Pumpable C150 self-leveling reactive powder concrete as well as preparation method and forming and curing method thereof

Abstract

The invention discloses pumpable C150 self-leveling reactive powder concrete as well as a preparation method and a forming and curing method thereof. Belongs to the civil engineering field. The invention aims to solve the problems of high manufacturing cost, low slump and difficulty in pumping of the existing reactive powder concrete. The concrete is prepared by stirring cement, silica fume, slag, quartz sand, fibers, a water reducing agent, a defoaming agent, water and fibers, wherein the fibers are PVA fibers, PP fibers or PE fibers. And forming and curing in a steam curing manner. The pumpable C150 self-leveling reactive powder concrete has high fluidity and low viscosity, is easy to pump, has the compressive strength of 150 MPa, can realize self-compaction without vibration in the forming process, can obviously improve the construction efficiency, and is suitable for engineering scenes such as bridge thin-wall structures, high-speed rail prefabricated parts and nuclear facility protection layers with harsh material performance requirements. The invention provides key technical support for engineering application of the reactive powder concrete.

Description

Technical Field

[0001] This invention belongs to the field of civil engineering, specifically relating to a pumpable C150 self-leveling reactive powder concrete and its preparation and curing methods. Background Technology

[0002] Existing self-leveling concrete typically uses ordinary Portland cement as its base material. To achieve good flowability, its design relies on a high water-cement ratio of 0.4–0.5 and high-efficiency water-reducing agents. However, this mix proportion system generally limits its strength to the C30–C60 range and results in poor durability. A more prominent contradiction lies in the fact that when the concrete spread needs to exceed 700 mm, its high flowability makes it difficult for the cementitious material system to form a dense microstructure, resulting in a porosity as high as 15%–20% and a permeability rating of only P8. This performance is completely unacceptable in highly corrosive environments such as nuclear power plants and chemical plants, fully exposing the sharp contradiction between high flowability and low strength.

[0003] On the other hand, in fields with stringent material performance requirements, such as nuclear power engineering, long-span bridges, and super high-rise buildings, traditional C80-C100 concrete often struggles to withstand the combined effects of long-term loads and extreme environments. While C150 grade RPC boasts a compressive strength exceeding 150 MPa and durability far surpasses ordinary concrete, it suffers from a significant drawback: extremely poor fluidity, making pumping impossible. Modern engineering applications, such as high-speed rail box girder prefabrication and deep foundation pit lining casting, generally require materials with excellent self-compacting and pumpability, capable of leveling and filling complex spaces solely by their own weight and being transported long distances via pipelines. Traditional RPC clearly cannot meet these core construction requirements.

[0004] A deep analysis of the performance limitations of traditional RPC reveals that its high strength relies on an ultra-low water-cement ratio of 0.14-0.18 and a high content of 20%-25% silica fume. However, this design leads to a dramatic increase in slurry viscosity. For example, when the water-cement ratio is below 0.18, the viscosity of the RPC mixture becomes too high, necessitating forced molding using a vibrating table, which contradicts its self-leveling properties. Furthermore, to ensure strength, traditional RPC must incorporate 1.5%-3% steel fiber by volume, further increasing the frictional resistance of the mixture and resulting in pumping pressure losses more than three times that of ordinary concrete. More importantly, the ultrafine powders in RPC (such as silica fume and nano-SiO2) are prone to agglomeration, and steel fibers also present difficulties in uniform dispersion. Agglomeration of fibers or powders not only weakens local strength but can also cause blockages during pumping.

[0005] Most importantly, the high steel fiber content, essential for traditional RPC, leads to a surge in costs, becoming the biggest bottleneck restricting its large-scale application. The steel fiber volume content needs to reach 2%-3% (approximately 150-225 kg / m³).3 Based on the current market price of 6 yuan / kg, the cost of steel fiber alone is as high as 900-1350 yuan / m. 3 This accounts for 40%-50% of the total cost of RPC. In comparison, the material cost of ordinary C60 concrete is only 350-450 yuan / m². 3 The cost difference between the two is extremely large.

[0006] In engineering practice, there are numerous rigid requirements for materials that simultaneously possess ultra-high strength and self-leveling properties. Taking the connection node between the core tube and steel structure of a super high-rise building as an example, the concrete must be able to self-compact under gravity within a confined space, and its 28-day compressive strength must exceed 150 MPa to effectively transfer vertical loads. The current situation is that existing self-leveling concrete lacks sufficient strength, and traditional RPC (Reinforced Polymer Concrete) lacks self-leveling capabilities, posing a severe challenge to such critical engineering requirements. Summary of the Invention

[0007] Currently, both self-leveling concrete and traditional reactive powder concrete (RPC) in the construction field have significant limitations in performance and application. In engineering practice, the demand for new materials that combine ultra-high strength and excellent self-leveling properties is becoming increasingly urgent, which has directly promoted the research and development of self-leveling reactive powder concrete with added PP fiber, PE fiber and PVA fiber.

[0008] Therefore, the development of self-leveling reactive powder concrete incorporating PP, PE, and PVA fibers has become a key research direction. By incorporating these organic fibers into reactive powder concrete, it is hoped that the cost can be effectively reduced while maintaining the material's high strength, achieving an organic combination of "high strength" and "self-leveling" performance to meet the needs of various demanding engineering scenarios.

[0009] The European Federation of Professional Building Chemicals and Concrete Systems (EFNARC) specification and guidelines for self-compacting concrete (2013) clearly states that the flow spread of self-compacting mortar must be ≥260mm. The technical specification for high-strength concrete application (JGJ / T 281-2012) indicates that the slump time of pumped high-strength concrete mixtures must be 5-20 seconds. However, the flow spread of traditional reactive powder concrete is 120mm-150mm, and the slump time is 20-28 seconds, clearly failing to meet the requirements for self-leveling and pumpability. This invention addresses the problem of low flow spread and difficulty in pumping traditional reactive powder concrete by providing a method for preparing pumpable C150 self-leveling reactive powder concrete. By adding high-efficiency water-reducing agents and defoamers, adjusting the content of silica fume and slag, and improving the sand-cement ratio and water-cement ratio, the pumpable C150 self-leveling reactive powder concrete of this invention has a flowability of 285~355mm and a decanting time of 5~7s. Compared with traditional reactive powder concrete, its flowability is improved by an average of 137%, and its pumpability is improved by an average of about 75%. Its molding process can achieve self-leveling without vibration and meets pumping requirements, which can significantly improve construction efficiency. Its compressive strength can reach 150MPa, making it suitable for engineering scenarios with stringent material performance requirements, such as thin-walled bridge structures, precast high-speed rail components, and nuclear facility protective layers. This invention provides key technical support for the engineering application of reactive powder concrete and fills the gap in the standardized application of pumpable C150 self-leveling reactive powder concrete in China.

[0010] The present invention discloses a pumpable C150 self-leveling reactive powder concrete, which is prepared from cement, silica fume, slag, quartz sand, water-reducing agent, defoamer, fiber and water, wherein the fiber is PVA fiber, PP fiber or PE fiber.

[0011] Further specified, the mass ratio of silica fume to cement is (0.15~0.25):1; the mass ratio of slag to cement is (0.25~0.35):1; the mass ratio of quartz sand to cement is (1.1~1.5):1; the dosage of PVA fiber is 0.2%~0.5% of the concrete volume; the dosage of PP fiber is 0.1%~0.3% of the concrete volume; the dosage of PE fiber is 0.4%~0.6% of the concrete volume; the mass ratio of defoamer to the total mass of cement, silica fume and slag is (0.1~0.5):100; the mass ratio of water-reducing agent to the total mass of cement, silica fume and slag is (1~3):100; the mass ratio of water to the total mass of cement, silica fume and slag is (0.15~0.2):1.

[0012] Furthermore, the mass ratio of silica fume to cement is 0.2:1; the mass ratio of slag to cement is 0.3:1; the mass ratio of quartz sand to cement is 1.2:1; the dosage of PVA fiber is 0.2% of the concrete volume; the dosage of PP fiber is 0.2% of the concrete volume; the dosage of PE fiber is 0.5% of the concrete volume; the mass ratio of defoamer to the total mass of cement, silica fume, and slag is 0.3:100; the mass ratio of water-reducing agent to the total mass of cement, silica fume, and slag is 2:100; and the mass ratio of water to the total mass of cement, silica fume, and slag is 0.18:1.

[0013] Further specifying, the water-reducing agent is a high-efficiency polycarboxylate water-reducing agent. The water-reducing agent has a pH value of 6-8, a water reduction rate of 25%-35%, and a specific gravity of 1.08±0.02 g / cm³. 3 The solid content is 40%.

[0014] Further specified, the defoamer has a bulk density of 600 g / L, a pH of 7 in a 1% aqueous solution, and a defoaming rate of 99%.

[0015] Further specified, the silica fume has a particle size of 0.1 μm to 0.3 μm and a specific surface area of ​​20 to 28 m². 2 / g.

[0016] Further specified, the quartz sand is a mixture of quartz sand with a mesh size of 40-70 mesh (0.6-0.36 mm) and quartz sand with a mesh size of 70-140 mesh (0.36-0.18 mm), and the mass ratio of the two mesh sizes of quartz sand is 1:1.

[0017] Further specified, the nominal length of the PP fiber is 19 mm and the equivalent diameter is 35 μm; the nominal length of the PE fiber is 19 mm and the equivalent diameter is 13 μm; the nominal length of the PVA fiber is 18 mm and the equivalent diameter is 20 μm.

[0018] The method for preparing a pumpable C150 self-leveling reactive powder concrete according to the present invention is carried out according to the following steps: 1. Add cement, silica fume, slag, and quartz sand into the mixer in sequence. Mix at a speed of 130 rpm to 150 rpm, a temperature of 17℃ to 23℃, and a relative humidity of 50% to 70% until homogeneous (2 to 4 minutes) to obtain a mixed dry material. 2. Mix water, water-reducing agent and defoamer evenly to obtain a mixed liquid; 3. Add part of the liquid mixture obtained in step 2 to the dry mixture obtained in step 1, and stir for 2 to 4 minutes at a speed of 130 rpm to 150 rpm; then add the remaining liquid mixture obtained in step 2, and then evenly sprinkle in the fiber, and stir for 4 to 5 minutes at a speed of 270 rpm to 290 rpm to obtain pumpable C150 self-leveling active powder concrete.

[0019] Further specifying, the temperature mentioned in step one is 20°C.

[0020] To further specify, the relative humidity mentioned in step one is 60%.

[0021] To further specify, the time mentioned in step one is 4 minutes.

[0022] Further specifying, the mass of the mixed liquid obtained in step two in step three is 50% of the mass of the mixed liquid obtained in step two.

[0023] Further specifying, in step three, stirring is performed at a speed of 130 rpm to 150 rpm for 4 minutes.

[0024] Further specifying, in step three, stirring is performed at a speed of 270 rpm to 290 rpm for 5 minutes.

[0025] The molding and curing method of pumpable C150 self-leveling reactive powder concrete according to the present invention is carried out according to the following steps: Step 1, casting: The mixed pumpable C150 self-leveling reactive powder concrete wet material is poured into the mold to obtain the specimen; Step 2, sealing: Seal the surface of the specimen obtained in Step 1 with plastic wrap and let it stand at room temperature for 22h~26h. Then remove the mold to obtain the cement-based material specimen. Step 3, Steam curing: The cement-based material specimens obtained in Step 2 are subjected to steam curing. The steam curing process is as follows: the cement-based material specimens are heated from room temperature to 80~100℃ at a heating rate of 2℃ / min~3℃ / min, and then cured at a constant temperature in a steam environment at this temperature for 2~4 days.

[0026] Further specifying, in step 2, the mixture is left to stand at room temperature for 24 hours.

[0027] Further specifying, the heating rate in step 3 is 2.5℃ / min.

[0028] Further specifying, step 4 involves curing in a steam environment at 90°C for 3 days.

[0029] The present invention discloses a method for preparing pumpable C150 self-leveling reactive powder concrete. First, quartz sand is used instead of coarse aggregate, and PP, PE, and PVA fibers are used instead of steel fibers. Based on the closest packing theory, the matrix density is improved by optimizing the particle size distribution. Second, the water-cement ratio of the RPC is reduced, and a high-efficiency water-reducing agent is used to improve the fluidity of the mixture, promote rapid cement hydration, and increase the strength of the RPC. By adding PP fibers, a three-dimensional network structure can be formed in the RPC. When the matrix is ​​under tension, the fibers delay crack propagation through stress transfer, reducing the risk of corrosive media penetrating through cracks. The price of PP fibers is only 70% of that of PVA fibers and 60% of that of steel fibers, significantly reducing costs. PE fibers can absorb energy of 20-30 kJ / m³ through a multi-stage energy-consuming process of tensile yielding, necking, and fracture. 3 This significantly improves the impact resistance of concrete structures; the density of PE fibers is 1.18 g / cm³. 3 It is steel fiber (7.85 g / cm³). 3With an RPC content of 0.5%, 15% of the concrete can reduce its weight by 33.35 kg per cubic meter, achieving lightweighting of the project. PVA fibers, through a multi-stage energy-consuming process of necking, slippage, and pull-out, form a three-dimensional network constraint in the RPC matrix, preventing microcrack propagation and reducing stress concentration. When the main crack appears, the PVA fibers delay crack penetration through pull-out work and interfacial friction, causing the RPC to exhibit pseudo-strain hardening characteristics. The microgroove structure on the surface of the PVA fibers forms a mechanical lock with the RPC hydration products, increasing the pull-out work by 50% and improving the interfacial bond strength. By adjusting the silica fume content, the cohesiveness and water retention of the concrete mixture are improved, achieving the best workability of the concrete. The ultrafine particle size of silica fume can fill the capillary pores and gel pores in the cement paste, reducing the total porosity of the concrete and improving its strength and durability. Silica fume has a large specific surface area, which can adsorb a large amount of free water and cement particles, increasing the viscosity (thixotropy) of the slurry and reducing segregation and bleeding during concrete pumping and pouring. By adding defoamers, these harmful air bubbles can be selectively eliminated, making the concrete slurry structure denser and the contact between particles more uniform. With fewer harmful air bubbles, the resistance of air bubbles in the slurry to flow is reduced, making the concrete easier to flow under its own weight or external force, improving fluidity. Eliminating harmful air bubbles can reduce "voids" in the slurry, improve the homogeneity and cohesion of the concrete, and reduce pumping costs. The process reduces the risk of segregation and bleeding caused by bubble rupture, while also reducing local resistance in the pipeline, making pumping smoother. By adding high-efficiency polycarboxylate superplasticizer, the slump loss of concrete during transportation and pouring can be reduced, maintaining its workability and significantly improving concrete fluidity. Through the steric hindrance effect, the dispersion of cement particles is maintained, reducing the "flocculation-settling" phenomenon. The slump loss of concrete can be controlled within 50mm within 1-2 hours, meeting the needs of long-distance transportation or large-volume pouring. High fluidity can reduce the frictional resistance of concrete in the pump pipe.

[0030] The molding and curing method of pumpable C150 self-leveling reactive powder concrete of the present invention adopts steam curing. Steam curing can promote the internal hydration reaction of RPC, increase the content of CSH gel and hard calcium silicate in the cement matrix, improve the microstructure, and thus improve the strength of RPC.

[0031] Compared with the prior art, the present invention has the following beneficial effects: The pumpable C150 self-leveling reactive powder concrete of the present invention has a compressive strength of up to 150MPa compared with traditional self-leveling concrete. By eliminating coarse aggregates through ultra-fine powder gradation (cement, silica fume, etc.), an ultra-dense structure is achieved. The mechanical properties such as axial compressive strength and elastic modulus far exceed those of ordinary concrete, meeting the requirements of ultra-high load.

[0032] The present invention provides pumpable C150 self-leveling reactive powder concrete that can self-compact and fill formwork without vibration, making it suitable for pouring concrete in areas with dense reinforcement and for irregularly shaped components, thus avoiding the defects of vibration. It has low viscosity and high fluidity, and its pumpability makes it suitable for long-distance / high-altitude transportation, significantly improving construction efficiency.

[0033] The pumpable C150 self-leveling reactive powder concrete of the present invention comprises C150 self-leveling reactive powder concrete reinforced with different fibers (PVA, PP, PE) and solids. Compared with traditional reactive powder concrete with added steel fibers, PVA-RPC focuses on crack resistance and interfacial compatibility, PP-RPC focuses on corrosion resistance and cost-effectiveness, PE-RPC emphasizes lightweight and impact resistance, and solid RPC is superior in self-leveling accuracy and cost control. It can be flexibly adapted according to different engineering requirements for toughness, environment, self-weight, and cost, thus expanding the application scenarios of pumpable C150 self-leveling RPC. Detailed Implementation

[0034] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but should not be considered as limiting the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0035] Example 1: A pumpable C150 self-leveling reactive powder concrete in this example is prepared from cement, silica fume, slag, quartz sand, PVA fiber, defoamer, water-reducing agent, and water. The mass ratio of silica fume to cement is 0.2:1; the mass ratio of slag to cement is 0.3:1; the mass ratio of quartz sand to cement is 1.2:1; the PVA fiber content is 0.2% of the concrete volume; the mass ratio of the defoamer to the total mass of cement, silica fume, and slag is 0.3:100; the mass ratio of the water-reducing agent to the total mass of cement, silica fume, and slag is 2:100; and the mass ratio of water to the total mass of cement, silica fume, and slag is 0.18:1. Specifically, it is prepared according to the following steps: 1. Add cement, silica fume, slag, and quartz sand into the mixer in sequence and mix evenly. The mixing parameters are: speed of 150 rpm, temperature of 20℃, relative humidity of 60%, and time of 4 minutes to obtain a mixed dry material. 2. Mix water, water-reducing agent and defoamer evenly to obtain a mixed liquid; 3. Add a portion of the liquid mixture obtained in step 2 (50% of the mass of the liquid mixture) to the dry mixture obtained in step 1, and stir for 4 minutes at a speed of 150 rpm; then add the remaining liquid mixture obtained in step 2, and then evenly sprinkle in the fiber, and stir for 5 minutes at a speed of 280 rpm to obtain pumpable C150 self-leveling reactive powder concrete.

[0036] In this embodiment, P·O 42.5 ordinary Portland cement is used. All indicators of the cement meet the quality requirements of GB175-1999 "Portland Cement, Ordinary Portland Cement".

[0037] The slag used in this embodiment is S95 grade slag, with a density of 2.85 g / cm³. 3 Specific surface area is 366m² 2 / kg.

[0038] The silica fume used in this embodiment is 1000 mesh, with a SiO2 content of 94% and a bulk density of 330 kg / m³. 3 The bulk density is 1700 kg / m³ 3 The average particle size is 0.2 μm, and the specific surface area is 21210 m². 2 / kg, with an appearance of blackish-gray ultrafine powder.

[0039] In this embodiment, the SiO2 content in the quartz powder and quartz sand exceeds 99.6%; the average particle size of the quartz powder is 0.05 mm, and the quartz sand is a mixture of medium quartz sand and fine quartz sand in a mass ratio of 1:1; the average particle size of the medium quartz sand is 0.48 mm, and the average particle size of the fine quartz sand is 0.27 mm.

[0040] The defoamer described in this embodiment is a white powder with a bulk density of 600 g / L, a pH of 7 in a 1% aqueous solution, and a defoaming rate of 99%.

[0041] The polycarboxylate superplasticizer described in this embodiment has a pH value of 6-8, a water reduction rate of 25%-35%, and a specific gravity of 1.08±0.02 g / cm³. 3 The solid content is 40%.

[0042] In this embodiment, the PVA fiber has a nominal length of 18 mm, an equivalent diameter of 20 μm, and a tensile strength of 1860 MPa; the PP fiber has a nominal length of 19 mm, an equivalent diameter of 35 μm, and a tensile strength of 480 MPa; and the PE fiber has a nominal length of 19 mm, an equivalent diameter of 13 μm, a tensile strength of 480 MPa, and a tensile strength of 1190 MPa.

[0043] The curing method for pumpable C150 self-leveling reactive powder concrete in this embodiment is carried out according to the following steps: 1. Casting: The mixed pumpable C150 self-leveling reactive powder concrete wet material is poured into a mold with a size of 100mm×100mm×100mm to obtain the specimen; 2. Sealing: Seal the surface of the specimen obtained in step one with plastic wrap, let it stand at room temperature for 24 hours, and then remove the mold to obtain the cement-based material specimen; 3. Steam curing: The cement-based material specimens obtained in step 2 are subjected to steam curing. The steam curing process is as follows: the cement-based material specimens are heated from room temperature to 90℃ at a heating rate of 2.5℃ / min, and then cured at a constant temperature of 90℃ and relative humidity of 95% or higher for 3 days.

[0044] Example 2: This example differs from Example 1 in that the fiber is PP fiber; the PP fiber content is 0.2% of the concrete volume. Other steps and parameters are the same as in Example 1.

[0045] Example 3: This example differs from Example 1 in that the fiber is PE fiber; the dosage of the PE fiber is 0.5% of the concrete volume. Other steps and parameters are the same as in Example 1.

[0046] The test results of fluidity and compressive strength of raw reactive powder concrete with different defoamer dosages are shown in Table 1. Taking into account both fluidity and strength results, the optimal dosage of defoamer is determined to be 0.3%, which meets the requirements of self-compacting and pumping.

[0047] Table 1. Flowability and compressive strength of reactive powder concrete

[0048] The flowability test results of reactive powder concrete with different PVA fiber contents are shown in Table 2. The PVA fiber content was determined to be 0.2%, which meets the requirements for self-compacting and pumping.

[0049] Table 2. Flowability of Powder Concrete with Different PVA Fiber Contents

[0050] The flowability test results of reactive powder concrete with different PP fiber dosages are shown in Table 3. The PP fiber dosage was determined to be 0.2%, which meets the requirements for self-compacting and pumping.

[0051] Table 2. Flowability of Powder Concrete with Different PP Fiber Contents

[0052] The flowability test results of reactive powder concrete with different PE fiber content are shown in Table 4. The PE fiber content was determined to be 0.5%, which meets the requirements of self-compacting and pumping.

[0053] Table 4. Flowability of Powder Concrete with Different PE Fiber Contents

[0054] Testing and experimentation: (i) The fluidity of the RPC and the fluidity loss over 1 hour were tested on the specimens after step one using the national standard GB / T 2419-2005 "Method for Determination of Flowability of Cement Mortar". The fluidity of C150 self-leveling PVA fiber active powder concrete, C150 self-leveling PP fiber active powder concrete, C150 self-leveling PE fiber active powder concrete and C150 self-leveling plain active powder concrete were within the range of 285~355mm, and the fluidity loss over 1 hour was less than 20%. Furthermore, it was observed that there was no bleeding or segregation of the expanded slurry, which met the requirements for self-compacting and pumpability.

[0055] (II) The viscosity of pumpable C150 self-leveling reactive powder concrete is reflected by the emptying time of the concrete mixture in the inverted slump cone. The longer the time, the greater the viscosity. The inverted slump cone emptying test was conducted in accordance with GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixture". The emptying time of the inverted slump cone for C150 self-leveling PVA fiber reactive powder concrete, C150 self-leveling PP fiber reactive powder concrete, C150 self-leveling PE fiber reactive powder concrete and C150 self-leveling plain reactive powder concrete was measured to be between 5 and 7 seconds, which meets the pumping requirements.

[0056] (iii) The compressive strength of C150 self-leveling PVA fiber reactive powder concrete, C150 self-leveling PP fiber reactive powder concrete, C150 self-leveling PE fiber reactive powder concrete and C150 self-leveling plain reactive powder concrete shall be measured according to the method specified in the national standard GB / T50081 Test Method for Mechanical Properties of Ordinary Concrete. The average compressive strength shall not be less than 150 MPa.

[0057] The specific embodiments of the present invention have been described in detail above. It should be noted that the present invention is not limited to the specific embodiments described above. Various modifications or alterations can be made by those skilled in the art without departing from the scope of protection defined by the claims, and all such modifications or alterations fall within the scope of the present invention.

Claims

1. A pumpable C150 self-leveling reactive powder concrete, characterized in that, C150 self-leveling reactive powder concrete is made from cement, silica fume, slag, quartz sand, water-reducing agent, defoamer, fiber and water, wherein the fiber is PVA fiber, PP fiber or PE fiber.

2. The concrete according to claim 1, characterized in that, The mass ratio of silica fume to cement is (0.15~0.25):1; the mass ratio of slag to cement is (0.25~0.35):1; the mass ratio of quartz sand to cement is (1.1~1.5):1; the dosage of PVA fiber is 0.2%~0.5% of the concrete volume; the dosage of PP fiber is 0.1%~0.3% of the concrete volume; the dosage of PE fiber is 0.4%~0.6% of the concrete volume; the mass ratio of defoamer to the total mass of cement, silica fume and slag is (0.1~0.5):100; the mass ratio of water-reducing agent to the total mass of cement, silica fume and slag is (1~3):100; the mass ratio of water to the total mass of cement, silica fume and slag is (0.15~0.2):

1.

3. The concrete according to claim 1, characterized in that, The mass ratio of silica fume to cement is 0.2:1; the mass ratio of slag to cement is 0.3:1; the mass ratio of quartz sand to cement is 1.2:1; the dosage of PVA fiber is 0.2% of the concrete volume; the dosage of PP fiber is 0.2% of the concrete volume; the dosage of PE fiber is 0.5% of the concrete volume; the mass ratio of defoamer to the total mass of cement, silica fume, and slag is 0.3:100; the mass ratio of water-reducing agent to the total mass of cement, silica fume, and slag is 2:100; and the mass ratio of water to the total mass of cement, silica fume, and slag is 0.18:

1.

4. The concrete according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent.

5. The method for preparing concrete according to any one of claims 1 to 4, characterized in that, Includes the following steps:

1. Add cement, silica fume, slag, and quartz sand into the mixer in sequence, and mix at a speed of 130 rpm to 150 rpm, a temperature of 17℃ to 23℃, and a relative humidity of 50% to 70% until uniform to obtain a mixed dry material.

2. Mix water, water-reducing agent and defoamer evenly to obtain a mixed liquid; 3. Add part of the mixed liquid obtained in step 2 to the mixed dry material obtained in step 1, and stir at a speed of 130 rpm to 150 rpm for 2 min to 4 min. Then add the remaining mixed liquid obtained in step 2, and then evenly sprinkle in the fiber. Stir at a speed of 270 rpm to 290 rpm for 4 min to 5 min to obtain the concrete.

6. The method according to claim 5, characterized in that, The temperature in step one is 20℃, the relative humidity is 60%, and the time is 4 minutes.

7. The method according to claim 5, characterized in that, Add 50 wt.% of the total mass of the mixed liquid to the mixed dry material.

8. The method for molding and curing concrete as described in any one of claims 1 to 4, characterized in that, The molding and curing method is carried out according to the following steps: Step 1, casting: The mixed pumpable C150 self-leveling reactive powder concrete wet material is poured into the mold to obtain the specimen; Step 2, sealing: Seal the surface of the specimen with plastic wrap and let it stand at room temperature for 22h~26h. Then remove the mold to obtain the cement-based material specimen. Step 3, Steam curing: The cement-based material specimens are steam cured. The steam curing process is as follows: the cement-based material specimens are heated from room temperature to 80~100℃ at a rate of 2℃ / min~3℃ / min, and then cured at a constant temperature for 2~4 days in a steam environment with relative humidity maintained above 95%.

9. The molding and curing method according to claim 8, characterized in that, The settling time in step 2 is 24 hours.

10. The molding and curing method according to claim 8, characterized in that, In step 3, the temperature is increased from room temperature to 90℃ at a rate of 2.5℃ / min, and then kept at that temperature and in a steam environment with a relative humidity of over 95% for 3 days.

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