75kg TPEG2400 and 200g modified sodium alginate and stir to dissolve in 50kg water; prepare an ammonium persulfate solution with an initiator concentration of 4wt%, an acrylic acid solution with a concentration of 10wt% and a sodium methacrylate sulfonate solution with a concentration of 0.7wt% for standby use; when the reaction starts, heat TPEG2400 and modified sodium alginate to 60°C, and simultaneously drip the ammonium persulfate solution, acrylic acid solution and sodium methacrylate sulfonate solution into the reaction system, and control the dripping time to be 120min. After the dripping is completed, heat to 75°C, keep warm for reaction for 3h, and when the reaction is finished, adjust the pH of the reaction system to 7 with 30% NaOH solution to obtain sodium alginate-polycarboxylic acid water reducer. Example Example

[0022] An ultra-high performance concrete mixed with waste is made according to the following proportions: Preparation of recycled fiber 1 / 2: The discarded wind turbine blade shell is cleaned and dried after cleaning. The blade shell is first cut in an industrial glass fiber reinforced plastic mechanical crushing device, and then put into a mobile crusher for crushing. After crushing, it is sieved to screen out recycled fibers with a size of (0.15-0.20) mm×(10-15) mm and a size of (0.08-0.12) mm×(6-8) mm; A tris(hydroxymethylaminomethane)-hydrochloric acid buffer solution with a pH value of 8.5 is prepared in advance for use; dopamine hydrochloride is added to the tris(hydroxymethylaminomethane)-hydrochloric acid buffer solution to prepare a dopamine solution with a concentration of 4 g / L for use; regenerated fibers with a size of (0.15-0.20) mm×(10-15) mm are taken, and the regenerated fibers are put into the dopamine solution at 20° C., and the weight ratio of the regenerated fibers to dopamine is controlled to be 1:0.4, and the immersion time is 24 hours. After the immersion is completed, the fibers are taken out, and the size of the montmorillonite powder is 1-50 μm. The regenerated fibers and the montmorillonite powder are continuously shaken and mixed for 1 minute to obtain a regenerated fiber 1; since the thickness of the montmorillonite powder and the polydopamine layer is relatively thin, the size change of the regenerated fiber 1 can be ignored; Take regenerated fiber with a size of (0.08-0.12) mm×(6-8) mm and set aside; put potassium permanganate into deionized water to prepare an oxidant solution with a concentration of 0.5wt%; put the regenerated fiber into the oxidant solution and soak it, control the weight ratio of the regenerated fiber to potassium permanganate to be 1:0.02, the soaking temperature to be 60°C, the soaking time to be 4h, take it out and wash and dry it; mix the regenerated fiber, hydroxy silane coupling agent KH570 and deionized water according to a weight ratio of 1:0.5:300, heat it to 60°C after mixing, keep it warm for 6h to obtain regenerated fiber 2; oxidation etching and polysilane coating on the surface of regenerated fiber 2 have almost no effect on its size change; Mixing: Take 400kg cement PO 52.5, 200kg microsilica, 150kg microspheres, 75kg fly ash, 150kg limestone, 8kg recycled fiber 1, 12kg recycled fiber 2, 5kg modified water reducer and 10kg expansion agent, and adjust the water-cement ratio to 1:0.15; Put cement, microsilica powder, microbeads, fly ash, limestone and expansive agent into a dry mixer and mix for 2 minutes, then add 1 / 2 of water and modified water reducer to the dry mixture, stir evenly, then add the remaining 1 / 2 of water and modified water reducer, mix evenly to obtain ultra-high performance concrete mortar, the ultra-high performance concrete mortar is mixed with recycled fiber 1 and recycled fiber 2, poured after mixing, and cured according to the method specified in the national standard, and ultra-high concrete is obtained after curing.

[0023] Embodiment 2-4 An ultra-high performance concrete doped with waste is different from Example 1 in that the sizes of the recycled fiber 1 and the recycled fiber 2 are different, as follows: In Example 2, the size of the regenerated fiber 1 is (0.1-0.15) mm×(30-50) mm, and the size of the regenerated fiber 2 is (0.05-0.1) mm×(10-15) mm; In Example 3, the size of the regenerated fiber 1 is (0.50-0.60) mm×(10-15) mm, and the size of the regenerated fiber 2 is (0.20-0.25) mm×(6-8) mm; In Example 4, the size of the regenerated fiber 1 is (0.08-0.12) mm×(6-8) mm, and the size of the regenerated fiber 2 is (0.15-0.20) mm×(10-15) mm. Example

[0024] An ultra-high performance concrete doped with waste, which is different from Example 1 in that the montmorillonite powder in the regenerated fiber 1 is different, as follows: In Example 5, the montmorillonite powder is 500 to 1000 nm; In Example 6, the montmorillonite powder is 100 to 200 μm.

[0025] Embodiment 7-9 An ultra-high performance concrete doped with waste is different from Example 1 in that the addition amount of each component and the corresponding water-binder ratio are different, as follows: In Example 7, in the mixing step: 430 kg of cement PO 52.5, 300 kg of microsilica powder, 150 kg of microspheres, 80 kg of fly ash, 200 kg of limestone, 10 kg of regenerated fiber 1, 20 kg of regenerated fiber 2, 5 kg of modified water reducing agent and 10 kg of expansion agent were taken, and the water-cement ratio was adjusted to 1:0.165; In Example 8, in the mixing step: 370 kg cement PO 52.5, 200 kg microsilica, 100 kg microspheres, 70 kg fly ash, 150 kg limestone, 5 kg regenerated fiber 1, 5 kg regenerated fiber 2, 1 kg modified water reducing agent and 5 kg expansion agent were taken, and the water-cement ratio was adjusted to 1:0.135; In Example 9, in the mixing step: take 400kg cement PO 52.5, 200kg microsilica powder, 150kg microspheres, 75kg fly ash, 150kg limestone, 10kg regenerated fiber 1, 11.5kg regenerated fiber 2, 5kg modified water reducer and 10kg expansion agent, and adjust the water-cement ratio to 1:0.15.

[0026] Comparative Example 1 A waste-doped concrete, which differs from Example 1 in that recycled fibers of equal weight and size of (0.15-0.20) mm×(10-15) mm are used instead of recycled fiber 1, and recycled fibers of equal weight and size of (0.08-0.12) mm×(6-8) mm are used instead of recycled fiber 2.

[0027] Comparative Example 2 A waste-doped concrete, which differs from Example 1 in that an equal weight of polycarboxylate water-reducing agent TPEG2400 is used instead of the modified water-reducing agent.

[0028] Preparation of test pieces: Test pieces were prepared according to the preparation methods of Examples 1-9 and Comparative Examples 1-2 and national standards. The sample specifications were 100 mm × 100 mm × 100 mm. After curing for 28 days, the surface was cleaned and dried.

[0029] Table 1. Performance test data of Examples 1-9 and Comparative Examples 1-2

[0030] According to the test data, we can see that: First, Example 1 and Comparative Example 1 form a single comparison. In Comparative Example 1, the regenerated fiber is not modified, the compatibility between the epoxy resin of the regenerated fiber and the gel material is poor, and there are loose pores in the internal structure of the concrete, resulting in a significant decrease in the compressive strength, flexural strength, tensile strength and other aspects of the concrete, and an increase in shrinkage, which cannot achieve good anti-self-shrinkage performance.

[0031] Second, Example 1 and Comparative Example 2 form a single comparison. In Comparative Example 2, a traditional polycarboxylate water-reducing agent is used. In Comparative Example 2, the traditional polycarboxylate water-reducing agent competes with the montmorillonite of the regenerated fiber for the adsorption of water molecules, resulting in a decrease in the fluidity of the concrete, an uneven distribution of the gel material in the concrete, and a decrease in the compressive strength of the concrete.

[0032] Third, Examples 1-4 form a single comparison, and the only difference is that the size of regenerated fiber 1 and regenerated fiber 2 is different; in Example 2, the aspect ratio of regenerated fiber 1 and regenerated fiber 2 is too large, and the regenerated fiber is more slender. Although it helps to improve the bending performance of concrete, the compressive performance is significantly reduced. The reason is that the regenerated fiber with a larger aspect ratio is prone to fiber bending and yielding in concrete, thereby weakening its reinforcing effect on concrete. In Example 3, the aspect ratio of regenerated fiber 1 and regenerated fiber 2 is too small, and the overall compressive performance of concrete is increased, but the flexural strength is significantly reduced. The reason is that the aspect ratio of the regenerated fiber is too small. Although it can better fill the internal pores of concrete, it is not conducive to the formation of an effective reinforcement system of the regenerated fiber in concrete, thereby reducing its flexural performance. In Example 4, the sizes of regenerated fiber 1 and regenerated fiber 2 are interchanged, and the bending and compressive strengths of the concrete are both reduced. The reasons are as follows: the regenerated fiber 2 floats up, and due to its larger size, it cannot effectively fill the external pores of the concrete, resulting in a decrease in the compressive strength of the concrete; the regenerated fiber 1 is small in size and absorbs less montmorillonite, resulting in an increase in the self-shrinkage of the concrete and a decrease in its crack resistance.

[0033] Fourth, Example 1 and Examples 5-6 form a single comparison, and the only difference is the size of the montmorillonite powder. The size of the montmorillonite powder in Example 5 is relatively small, and the size of the montmorillonite powder in Example 6 is relatively large, but the compressive strength of the concrete made in Examples 5-6 is lower than that in Example 1. The reason is that: when the size of the montmorillonite powder is relatively small, the specific surface area of ​​montmorillonite increases, part of the water is adsorbed, the fluidity of the concrete decreases, the gel material and the regenerated fiber one / two in the concrete are unevenly distributed, and the compressive strength decreases; when the size of the montmorillonite powder is relatively large, the amount of montmorillonite attached to the regenerated fiber one decreases, and the content of incompletely hydrated cement in the concrete increases, resulting in a decrease in the final compressive strength.

[0034] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0035] Moreover, the above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. An ultra-high performance concrete doped with waste, characterized in that: The invention comprises the following raw materials in parts by weight: 370-430 parts of cement, 200-300 parts of microsilica powder, 100-150 parts of microspheres, 70-80 parts of fly ash, 100-200 parts of limestone, 5-10 parts of recycled fiber 1, 5-20 parts of recycled fiber 2, 1-5 parts of modified water reducing agent and 5-10 parts of expansion agent; Control the water-binder ratio to 0.135-0.165; The preparation methods of the regenerated fiber 1 and the regenerated fiber 2 are as follows: Use discarded wind turbine blade shells, crush and grind them to millimeter level to obtain recycled fibers; Take a part of the regenerated fiber and immerse it in the dopamine solution, keep it warm and stir it at room temperature until the polydopamine layer adheres to the surface of the regenerated fiber, take it out and put it in micron-sized montmorillonite powder, mix it and take it out to obtain regenerated fiber 1; Taking part of the regenerated fiber and immersing it in the oxidant solution, the immersion temperature of the regenerated fiber in the oxidant solution is 50-70°C, the immersion time is 2-6 hours, washing and drying after the immersion is completed, and then placing it in a mixed solution of silane coupling agent and water, heating and stirring, filtering the product, washing with alcohol, and drying to obtain regenerated fiber II; The modified water-reducing agent is a sodium alginate modified polycarboxylic acid water-reducing agent.

2. The waste-doped ultra-high performance concrete according to claim 1, characterized in that: The weight ratio of the regenerated fiber 1 to the regenerated fiber 2 is 1:(1.15-1.5).

3. The waste-doped ultra-high performance concrete according to claim 1, characterized in that: The size of the regenerated fiber 1 is (0.15-0.20) mm×(10-15) mm.

4. The waste-doped ultra-high performance concrete according to claim 3, characterized in that: The size of the regenerated fiber 2 is (0.08-0.12) mm×(6-8) mm.

5. The waste-doped ultra-high performance concrete according to claim 1, characterized in that: The particle size of the montmorillonite powder is 1 to 50 μm.

6. The waste-doped ultra-high performance concrete according to claim 1, characterized in that: In the regenerated fiber preparation step, the regenerated fiber is immersed in the dopamine solution at a temperature of 20 to 25° C., for a time of 24 to 48 hours, and a weight ratio of the regenerated fiber to dopamine is 1:(0.35 to 0.45).

7. The waste-doped ultra-high performance concrete according to claim 1, characterized in that: In the second regenerated fiber preparation step, the weight ratio of the regenerated fiber to the silane coupling agent is 1:(0.3-1), and the mixture is heated to 55-65° C. and kept warm for 6-8 hours.

8. The waste-doped ultra-high performance concrete according to claim 1, characterized in that: The preparation steps of the modified water reducing agent are as follows: Sodium alginate is dissolved in water, the pH value of the sodium alginate solution is adjusted, and then formaldehyde, acrylamide and cyclohexyl isonitrile are added to react at room temperature to obtain modified sodium alginate; The modified sodium alginate and the polyether monomer of the polycarboxylate water reducer are dissolved in water, and an initiator solution, an acrylic acid solution and a sodium methacrylate sulfonate solution are added dropwise, and the mixture is kept warm at 60 to 75° C. for 2 to 4 hours, and the pH value of the reaction system is adjusted to 7 to obtain a sodium alginate-polycarboxylate water reducer.

9. The waste-doped ultra-high performance concrete according to claim 1, characterized in that: The water-to-binder ratio is 0.

15.

10. The waste-doped ultra-high performance concrete according to claim 1, characterized in that: The weight ratio of the cement, microsilica powder, microbeads, fly ash, limestone, recycled fiber one, recycled fiber two, modified water reducing agent and expansion agent is 400:200:150:75:150:8:12:5:10.

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