A non-shrinkage ferroaluminate cement-based ultra-high performance concrete and its preparation method

Abstract

The present invention discloses a non-shrinkage ferroaluminate cement-based ultra-high performance concrete and a preparation method thereof, which belongs to the technical field of new wall materials and includes the following components: activated cementitious materials, mineralized aggregates, admixtures, reinforcing fibers and mixing water. The sustained-release effect of the methylcellulose coating on the composite expansion agent achieves precise compensation for autogenous shrinkage and effectively suppresses shrinkage deformation during maintenance and use. The unique mineral composition of ferroaluminate cement increases the early strength of concrete sharply and greatly shortens the production cycle of prefabricated components. The steel fibers modified by sandblasting and pre-wrapping can effectively bridge microcracks inside the concrete and limit crack propagation; the nano-carbon fibers modified by dispersion of polycarboxylic acid water-reducing agent suppress crack initiation at the microscopic level. The two synergistically significantly improve the mechanical properties of the joints and prefabricated components, such as flexural resistance and impact resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of new wall materials for prefabricated construction, and in particular to a non-shrinkage ferroaluminate cement-based ultra-high performance concrete and a preparation method thereof. Background Art

[0002] As a core component of standardized production and rapid assembly and construction for prefabricated buildings, the performance of new wall materials directly impacts the quality and service life of the building. During the modular construction of prefabricated buildings, the performance of joint materials plays a key role in the overall quality and service life of the building. Ferroaluminate cement-based ultra-high performance concrete, with its rapid hardening, early strength, and excellent volume stability, can achieve the same effect as cast-in-place construction, significantly accelerating construction efficiency. Its high corrosion resistance can effectively enhance the durability of buildings in complex environments such as marine and saline-alkali environments, and is of great significance for extending the service life of key national infrastructure, such as nuclear power project modules.

[0003] However, traditional joint materials generally suffer from significant shrinkage. In modular prefabricated building construction, this significant shrinkage can lead to dimensional deviations in prefabricated components during maintenance and use, compromising the precision and integrity of connections between components, increasing installation difficulty and construction errors, and even posing structural safety risks. Furthermore, shrinkage-induced cracks reduce the airtightness and watertightness of joints, weakening the prefabricated building's thermal insulation, making it difficult to maintain stable indoor temperature and humidity, and failing to meet building energy-saving requirements. Furthermore, cracks allow for the intrusion of moisture and harmful gases, accelerating material aging and corrosion, reducing structural durability and safety, and increasing subsequent maintenance costs. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the present invention provides a non-shrinkage ferroaluminate cement-based ultra-high performance concrete and a preparation method thereof.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0006] A non-shrinkage ferroaluminate cement-based ultra-high performance concrete comprising the following components by weight:

[0007] 96-120 parts of activated gelling material;

[0008] The mass ratio of ferroaluminate cement, silica fume, slag powder and fly ash in the activated cementitious material is 55-60:10-15:10-15:5-8;

[0009] The silica fume, slag powder and fly ash are modified by acid etching, drying and microwave activation;

[0010] 30-40 parts of mineralized aggregate;

[0011] The mass ratio of mineralized ceramsite to machine-made sand in the mineralized aggregate is 12-25:21-32;

[0012] The mineralized ceramsite is modified by soaking and mineralizing solution;

[0013] 5.3-7.5 parts of admixture;

[0014] The mass ratio of the polycarboxylate water-reducing agent, the composite expansion agent and the nano-modifier in the admixture is 0.8-1.2:4-5.5:0.5-0.8;

[0015] The mass ratio of calcium sulfoaluminate to magnesium oxide in the composite expansion agent is 3-4:1; the nano-modifier is nano- With Nano The mass ratio is 3-4:2-3;

[0016] The composite expansion agent is modified by methyl cellulose coating;

[0017] 2.5-3.6 parts of reinforcing fiber;

[0018] The mass ratio of steel fiber to nano carbon fiber in the reinforcing fiber is 1.5-2.5:0.05-0.1;

[0019] The steel fibers are modified by sandblasting and pre-wrapping;

[0020] The nano-carbon fibers are dispersed and modified by a polycarboxylate water-reducing agent;

[0021] 15-18 parts of mixing water; the mixing water contains 28-32% acid etching solution.

[0022] A method for preparing the non-shrinkage ferroaluminate cement-based ultra-high performance concrete comprises the following steps:

[0023] S1: Cementitious material modification;

[0024] Activation of ferroaluminate cement, high-speed crushing of ferroaluminate cement;

[0025] Silica fume, slag powder and fly ash are mixed to obtain a siliceous admixture, which is immersed in an acid solution and etched at room temperature. After acid etching, quicklime is added to the waste liquid to neutralize it, and gypsum is precipitated and separated. The acid etching clear liquid is tested and used for subsequent mixing water. The acid-etched siliceous admixture is dried and microwave-treated to obtain a microwave-activated siliceous admixture.

[0026] The microwave activated silica admixture and ferroaluminate cement are compounded to obtain an activated cementitious material;

[0027] S2: aggregate modification;

[0028] Soak the ceramsite in stirred and clean water filtered by magnetic grid and then dry it to improve the surface roughness of the ceramsite;

[0029] Dissolve calcium nitrate and water glass in mixing water and adjust the pH to obtain a mineralized solution;

[0030] The ceramsite is immersed in a mineralizing solution and heated in a water bath to form a calcium silicate gel layer on the surface of the ceramsite to obtain mineralized ceramsite;

[0031] The machine-made sand is sieved to remove large particles, washed with a high-pressure water gun to remove surface mud and powder, and dried;

[0032] Compounding mineralized ceramsite and machine-made sand to obtain mineralized aggregate;

[0033] S3: fiber modification;

[0034] Brown corundum is used to sandblast steel fibers to improve the surface roughness of the steel fibers;

[0035] The steel fiber is immersed in a ferroaluminate cement slurry containing a silane coupling agent, and the slurry is rolled and dried to form a pre-coated layer, thereby obtaining a pre-coated steel fiber;

[0036] The nanocarbon fibers are mixed with a polycarboxylate water reducer and dispersed in a high-speed shearing machine to form a stable suspension of the nanocarbon fibers;

[0037] The pre-wrapped steel fibers and the nano-carbon fiber stable suspension are compounded to obtain the reinforced fibers;

[0038] S4: expansion agent modification;

[0039] A calcium sulfoaluminate expansion agent and a magnesium oxide expansion agent are uniformly mixed to obtain a composite expansion agent, and a methyl cellulose ethanol solution is spray-dried to form a controllable degradation film on the surface of the composite expansion agent;

[0040] S5: compounding;

[0041] Dry mixing: put the activated cementitious material and mineralized aggregate into a forced mixer, pre-mix at low speed, and then disperse at high speed to form a coarse aggregate-fine cementitious material skeleton structure;

[0042] Wet mixing stage: add 78-82% mixing water, polycarboxylate water reducer, nano modifier and stir evenly;

[0043] Fiber / expansion agent addition: Add reinforcing fiber and composite expansion agent, shear and disperse;

[0044] Conditioning stage: add the remaining mixing water and stir to obtain a mixture;

[0045] S6: Forming and curing;

[0046] The mixture is poured into a mold coated with a release agent, and internal bubbles are removed by vibration. The surface is scraped flat and covered with a plastic film to obtain a concrete component after molding.

[0047] The concrete is subjected to pre-curing, temperature-raising curing, gradient cooling and natural curing.

[0048] Furthermore, S1 specifically comprises: crushing the ferroaluminate cement at a high speed of 1000-1500 r / min;

[0049] The silica admixture is obtained by mixing silica fume, slag powder and fly ash, and then immersed in 10-15% industrial waste hydrochloric acid, and etched at room temperature for 40-60 minutes, with the solid-liquid ratio controlled at 1:3-5. After acid etching, quicklime is added to the waste liquid to neutralize it to a pH value of 6-7, and gypsum is separated by precipitation. The acid etching clear liquid is tested. After the content does not exceed 0.06%, it is used for subsequent mixing water; after acid etching, the siliceous admixture is dried at 60-70℃ until the moisture content does not exceed 1%, and then passed through a tunnel microwave kiln, at a power of 800-1000W and a speed of 0.5-1m / min, microwave treatment for 3-4 minutes to obtain microwave-activated siliceous admixture;

[0050] The activated cementitious material is obtained by compounding microwave activated siliceous admixture and ferroaluminate cement.

[0051] Furthermore, S2 specifically comprises: soaking the ceramsite in stirred and clean water filtered by the magnetic grid for 5-10 minutes and then drying it to improve the surface roughness of the ceramsite;

[0052] Dissolve industrial-grade calcium nitrate and water glass in a molar ratio of 4-6:1 in mixing water, and adjust the pH value to between 9.5 and 10.5 to obtain a mineralization solution;

[0053] Immerse the ceramsite in a mineralizing solution and heat it in a water bath at 50-60°C for 40-60 minutes to form a calcium silicate gel layer on the surface of the ceramsite to obtain mineralized ceramsite;

[0054] The machine-made sand is sieved to remove large particles, washed to remove surface mud powder, so that the mud content does not exceed 1%, and dried at 55-65℃ to a moisture content of no more than 0.5%;

[0055] The mineralized ceramsite and machine-made sand are compounded to obtain the mineralized aggregate.

[0056] Furthermore, S3 specifically includes: using brown corundum with a particle size of 0.8 mm to sandblast the steel fiber for 30 seconds at a pressure of 0.4-0.5 MPa to improve the surface roughness of the steel fiber;

[0057] The steel fiber is immersed in a ferroaluminate cement slurry containing γ-aminopropyltriethoxysilane at a water-binder ratio of 0.25-0.35, and the slurry is rolled and dried at 55-65° C. to form a pre-coated layer, thereby obtaining a pre-coated steel fiber;

[0058] Mix the nanocarbon fibers and the polycarboxylate water reducer in a mass ratio of 1:4.5-5.5, and disperse them in a high-speed shearing machine at 2800-3200 r / min for 18-22 minutes to form a stable suspension of nanocarbon fibers;

[0059] The pre-wrapped steel fibers and the nano-carbon fiber stable suspension are compounded to obtain the reinforced fibers.

[0060] Furthermore, S4 is specifically as follows: a calcium sulfoaluminate expansion agent and a magnesium oxide expansion agent are uniformly mixed to obtain a composite expansion agent, and a methyl cellulose ethanol solution with a solid content of 9-11% and a viscosity of 18000-22000 mPa·s is spray-dried at an inlet air temperature of 175-185°C and an outlet air temperature of 75-85°C to form a controllable degradation film on the surface of the composite expansion agent.

[0061] Furthermore, S5 is specifically as follows: the activated cementitious material and the mineralized aggregate are put into a forced mixer, premixed at a low speed of 30-50 r / min for 3-4 minutes, and then dispersed at a higher speed of 150-200 r / min for 5-6 minutes to form a coarse aggregate-fine cementitious material skeleton structure;

[0062] Add 78-82% mixing water, polycarboxylate water reducer, and nano modifier, and stir at a speed of 95-105r / min for 3.5-4.5min;

[0063] Add reinforcing fiber and composite expansion agent, and shear and disperse in a high-speed shear mixer at a speed of 190-210 r / min for 5.5-6.5 minutes;

[0064] Add the remaining mixing water and stir in a mixer at a speed of 75-85 r / min for 2.5-3.5 min to obtain a mixture.

[0065] Furthermore, S6 specifically comprises: pouring the mixture into a mold coated with a release agent, vibrating the mold at a frequency of 48-52 Hz and an amplitude of 0.5-1.0 mm for 30-60 seconds to remove internal bubbles, smoothing the surface and covering it with a plastic film to prevent water evaporation, and forming a concrete component;

[0066] Pre-curing for 1-2 hours, temperature 24-26℃, humidity not less than 95%;

[0067] Heat up and cure for 2-3 hours, raising the temperature to 58-62℃ at a heating rate of 13-15℃ / h;

[0068] Gradient cooling for 2-4 hours: Cool down at a rate of 8-10℃ / h. When the difference between the final temperature and the ambient temperature does not exceed 15℃, remove the container from the curing box.

[0069] Move to the natural environment, cover the surface with a moisturizing film, and maintain naturally.

[0070] Compared with the prior art, the present invention has the following beneficial effects:

[0071] 1. The methylcellulose coating's slow-release effect on the composite expansive agent precisely controls the release rhythm of the expansive agent in concrete. Early on, the coating isolates the expansive agent particles from contact with moisture, preventing excessive reaction of the expansive agent that could lead to internal stress concentration and uneven expansion, thus avoiding early microcracks in the joint materials and prefabricated components due to expansion stress. As the hydration process progresses, the coating erodes and dissolves, allowing the active ingredients of the expansive agent to be continuously and steadily released, synchronized with the autogenous shrinkage of the concrete, achieving precise compensation for this shrinkage and effectively suppressing shrinkage and deformation of the joint materials and prefabricated components during maintenance and use. This ensures their dimensional stability, meets the stringent requirements of prefabricated buildings for component dimensional accuracy, ensures precise splicing between prefabricated wall components, and maintains the overall structural load-bearing capacity and sealing.

[0072] 2. The unique mineral composition of ferroaluminate cement allows for rapid hydration, generating a large amount of hydrated calcium aluminate. This rapidly forms a spatial, network-like, rigid skeleton within the concrete, limiting volume shrinkage caused by water migration and dramatically increasing the concrete's early strength. This significantly shortens the production cycle for prefabricated components, speeds up construction progress, and meets the requirements of rapid assembly and construction for prefabricated buildings, improving construction efficiency and reducing project costs. The alkaline hydration environment of ferroaluminate cement accelerates the hydrolysis of the methylcellulose coating, allowing the expansive agent to release its active ingredients in a timely manner. The resulting composite hydration products enhance interfacial bond strength, further increasing the concrete's early strength development rate, enabling it to reach a high-strength state in a short period of time. This enhances its mechanical properties during transportation and hoisting, reduces the risk of component damage, and ensures construction quality.

[0073] 3. The sandblasted and pre-wrapped modified steel fibers have a rough surface and good compatibility with the matrix, effectively bridging microcracks within the concrete and limiting crack propagation. The nanocarbon fibers, modified by the polycarboxylate superplasticizer, are evenly dispersed in the concrete matrix. Their high specific surface area and high strength inhibit crack initiation at the microscopic level. The two synergistically form a multi-scale reinforcement system, significantly improving the mechanical properties of joint materials and prefabricated components, including flexural and impact resistance. This meets the high strength and stability requirements of prefabricated buildings, ensuring the integrity and reliability of components under complex loads. The micro-expansion stress generated by the modified composite expansive agent densifies the internal microstructure of the concrete. At the same time, it interacts with the composite fibers, creating a synergistic effect similar to "fiber reinforcement-expansion compaction," further enhancing the overall strength and toughness of the new wall material, enhancing its resistance to external loads and environmental erosion, extending its service life, and reducing subsequent maintenance costs, providing a higher-quality, more durable joint material and prefabricated component option for prefabricated buildings.

[0074] 4. The present invention achieves dual innovations in terms of material performance optimization and environmental protection. By deeply filtering and stirring the cleaning water through magnetic grating, and using it for pretreatment of ceramsite soaking, the surface activity of the ceramsite is effectively activated, and its roughness is significantly improved, creating better conditions for the interfacial bonding between the ceramsite and cement-based materials, thereby enhancing the overall mechanical properties of the concrete. At the same time, industrial waste hydrochloric acid is transformed into an acid etching medium for siliceous admixtures in a breakthrough manner. After the acid etching process is completed, the resulting acid etching clear liquid is added to the mixing water in a scientific proportion, realizing the value transformation of industrial waste liquid from a pollutant to a functional material component. This process not only avoids the environmental pollution risks brought about by the direct discharge of waste acid, but also reduces water resource consumption and the demand for new production raw materials through material recycling, building a multi-circulation chain of "waste liquid recovery-material regeneration-energy conservation", and practicing the concept of low-carbon environmental protection with a systematic technical solution, providing a sustainable development path for the green production of new wall materials. DETAILED DESCRIPTION

[0075] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0076] Example 1: This example provides a method for preparing shrinkage-free ferroaluminate cement-based ultra-high performance concrete, comprising the following steps:

[0077] S1: weigh the raw materials;

[0078] 120 parts activated gelling material;

[0079] The mass ratio of ferroaluminate cement, silica fume, S95 grade slag powder and grade II fly ash in the activated cementitious material is 60:15:15:8;

[0080] Ferroaluminate cement is obtained by sintering calcium raw materials, aluminum raw materials and iron raw materials in a mass ratio of 5:2:3;

[0081] silica fume Content ≥ 90%, average particle size 1μm, loss on ignition not higher than 3%; 28-day activity index of slag fine powder not lower than 95%; fly ash fineness (45μm sieve residue) not higher than 20% (after sieving through a 45μm sieve, the weight of the fly ash particles remaining on the sieve accounts for no more than 20% of the total weight of the fly ash sample taken);

[0082] 40 parts mineralized aggregate;

[0083] The mass ratio of mineralized ceramsite to manufactured sand in the mineralized aggregate is 25:32;

[0084] In the mineralized ceramsite, the mass ratio of 5mm particle size to 8mm particle size is 7:4; the fineness modulus of the manufactured sand is 2.8, and the stone powder content does not exceed 5%;

[0085] 7.5 parts admixture;

[0086] The mass ratio of polycarboxylate water reducer, composite expansion agent and nano-modifier in the admixture is 1.2:5.5:0.8;

[0087] The content of sodium sulfate in polycarboxylate water reducer shall not exceed 5%; the mass ratio of calcium sulfoaluminate to magnesium oxide in composite expansion agent shall be 4:1; the nanometer content in nanometer modifier shall be less than 1%. With Nano The mass ratio is 4:3, and the average particle size does not exceed 50nm;

[0088] 3.6 parts of reinforcing fiber;

[0089] The mass ratio of steel fiber to nanocarbon fiber in the reinforcing fiber is 2.5:0.1;

[0090] The steel fiber has a diameter of 0.3 mm and a length of 16 mm; the carbon nanofiber is 15 μm long and the diameter of the single fiber does not exceed 20 nm;

[0091] 18 parts of mixing water; the mixing water contains 32% acid etching solution;

[0092] S2: Cementitious material modification;

[0093] Activation of ferroaluminate cement: put the ferroaluminate cement into the air flow mill and grind it at a high speed of 1500r / min;

[0094] Silica admixture was obtained by mixing silica fume, slag powder and fly ash, and immersed in 15% industrial waste hydrochloric acid. It was etched at room temperature for 60 minutes, and the solid-liquid ratio was controlled at 1:5. After acid etching, quicklime was added to the waste liquid to neutralize it to pH 7, and gypsum was precipitated and separated. The acid etching clear liquid was tested for Cl - After the content does not exceed 0.06%, it is used for subsequent mixing water; after acid etching, the siliceous admixture is dried at 70°C to a moisture content of no more than 1%, and then passed through a tunnel microwave kiln, at a power of 1000W and a speed of 1m / min, for microwave treatment for 4min to obtain microwave-activated siliceous admixture;

[0095] The microwave activated silica admixture and ferroaluminate cement are compounded to obtain an activated cementitious material;

[0096] S3: Aggregate modification;

[0097] Soak the ceramsite in stirred and clean water filtered by magnetic grid for 10 minutes and then dry it to improve the surface roughness of the ceramsite;

[0098] Mixer wash water that undergoes magnetic grating filtration primarily comes from wastewater generated during the cleaning of mixing equipment and transport vehicles during concrete production. To ensure proper equipment operation and clean transport vehicles, concrete mixing plants require regular flushing of the main mixer and truck tanks, generating significant amounts of wastewater. Direct discharge of this wastewater not only wastes water resources but can also negatively impact the environment due to contaminants such as cement particles, gravel debris, and admixture residue. To achieve water recycling and environmental protection goals, concrete mixing plants typically employ dedicated wastewater treatment systems. These systems typically initially intercept larger impurities through a screen to prevent them from entering subsequent treatment processes and potentially clogging equipment. The wastewater then flows into a sedimentation tank, where gravity settles denser solid particles such as gravel, achieving initial solid-liquid separation. The supernatant still contains some fine particles and colloidal matter, which is then passed through magnetic grating filtration. Using the principle of magnetic adsorption, magnetic grating filtration effectively removes residual ferromagnetic impurities and some fine suspended matter, further purifying the water.

[0099] Industrial-grade calcium nitrate (concentration 0.3 mol / L) and water glass (concentration 5%) were dissolved in mixing water at a molar ratio of 6:1, and the pH was adjusted to 10.5 to obtain a mineralization solution;

[0100] The ceramsite is immersed in a mineralizing solution and heated in a water bath at 60°C for 60 minutes to form a calcium silicate gel layer on the surface of the ceramsite to obtain mineralized ceramsite;

[0101] The machine-made sand is first sieved through a 2.36mm sieve to remove large particles, then washed with a high-pressure water gun at a pressure of 5MPa to remove surface mud powder so that the mud content does not exceed 1%, and then dried at 65℃ to a moisture content of no more than 0.5%;

[0102] Compounding mineralized ceramsite and machine-made sand to obtain mineralized aggregate;

[0103] S4: fiber modification;

[0104] Using brown corundum with a particle size of 0.8 mm, the steel fiber was sandblasted for 30 seconds at a pressure of 0.5 MPa to improve the surface roughness of the steel fiber;

[0105] The steel fiber was immersed in a ferroaluminate cement paste (containing 0.5% γ-aminopropyltriethoxysilane) with a water-binder ratio of 0.35, and then rolled and dried at 65°C to form a pre-coated layer to obtain a pre-coated steel fiber;

[0106] The nanocarbon fibers and polycarboxylate water-reducing agent were mixed at a mass ratio of 1:5.5 and dispersed in a high-speed shearing machine at 3200 r / min for 22 min to form a stable nanocarbon fiber suspension;

[0107] The pre-wrapped steel fibers and the nano-carbon fiber stable suspension are compounded to obtain the reinforced fibers;

[0108] S5: expansion agent modification;

[0109] A composite expander was prepared by uniformly mixing calcium sulfoaluminate and magnesium oxide. A methyl cellulose (viscosity 22,000 mPa·s) aqueous solution (solid content 11%) was spray-dried (inlet air temperature 185°C, outlet air temperature 85°C) to form a controllable degradation film on the surface of the composite expander.

[0110] S6: compounding;

[0111] Dry mixing: put the activated cementitious material and mineralized aggregate into a forced mixer, premix them at a low speed of 50r / min for 4 minutes, and then disperse them at a higher speed of 200r / min for 6 minutes to form a coarse aggregate-fine cementitious material skeleton structure;

[0112] Wet mixing stage: add 82% mixing water, polycarboxylate water reducer, and nano modifier, and stir in a planetary mixer at a speed of 105r / min for 4.5min to fully hydrate the cementitious material, disperse the water reducer particles, and fill the pores with the nano modifier;

[0113] Fiber / swelling agent addition: Add reinforcing fiber and composite swelling agent, and shear and disperse them in a high-speed shear mixer at a speed of 210r / min for 6.5min to ensure that the fiber monofilaments are dispersed and the swelling agent is evenly distributed;

[0114] Tempering stage: add the remaining mixing water and stir in a mixer at a speed of 85r / min for 3.5min to obtain a mixture. Adjust the slump to 180mm and the spread to 700mm to meet the pumping construction requirements;

[0115] S7: Forming and curing;

[0116] The mixture is poured into a mold coated with a release agent, and vibrated on a vibration table at a frequency of 52 Hz and an amplitude of 1.0 mm for 60 seconds to remove internal bubbles. The surface is then scraped flat and covered with a plastic film to prevent moisture evaporation. After molding, a concrete component is obtained;

[0117] Pre-curing (2h): Place the formed concrete components in a curing box with a temperature controlled at 26°C and a humidity of not less than 95%. Use a steam generator to automatically replenish moisture to promote the early reaction of the calcium sulfoaluminate expansion agent and compensate for early shrinkage.

[0118] Heating and curing (3h): Raise the temperature of the curing box to 62℃ at a heating rate of 15℃ / h for curing. During the heating process, start the infrared thermometer for real-time monitoring to prevent local overheating and fiber damage;

[0119] Gradient cooling: After the temperature rise and curing is completed, gradient ventilation cooling is adopted at a rate of 10°C / h to allow the concrete components to cool slowly. When the difference between the final temperature and the ambient temperature does not exceed 15°C, the concrete components are removed from the curing box.

[0120] Natural curing: After steam curing, move to the natural environment, cover the surface with a moisturizing film, maintain humidity not less than 80% for 28 days to complete the hydration reaction and continuously increase the strength (28d compressive strength not less than 120MPa, flexural strength not less than 15MPa).

[0121] Example 2: This example provides a method for preparing shrinkage-free ferroaluminate cement-based ultra-high performance concrete, comprising the following steps:

[0122] S1: weigh the raw materials;

[0123] 96 parts of activated gelling material;

[0124] The mass ratio of ferroaluminate cement, silica fume, S95 grade slag powder and grade II fly ash in the activated cementitious material is 55:10:10:5;

[0125] Ferroaluminate cement is obtained by sintering calcium raw materials, aluminum raw materials and iron raw materials in a mass ratio of 5:2:3;

[0126] silica fume Content ≥ 90%, average particle size 0.1μm, loss on ignition not higher than 3%; slag powder 28d activity index not lower than 95%; fly ash fineness (45μm sieve residue) not higher than 20%;

[0127] 30-40 parts of mineralized aggregate;

[0128] The mass ratio of mineralized ceramsite to manufactured sand in the mineralized aggregate is 12:21;

[0129] In the mineralized ceramsite, the mass ratio of 3mm particle size to 5mm particle size is 6:3; the fineness modulus of the manufactured sand is 2.4, and the stone powder content does not exceed 5%;

[0130] 5.3 parts admixture;

[0131] The mass ratio of polycarboxylate water reducer, composite expansion agent and nano-modifier in the admixture is 0.8:4:0.5;

[0132] The sodium sulfate content in the polycarboxylate water reducer shall not exceed 5%; the mass ratio of calcium sulfoaluminate to magnesium oxide in the composite expansion agent shall be 3:1; the nano-modifier shall contain nano- With Nano The mass ratio is 3:2, and the average particle size does not exceed 50nm;

[0133] 2.5 parts of reinforcing fiber;

[0134] The mass ratio of steel fiber to nanocarbon fiber in the reinforcing fiber is 1.5:0.05;

[0135] The steel fiber has a diameter of 0.2 mm and a length of 12 mm; the carbon nanofiber is 5 μm long and the diameter of the single fiber does not exceed 20 nm;

[0136] 15 parts of mixing water; the mixing water contains 28% acid etching solution;

[0137] S2: Cementitious material modification;

[0138] Activation of ferroaluminate cement: put the ferroaluminate cement into the air flow mill and grind it at a high speed of 1000r / min;

[0139] Silica admixture was obtained by mixing silica fume, slag powder and fly ash, immersed in 10% industrial waste hydrochloric acid, etched at room temperature for 40 minutes, and the solid-liquid ratio was controlled at 1:3. After acid etching, quicklime was added to the waste liquid to neutralize it to pH 6, and gypsum was precipitated and separated. The acid etching clear liquid was tested. After the content does not exceed 0.06%, it is used for subsequent mixing water; after acid etching, the siliceous admixture is dried at 60°C to a moisture content of no more than 1%, and then passed through a tunnel microwave kiln, at a power of 800W and a speed of 0.5m / min, microwave treatment for 3min to obtain microwave-activated siliceous admixture;

[0140] The microwave activated silica admixture and ferroaluminate cement are compounded to obtain an activated cementitious material;

[0141] S3: Aggregate modification;

[0142] Soak the ceramsite in stirred and clean water filtered by magnetic grid for 5 minutes and then dry it to improve the surface roughness of the ceramsite;

[0143] Dissolve industrial-grade calcium nitrate (concentration 0.2 mol / L) and water glass (concentration 5%) in mixing water at a molar ratio of 4:1, and adjust the pH to 9.5 to obtain a mineralization solution;

[0144] The ceramsite is immersed in a mineralizing solution and heated in a water bath at 50°C for 40 minutes to form a calcium silicate gel layer on the surface of the ceramsite to obtain mineralized ceramsite;

[0145] The machine-made sand is first sieved through a 2.36mm sieve to remove large particles, then washed with a high-pressure water gun at a pressure of 5MPa to remove surface mud powder so that the mud content does not exceed 1%, and then dried at 55℃ to a moisture content of no more than 0.5%;

[0146] Compounding mineralized ceramsite and machine-made sand to obtain mineralized aggregate;

[0147] S4: fiber modification;

[0148] Brown corundum with a particle size of 0.8 mm was used to sandblast the steel fiber for 30 seconds at a pressure of 0.4 MPa to improve the surface roughness of the steel fiber.

[0149] The steel fiber is immersed in alumina-ferrocement slurry (containing 0.5% γ-aminopropyltriethoxysilane) with a water-binder ratio of 0.25, and then rolled and dried at 55°C to form a pre-coated layer to obtain pre-coated steel fiber;

[0150] The nanocarbon fibers and polycarboxylate water reducer were mixed at a mass ratio of 1:4.5 and dispersed in a high-speed shearing machine at 2800 r / min for 18 min to form a stable suspension of nanocarbon fibers;

[0151] The pre-wrapped steel fibers and the nano-carbon fiber stable suspension are compounded to obtain the reinforced fibers;

[0152] S5: expansion agent modification;

[0153] A composite expander was prepared by uniformly mixing calcium sulfoaluminate and magnesium oxide expanders. A methyl cellulose (viscosity 18,000 mPa·s) aqueous solution (solid content 9%) was spray-dried (inlet air temperature 175°C, outlet air temperature 75°C) to form a controllable degradation film on the surface of the composite expander.

[0154] S6: compounding;

[0155] Dry mixing: put the activated cementitious material and mineralized aggregate into a forced mixer, pre-mix at a low speed of 30r / min for 3 minutes, and then disperse at a higher speed of 150r / min for 5 minutes to form a coarse aggregate-fine cementitious material skeleton structure;

[0156] Wet mixing stage: add 78% mixing water, polycarboxylate water reducer, and nano modifier, and stir in a planetary mixer at a speed of 95r / min for 3.5min to fully hydrate the cementitious material, disperse the water reducer particles, and fill the pores with the nano modifier;

[0157] Fiber / swelling agent addition: Add reinforcing fiber and composite swelling agent, and shear and disperse them in a high-speed shear mixer at a speed of 190r / min for 5.5 minutes to ensure that the fiber monofilaments are dispersed and the swelling agent is evenly distributed;

[0158] Tempering stage: add the remaining mixing water and stir in a mixer at a speed of 75r / min for 2.5min to obtain a mixture. Adjust the slump to 180mm and the spread to 700mm to meet the pumping construction requirements;

[0159] S7: Forming and curing;

[0160] The mixture is poured into a mold coated with a release agent, and vibrated on a vibration table at a frequency of 48 Hz and an amplitude of 0.5 mm for 30 seconds to remove internal bubbles. The surface is then scraped flat and covered with a plastic film to prevent moisture evaporation. After molding, a concrete component is obtained;

[0161] Pre-curing (1h): Place the formed concrete components in a curing box with a temperature controlled at 24°C and a humidity of not less than 95%. Use a steam generator to automatically replenish moisture to promote the early reaction of the calcium sulfoaluminate expansion agent and compensate for early shrinkage.

[0162] Heating and curing (2h): Raise the temperature of the curing box to 58°C at a heating rate of 13°C / h for curing. During the heating process, start the infrared thermometer for real-time monitoring to prevent local overheating and fiber damage.

[0163] Gradient cooling: After the temperature rise and curing is completed, gradient ventilation cooling is adopted at a rate of 8°C / h to allow the concrete components to cool slowly. When the difference between the final temperature and the ambient temperature does not exceed 15°C, the concrete components are removed from the curing box.

[0164] Natural curing: After steam curing, move to the natural environment, cover the surface with a moisturizing film, maintain humidity not less than 80% for 28 days to complete the hydration reaction and continuously increase the strength (28d compressive strength not less than 120MPa, flexural strength not less than 15MPa).

[0165] Example 3: This example provides a method for preparing shrinkage-free ferroaluminate cement-based ultra-high performance concrete, comprising the following steps:

[0166] The following steps are involved:

[0167] S1: weigh the raw materials;

[0168] 108 parts of activated gelling material;

[0169] The mass ratio of ferroaluminate cement, silica fume, S95 grade slag powder and grade II fly ash in the activated cementitious material is 58:12:13:7;

[0170] Ferroaluminate cement is obtained by sintering calcium raw materials, aluminum raw materials and iron raw materials in a mass ratio of 5:2:3;

[0171] silica fume Content ≥ 90%, average particle size 0.5μm, loss on ignition not higher than 3%; slag powder 28d activity index not lower than 95%; fly ash fineness (45μm sieve residue) not higher than 20%;

[0172] 30-40 parts of mineralized aggregate;

[0173] The mass ratio of mineralized ceramsite to manufactured sand in the mineralized aggregate is 18:27;

[0174] In the mineralized ceramsite, the mass ratio of 4mm particle size to 6mm particle size is 6:4; the fineness modulus of the manufactured sand is 2.4, and the stone powder content does not exceed 5%;

[0175] 6.3 parts of admixture;

[0176] The mass ratio of polycarboxylate water reducer, composite expansion agent and nano-modifier in the admixture is 1.1:4.8:0.7;

[0177] The sodium sulfate content in the polycarboxylate water reducer shall not exceed 5%; the mass ratio of calcium sulfoaluminate to magnesium oxide in the composite expansion agent shall be 3:1; the nano-modifier shall contain nano- With Nano The mass ratio is 4:2.7, and the average particle size does not exceed 50nm;

[0178] 3.3 parts of reinforcing fiber;

[0179] The mass ratio of steel fiber to nanocarbon fiber in the reinforcing fiber is 2.2:0.08;

[0180] The steel fiber has a diameter of 0.2 mm and a length of 14 mm; the carbon nanofiber is 10 μm long and the diameter of the single fiber does not exceed 20 nm;

[0181] 17 parts mixing water; the mixing water contains 28-32% acid etching solution;

[0182] S2: Cementitious material modification;

[0183] Activation of ferroaluminate cement: put the ferroaluminate cement into the air flow mill and grind it at a high speed of 1300r / min;

[0184] Silica admixture was obtained by mixing silica fume, slag powder and fly ash, and immersed in 12% industrial waste hydrochloric acid, and etched at room temperature for 50 minutes, with the solid-liquid ratio controlled at 1:4. After acid etching, quicklime was added to the waste liquid to neutralize it to pH 6.8, and gypsum was precipitated and separated. The acid etching clear liquid was tested. After the content does not exceed 0.06%, it is used for subsequent mixing water; after acid etching, the siliceous admixture is dried at 66°C to a moisture content of no more than 1%, and then passed through a tunnel microwave kiln, at a power of 900W and a speed of 0.7m / min, for microwave treatment for 4min to obtain microwave-activated siliceous admixture;

[0185] The microwave activated silica admixture and ferroaluminate cement are compounded to obtain an activated cementitious material;

[0186] S3: aggregate modification;

[0187] Soak the ceramsite in stirred and clean water filtered by magnetic grid for 8 minutes and then dry it to improve the surface roughness of the ceramsite;

[0188] Dissolve industrial-grade calcium nitrate (concentration 0.25 mol / L) and water glass (concentration 5%) in mixing water at a molar ratio of 5:1, and adjust the pH to 10 to obtain a mineralization solution;

[0189] Immerse the ceramsite in a mineralizing solution and heat it in a water bath at 50-60°C for 40-60 minutes to form a calcium silicate gel layer on the surface of the ceramsite to obtain mineralized ceramsite;

[0190] The machine-made sand is first sieved through a 2.36mm sieve to remove large particles, then washed with a high-pressure water gun at a pressure of 5MPa to remove surface mud powder so that the mud content does not exceed 1%, and then dried at 62℃ to a moisture content of no more than 0.5%;

[0191] Compounding mineralized ceramsite and machine-made sand to obtain mineralized aggregate;

[0192] S4: fiber modification;

[0193] Brown corundum with a particle size of 0.8 mm was used to sandblast the steel fiber for 30 seconds at a pressure of 0.4 MPa to improve the surface roughness of the steel fiber.

[0194] The steel fiber was immersed in alumina-ferrocement slurry (containing 0.5% γ-aminopropyltriethoxysilane) with a water-binder ratio of 0.32, and then rolled and dried at 62°C to form a pre-coated layer to obtain pre-coated steel fiber;

[0195] Nanocarbon fibers and polycarboxylate water reducer were mixed at a mass ratio of 1:5.2 and dispersed in a high-speed shearing machine at 2900 r / min for 21 min to form a stable nanocarbon fiber suspension;

[0196] The pre-wrapped steel fibers and the nano-carbon fiber stable suspension are compounded to obtain the reinforced fibers;

[0197] S5: expansion agent modification;

[0198] A composite expander was prepared by uniformly mixing calcium sulfoaluminate and magnesium oxide expanders. A methyl cellulose (viscosity 20,000 mPa·s) aqueous solution (solid content 10%) was spray-dried (inlet air temperature 182°C, outlet air temperature 81°C) to form a controllable degradation film on the surface of the composite expander.

[0199] S6: compounding;

[0200] Dry mixing: put the activated cementitious material and mineralized aggregate into a forced mixer, pre-mix at a low speed of 40r / min for 3 minutes, and then disperse at a higher speed of 160r / min for 6 minutes to form a coarse aggregate-fine cementitious material skeleton structure;

[0201] Wet mixing stage: add 80% of mixing water, polycarboxylate water reducer and nano modifier, and stir in a planetary mixer at a speed of 100r / min for 4 minutes to fully hydrate the cementitious material, disperse the water reducer particles, and fill the pores with the nano modifier;

[0202] Fiber / swelling agent addition: Add reinforcing fiber and composite swelling agent, and shear and disperse them in a high-speed shear mixer at a speed of 200r / min for 6 minutes to ensure that the fiber monofilaments are dispersed and the swelling agent is evenly distributed;

[0203] Tempering stage: add the remaining mixing water and stir in a mixer at a speed of 82r / min for 3 minutes to obtain a mixture. Adjust the slump to 180mm and the spread to 700mm to meet the pumping construction requirements;

[0204] S7: Forming and curing;

[0205] The mixture is poured into a mold coated with a release agent, and vibrated on a vibration table at a frequency of 50 Hz and an amplitude of 0.8 mm for 50 seconds to remove internal bubbles. The surface is then scraped flat and covered with a plastic film to prevent moisture evaporation. After molding, a concrete component is obtained;

[0206] Pre-curing (1h): Place the formed concrete components in a curing box with a temperature controlled at 25°C and a humidity of not less than 95%. Use a steam generator to automatically replenish moisture to promote the early reaction of the calcium sulfoaluminate expansion agent and compensate for early shrinkage.

[0207] Heating and curing (2h): Raise the temperature of the curing box to 60℃ at a heating rate of 14℃ / h for curing. During the heating process, start the infrared thermometer for real-time monitoring to prevent local overheating and fiber damage;

[0208] Gradient cooling: After the temperature rise and curing is completed, gradient ventilation cooling is adopted at a rate of 9°C / h to allow the concrete components to cool slowly. When the difference between the final temperature and the ambient temperature does not exceed 15°C, the concrete components are removed from the curing box.

[0209] Natural curing: After steam curing, move to the natural environment, cover the surface with a moisturizing film, maintain humidity not less than 80% for 28 days to complete the hydration reaction and continuously increase the strength (28d compressive strength not less than 120MPa, flexural strength not less than 15MPa).

[0210] Comparative Example 1: This comparative example differs from Example 3 in that Portland cement is used instead of ferroaluminate cement. The Portland cement is obtained by sintering calcium oxide, silicon dioxide, aluminum oxide, and ferrosoferric oxide in a mass ratio of 60:20:7:5.

[0211] Comparative Example 2: The difference between this comparative example and Example 3 is that in this comparative example, the methyl cellulose ethanol solution is not spray-dried to form a controllable degradation film on the surface of the composite expansion agent.

[0212] Comparative Example 3: The difference between this comparative example and Example 3 is that the steel fiber and nano-carbon fiber are not modified in this comparative example.

[0213] Comparative Example 4: The difference between this comparative example and Example 3 is that, in this comparative example, the methylcellulose ethanol solution is not spray-dried to form a controllable degradation film on the surface of the composite expansion agent; nor is the steel fiber and nano-carbon fiber modified.

[0214] Comparative Example 5: The difference between this comparative example and Example 3 is that, in this comparative example, the methylcellulose ethanol solution is not spray-dried to form a controllable degradation film on the surface of the composite expansion agent, and silicate cement is selected instead of ferroaluminate cement.

[0215] Experimental Example 1: Rapid hardening and early strength performance test;

[0216] According to GB / T 17671-1999 “Test method for strength of cement mortar (ISO method)”, prismatic specimens with a size of 40 mm × 40 mm × 160 mm were prepared, with 3 pieces in each group. The compressive strength P (MPa) at the test age of 1 day, 3 days, and 7 days was measured.

[0217] The results are shown in Table 1:

[0218]

[0219] Table 1

[0220] Analysis of the data in the above table shows that compared with silicate cement, ferroaluminate cement can make the early strength of concrete increase rapidly, quickly reach higher strength, significantly shorten the project period, and speed up the construction progress. In addition, the compounding of ferroaluminate cement and composite expansive agent modified by methyl cellulose coating has a synergistic effect on improving the rapid hardening and early strength properties of concrete.

[0221] Experimental Example 2: Compressive strength, flexural strength and toughness testing;

[0222] The compressive strength and flexural strength at 28 days were tested according to GB / T 50081-2019. Specimens were 100×100×100 mm cubes (compressive) and 100×100×400 mm prisms (flexural). The loading rates were 0.5 MPa / s for compression and 0.05 MPa / s for flexural.

[0223] According to JGJ / T 221-2010, bending toughness (0-5.5mm deformation energy) was tested and a 100×100×400mm specimen was prepared.

[0224] The results are shown in Table 2:

[0225] Table 2

[0226]

[0227] Analysis of the data in the above table shows that the strength and toughness of concrete can be improved by sandblasting and pre-wrapping the steel fibers in the composite fibers, and dispersing and modifying the nano-carbon fibers with polycarboxylic acid water-reducing agent. Although the composite expansive agent modified by methyl cellulose coating has no effect on the mechanical properties of concrete, it can further strengthen the mechanical properties of concrete when compounded with the composite fibers.

[0228] Experimental Example 3: Autogenous shrinkage performance test;

[0229] The autogenous shrinkage rate was tested in accordance with GB / T 50082-2024. A non-contact concrete shrinkage deformation measuring instrument was used. The specimen was a 100×100×515mm prism. The specimen was immediately sealed with plastic film after casting and vibration. The test environment temperature was (20±2)°C. The autogenous shrinkage rate P was tested from the beginning of initial setting to 72 hours after initial setting (the smaller the autogenous shrinkage rate, the better the shrinkage resistance of the concrete).

[0230] The results are shown in Table 3:

[0231] Table 3

[0232]

[0233] Analysis of the data in the table above shows that methylcellulose coating of a composite expansive agent composed of a mixture of calcium sulfoaluminate and magnesium oxide expansive agents significantly improves the autogenous shrinkage of concrete. The mechanism is as follows: the methylcellulose coating provides a slow-release effect on the composite expansive agent. In the early stages of concrete development, the coating envelops the expansive agent particles, preventing the calcium sulfoaluminate and magnesium oxide components within them from reacting with water too rapidly during the initial hydration phase. This prevents internal structural stress concentration and uneven expansion caused by excessive hydration of the expansive agent in the early stages of concrete development. As the concrete hydration process progresses, the methylcellulose coating is gradually eroded or dissolved by the hydration products, allowing the expansive agent particles to continuously and stably release their active ingredients, achieving sustained and controllable expansion. This better matches the development of concrete's autogenous shrinkage and enhances its compensation effect.

[0234] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A non-shrinkage ferroaluminate cement-based ultra-high performance concrete, characterized in that: By weight, it comprises the following components: 96-120 parts of activated gelling material; The mass ratio of ferroaluminate cement, silica fume, slag powder and fly ash in the activated cementitious material is 55-60:10-15:10-15:5-8; The silica fume, slag powder and fly ash are modified by acid etching, drying and microwave activation; 30-40 parts of mineralized aggregate; The mass ratio of mineralized ceramsite to machine-made sand in the mineralized aggregate is 12-25:21-32; The mineralized ceramsite is modified by soaking and mineralizing solution; 5.3-7.5 parts of admixture; The mass ratio of the polycarboxylate water-reducing agent, the composite expansion agent and the nano-modifier in the admixture is 0.8-1.2:4-5.5:0.5-0.8; The mass ratio of calcium sulfoaluminate to magnesium oxide in the composite expansion agent is 3-4:1; the nano-modifier With Nano The mass ratio is 3-4:2-3; The composite expansion agent is modified by methyl cellulose coating; 2.5-3.6 parts of reinforcing fiber; The mass ratio of steel fiber to nano carbon fiber in the reinforcing fiber is 1.5-2.5:0.05-0.1; The steel fibers are modified by sandblasting and pre-wrapping; The nano-carbon fibers are dispersed and modified by a polycarboxylate water-reducing agent; 15-18 parts of mixing water; the mixing water contains 28-32% acid etching solution.

2. A method for preparing the non-shrinkage ferroaluminate cement-based ultra-high performance concrete according to claim 1, characterized in that: The following steps are involved: S1: Cementitious material modification; Activation of ferroaluminate cement, high-speed crushing of ferroaluminate cement; Silica fume, slag powder and fly ash are mixed to obtain a siliceous admixture, which is immersed in an acid solution and etched at room temperature. After acid etching, quicklime is added to the waste liquid to neutralize it, and gypsum is precipitated and separated. The acid etching clear liquid is tested and used for subsequent mixing water. The acid-etched siliceous admixture is dried and microwave-treated to obtain a microwave-activated siliceous admixture. The activated cementitious material is obtained by compounding microwave activated silica admixture and ferroaluminate cement; S2: aggregate modification; Soak the ceramsite in stirred and clean water filtered by magnetic grid and then dry it to improve the surface roughness of the ceramsite; Dissolve calcium nitrate and water glass in mixing water and adjust the pH to obtain a mineralized solution; The ceramsite is immersed in a mineralizing solution and heated in a water bath to form a calcium silicate gel layer on the surface of the ceramsite to obtain mineralized ceramsite; The machine-made sand is sieved to remove large particles, washed with a high-pressure water gun to remove surface mud and powder, and dried; Compounding mineralized ceramsite and machine-made sand to obtain mineralized aggregate; S3: fiber modification; Brown corundum is used to sandblast steel fibers to improve the surface roughness of the steel fibers; The steel fiber is immersed in a ferroaluminate cement slurry containing a silane coupling agent, and the slurry is rolled and dried to form a pre-coated layer, thereby obtaining a pre-coated steel fiber; The nanocarbon fibers are mixed with a polycarboxylate water reducer and dispersed in a high-speed shearing machine to form a stable suspension of the nanocarbon fibers; The pre-wrapped steel fibers and the nano-carbon fiber stable suspension are compounded to obtain the reinforced fibers; S4: expansion agent modification; A calcium sulfoaluminate expansion agent and a magnesium oxide expansion agent are uniformly mixed to obtain a composite expansion agent, and a methyl cellulose ethanol solution is spray-dried to form a controllable degradation film on the surface of the composite expansion agent; S5: compounding; Dry mixing: put the activated cementitious material and mineralized aggregate into a forced mixer, pre-mix at low speed, and then disperse at high speed to form a coarse aggregate-fine cementitious material skeleton structure; Wet mixing stage: add 78-82% mixing water, polycarboxylate water reducer, nano modifier and stir evenly; Fiber / expansion agent addition: Add reinforcing fiber and composite expansion agent, shear and disperse; Conditioning stage: add the remaining mixing water and stir to obtain a mixture; S6: Forming and curing; The mixture is poured into a mold coated with a release agent, and internal bubbles are removed by vibration. The surface is scraped flat and covered with a plastic film to obtain a concrete component after molding. The concrete is subjected to pre-curing, temperature-raising curing, gradient cooling and natural curing.

3. The method for preparing the non-shrinkage ferroaluminate cement-based ultra-high performance concrete according to claim 2, characterized in that: S1 specifically comprises: crushing the ferroaluminate cement at a high speed of 1000-1500 r / min; The silica admixture is obtained by mixing silica fume, slag powder and fly ash, and then immersed in 10-15% industrial waste hydrochloric acid, and etched at room temperature for 40-60 minutes, with the solid-liquid ratio controlled at 1:3-5. After acid etching, quicklime is added to the waste liquid to neutralize it to a pH value of 6-7, and gypsum is separated by precipitation. The acid etching clear liquid is tested. After the content does not exceed 0.06%, it is used for subsequent mixing water; after acid etching, the siliceous admixture is dried at 60-70°C to a moisture content of no more than 1%, and microwave-treated for 3-4 minutes at a power of 800-1000W and a speed of 0.5-1m / min to obtain microwave-activated siliceous admixture; The activated cementitious material is obtained by compounding microwave activated siliceous admixture and ferroaluminate cement.

4. The method for preparing the non-shrinkage ferroaluminate cement-based ultra-high performance concrete according to claim 2, wherein: S2 is specifically as follows: soaking the ceramsite in stirred and clean water filtered by the magnetic grid for 5-10 minutes and then drying it to increase the surface roughness of the ceramsite; Dissolve industrial-grade calcium nitrate and water glass in a molar ratio of 4-6:1 in mixing water, and adjust the pH value to between 9.5 and 10.5 to obtain a mineralization solution; Immerse the ceramsite in a mineralizing solution and heat it in a water bath at 50-60°C for 40-60 minutes to form a calcium silicate gel layer on the surface of the ceramsite to obtain mineralized ceramsite; The machine-made sand is sieved to remove large particles, washed to remove surface mud powder, so that the mud content does not exceed 1%, and dried at 55-65℃ to a moisture content of no more than 0.5%; The mineralized ceramsite and machine-made sand are compounded to obtain the mineralized aggregate.

5. The method for preparing the non-shrinkage ferroaluminate cement-based ultra-high performance concrete according to claim 2, characterized in that: S3 specifically involves sandblasting the steel fiber for 30 seconds using brown corundum with a particle size of 0.8 mm at a pressure of 0.4-0.5 MPa to improve the surface roughness of the steel fiber; The steel fiber is immersed in a ferroaluminate cement slurry containing γ-aminopropyltriethoxysilane at a water-binder ratio of 0.25-0.35, and the slurry is rolled and dried at 55-65° C. to form a pre-coated layer, thereby obtaining a pre-coated steel fiber; Mix the nanocarbon fibers and the polycarboxylate water reducer in a mass ratio of 1:4.5-5.5, and disperse them in a high-speed shearing machine at 2800-3200 r / min for 18-22 minutes to form a stable suspension of nanocarbon fibers; The pre-wrapped steel fibers and the nano-carbon fiber stable suspension are compounded to obtain the reinforced fibers.

6. The method for preparing the non-shrinkage ferroaluminate cement-based ultra-high performance concrete according to claim 2, characterized in that: S4 specifically comprises: uniformly mixing calcium sulfoaluminate expansion agent and magnesium oxide expansion agent to obtain a composite expansion agent; spray drying a methyl cellulose ethanol solution with a solid content of 9-11% and a viscosity of 18,000-22,000 mPa·s at an inlet air temperature of 175-185°C and an outlet air temperature of 75-85°C to form a controllable degradation film on the surface of the composite expansion agent.

7. The method for preparing the non-shrinkage ferroaluminate cement-based ultra-high performance concrete according to claim 2, characterized in that: S5 is specifically as follows: the activated cementitious material and mineralized aggregate are put into a forced mixer, premixed at a low speed of 30-50 r / min for 3-4 minutes, and then dispersed at a higher speed of 150-200 r / min for 5-6 minutes to form a coarse aggregate-fine cementitious material skeleton structure; Add 78-82% mixing water, polycarboxylate water reducer, and nano modifier, and stir at a speed of 95-105r / min for 3.5-4.5min; Add reinforcing fiber and composite expansion agent, and shear and disperse in a high-speed shear mixer at a speed of 190-210 r / min for 5.5-6.5 minutes; Add the remaining mixing water and stir in a mixer at a speed of 75-85 r / min for 2.5-3.5 min to obtain a mixture.

8. The method for preparing the non-shrinkage ferroaluminate cement-based ultra-high performance concrete according to claim 2, characterized in that: S6 specifically comprises: pouring the mixture into a mold coated with a release agent, vibrating the mixture at a frequency of 48-52 Hz and an amplitude of 0.5-1.0 mm for 30-60 seconds to remove internal bubbles, smoothing the surface and covering it with a plastic film to prevent moisture evaporation, and then forming a concrete component; Pre-curing for 1-2 hours, temperature 24-26℃, humidity not less than 95%; Heat up and cure for 2-3 hours, raising the temperature to 58-62℃ at a heating rate of 13-15℃ / h; Gradient cooling for 2-4 hours: Cool down at a rate of 8-10℃ / h. When the difference between the final temperature and the ambient temperature does not exceed 15℃, remove the container from the curing box. Move to the natural environment, cover the surface with a moisturizing film, and maintain naturally.

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