High-strength ultra-high performance concrete and preparation method thereof

Abstract

The application relates to the technical field of building materials, and particularly discloses high-strength ultra-high-performance concrete and a preparation method thereof. The high-strength ultra-high-performance concrete comprises cementitious materials, modified infusion tubes, composite reinforcing fibers, graded quartz sand, composite admixtures and water; the modified infusion tubes are prepared by grafting modification of infusion tubes through ultraviolet radiation and a silane coupling agent. The modified infusion tubes can improve the elasticity, ductility, crack resistance and impermeability of the UHPC. By introducing the modified infusion tubes, optimizing the cementitious materials (cement, fly ash, granulated blast furnace slag and modified biomass), the composite reinforcing fibers and the composite admixtures, the application realizes the synergistic improvement of the mechanical properties, the durability and the construction performance; and by limiting the raw materials and the proportioning of the high-strength ultra-high-performance concrete, the synergistic effect among the raw materials is realized.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a high-strength, ultra-high-performance concrete and its preparation method. Background Technology

[0002] In the field of civil engineering, ultra-high performance concrete (UHPC) has become a key material for core projects such as super high-rise buildings, long-span transportation projects, marine anti-corrosion projects, and special protective facilities due to its excellent mechanical properties and durability.

[0003] With the advancement of the national "dual carbon" strategy and the increasing requirements for service life in engineering construction, the existing concrete material system has gradually exposed insurmountable technical bottlenecks and cannot meet the stringent requirements of high-end projects. Specifically, the existing technology has the following core defects: (1) Poor synergy between strength and toughness. In order to pursue high compressive strength, traditional high-strength concrete usually adopts a low water-cement ratio formula, which leads to a significant increase in material brittleness, insufficient flexural strength and fracture toughness. Under dynamic loads such as earthquakes and impacts, it is easy to suffer sudden damage, making it difficult to ensure the safety of engineering structures. Some ultra-high performance concrete improves toughness by incorporating steel fibers, but due to uneven fiber dispersion and weak bonding with the matrix interface, it is easy to have large strength dispersion and limited toughness improvement. (2) Insufficient durability and poor environmental adaptability. There are a large number of harmful pores and interface transition zone defects in the existing concrete. Under harsh conditions such as chloride ion corrosion in marine environments, freeze-thaw cycles in cold regions, and sulfate corrosion in industrial environments, defects such as steel corrosion, matrix cracking, and surface spalling are prone to occur, significantly shortening the service life of the structure and increasing the later maintenance costs. (3) Imbalance between greenness and economy. Some high-performance concrete relies on high cement content to ensure strength, which not only leads to high carbon emissions during production, but also causes temperature cracks due to excessive heat of hydration. At the same time, some high-performance concrete relies excessively on expensive materials such as imported silica fume and ultrafine steel fibers, or adopts complex preparation processes, resulting in excessively high material costs and limiting its large-scale industrial application. (4) Poor construction adaptability. The high viscosity characteristics caused by the low water-cement ratio make the concrete mix have poor fluidity and high pumping resistance. Especially in the casting of complex components such as core tubes and joints with dense reinforcement, problems such as insufficient compaction and increased internal defects are likely to occur, affecting the quality of structural construction.

[0004] Although existing technologies have attempted to improve concrete performance through composite mineral admixtures, optimized aggregate gradation, and the development of novel admixtures, a synergistic optimization of strength, toughness, durability, and workability has yet to be achieved. Single mineral admixtures struggle to achieve multi-level particle density packing in the cementitious system, failing to fundamentally reduce porosity. Fiber modification technology is immature and has not effectively addressed fiber agglomeration and interfacial bonding issues. Therefore, developing a high-strength, ultra-high-performance concrete that combines ultra-high strength, excellent toughness, long-term durability, good workability, and controllable cost has become an urgent need to overcome current engineering material technology bottlenecks and support high-end engineering construction and low-carbon development. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a high-strength, ultra-high-performance concrete and its preparation method. By introducing a modified infusion tube and optimizing the cementitious materials, composite reinforcing fibers, and composite admixtures, a synergistic improvement in mechanical properties, durability, and workability is achieved.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a high-strength, ultra-high-performance concrete, comprising the following raw materials: cementitious materials, modified infusion pipes, composite reinforcing fibers, graded quartz sand, composite admixtures, and water; The modified infusion tubing is prepared by grafting and modifying an infusion tubing with ultraviolet radiation and a silane coupling agent.

[0007] Compared to existing technologies, the high-strength, ultra-high-performance concrete provided by this invention incorporates a modified infusion tube (polymer material). Ultraviolet radiation induces active groups such as carbonyl and hydroxyl groups on the surface of the infusion tube, while simultaneously triggering slight surface etching. A silane coupling agent acts as a "molecular bridge," with its silanol end undergoing dehydration condensation with CSH gel and hydrated calcium silicate in the concrete, while its amino / epoxy groups form covalent bonds with the active groups on the surface of the infusion tube. This dual effect of chemical bonding and mechanical interlocking significantly improves the interfacial bond strength between the infusion tube and UHPC, far surpassing the bonding effect of physical interlocking, thus eliminating the potential cracking hazards of high-strength concrete caused by interfacial gaps and stress concentration.

[0008] Modified infusion tubing can improve the elasticity, ductility, crack resistance, and impermeability of UHPC. As a flexible reinforcing phase, the high ductility of the polymer material in the modified infusion tubing complements the high rigidity of UHPC: when microcracks develop in the concrete under tension, the modified infusion tubing transfers stress through strong interfacial bonding, hindering crack propagation and improving the fracture toughness and flexural strength of the composite material. The interfacial bonding fatigue resistance of the modified infusion tubing is significantly improved, making it less prone to interfacial delamination between the tubing and concrete under repeated loading. Simultaneously, the energy dissipation characteristics of the polymer tubing can absorb impact energy, enhancing the impact resistance of the composite material, making it suitable for special engineering scenarios such as explosion-proof and impact-resistant applications.

[0009] Preferably, the high-strength ultra-high-performance concrete comprises the following raw materials in parts by weight: 750-1000 parts of cementitious material, 5-15 parts of modified infusion tubing, 70-120 parts of composite reinforcing fiber, 700-900 parts of graded quartz sand, and 35-65 parts of composite admixture.

[0010] More preferably, the high-strength ultra-high-performance concrete comprises the following raw materials in parts by weight: 820-950 parts of cementitious material, 8-12 parts of modified infusion tubing, 85-110 parts of composite reinforcing fiber, 750-850 parts of graded quartz sand, and 43-57 parts of composite admixture.

[0011] Preferably, the water-cement ratio in the high-strength ultra-high-performance concrete is 0.16~0.22.

[0012] In this invention, "water-cement ratio" refers to the mass ratio of water to cementitious material.

[0013] Preferably, the cementitious material includes cement, fly ash, granulated blast furnace slag, and modified biomass; the modified biomass is prepared by sequentially carbonizing, alkali etching, modifying with silane coupling agent, and polyvinyl alcohol.

[0014] This invention uses modified biomass as an auxiliary cementitious material. Biochar, with its porous structure and highly active SiO2 and Al2O3, can react with cement hydration products (such as Ca(OH)2) in a pozzolanic reaction, generating more CSH gel to fill the pores inside the concrete, thereby improving the compressive and flexural strength of UHPC. The porous structure of biochar can buffer the water expansion stress during freeze-thaw cycles, significantly reducing the strength loss rate of UHPC after freeze-thaw cycles. The microfiber structure retained by biochar can form a "fiber bridging" effect in the concrete matrix, inhibiting crack propagation and thus improving the fracture toughness of UHPC and reducing early shrinkage cracks. Furthermore, the introduction of fly ash, granulated blast furnace slag, and modified biomass reduces cement usage, lowering production costs and enabling the resource utilization of solid waste, reducing pollution from solid waste treatment, and aligning with the development direction of green building materials.

[0015] More preferably, the mass ratio of the cement, fly ash, granulated blast furnace slag and modified biomass is (500~700):(80~150):(120~200):(10~30).

[0016] More preferably, the mass ratio of the cement, fly ash, granulated blast furnace slag and modified biomass is (550~650):(100~130):(150~180):(15~25).

[0017] More preferably, the cement comprises silicate cement of grade 42.5 or higher.

[0018] More preferably, the fly ash includes Grade I fly ash with a particle size of 1μm to 20μm.

[0019] More preferably, the granulated blast furnace slag includes S95 grade granulated blast furnace slag powder.

[0020] More preferably, the method for preparing the modified biomass includes the following steps: S1. Roasting biomass at 250℃~300℃ produces porous charcoal powder; S2. The porous carbon powder is soaked in an alkaline solution, and the resulting activated carbon powder is ball-milled with a silane coupling agent to obtain silane-modified carbon powder. S3. Add the silane-modified carbon powder to the polyvinyl alcohol solution, mix evenly, remove water, and obtain the modified biomass.

[0021] The modified biomass preparation method provided by this invention involves calcining the biomass at a specific temperature to prevent the complete destruction of the straw fiber structure by high temperatures, retaining some microfiber skeletons to form loose and porous charcoal powder. Then, an alkaline solution is penetrated into the fiber pores to achieve alkaline etching, promoting the dissociation of amorphous SiO2 and enhancing the pozzolanic activity of the porous charcoal powder. The amino groups on the silane coupling agent molecular chain can form stable hydrogen bonds with the hydroxyl groups on the activated charcoal powder surface, while the alkoxy groups at the other end can undergo condensation reactions with cement hydration products, significantly improving the interfacial compatibility between biochar and the concrete matrix and solving the problem of easy agglomeration of inorganic powders in cement-based materials. The impact and shear forces during ball milling can mechanically activate and break the inert chemical bonds on the charcoal powder surface, while simultaneously promoting in-situ grafting of silane coupling agent molecules onto the charcoal powder surface. The hydrophilic groups of polyvinyl alcohol (PVA) molecules can adsorb onto the surface of biochar particles, forming a steric hindrance layer that effectively prevents powder particle agglomeration and ensures the uniform dispersion of the material during concrete mixing.

[0022] More preferably, in S1, the biomass includes corn stalks.

[0023] For example, in S1, the particle size of the biomass is ≤2mm. It can be pulverized using a pulverizer.

[0024] More preferably, in S1, the calcination time is 1.5h to 2.5h.

[0025] More preferably, in S2, the alkaline solution comprises a 5wt% to 10wt% sodium hydroxide solution.

[0026] In this invention, the straw fibers are relatively loose. The low concentration of alkali solution can both peel off the inert layer on the surface of the straw charcoal through alkali etching, exposing more active hydroxyl groups and silicon-oxygen bond sites, and avoid excessive dissolution of the fiber skeleton by high concentration of alkali solution, thus ensuring the structural integrity of the charcoal powder.

[0027] More preferably, in S2, the mass-to-volume ratio of the porous carbon powder to the alkaline solution is 1g:(10~15)mL.

[0028] More preferably, in S2, the soaking temperature is 50℃~70℃, and the soaking time is 1h~2h.

[0029] This invention, by limiting the soaking temperature and time, allows the alkaline solution to fully penetrate into the pores of biomass fibers, thereby fully activating the porous carbon powder.

[0030] For example, in S2, after soaking, the process also includes: solid-liquid separation, washing with water until neutral, drying, and obtaining activated carbon powder.

[0031] More preferably, in S2, the mass ratio of the activated carbon powder to the silane coupling agent is 1:(3~5).

[0032] More preferably, in S2, the silane coupling agent includes KH550.

[0033] In this invention, KH550 has good compatibility with the hydroxyl groups of straw charcoal.

[0034] More preferably, in S2, the ball-to-material ratio of the ball mill is (3.5~4.5):1, the ball milling speed is 200rpm~250rpm, and the ball milling time is 30min~50min.

[0035] More preferably, in S2, the particle size D50 of the silane-modified carbon powder is 5μm~8μm.

[0036] More preferably, in S3, the concentration of the polyvinyl alcohol solution is 0.2% to 0.3%.

[0037] More preferably, in S3, the mass ratio of the silane-modified carbon powder to the polyvinyl alcohol solution is 1:(20~25).

[0038] For example, in S3, the method of removing moisture can be drying, with the moisture content of the modified biomass ≤0.5%; after drying, it should be sieved immediately to remove agglomerated particles and stored in a sealed container.

[0039] Preferably, the method for preparing the modified infusion tubing includes the following steps: The infusion tubing was subjected to ultraviolet radiation, then immersed in a silane coupling agent solution, and baked at 80℃~90℃ to obtain a modified infusion tubing.

[0040] For example, the material of the infusion tubing includes at least one of polyvinyl chloride, ultra-low density polyethylene, polyolefin elastomer, or polyurethane.

[0041] More preferably, the power density of the ultraviolet radiation is 3 W / m². 2 ~4W / m 2 The radiation time is 0.5h to 1h.

[0042] Under specific ultraviolet radiation conditions, the surface of the infusion tube becomes brittle, and the smooth surface becomes rough, which increases the adhesion between the infusion tube and the concrete substrate, allowing it to better integrate into the substrate and thus perform its corresponding function. At the same time, ultraviolet radiation under specific conditions can better kill bacteria and viruses on the surface of the infusion tube, preventing the spread of diseases.

[0043] For example, after the ultraviolet radiation ends but before soaking, the process also includes: crushing to a particle size of 0.1mm~0.5mm.

[0044] More preferably, the silane coupling agent includes KH550, and the mass concentration of the silane coupling agent solution is 1% to 3%.

[0045] More preferably, the solvent of the silane coupling agent solution comprises ethanol and water in a volume ratio of (8.5~9.5):1, and the pH of the silane coupling agent solution is 3~5.

[0046] More preferably, the soaking time is 30 min to 50 min.

[0047] This invention does not have special requirements on the amount of silane coupling agent solution used; the infusion tube can be immersed in ultraviolet radiation.

[0048] More preferably, the baking time is 30 min to 50 min.

[0049] Preferably, the composite reinforcing fiber comprises steel fiber, inorganic fiber and organic fiber in a mass ratio of (60~100):(5~15):(3~8).

[0050] This invention uses steel fiber as the main reinforcing fiber and inorganic and organic fibers as auxiliary reinforcing fibers to avoid competition between surface fibers that would reduce the reinforcing effect.

[0051] More preferably, the composite reinforcing fiber comprises steel fiber, inorganic fiber and organic fiber in a mass ratio of (70~90):(8~15):(5~8).

[0052] More preferably, the steel fiber has a length of 15mm to 20mm and a diameter of 0.2mm to 0.3mm.

[0053] More preferably, the inorganic fiber includes slag wool fiber, the length of which is 5mm~8mm and the diameter is 20μm~30μm.

[0054] More preferably, the organic fiber includes polyester fiber, the polyester fiber having a length of 8mm to 12mm and a diameter of 30μm to 50μm.

[0055] In this invention, slag wool is an industrial byproduct with low cost and can improve early crack resistance; the polyester fiber can be recycled PET fiber, a low-cost recycled material that can further enhance impact resistance. Fibers of specific lengths can better fulfill their respective functions, thereby further improving the ductility and tensile strength of the concrete.

[0056] Compared to single fiber reinforcement systems, this invention employs a multi-scale combination of multiple fiber composite reinforcement systems, along with modified infusion tubes, which greatly enhances the toughness of concrete. This allows it to exhibit excellent crack resistance and ductility when subjected to impact loads, vibration loads, or high strain rates, thus avoiding the brittle failure problem of traditional UHPC.

[0057] Preferably, the graded quartz sand comprises quartz sand with particle sizes of 0.15mm~0.3mm, 0.3mm~0.6mm and 0.6mm~1.2mm respectively, in a mass ratio of 1:(1.2~1.5):(0.9~1.1).

[0058] Preferably, the composite admixture includes a water-reducing agent and an expanding agent in a mass ratio of (15~25):(20~40).

[0059] More preferably, the water-reducing agent is a polycarboxylate water-reducing agent.

[0060] More preferably, the expanding agent is an ettringite-type expanding agent.

[0061] Secondly, the present invention provides a method for preparing the aforementioned high-strength, ultra-high-performance concrete, comprising the following steps: The modified infusion tubing is mixed with the first portion of graded quartz sand to obtain a pretreated modified infusion tubing. The expansion agent is mixed with a portion of the cement to obtain a pre-treated expansion agent; Mix the water-reducing agent with some water to obtain a water-reducing agent solution; The steel fibers are mixed with the second batch of graded quartz sand to obtain pretreated steel fibers; Inorganic fibers are mixed with organic fibers to obtain mixed fibers; Mix the remaining cement, fly ash, and granulated blast furnace slag; add modified biomass, the pretreated modified infusion pipe, and the pretreated expansion agent, and mix evenly; then add the remaining graded quartz sand to obtain a dry mix; Add the water-reducing agent solution and the remaining water to the dry mixture and mix thoroughly; then add the pretreated steel fiber and the mixed fiber to obtain the wet mixture. The wet mixture is poured into molds and cured to obtain high-strength, ultra-high-performance concrete.

[0062] The method for preparing high-strength, ultra-high-performance concrete provided by this invention involves mixing graded quartz sand with modified infusion tubing, ensuring that ultrafine quartz powder uniformly coats the surface of the modified infusion tubing particles, preventing the tubing from floating and stratifying in the slurry. Premixing the expansive agent with a portion of the cement effectively prevents agglomeration of the expansive agent, thus avoiding its impact on shrinkage compensation. Premixing the water-reducing agent with a portion of water improves its dispersion efficiency and prevents excessively high local concentrations that could entrain air. Pre-dispersing the graded quartz sand with steel fibers effectively prevents the steel fibers from tangling and clumping during subsequent dry mixing.

[0063] Preferably, the mass ratio of the modified infusion tubing to the first portion of graded quartz sand is 1:(0.9~1.1).

[0064] Preferably, the mass ratio of the expansive agent to a portion of the cement is 1:(0.9~1.1).

[0065] Preferably, the mass ratio of the water-reducing agent to a portion of the water is 1:(4.5~5.5).

[0066] Preferably, the mass ratio of the steel fiber to the second portion of graded quartz sand is 1:(1.8~2.2).

[0067] Preferably, the addition rates of the water-reducing agent solution and the remaining water are 40 mL / s to 50 mL / s, respectively.

[0068] This invention ensures that water is evenly distributed into the dry mix by controlling the rate at which water is added during wet mixing, thus preventing excessive local moisture from causing the modified infusion tube to float or insufficient moisture from causing the solid powder to clump together.

[0069] This invention requires controlling the total wet mixing time to ≤8min to prevent fiber breakage and slurry temperature from exceeding 35℃ (excessive temperature will cause the PVA coating layer on the modified biomass surface to soften, affecting its interfacial bonding strength with the matrix).

[0070] The present invention has the following beneficial effects: The modified infusion tubing exhibits improved compatibility with UHPC, eliminating the need for additional interface agents or adhesive layers. It can be directly embedded in concrete slurry for molding, shortening the construction cycle and reducing project costs. UHPC has extremely low porosity and high crystallinity of its hydration products, resulting in poor interfacial compatibility with polymer materials. After modification with ultraviolet radiation and silane coupling agents, the polar groups on the tubing surface can form a hydrogen bond network with the hydration products of UHPC, filling the microscopic gaps at the interface, reducing the thickness of the interfacial transition zone, and forming a continuous and dense interfacial layer that better matches the ultra-high strength properties of UHPC.

[0071] UHPC itself has excellent impermeability, but the interface region is still the main penetration channel for corrosive media (such as chloride ions and sulfates). The dense interface layer of the modified infusion tube can effectively block the intrusion of corrosive media and reduce the risk of corrosion of the steel reinforcement inside the concrete; at the same time, the hydrophobic groups of the silane coupling agent can form a protective film on the surface of the infusion tube, inhibiting further photo-oxidative degradation of the tube after ultraviolet irradiation and improving the weather resistance of the infusion tube.

[0072] The thermal expansion coefficients of polymer pipes and concrete differ significantly, and temperature changes can easily lead to thermal stress at the interface. The strong interfacial bonding of modified infusion tubing can mitigate interfacial cracking caused by thermal expansion and contraction through stress transfer, reducing the destructive effects of temperature and humidity cycles on the composite structure, making it particularly suitable for outdoor projects with large temperature differences.

[0073] This invention uses modified biomass as an auxiliary cementitious material. The carbonaceous components of biochar can inhibit the diffusion of CO2 into the concrete interior and reduce the carbonation depth of UHPC. At the same time, biochar has the effect of refining pores, which can improve the concrete's resistance to chloride ion penetration.

[0074] This invention achieves synergistic effects among raw materials by limiting the raw materials and proportions of high-strength, ultra-high-performance concrete. Cement is the core source of system strength; a high dosage ensures sufficient hydration products, meeting the dense structure requirements of UHPC. Low-calcium fly ash is used to leverage the "ball bearing effect" and pozzolanic effect, optimizing workability and reducing heat of hydration. Granulated blast furnace slag has high activity and can react with cement hydration products Ca(OH)2 to generate CSH gel, significantly improving later-stage strength and durability. Excessive use of modified biomass will reduce system density and strength, while insufficient use will result in insignificant modification effects. Excessive use of modified infusion tubing will lead to a decrease in strength due to the low elastic modulus of the polymer. Steel fibers are a key reinforcing phase for high strength in UHPC, effectively preventing crack propagation; excessive use can easily lead to agglomeration. Inorganic fibers can synergistically refine pores and improve crack resistance with steel fibers; excessive use will increase water demand. Organic fibers synergistically improve the toughness and impact resistance of concrete with inorganic fibers; excessive use will reduce interfacial bond strength. Graded quartz sand has a high bulk density, which can reduce the amount of slurry used and improve the density of the system; the total amount of aggregate should account for 40% to 50% of the volume to avoid excessive slurry leading to increased shrinkage. Detailed Implementation

[0075] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0076] This invention provides a high-strength, ultra-high-performance concrete, comprising the following raw materials in parts by weight: 500-700 parts cement, 80-150 parts fly ash, 120-200 parts granulated blast furnace slag, 10-30 parts modified biomass, 5-15 parts modified infusion pipe, 60-100 parts steel fiber, 5-15 parts inorganic fiber, 3-8 parts organic fiber, 700-900 parts graded quartz sand, 15-25 parts water-reducing agent, 20-40 parts expansion agent, and 130-190 parts water; The modified biomass is obtained by sequentially carbonizing, alkali etching, modifying with silane coupling agent and polyvinyl alcohol; the modified infusion tube is obtained by grafting modification of the infusion tube with ultraviolet radiation and silane coupling agent.

[0077] In some embodiments, the high-strength ultra-high-performance concrete comprises the following raw materials in parts by weight: 550-650 parts cement, 100-130 parts fly ash, 150-180 parts granulated blast furnace slag, 15-25 parts modified biomass, 8-12 parts modified infusion tubing, 70-90 parts steel fiber, 8-15 parts inorganic fiber, 5-8 parts organic fiber, 750-850 parts graded quartz sand, 18-22 parts water-reducing agent, 25-35 parts expansion agent, and 130-190 parts water.

[0078] In this embodiment of the invention, the cement used is 42.5 grade silicate cement; the fly ash used is Grade I fly ash with a particle size of 1μm~20μm; the granulated blast furnace slag used is S95 grade granulated blast furnace slag powder; the steel fibers are all 15mm~20mm in length and 0.2mm~0.3mm in diameter; the slag wool fibers are all 5mm~8mm in length and 20μm~30μm in diameter; the polyester fibers are all 8mm~12mm in length and 30μm~50μm in diameter; the water-reducing agent is all polycarboxylate water-reducing agent; and the expanding agent is all ettringite-type expanding agent. Unless otherwise specified, all materials used in this embodiment of the invention are commercially available products.

[0079] To better illustrate the present invention, further examples are provided below.

[0080] Example 1 This embodiment provides a high-strength, ultra-high-performance concrete, comprising the following raw materials in parts by weight: 600 parts cement, 120 parts fly ash, 165 parts granulated blast furnace slag, 20 parts modified biomass, 10 parts modified infusion tubing, 80 parts steel fiber, 12 parts slag wool fiber, 6 parts polyester fiber, 800 parts graded silica sand, 20 parts water-reducing agent, 30 parts expansion agent, and 165 parts water. The water-cement ratio is 0.18. The graded silica sand is composed of silica sand with particle sizes of 0.15mm~0.3mm, 0.3mm~0.6mm, and 0.6mm~1.2mm, respectively, in a mass ratio of 1:1.3:1.

[0081] The above-mentioned method for preparing modified biomass includes the following steps: S1. At 280℃ in air, corn stalks are roasted for 2 hours and then cooled to obtain porous charcoal powder.

[0082] S2. Porous carbon powder was soaked in an 8 wt% sodium hydroxide solution at a mass-to-volume ratio of 1 g:12 mL. After stirring at 60 °C for 1.5 h, the solid and liquid were separated, washed with water until neutral, and dried to obtain activated carbon powder. The activated carbon powder at a mass ratio of 1:4 was ball-milled with a KH550 ball mill at a ball-to-material ratio of 4:1 for 40 min at 220 rpm to obtain silane-modified carbon powder with a D50 of 6.3 μm.

[0083] S3. Add silane-modified carbon powder to a 0.25wt% polyvinyl alcohol solution. The mass ratio of silane-modified carbon powder to polyvinyl alcohol solution is 1:22. Mix evenly and remove moisture to obtain modified biomass.

[0084] The preparation method of the above-mentioned modified infusion tubing includes the following steps: Set the infusion tubing to 3.5W / m 2The sample was subjected to ultraviolet radiation for 1 hour, then crushed to a particle size of 0.1 mm to 0.5 mm. It was then immersed in a 2 wt% KH550 solution (pH 4, solvent is ethanol and water in a volume ratio of 9:1), stirred for 40 min, and then taken out and baked at 85℃ for 40 min to obtain the modified infusion tube.

[0085] The preparation method of the above-mentioned high-strength and ultra-high-performance concrete includes the following steps: S100, Pretreatment of each raw material: The modified infusion tubing is mixed with an equal mass of graded quartz sand to obtain a pretreated modified infusion tubing.

[0086] The expansion agent is mixed with an equal mass of cement to obtain the pretreatment expansion agent.

[0087] The water-reducing agent is mixed with water at a mass ratio of 1:4 to obtain a water-reducing agent solution.

[0088] Steel fibers and graded quartz sand are mixed at a mass ratio of 1:2 to obtain pretreated steel fibers.

[0089] Inorganic fibers are mixed with organic fibers to obtain mixed fibers.

[0090] S200. Mix the remaining cement, fly ash and granulated blast furnace slag; add modified biomass, pretreated modified infusion pipe and pretreated expansion agent, mix evenly; then add the remaining graded quartz sand to obtain dry mix.

[0091] S300. Add the water-reducing agent solution and remaining water to the dry mix at a rate of 45 mL / s, and mix thoroughly. Then add the pretreated steel fibers and mixed fibers to obtain the wet mix. Note: The total wet mixing time is 7 minutes, and the slurry temperature should not exceed 35℃.

[0092] S400 involves pouring wet-mixed materials into molds and then curing them to obtain high-strength, ultra-high-performance concrete.

[0093] Example 2 This embodiment provides a high-strength, ultra-high-performance concrete, comprising the following raw materials in parts by weight: 650 parts cement, 100 parts fly ash, 180 parts granulated blast furnace slag, 15 parts modified biomass, 12 parts modified infusion tubing, 90 parts steel fiber, 12 parts slag wool fiber, 8 parts polyester fiber, 850 parts graded silica sand, 22 parts water-reducing agent, 35 parts expansion agent, and 180 parts water. The water-cement ratio is 0.19. The graded silica sand is composed of silica sand with particle sizes of 0.15mm~0.3mm, 0.3mm~0.6mm, and 0.6mm~1.2mm, respectively, in a mass ratio of 1:1.5:1.1.

[0094] The above-mentioned method for preparing modified biomass includes the following steps: S1. At 300℃ in air, corn stalks are roasted for 1.5 hours and then cooled to obtain porous charcoal powder.

[0095] S2. Porous carbon powder was soaked in a 5 wt% sodium hydroxide solution at a mass-to-volume ratio of 1 g:15 mL. After stirring at 70 °C for 1 h, the solid and liquid were separated, washed with water until neutral, and dried to obtain activated carbon powder. The activated carbon powder at a mass ratio of 1:5 was ball-milled with a KH550 ball mill at a ball-to-material ratio of 4.5:1 for 30 min at 250 rpm to obtain silane-modified carbon powder with a D50 of 7.8 μm.

[0096] S3. Add silane-modified carbon powder to a 0.2wt% polyvinyl alcohol solution. The mass ratio of silane-modified carbon powder to polyvinyl alcohol solution is 1:25. Mix evenly and remove moisture to obtain modified biomass.

[0097] The preparation method of the above-mentioned modified infusion tubing includes the following steps: Set the infusion tubing to 4W / m 2 The sample was subjected to ultraviolet radiation for 1 hour, then crushed to a particle size of 0.1 mm to 0.5 mm. It was then immersed in a 3 wt% KH550 solution (pH 5, solvent is ethanol and water in a volume ratio of 9:1), stirred for 50 min, and then taken out and baked at 80℃ for 50 min to obtain the modified infusion tube.

[0098] The preparation method of the above-mentioned high-strength and ultra-high-performance concrete includes the following steps: S100, Pretreatment of each raw material: The modified infusion tubing is mixed with an equal mass of graded quartz sand to obtain a pretreated modified infusion tubing.

[0099] The expansion agent is mixed with an equal mass of cement to obtain the pretreatment expansion agent.

[0100] The water-reducing agent is mixed with water at a mass ratio of 1:4.5 to obtain a water-reducing agent solution.

[0101] Steel fibers and graded quartz sand are mixed at a mass ratio of 1:2 to obtain pretreated steel fibers.

[0102] Inorganic fibers are mixed with organic fibers to obtain mixed fibers.

[0103] S200. Mix the remaining cement, fly ash and granulated blast furnace slag; add modified biomass, pretreated modified infusion pipe and pretreated expansion agent, mix evenly; then add the remaining graded quartz sand to obtain dry mix.

[0104] S300: Add water-reducing agent solution and remaining water to the dry mix at a rate of 50 mL / s, and mix thoroughly. Then add pretreated steel fibers and mixed fibers to obtain the wet mix. Note: The total wet mixing time is 8 minutes, and the slurry temperature should not exceed 35℃.

[0105] S400 involves pouring wet-mixed materials into molds and then curing them to obtain high-strength, ultra-high-performance concrete.

[0106] Example 3 This embodiment provides a high-strength, ultra-high-performance concrete, comprising the following raw materials in parts by weight: 550 parts cement, 100 parts fly ash, 155 parts granulated blast furnace slag, 18 parts modified biomass, 10 parts modified infusion tubing, 72 parts steel fiber, 8 parts slag wool fiber, 5 parts polyester fiber, 750 parts graded silica sand, 18 parts water-reducing agent, 25 parts expansion agent, and 135 parts water. The water-cement ratio is 0.16. The graded silica sand is composed of silica sand with particle sizes of 0.15mm~0.3mm, 0.3mm~0.6mm, and 0.6mm~1.2mm, respectively, in a mass ratio of 1:1.2:0.9.

[0107] The preparation method of the modified biomass described above is the same as that in Example 1, and will not be repeated here.

[0108] The preparation method of the modified infusion tubing is the same as that in Example 1, and will not be repeated here.

[0109] The preparation method of the above-mentioned high-strength and ultra-high-performance concrete includes the following steps: S100, Pretreatment of each raw material: The modified infusion tubing is mixed with an equal mass of graded quartz sand to obtain a pretreated modified infusion tubing.

[0110] The expansion agent is mixed with an equal mass of cement to obtain the pretreatment expansion agent.

[0111] The water-reducing agent is mixed with water at a mass ratio of 1:5.5 to obtain a water-reducing agent solution.

[0112] Steel fibers and graded quartz sand are mixed at a mass ratio of 1:2 to obtain pretreated steel fibers.

[0113] Inorganic fibers are mixed with organic fibers to obtain mixed fibers.

[0114] S200. Mix the remaining cement, fly ash and granulated blast furnace slag; add modified biomass, pretreated modified infusion pipe and pretreated expansion agent, mix evenly; then add the remaining graded quartz sand to obtain dry mix.

[0115] S300: Add water-reducing agent solution and remaining water to the dry mix at a rate of 40 mL / s, and mix thoroughly. Then add pretreated steel fibers and mixed fibers to obtain the wet mix. Note: The total wet mixing time is 7 minutes, and the slurry temperature should not exceed 35℃.

[0116] S400 involves pouring wet-mixed materials into molds and then curing them to obtain high-strength, ultra-high-performance concrete.

[0117] Example 4 This embodiment provides a high-strength, ultra-high-performance concrete, comprising the following raw materials in parts by weight: 600 parts cement, 130 parts fly ash, 150 parts granulated blast furnace slag, 25 parts modified biomass, 8 parts modified infusion tubing, 80 parts steel fiber, 15 parts slag wool fiber, 8 parts polyester fiber, 800 parts graded silica sand, 20 parts water-reducing agent, 30 parts expansion agent, and 190 parts water. The water-cement ratio is 0.21. The graded silica sand is composed of silica sand with particle sizes of 0.15mm~0.3mm, 0.3mm~0.6mm, and 0.6mm~1.2mm, respectively, in a mass ratio of 1:1.4:1.

[0118] The above-mentioned method for preparing modified biomass includes the following steps: S1. At 250℃ in air, corn stalks are roasted for 2.5 hours and then cooled to obtain porous charcoal powder.

[0119] S2. Porous carbon powder was soaked in a 10wt% sodium hydroxide solution at a mass-to-volume ratio of 1g:10mL. After stirring at 50℃ for 2h, the solid and liquid were separated, washed with water until neutral, and dried to obtain activated carbon powder. The activated carbon powder at a mass ratio of 1:3 was ball-milled with a KH550 ball mill at a ball-to-material ratio of 3.5:1 for 50min at 200rpm to obtain silane-modified carbon powder with a D50 of 5.2μm.

[0120] S3. Add silane-modified carbon powder to a 0.3wt% polyvinyl alcohol solution. The mass ratio of silane-modified carbon powder to polyvinyl alcohol solution is 1:20. Mix evenly and remove moisture to obtain modified biomass.

[0121] The preparation method of the above-mentioned modified infusion tubing includes the following steps: Set the infusion tubing to 3W / m 2 The sample was subjected to ultraviolet radiation for 0.5 hours, then crushed to a particle size of 0.1 mm to 0.5 mm. It was then immersed in a 1 wt% KH550 solution (pH 3, solvent is ethanol and water in a volume ratio of 9.5:1), stirred for 30 minutes, and then taken out and baked at 90°C for 30 minutes to obtain the modified infusion tube.

[0122] The preparation method of the high-strength and ultra-high-performance concrete described above is the same as that in Example 1, and will not be repeated here.

[0123] Example 5 This embodiment provides a high-strength, ultra-high-performance concrete, whose composition and preparation method are similar to those of Example 1, except that the modified biomass is replaced with an equal mass of silica fume. All other conditions are the same as in Example 1 and will not be repeated.

[0124] Example 6 This embodiment provides a high-strength, ultra-high-performance concrete, whose composition and preparation method are similar to those of Example 1, except that the modified biomass is replaced with an equal mass of porous carbon powder (i.e., corn stalks are only carbonized). The preparation method of the porous carbon powder is the same as the preparation method of "porous carbon powder" in S1 of the modified biomass preparation method in Example 1. The remaining conditions are the same as in Example 1 and will not be repeated.

[0125] Example 7 This embodiment provides a high-strength, ultra-high-performance concrete, whose composition and preparation method are similar to those of Example 1, except that the modified biomass is replaced with an equal mass of silane-modified carbon powder (i.e., corn stalks are carbonized, alkali-etched, and modified with a silane coupling agent, but without polyvinyl alcohol coating modification). The preparation method of the silane-modified carbon powder is the same as the preparation method of "silane-modified carbon powder" in S1~S2 of the modified biomass preparation method in Example 1. All other conditions are the same as in Example 1 and will not be repeated.

[0126] Comparative Example 1 This comparative example provides an ultra-high performance concrete, whose composition and preparation method are similar to those of Example 1, except that the modified infusion tube is replaced with an ultraviolet radiation infusion tube of equal mass (i.e., the infusion tube is not modified by silane coupling agent grafting after ultraviolet radiation). All other conditions are the same as in Example 1 and will not be repeated.

[0127] The preparation method of ultraviolet radiation infusion tubing includes the following steps: The infusion tubing is heated to 3.5W / m 2 The tube is subjected to ultraviolet radiation and broken down to a particle size of 0.1 mm to 0.5 mm after 1 hour to obtain an ultraviolet radiation infusion tube.

[0128] Comparative Example 2 This comparative example provides an ultra-high performance concrete, whose composition and preparation method are similar to those of Example 1, except that the addition of the modified infusion tube is omitted. Specifically, the ultra-high performance concrete comprises the following raw materials in parts by weight: 600 parts cement, 120 parts fly ash, 165 parts granulated blast furnace slag, 20 parts modified biomass, 80 parts steel fiber, 12 parts slag wool fiber, 6 parts polyester fiber, 80 parts graded quartz sand, 20 parts water-reducing agent, 30 parts expansion agent, and 165 parts water. All other conditions are the same as in Example 1 and will not be repeated.

[0129] Comparative Example 3 This comparative example provides an ultra-high performance concrete, the preparation method of which is similar to that of Example 1, except that the slag wool fiber and polyester fiber are replaced with steel fibers, respectively. Specifically, the ultra-high performance concrete comprises the following raw materials in parts by weight: 600 parts cement, 120 parts fly ash, 165 parts granulated blast furnace slag, 20 parts modified biomass, 10 parts modified infusion pipe, 98 parts steel fiber, 80 parts graded quartz sand, 20 parts water-reducing agent, 30 parts expansion agent, and 165 parts water. All other conditions are the same as in Example 1 and will not be repeated.

[0130] Verification test Referring to T / CECS 864-2021 "Standard for Test Methods of Ultra-High Performance Concrete", the performance of ultra-high performance concrete prepared in Examples 1-7 and Comparative Examples 1-3 was tested, and the results are shown in Table 1.

[0131] The compressive strength, splitting tensile strength, and flexural strength were tested according to the methods in GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (standard curing, 28 days). The chloride ion penetration resistance of ultra-high performance concrete was evaluated using the ASTM C1202 rapid chloride ion penetration method (6h current flow, high impermeability grade, standard curing, 28 days).

[0132] Table 1 Performance test results of ultra-high performance concrete

[0133] As shown in the table above, the high-strength, ultra-high-performance concrete provided in Examples 1-4 of this invention is significantly superior to Examples 5-7 and Comparative Examples 1-3 in terms of compressive strength, splitting tensile strength, flexural strength, and chloride ion penetration resistance. Compared to Examples 1-4, the cementitious materials in Examples 5-7 did not use modified biomass, resulting in a certain degree of decrease in their mechanical properties and chloride ion penetration resistance. Compared to Examples 1-4, Comparative Examples 1-3 did not use modified infusion tubing or only used single steel fibers, resulting in a significant decrease in their mechanical properties and chloride ion penetration resistance.

[0134] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-strength, ultra-high-performance concrete, characterized in that: Including the following raw materials: Cementitious materials, modified infusion tubing, composite reinforcing fibers, graded quartz sand, composite additives, and water; The modified infusion tubing is prepared by grafting and modifying an infusion tubing with ultraviolet radiation and a silane coupling agent.

2. The high-strength, ultra-high-performance concrete as described in claim 1, characterized in that: The high-strength ultra-high-performance concrete comprises the following raw materials in parts by weight: 750-1000 parts of cementitious material, 5-15 parts of modified infusion tubing, 70-120 parts of composite reinforcing fiber, 700-900 parts of graded quartz sand, and 35-65 parts of composite admixture. The water-cement ratio in the high-strength, ultra-high-performance concrete is 0.16~0.

22.

3. The high-strength, ultra-high-performance concrete as described in claim 1, characterized in that: The cementitious material includes cement, fly ash, granulated blast furnace slag, and modified biomass; the modified biomass is prepared by sequentially carbonizing, alkali etching, modifying with silane coupling agent and polyvinyl alcohol.

4. The high-strength, ultra-high-performance concrete as described in claim 3, characterized in that: The mass ratio of the cement, fly ash, granulated blast furnace slag and modified biomass is (500~700):(80~150):(120~200):(10~30).

5. The high-strength, ultra-high-performance concrete as described in claim 3, characterized in that: The method for preparing the modified biomass includes the following steps: S1. Roasting biomass at 250℃~300℃ produces porous charcoal powder; S2. The porous carbon powder is soaked in an alkaline solution, and the resulting activated carbon powder is ball-milled with a silane coupling agent to obtain silane-modified carbon powder. S3. Add the silane-modified carbon powder to the polyvinyl alcohol solution, mix evenly, remove water, and obtain the modified biomass.

6. The high-strength, ultra-high-performance concrete as described in claim 5, characterized in that: In S1, the biomass includes corn stalks; the roasting time is 1.5h to 2.5h. In S2, the alkaline solution comprises a 5wt%~10wt% sodium hydroxide solution; the mass-to-volume ratio of the porous carbon powder to the alkaline solution is 1g:(10~15)mL; the soaking temperature is 50℃~70℃, and the soaking time is 1h~2h. In S2, the mass ratio of activated carbon powder to silane coupling agent is 1:(3~5); the silane coupling agent includes KH550; the ball-to-material ratio of ball milling is (3.5~4.5):1, the ball milling speed is 200rpm~250rpm, and the ball milling time is 30min~50min; the particle size D50 of the silane-modified carbon powder is 5μm~8μm. In S3, the concentration of the polyvinyl alcohol solution is 0.2%~0.3%; the mass ratio of the silane-modified carbon powder to the polyvinyl alcohol solution is 1:(20~25).

7. The high-strength, ultra-high-performance concrete as described in claim 1, characterized in that: The method for preparing the modified infusion tubing includes the following steps: The infusion tubing was subjected to ultraviolet radiation, then immersed in a silane coupling agent solution, and baked at 80℃~90℃ to obtain a modified infusion tubing.

8. The high-strength, ultra-high-performance concrete as described in claim 7, characterized in that: The power density of the ultraviolet radiation is 3 W / m². 2 ~4W / m 2 The radiation time is 0.5h~1h; The silane coupling agent includes KH550, and the mass concentration of the silane coupling agent solution is 1%~3%; the solvent of the silane coupling agent solution includes ethanol and water in a volume ratio of (8.5~9.5):1, and the pH of the silane coupling agent solution is 3~5. The soaking time is 30-50 minutes; the baking time is 30-50 minutes.

9. The high-strength, ultra-high-performance concrete as described in claim 1, characterized in that: The composite reinforcing fiber comprises steel fiber, inorganic fiber and organic fiber in a mass ratio of (60~100):(5~15):(3~8); The composite admixture includes a water-reducing agent and an expanding agent in a mass ratio of (15~25):(20~40).

10. The method for preparing high-strength, ultra-high-performance concrete according to any one of claims 1 to 9, characterized in that: Includes the following steps: The modified infusion tubing is mixed with the first portion of graded quartz sand to obtain a pretreated modified infusion tubing. The expansion agent is mixed with a portion of the cement to obtain a pre-treated expansion agent; Mix the water-reducing agent with some water to obtain a water-reducing agent solution; The steel fibers are mixed with the second batch of graded quartz sand to obtain pretreated steel fibers; Inorganic fibers are mixed with organic fibers to obtain mixed fibers; Mix the remaining cement, fly ash and granulated blast furnace slag; Add the modified biomass, the pretreated modified infusion tubing, and the pretreated expanding agent, and mix thoroughly; then add the remaining graded quartz sand to obtain a dry mixture; Add the water-reducing agent solution and the remaining water to the dry mixture and mix thoroughly; then add the pretreated steel fiber and the mixed fiber to obtain the wet mixture. The wet mixture is poured into molds and cured to obtain high-strength, ultra-high-performance concrete.

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