A high performance concrete and a method for preparing the same

Abstract

The application relates to the technical field of concrete materials, and specifically discloses high-performance concrete and a preparation method thereof. The high-performance concrete is prepared from the following raw materials in parts by mass: cement 9-12 parts, fly ash 1.5-3 parts, metakaolin 1.2-2.4 parts, calcium sulfoaluminate 0.4-0.6 parts, fine aggregate 10.5-13.5 parts, composite admixture 0.38-0.48 parts, steel fiber 1.5-3 parts, modified resin 0.6-1.2 parts and water 1.5-2.4 parts; the composite admixture comprises a polycarboxylate-type water reducing agent, sodium gluconate and a defoaming agent; the modified resin is prepared from hydroxypropyl methylcellulose, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid and a crosslinking agent through a water solution polymerization method. The high-performance concrete prepared by the application realizes the synergistic improvement of strength and toughness, and has excellent comprehensive mechanical properties.

Description

Technical Field

[0001] This application relates to the technical field of concrete materials, and more specifically, to a high-performance concrete and a method for its preparation. Background Technology

[0002] High-performance concrete is a new type of concrete material produced using conventional materials and processes. It possesses all the mechanical properties required for concrete structures, while also exhibiting high durability, high workability, and high volume stability. Its core characteristic is the use of a low water-cement ratio. However, when the water-cement ratio is reduced to a certain threshold (e.g., below 0.30), the existing technology reveals its inherent limitations. The free water required for the hydration of the cementitious materials is severely lacking. The cement hydration process rapidly consumes this limited water, leading to a rapid decrease in internal relative humidity and triggering severe early autogenous shrinkage. This autogenous shrinkage occurs in the early stages of concrete microstructure formation, and traditional curing methods are insufficient to effectively inhibit shrinkage cracking.

[0003] Existing technologies typically employ expanding agents (such as calcium vanadium) to compensate for shrinkage, but the full realization of their expanding effectiveness also depends on a continuous and sufficient supply of moisture. In environments with low water-cement ratios, moisture is rapidly depleted, forcing the hydration reaction of the expanding agent to cease, resulting in a compensation effectiveness far below the theoretical value and an inability to effectively suppress cracking.

[0004] Patent application CN119874300A discloses a high-performance concrete comprising the following raw materials in parts by weight: 200-230 parts cement, 10-20 parts modified bentonite, 10-20 parts nano-potassium feldspar powder, 650-700 parts fine aggregate, 950-1000 parts coarse aggregate, 30-40 parts mineral powder, 30-40 parts fly ash, 5-10 parts water-reducing agent, and 140-150 parts water.

[0005] In this technical solution, in order to further improve the mechanical properties of concrete, modified bentonite, nano-potassium feldspar powder and other active components are introduced to form a multi-component composite system together with mineral powder and fly ash. However, this technical solution simply combines multiple components with significant differences in hydration activity and reaction rate, which can easily lead to hydration competition and product interference. Not only is it difficult to control shrinkage in a coordinated manner, but the asynchronous hydration also aggravates internal stress, resulting in uneven distribution of hydration products and weakening of the interface transition zone. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this application provides a high-performance concrete and a method for preparing the same.

[0007] In the first aspect, this application provides a high-performance concrete, which adopts the following technical solution:

[0008] A high-performance concrete is prepared from the following raw materials in parts by weight:

[0009] The ingredients are: 9-12 parts cement, 1.5-3 parts fly ash, 1.2-2.4 parts metakaolin, 0.4-0.6 parts calcium sulfoaluminate, 10.5-13.5 parts fine aggregate, 0.38-0.48 parts composite admixture, 1.5-3 parts steel fiber, 0.6-1.2 parts modified resin, and 1.5-2.4 parts water.

[0010] The composite admixture includes a polycarboxylate superplasticizer, sodium gluconate, and an antifoaming agent;

[0011] The modified resin is prepared by aqueous solution polymerization using hydroxypropyl methylcellulose, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid and crosslinking agent as raw materials.

[0012] This technical solution is based on a low water-cement ratio and constructs a high-performance concrete system through the synergistic effect of multiple components: modified resin is polymerized in aqueous solution to form a three-dimensional network with specific pore sizes, achieving moisture locking and continuous internal curing; calcium sulfoaluminate is fully hydrated by the internal curing moisture to generate an expansion effect; composite admixtures improve the workability defects caused by the low water-cement ratio and high fiber content; fly ash and metakaolin optimize the pore structure through gradient hydration; steel fibers and resin synergistically bridge cracks, and the functions of each component are complementary, ultimately achieving a unity of workability, volume stability and durability.

[0013] Preferably, the method for preparing the modified resin includes the following steps:

[0014] Under an inert atmosphere, hydroxypropyl methylcellulose is added to water and mixed evenly. An initiator is added, and the temperature is raised to 70-90°C. A premix of acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and a crosslinking agent is added. The mixture is kept at this temperature for 3-5 hours, and the solid and liquid are separated. The mixture is then dried and pulverized to obtain the modified resin.

[0015] Preferably, the mass ratio of acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, crosslinking agent, hydroxypropyl methylcellulose and water is (2.5~3.5):1:(0.01~0.03):(0.05~0.1):10.

[0016] Preferably, the initiator includes sodium persulfate and sodium sulfite.

[0017] Preferably, the initiator is used in an amount of 0.8% to 1.5% of the total mass of acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid.

[0018] Preferably, the mass ratio of sodium persulfate to sodium sulfite is (2~3):1.

[0019] Preferably, the crosslinking agent is N,N'-methylenebisacrylamide.

[0020] In this technical solution, the modified resin undergoes copolymerization of acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid under the action of a crosslinking agent to form a crosslinked polymer network. Simultaneously, pre-dissolved hydroxypropyl methylcellulose long-chain molecules are physically encapsulated, entangled, and fixed by the in-situ generated and continuously shrinking polymer network, thus constructing a stable composite system. During the concrete mixing stage, the sulfonic acid groups provided by 2-acrylamide-2-methylpropanesulfonic acid endow the resin with excellent calcium ion resistance, enabling it to maintain long-term performance in a cement-based environment. It also provides continuous internal curing for the concrete through a water absorption-slow release mechanism, effectively inhibiting autogenous shrinkage. The organic composite phase formed after curing enhances the toughness of the matrix and synergistically improves the crack resistance and durability of the concrete with the fiber materials.

[0021] Preferably, the hydroxypropyl methylcellulose undergoes the following pretreatment steps before use:

[0022] Mix the vinylsilane coupling agent and the aqueous ethanol solution evenly, adjust the pH to 4-5, add hydroxypropyl methylcellulose, heat to 50-70℃, react for 4-6 hours, extract, wash, and dry to obtain pretreated hydroxypropyl methylcellulose.

[0023] Preferably, the vinyl silane coupling agent is silane coupling agent KH570.

[0024] Preferably, the mass ratio of the vinylsilane coupling agent to the aqueous ethanol solution is (10~15):(485~490).

[0025] Preferably, the fly ash is surface-modified fly ash, and its preparation method includes the following steps:

[0026] Fly ash, anhydrous calcium sulfate and lithium hydroxide are mixed evenly in a mass ratio of 100:(2~5):(1~3) and ground for 2~3 hours to obtain surface-modified fly ash.

[0027] In this technical solution, the dense glassy shell on the surface of the fly ash is first broken by mechanical grinding, exposing the active silica-alumina phase inside. Simultaneously, anhydrous calcium sulfate and lithium hydroxide added during grinding adhere uniformly to the newly formed surface. Upon contact with water, they rapidly establish a strongly alkaline environment, effectively stimulating the depolymerization of the silica-alumina glassy network structure and promoting the rapid dissolution of active SiO2 and Al2O3. These dissolved active components react rapidly with Ca(OH)2 released during cement hydration, thus generating a large amount of CSH gel in the early stages of hydration. This early-formed gel effectively fills capillary pores, significantly reducing early self-shrinkage. Simultaneously, its hydration products intertwine with the ettringite formed from calcium sulfoaluminate, forming a stable microscopic support framework and significantly improving the compensation efficiency of the expansion agent. Furthermore, the early hydration rate of the modified fly ash increases after activation, leading to increased water consumption. The continuous internal curing water release of the modified resin precisely replenishes this demand, forming a dynamic supply-consumption balance and ensuring the continuous progress of the hydration reaction.

[0028] Preferably, the steel fiber is a surface-modified steel fiber, and its preparation method includes the following steps:

[0029] Sodium silicate nonahydrate, polyvinyl alcohol, and water are mixed evenly, and the pH is adjusted to 10.5-11.5. Steel fibers are added, and the mixture is stirred for 15-25 minutes. Solid-liquid separation is performed, followed by washing. The mixture is then immersed in calcium nitrate solution, and the pH is adjusted to 9.5-10.5. The mixture is stirred for 40-60 minutes, and the solid-liquid separation is performed. Under an inert atmosphere, the mixture is first kept at 80-100℃ for 40-60 minutes, and then kept at 150-200℃ for 1.5-2.5 hours. After cooling, surface-modified steel fibers are obtained.

[0030] Before the steel fibers are added, they undergo acid washing, alkali washing and drying pretreatment.

[0031] Preferably, the steel fiber is a corrugated steel fiber.

[0032] Preferably, the mass ratio of the steel fiber, sodium silicate nonahydrate, polyvinyl alcohol and water is 10:(0.8~1.2):(0.2~0.4):(12~15).

[0033] Preferably, the calcium nitrate solution has a mass fraction of 15% to 25%.

[0034] In this technical solution, sodium silicate nonahydrate dissolves in water and hydrolyzes to generate nano-silica sol, which forms a mixed system with polyvinyl alcohol. Steel fibers, after acid and alkali washing, are added, and then treated with calcium nitrate to generate a nano-calcium silicate-polymer composite coating. At the macroscopic level, the wavy structure provides strong anchoring force through mechanical interlocking; at the microscopic level, the nano-calcium silicate in the composite coating chemically bonds with cement hydration products, significantly strengthening the weakest fiber-matrix interface transition zone. The combined effect of these two processes ensures effective stress transfer across different scales, thereby significantly improving the toughness and crack resistance of the concrete.

[0035] Preferably, the high-performance concrete further includes 0.5 to 1 part by weight of basalt fiber.

[0036] Preferably, the basalt fiber has a length of 12-15 mm and a diameter of 10-15 μm.

[0037] In this technical solution, surface-modified corrugated steel fibers, with their high elastic modulus and excellent ductility, primarily bear macroscopic loads in concrete. Through the strong mechanical anchoring force of the corrugated structure, they effectively bridge and inhibit the propagation of macroscopic cracks, making them the main contributor to toughness. Basalt fibers, due to their slender shape and high dispersibility, can be more evenly distributed in the concrete matrix, intervening in the early stages of stress, effectively refining microscopic cracks and inhibiting their initiation and merging. Their three-dimensional interweaving with steel fibers jointly dissipates energy, significantly improving the impact and fatigue resistance of concrete.

[0038] Preferably, the high-performance concrete further includes 0.15 to 0.25 parts by weight of nano-montmorillonite.

[0039] In this technical solution, nano-montmorillonite adsorbs and stores moisture through its layered structure, while modified resin achieves slow and gradual release of moisture through a three-dimensional network. The two form a stepped internal curing system: montmorillonite can quickly replenish early hydration moisture, while modified resin continuously supplies moisture in the later stages, together maintaining a stable humidity environment inside the concrete and inhibiting autogenous shrinkage.

[0040] Preferably, the high-performance concrete further includes 0.2 to 0.4 parts by weight of ultrafine calcium carbonate.

[0041] Preferably, the ultrafine calcium carbonate has a particle size distribution of 1~5μm.

[0042] In this technical solution, ultrafine calcium carbonate mainly plays a physical filling role. Its micron-sized particles can effectively fill the gaps between aggregates, and work synergistically with nano-montmorillonite to optimize the pore structure, improve the density of the system, and provide stable mechanical support for concrete.

[0043] Secondly, this application provides a method for preparing high-performance concrete, comprising the following steps:

[0044] S1: Add cement, fly ash, metakaolin and calcium sulfoaluminate to a high-speed mixer and mix for 3-5 minutes. Add fine aggregate and continue mixing for 5-8 minutes to obtain dry mix.

[0045] S2: Mix the composite admixture, modified resin and water evenly, add it to the dry mix, mix for 5-8 minutes, add steel fiber, and continue mixing for 5-8 minutes to obtain high-performance concrete.

[0046] In this technical solution, during the dry mixing stage, the cementitious materials and aggregates are first mixed to form a homogeneous matrix, and then steel fibers are added to ensure uniform dispersion. During the wet mixing stage, the composite admixture and modified resin are pre-dissolved in water and added to the dry mix in stages. This ensures the formation of the internal curing network within the modified resin and allows each functional component to fully function. This process of first drying and then wetting, with staged liquid addition, effectively coordinates the timing of moisture control, expansion compensation, and fiber reinforcement, achieving excellent workability and durability of concrete at ultra-low water-cement ratios.

[0047] Preferably, in step S1, when adding steel fibers, the step of adding basalt fibers is also included.

[0048] Preferably, in step S1, after calcium sulfoaluminate, a step of adding nano-montmorillonite is also included.

[0049] Preferably, in step S1, after calcium sulfoaluminate, the step of adding ultrafine calcium carbonate is further included.

[0050] In summary, this application has the following beneficial effects:

[0051] This application focuses on a low water-cement ratio and imparts superior comprehensive performance to concrete through multi-component synergy: Modified resin, polymerized in aqueous solution, forms a three-dimensional network with specific pore sizes, which not only locks in moisture for continuous internal curing and effectively inhibits concrete auto-shrinkage, but also synergistically bridges microcracks with steel fibers, significantly improving matrix toughness; the moisture released during internal curing ensures full hydration of calcium sulfoaluminate, whose moderate expansion effect compensates for shrinkage, further enhancing volume stability; the composite admixture combines water-reducing, retarding, and defoaming functions, specifically addressing workability challenges caused by low water-cement ratios and high fiber content; fly ash and metakaolin, due to their different hydration rates, create a gradient hydration effect, rapidly filling pores in the early stages and continuously densifying the structure in the later stages, significantly optimizing the internal pore morphology. The complementary functions and synergistic effects of each component ultimately achieve a simultaneous leap in workability, volume stability, and durability of concrete under low water-cement ratio conditions. Detailed Implementation

[0052] The present application will be further described in detail below with reference to the embodiments.

[0053] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0054] Cement: P·O 52.5 Portland cement;

[0055] The fly ash is grade I fly ash, with a sieve residue of ≤8% on a 45μm square hole sieve and a total content of SiO2, Al2O3, and Fe2O3 ≥80%.

[0056] Metakaolin: Specific surface area ≥ 800 m² 2 / kg, volcanic ash activity index ≥110%, loss on ignition ≤3.0%;

[0057] Fine aggregate: Extra-high grade medium sand, fineness modulus 2.7~3.0, continuous gradation (0.15~5mm), mud content ≤0.5%, bulk density ≥1700kg / m³ 3 Apparent density ≥ 2650 kg / m³ 3 ;

[0058] The steel fibers are corrugated steel fibers: diameter 0.15~0.25mm, length 12~15mm, tensile strength ≥2800MPa;

[0059] Basalt fiber: length 12~15mm, diameter 13~15μm, high temperature resistance ≥800℃, tensile strength ≥3000MPa;

[0060] Calcium sulfoaluminate: with anhydrous calcium sulfoaluminate as the main component, purity ≥90%, and particle size ≤60μm;

[0061] Ultrafine calcium carbonate: particle size 1~5μm, purity ≥98%.

[0062] Preparation Examples 1-3 Modified Resins

[0063] Preparation Example 1

[0064] The preparation method of the modified resin in this example includes the following steps:

[0065] S11: Add 2.5 kg of acrylic acid, 1 kg of 2-acrylamide-2-methylpropanesulfonic acid and 0.01 kg of N,N'-methylenebisacrylamide to a container and stir at 300 r / min for 20 min to obtain a premix;

[0066] S12: Under a nitrogen atmosphere, 0.05 kg of hydroxypropyl methylcellulose was added to 10 kg of deionized water and stirred at 300 r / min for 20 min. 31.5 g of sodium persulfate and 10.5 g of sodium sulfite were added and stirred for another 5 min. The temperature was raised to 70 °C and held for 10 min. The premix was then added. After the addition was complete, the temperature was held for 5 h. 2.5 kg of anhydrous ethanol was added and the system temperature was maintained at 50 °C. After stirring for 30 min, the mixture was filtered while hot and then dried at 60 °C to constant weight. The mixture was pulverized and passed through a 200 mesh standard sieve. The sieve residue was collected to obtain the modified resin.

[0067] Preparation Example 2

[0068] The preparation method of the modified resin in this example includes the following steps:

[0069] S11: Add 3.5 kg of acrylic acid, 1 kg of 2-acrylamide-2-methylpropanesulfonic acid and 0.03 kg of N,N'-methylenebisacrylamide to a container and stir at 300 r / min for 30 min to obtain a premix;

[0070] S12: Under a nitrogen atmosphere, 0.1 kg of hydroxypropyl methylcellulose was added to 10 kg of deionized water and stirred at 300 r / min for 20 min. 24 g of sodium persulfate and 12 g of sodium sulfite were added and stirred for another 5 min. The mixture was heated to 90 °C and kept at that temperature for 10 min. The premix was then added. After the addition was complete, the mixture was kept at that temperature for 3 h. 3.5 kg of anhydrous ethanol was added and the system temperature was maintained at 50 °C. The mixture was stirred for 30 min and then filtered while hot. The mixture was then dried at 60 °C to constant weight, pulverized, and passed through a 200-mesh standard sieve. The sieve residue was collected to obtain the modified resin.

[0071] Hydroxypropyl methylcellulose undergoes the following pretreatment steps before use:

[0072] 10g of silane coupling agent KH570 and 490g of 25% ethanol aqueous solution were added to the reactor and stirred until homogeneous. The pH was adjusted to 4 using 8% glacial acetic acid. Then, 0.1kg of hydroxypropyl methylcellulose was added and stirred until homogeneous. The mixture was heated to 50℃ and reacted for 6 hours. After extraction with anhydrous ethanol, the mixture was washed three times with anhydrous ethanol, dried at 60℃ to constant weight, and then lightly ground and dispersed for later use.

[0073] Preparation Example 3

[0074] The preparation method of the modified resin in this example includes the following steps:

[0075] S11: Add 3 kg of acrylic acid, 1 kg of 2-acrylamide-2-methylpropanesulfonic acid and 0.02 kg of N,N'-methylenebisacrylamide to a container and stir at 300 r / min for 25 min to obtain a premix;

[0076] S12: Under a nitrogen atmosphere, 0.08 kg of hydroxypropyl methylcellulose was added to 10 kg of deionized water and stirred at 300 r / min for 20 min. 30 g of sodium persulfate and 10 g of sodium sulfite were added and stirred for another 5 min. The temperature was raised to 80 °C and kept at that temperature for 10 min. Then the premix was added. After the addition was complete, the temperature was kept at that temperature for 4 h. 3 kg of anhydrous ethanol was added and the system temperature was kept at 50 °C. After stirring for 30 min, the mixture was filtered while hot and then dried at 60 °C to constant weight. The mixture was pulverized and passed through a 200-mesh standard sieve. The sieve residue was taken to obtain the modified resin.

[0077] Hydroxypropyl methylcellulose undergoes the following pretreatment steps before use:

[0078] 15g of silane coupling agent KH570 and 485g of 25% ethanol aqueous solution were added to the reactor and stirred until homogeneous. The pH was adjusted to 5 with 8% glacial acetic acid. Then, 0.08kg of hydroxypropyl methylcellulose was added and stirred until homogeneous. The mixture was heated to 70℃ and reacted for 4 hours. After extraction with anhydrous ethanol, the mixture was washed three times with anhydrous ethanol, dried at 60℃ to constant weight, and then lightly ground and dispersed for later use.

[0079] Preparation Examples 4-6: Surface-Modified Fly Ash

[0080] Preparation Example 4

[0081] The preparation method of surface-modified fly ash in this example includes the following steps:

[0082] Add 10 kg of fly ash, 0.2 kg of anhydrous calcium sulfate and 0.1 kg of lithium hydroxide to a dry powder mixer and stir at 500 r / min for 30 min. Then transfer it to a grinding equipment and grind for 3 h. During the grinding process, control the temperature to not exceed 60℃ through the equipment's circulating cooling system. After grinding, cool it to below 40℃ to obtain surface-modified fly ash.

[0083] Preparation Example 5

[0084] The preparation method of surface-modified fly ash in this example includes the following steps:

[0085] Add 10 kg of fly ash, 0.5 kg of anhydrous calcium sulfate, and 0.3 kg of lithium hydroxide to a dry powder mixer and stir at 500 r / min for 30 min. Then transfer the mixture to a grinding equipment and grind for 2 h. During the grinding process, control the temperature to not exceed 60℃ through the equipment's circulating cooling system. After grinding, cool the mixture to below 40℃ to obtain surface-modified fly ash.

[0086] Preparation Example 6

[0087] The preparation method of surface-modified fly ash in this example includes the following steps:

[0088] Add 10 kg of fly ash, 0.4 kg of anhydrous calcium sulfate, and 0.2 kg of lithium hydroxide to a dry powder mixer and stir at 500 r / min for 30 min. Then transfer the mixture to a grinding equipment and grind for 2.5 h. During the grinding process, control the temperature to not exceed 60℃ through the equipment's circulating cooling system. After grinding, cool the mixture to below 40℃ to obtain surface-modified fly ash.

[0089] Preparation Examples 7-9: Surface-Modified Steel Fibers

[0090] Preparation Example 7

[0091] The preparation method of the surface-modified steel fiber in this example includes the following steps:

[0092] S21: 10 kg of steel fiber is immersed in 5% dilute sulfuric acid and stirred for 20 min. After filtration, it is immersed in 4% sodium hydroxide solution and stirred for 20 min. After filtration, it is washed with deionized water until neutral and dried at 60°C to constant weight to obtain pretreated steel fiber.

[0093] S22: Mix 0.8 kg of sodium silicate nonahydrate, 0.2 kg of polyvinyl alcohol, and 12 kg of deionized water evenly. Adjust the pH to 10.5 with 5% dilute nitric acid. Add pretreated steel fibers and stir at 200 r / min for 25 min. Filter and rinse twice with deionized water. Then immerse in a 15% calcium nitrate solution. Adjust the pH to 9.5 with 5% sodium hydroxide. Continue stirring for 60 min. Filter and heat at 80℃ for 40 min under a nitrogen atmosphere. Continue heating to 150℃ and heat for 1.5 h. Cool to room temperature to obtain surface-modified steel fibers.

[0094] Preparation Example 8

[0095] The preparation method of the surface-modified steel fiber in this example includes the following steps:

[0096] S21: 10 kg of steel fiber is immersed in 5% dilute sulfuric acid and stirred for 20 min. After filtration, it is immersed in 4% sodium hydroxide solution and stirred for 20 min. After filtration, it is washed with deionized water until neutral and dried at 60°C to constant weight to obtain pretreated steel fiber.

[0097] S22: Mix 1.2 kg of sodium silicate nonahydrate, 0.4 kg of polyvinyl alcohol, and 15 kg of deionized water evenly. Adjust the pH to 11.5 with 5% dilute nitric acid. Add pretreated steel fibers and stir at 200 r / min for 15 min. Filter and rinse twice with deionized water. Then immerse in a 25% calcium nitrate solution. Adjust the pH to 10.5 with 5% sodium hydroxide. Continue stirring for 40 min. Filter and heat at 100℃ for 60 min under a nitrogen atmosphere. Increase the temperature to 200℃ and heat for 2.5 h. Cool to room temperature to obtain surface-modified steel fibers.

[0098] Preparation Example 9

[0099] The preparation method of the surface-modified steel fiber in this example includes the following steps:

[0100] S21: 10 kg of steel fiber is immersed in 5% dilute sulfuric acid and stirred for 20 min. After filtration, it is immersed in 4% sodium hydroxide solution and stirred for 20 min. After filtration, it is washed with deionized water until neutral and dried at 60°C to constant weight to obtain pretreated steel fiber.

[0101] S22: Mix 1 kg of sodium silicate nonahydrate, 0.3 kg of polyvinyl alcohol, and 13 kg of deionized water evenly. Adjust the pH to 11 with 5% dilute nitric acid. Add pretreated steel fibers and stir at 200 r / min for 20 min. Filter and rinse twice with deionized water. Then immerse in 20% calcium nitrate solution and adjust the pH to 10 with 5% sodium hydroxide. Continue stirring for 50 min. Filter and heat at 90℃ for 50 min under nitrogen atmosphere. Continue heating to 160℃ and heat for 2 h. Cool to room temperature to obtain surface-modified steel fibers.

[0102] Example 1

[0103] The method for preparing high-performance concrete in this embodiment includes the following steps:

[0104] S1: Add 9 kg of cement, 1.5 kg of fly ash, 1.2 kg of metakaolin and 0.4 kg of calcium sulfoaluminate to a high-speed mixer and mix at 1000 r / min for 3 min. Add 10.5 kg of fine aggregate and continue mixing for 5 min to obtain dry mix.

[0105] S2: 0.38 kg of composite admixture, 0.6 kg of modified resin and 1.5 kg of deionized water are processed in a high-shear emulsifier for 5 minutes and then slowly added to the dry mix. The mixture is stirred at 800 r / min for 5 minutes. Then the speed is adjusted to 500 r / min and 1.5 kg of steel fiber is added in 3 batches. After the addition is completed, the mixture is stirred for another 5 minutes to obtain high-performance concrete.

[0106] The composite admixtures include 0.3 kg of polycarboxylate-based high-efficiency water-reducing agent (40% solid content), 0.05 kg of sodium gluconate, and 0.03 kg of organosilicon defoamer; the modified resin is from Preparation Example 1.

[0107] Example 2

[0108] The difference between this embodiment and Embodiment 1 is that:

[0109] The fly ash is surface-modified fly ash, which is derived from preparation example 4;

[0110] Everything else is the same as in Example 1.

[0111] Example 3

[0112] The difference between this embodiment and Embodiment 2 is as follows:

[0113] The steel fiber is a surface-modified steel fiber, which is derived from Preparation Example 7;

[0114] Everything else is the same as in Example 2.

[0115] Example 4

[0116] The method for preparing high-performance concrete in this embodiment includes the following steps:

[0117] S1: Add 12kg of cement, 3kg of fly ash, 2.4kg of metakaolin and 0.6kg of calcium sulfoaluminate to a high-speed mixer and mix at 1000r / min for 5min. Add 13.5kg of fine aggregate and continue mixing for 8min to obtain dry mix.

[0118] S2: 0.48 kg of composite admixture, 1.2 kg of modified resin and 2.4 kg of deionized water are processed in a high-shear emulsifier for 10 min and then slowly added to the dry mix. The mixture is stirred at 800 r / min for 8 min. Then the speed is adjusted to 500 r / min and 3 kg of steel fiber is added in 5 portions. After the addition is complete, the mixture is stirred for another 8 min to obtain high-performance concrete.

[0119] The composite admixtures include 0.35 kg of polycarboxylate-based high-efficiency water-reducing agent (40% solid content), 0.08 kg of sodium gluconate, and 0.05 kg of organosilicon defoamer; the modified resin is from Preparation Example 2; the fly ash is surface-modified fly ash, which is from Preparation Example 5; and the steel fiber is surface-modified steel fiber, which is from Preparation Example 8.

[0120] Example 5

[0121] The method for preparing high-performance concrete in this embodiment includes the following steps:

[0122] S1: Add 10kg of cement, 2.2kg of fly ash, 1.8kg of metakaolin and 0.5kg of calcium sulfoaluminate to a high-speed mixer and mix at 1000r / min for 5min. Add 12kg of fine aggregate and continue mixing for 8min to obtain dry mix.

[0123] S2: 0.43 kg of composite admixture, 0.9 kg of modified resin and 2.0 kg of deionized water are processed in a high-shear emulsifier for 10 min and then slowly added to the dry mix. The mixture is stirred at 800 r / min for 8 min. Then the speed is adjusted to 500 r / min and 2.4 kg of steel fiber is added in 4 batches. After the addition is completed, the mixture is stirred for another 8 min to obtain high-performance concrete.

[0124] The composite admixtures include 0.33 kg of polycarboxylate-based high-efficiency water-reducing agent (40% solid content), 0.06 kg of sodium gluconate, and 0.04 kg of organosilicon defoamer; the modified resin is from Preparation Example 3; the fly ash is surface-modified fly ash, which is from Preparation Example 6; and the steel fiber is surface-modified steel fiber, which is from Preparation Example 9.

[0125] Example 6

[0126] The difference between this embodiment and embodiment 5 is as follows:

[0127] S2: 0.43 kg of composite admixture, 0.9 kg of modified resin and 2.0 kg of deionized water are processed in a high-shear emulsifier for 10 min and then slowly added to the dry mix. The mixture is stirred at 800 r / min for 8 min. Then the speed is adjusted to 500 r / min and 2.4 kg of steel fiber and 0.5 kg of basalt fiber are added. The steel fiber is added in 4 batches. After the addition is completed, the mixture is stirred for another 8 min to obtain high-performance concrete.

[0128] The rest is the same as in Example 5.

[0129] Example 7

[0130] The difference between this embodiment and embodiment 6 is that:

[0131] S1: Add 10kg of cement, 2.2kg of fly ash, 1.8kg of metakaolin, 0.5kg of calcium sulfoaluminate and 0.15kg of nano-montmorillonite to a high-speed mixer and mix at 1000r / min for 5min. Add 12kg of fine aggregate and continue mixing for 8min to obtain dry mix.

[0132] The rest is the same as in Example 6.

[0133] Example 8

[0134] The difference between this embodiment and embodiment 6 is that:

[0135] S1: Add 10kg of cement, 2.2kg of fly ash, 1.8kg of metakaolin, 0.5kg of calcium sulfoaluminate and 0.25kg of nano-montmorillonite to a high-speed mixer and mix at 1000r / min for 5min. Add 12kg of fine aggregate and continue mixing for 8min to obtain dry mix.

[0136] The rest is the same as in Example 6.

[0137] Example 9

[0138] The difference between this embodiment and embodiment 6 is that:

[0139] S1: Add 10kg of cement, 2.2kg of fly ash, 1.8kg of metakaolin, 0.5kg of calcium sulfoaluminate and 0.2kg of ultrafine calcium carbonate to a high-speed mixer and mix for 5 minutes at a speed of 1000r / min. Add 12kg of fine aggregate and continue mixing for 8 minutes to obtain dry mix.

[0140] The rest is the same as in Example 6.

[0141] Example 10

[0142] The method for preparing high-performance concrete in this embodiment includes the following steps:

[0143] S1: Add 10kg of cement, 2.2kg of fly ash, 1.8kg of metakaolin, 0.5kg of calcium sulfoaluminate and 0.4kg of ultrafine calcium carbonate to a high-speed mixer and mix at 1000r / min for 5min. Add 12kg of fine aggregate and continue mixing for 8min to obtain dry mix.

[0144] S2: 0.43 kg of composite admixture, 0.9 kg of modified resin and 2.0 kg of deionized water are processed in a high-shear emulsifier for 10 min and then slowly added to the dry mix. The mixture is stirred at 800 r / min for 8 min. Then the speed is adjusted to 500 r / min and 2.4 kg of steel fiber and 1 kg of basalt fiber are added. The steel fiber is added in 4 batches. After the addition is completed, the mixture is stirred for another 8 min to obtain high-performance concrete.

[0145] The composite admixtures include 0.33 kg of polycarboxylate-based high-efficiency water-reducing agent (40% solid content), 0.06 kg of sodium gluconate, and 0.04 kg of organosilicon defoamer; the modified resin is from Preparation Example 3; the fly ash is surface-modified fly ash, which is from Preparation Example 6; and the steel fiber is surface-modified steel fiber, which is from Preparation Example 9.

[0146] Comparative Example 1

[0147] The difference between this comparative example and Example 1 is as follows:

[0148] No modified resin was added;

[0149] Everything else is the same as in Example 1.

[0150] Performance testing

[0151] The high-performance concretes prepared in Examples 1-10 and Comparative Example 1 were molded into specimens and cured for 28 days according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete" and GB / T 31387-2015 "Reactive Powder Concrete" (temperature 20±2℃, relative humidity ≥95%). Their mechanical properties were then tested. In addition, according to GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", the autogenous shrinkage value at 3 days was determined by sealing the concrete in a mold (temperature 20±2℃). The specific test results are shown in Table 1.

[0152] Table 1. Performance characterization of high-performance concrete obtained in Examples 1-10 and Comparative Example 1

[0153]

[0154] The performance test data from Example 1 and Comparative Example 1 show that Comparative Example 1, without the addition of modified resin, has significantly lower performance indicators than Example 1 in all aspects. This indicates that the three-dimensional network structure of the modified resin plays multiple key roles in the ultra-low water-cement ratio system: First, its excellent water absorption and retention capacity provides continuous internal curing, effectively inhibiting early self-shrinkage and ensuring the full hydration of the cementitious material (especially calcium sulfoaluminate) and the stable growth of hydration products; second, as an organic polymer phase, it can effectively toughen and strengthen the interface and improve the cohesiveness of the material.

[0155] Performance test data from Examples 1-3 show that after mechanochemical modification, the surface activity and reactivity of fly ash are activated. This allows fly ash particles to form stronger chemical bonds with cement hydration products, thereby optimizing the interfacial transition zone structure and improving the homogeneity and density of the matrix. This optimization process also helps reduce autogenous shrinkage caused by pore water loss. The coating on the surface of the steel fiber greatly enhances the chemical adhesion and mechanical interlocking force between the fiber and the cement matrix, enabling the fiber to more effectively transfer stress under load and delaying the pull-out process, thus significantly improving flexural strength and fracture toughness.

[0156] The performance test data from Examples 3 to 5 show that, based on Example 3, Examples 4 to 5 achieved simultaneous optimization of mechanical properties and volume stability by optimizing the raw material composition.

[0157] The performance test data from Examples 6-8 show that in Example 6, while the compressive strength increased slightly, the flexural strength and fracture toughness significantly improved, and the self-shrinkage value further decreased. This reflects the synergistic crack-resistant effect of the hybrid fibers. In Examples 7-8, the performance improvement was mainly reflected in the compressive strength and elastic modulus, and the self-shrinkage value also decreased. This is attributed to the large specific surface area and activity of nano-montmorillonite, which can further fill micropores, promote the dense accumulation of hydration products, thereby significantly optimizing the microstructure of the material and effectively suppressing self-shrinkage.

[0158] The performance test data from Examples 9-10 show that ultrafine calcium carbonate mainly acts as a highly efficient nucleating agent and micro-aggregate, which can accelerate hydration and refine the structure of hydration products. Its physical filling effect makes the matrix more compact, thus contributing significantly to improving compressive strength, while also bringing about a simultaneous reduction in the self-shrinkage value.

[0159] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-performance concrete, characterized in that, The raw materials include the following parts by weight: The ingredients are: 9-12 parts cement, 1.5-3 parts fly ash, 1.2-2.4 parts metakaolin, 0.4-0.6 parts calcium sulfoaluminate, 10.5-13.5 parts fine aggregate, 0.38-0.48 parts composite admixture, 1.5-3 parts steel fiber, 0.6-1.2 parts modified resin, and 1.5-2.4 parts water. The composite admixture includes a polycarboxylate superplasticizer, sodium gluconate, and an antifoaming agent; The modified resin is prepared by aqueous solution polymerization using hydroxypropyl methylcellulose, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid and crosslinking agent as raw materials; the mass ratio of acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, crosslinking agent, hydroxypropyl methylcellulose and water is (2.5~3.5):1:(0.01~0.03):(0.05~0.1):

10. The fly ash is surface-modified fly ash, which is prepared by the following method: fly ash, anhydrous calcium sulfate and lithium hydroxide are mixed evenly in a mass ratio of 100:(2~5):(1~3), and ground for 2~3 hours to obtain the fly ash. The steel fiber is a surface-modified steel fiber, prepared by the following method: sodium silicate nonahydrate, polyvinyl alcohol and water are mixed evenly, the pH is adjusted to 10.5~11.5, steel fiber is added, mixed for 15~25 min, solid-liquid separation is performed, the fiber is washed, and then immersed in calcium nitrate solution, the pH is adjusted to 9.5~10.5, mixed for 40~60 min, solid-liquid separation is performed, and under an inert atmosphere, the fiber is first kept at 80~100℃ for 40~60 min, then kept at 150~200℃ for 1.5~2.5 h, and then cooled to obtain the final product. Before the steel fibers are added, they undergo pickling, alkali washing and drying pretreatment. Before use, the hydroxypropyl methylcellulose undergoes the following pretreatment steps: the vinyl silane coupling agent and the ethanol aqueous solution are mixed evenly, the pH is adjusted to 4-5, hydroxypropyl methylcellulose is added, the temperature is raised to 50-70℃, the reaction is carried out for 4-6 hours, extraction is performed, washing is performed, and drying is performed to obtain pretreated hydroxypropyl methylcellulose.

2. The high-performance concrete according to claim 1, characterized in that, The modified resin is prepared by the following method: Under an inert atmosphere, hydroxypropyl methylcellulose is added to water and mixed evenly. An initiator is added, and the temperature is raised to 70-90°C. A premix of acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and a crosslinking agent is added. The mixture is kept at this temperature for 3-5 hours, and the solid and liquid are separated. The mixture is then dried and pulverized to obtain the modified resin.

3. The high-performance concrete according to claim 1, characterized in that, The mass ratio of the steel fiber, sodium silicate nonahydrate, polyvinyl alcohol, and water is 10:(0.8~1.2):(0.2~0.4):(12~15).

4. The high-performance concrete according to claim 1, characterized in that, The high-performance concrete also includes 0.5 to 1 part by weight of basalt fiber.

5. A method for preparing high-performance concrete as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Add cement, fly ash, metakaolin and calcium sulfoaluminate to a high-speed mixer and mix for 3-5 minutes. Add fine aggregate and continue mixing for 5-8 minutes to obtain dry mix. S2: Mix the composite admixture, modified resin and water evenly, add it to the dry mix, mix for 5-8 minutes, add steel fiber, and continue mixing for 5-8 minutes to obtain high-performance concrete.

6. The method for preparing high-performance concrete according to claim 5, characterized in that, In step S1, when adding steel fibers, the step of adding basalt fibers is also included.

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