High-strength weather-resistant self-repairing ultra-high performance concrete and preparation method thereof

Abstract

The invention discloses high-strength weather-resistant self-repairing ultra-high performance concrete as well as a preparation method and application thereof, and belongs to the technical field of building materials. The concrete comprises a gel material, quartz sand aggregate, polyester composite fibers, a composite high-efficiency water reducing agent and water, the gel material is prepared by compounding Portland cement and silica fume, and the composite high-efficiency water reducing agent is prepared by activating a polycarboxylic acid water reducing agent and then grafting internal curing microspheres and aminated drug-loaded nano silicon dioxide; the preparation method comprises the steps of raw material premixing, functional agent water solution adding and stirring, forming and curing. Aiming at the problems that high strength and weather resistance are difficult to cooperate, functional aids are poor in compatibility, self-repairing efficiency is low and the like in the prior art, through component modification and function integrated design, the compressive strength of the concrete is larger than or equal to 120 MPa, the 300-time freeze-thaw cycle performance retention rate is 100%, the micro-crack self-repairing rate within 0.3 mm is larger than or equal to 95%, and the concrete is suitable for severe scenes such as building exterior decoration and bridges.

Description

Technical Field

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

[0002] Ultra-high performance concrete (UHPC), with its core advantages of low porosity and high strength, has become a key material for demanding applications such as building exterior decoration and bridge structures. Its ultra-high strength and excellent weather resistance directly determine the service life and safety of projects in extreme environments such as frigid zones, coastal areas, and chemical plants. As engineering requirements for material performance continue to upgrade, the market urgently needs integrated UHPC that combines high strength, high weather resistance, and self-healing functions. However, traditional technologies struggle to balance the synergy of multiple performance characteristics, becoming a technical pain point in the industry.

[0003] To achieve high strength and high weather resistance, existing technologies mostly optimize performance by improving the activity of cementitious materials, reducing the water-cement ratio, or adding single-functional additives. They also attempt to use a combination of ordinary aggregates and fibers to enhance the density of the material structure. Some solutions improve weather resistance by adding antifreeze or corrosion inhibitors separately, or pursue high strength by increasing fiber content.

[0004] However, existing solutions have significant drawbacks: First, reducing the water-cement ratio in pursuit of high strength can easily lead to internal shrinkage and cracking of the material, which weakens weather resistance and makes it difficult to achieve synergistic improvement. Second, in the multi-agent mode, the functional additives have poor compatibility, and the water-reducing, curing, and repairing functions interfere with each other, further restricting the performance of high strength and high weather resistance. Third, the aggregates and fibers have not undergone targeted modification, resulting in weak interfacial bonding with the cementitious matrix, forming micro-defects that affect strength stability and weather resistance durability. Fourth, the self-healing function is inefficient and cannot repair micro-cracks during service in a timely manner, leading to a continuous decline in high strength and high weather resistance, and some processes are complex, making large-scale application difficult. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a high-strength, weather-resistant, self-healing, ultra-high-performance concrete and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: S1. Preparation of composite high-efficiency water-reducing agent: S101. Dilute the polycarboxylate superplasticizer solution with deionized water to a solid content of 20%. Under ice-water bath cooling and stirring, add a carbodiimide condensing agent and N-hydroxysuccinimide. The amount of condensing agent is 1.0-1.2 times the number of carboxyl groups in the polycarboxylate superplasticizer, and the amount of N-hydroxysuccinimide is equivalent to that of the condensing agent. Stir and react at room temperature for 2-4 hours to obtain an activated polycarboxylate superplasticizer solution. The core of this step is the activation of the carboxyl group: This reaction is a carbodiimide-mediated carboxyl activation reaction, which belongs to the preparation reaction of active esters in organic synthesis. The purpose is to activate the carboxyl group (-COOH) on the molecular chain of polycarboxylic acid water-reducing agent into N-hydroxy succinimide ester (-COONHS), which is more easily reacted with hydroxyl (-OH) and amino (-NH2), laying the foundation for subsequent covalent grafting of functional units. This process is divided into two steps. Firstly, under ice-water bath conditions, the isocyanate group (-N=C=N-) in the carbodiimide condensing agent molecule has high reactivity. Its nitrogen atom at one end attacks the carboxyl carbon in R-COOH, and then a proton transfer and elimination reaction occurs to form an O-acyl isourea intermediate. The role of ice-water bath is to inhibit the hydrolysis of the condensing agent itself and improve the efficiency of intermediate formation. Secondly, N-hydroxysuccinimide acts as a nucleophile to attack the acyl carbon of the O-acyl isourea intermediate, replacing the original isourea group to form a thermodynamically stable active ester (R-COONHS). The electrophilicity of the acyl carbon of this active ester is significantly enhanced, and it can subsequently undergo esterification or amidation reactions with the -OH of the hydroxyl-terminated polyethylene glycol microspheres and the -NH2 of the aminated drug-loaded nano-SiO2 under mild conditions (40-50℃, pH 5-7) to achieve covalent grafting.

[0007] S102. Mix 45 parts of polyethylene glycol, 6 parts of acrylic acid, and 0.4 parts of N,N'-methylenebisacrylamide evenly. Add 110 parts of liquid paraffin containing 4 parts of emulsifier, stir for 5 minutes, heat to 65°C, add 0.4 parts of potassium persulfate, and keep the reaction at this temperature for 2 hours. Filter while hot, wash twice with anhydrous ethanol, and dry to obtain hydroxyl-terminated polyethylene glycol internally conditioned microspheres. Polyethylene glycol (water-soluble), acrylic acid (water-soluble monomer), and N,N'-methylenebisacrylamide (water-soluble crosslinking agent) are mixed to form an aqueous phase. Liquid paraffin containing an emulsifier (oil phase) is then added and stirred to form a water-in-oil emulsion in which "micro-droplets of the aqueous phase are dispersed in the oil phase". One end of the emulsifier is lipophilic (compatible with liquid paraffin) and the other end is hydrophilic (combines with water). It forms a protective film at the water-oil interface to prevent the aqueous phase droplets from merging and to provide an independent reaction space for subsequent microsphere polymerization. When the temperature is raised to 65℃, potassium persulfate molecules undergo homolytic cleavage, decomposing to produce sulfate free radicals (SO4). -The free radical (·) has strong oxidizing properties and can remove hydrogen atoms from acrylic acid monomer molecules, causing acrylic acid monomers to form active free radicals (CH2=CH-COO·). The active free radicals of acrylic acid combine with each other and undergo addition polymerization to form linear polyacrylic acid chains. The active sites on the linear polyacrylic acid chains react with the carbon-carbon double bonds at both ends of the crosslinking agent molecules. The crosslinking agent acts as a bridge to connect multiple linear chains, forming a three-dimensional network structure, which ultimately physically encapsulates polyethylene glycol inside the network to prevent its loss. The role of the post-processing stage: Hot filtration: Separate microspheres from liquid paraffin (oil phase); Anhydrous ethanol washing: removes residual emulsifiers and unreacted monomers (acrylic acid) from the surface of the microspheres. S103. Dissolve 13 parts of sodium silicate and 6 parts of lithium carbonate in 90 parts of deionized water to prepare an aqueous repair agent solution. Mix 22 parts of tetraethyl orthosilicate and 55 parts of ethanol evenly, and slowly add the aqueous repair agent solution while stirring for 30 minutes. Adjust the pH to 9.5 with ammonia, raise the temperature to 45°C, and keep the reaction at this temperature for 4 hours. Add 4 parts of silane coupling agent KH-550 and continue the reaction for 2 hours. Allow the mixture to stand and separate into layers, wash twice with deionized water, and dry to obtain aminated drug-loaded nano-silica. The first step is the physical dissolution process, in which sodium silicate and lithium carbonate are dissolved in deionized water to prepare an aqueous solution of the repair agent. Both are water-soluble substances, and only physical dissolution occurs without any chemical reaction. At the same time, tetraethyl orthosilicate and ethanol are mixed evenly. Ethanol acts as a solvent to reduce the surface tension of tetraethyl orthosilicate, creating conditions for subsequent uniform dispersion and reaction. Subsequently, the tetraethyl orthosilicate-ethanol mixture was slowly added to the repair agent aqueous solution and stirred. The pH was adjusted to 9.5 (alkaline environment) with ammonia, and the temperature was raised to 45°C to initiate the sol-gel reaction: The first step is the hydrolysis reaction of tetraethyl orthosilicate (TEOS, structural formula Si(OC2H5)4). Under alkaline conditions, water molecules attack the Si-O-C2H5 bond in the tetraethyl orthosilicate molecule, replacing the ethoxy group (-OC2H5) to generate silanol (Si-OH), while releasing ethanol. The reaction formula is as follows:

[0008] The second step is a condensation reaction, where the hydroxyl groups (-OH) in adjacent silanol molecules dehydrate each other to form Si-O-Si covalent bonds, gradually building a three-dimensional network SiO2 structure. During this process, the SiO2 network will encapsulate the repair agent aqueous solution inside, forming a nanocapsule with the repair agent as the core and SiO2 as the shell. After the sol-gel reaction is completed, silane coupling agent KH-550 is added to carry out a surface amination reaction: the ethoxy group (-OC2H5) in the KH-550 molecule undergoes a condensation reaction with the silanol group (Si-OH) remaining on the surface of the SiO2 shell, releasing ethanol and forming Si-O-Si chemical bonds, anchoring the KH-550 molecule to the surface of the nanocapsule. The terminal amino group (-NH2) is exposed on the capsule surface, providing active sites for subsequent amide bond grafting with polycarboxylate superplasticizers. The reaction formula is as follows:

[0009] Finally, physical post-treatment is performed: static stratification allows the nanocapsules to settle, the supernatant is poured off, and deionized water is used to wash away unreacted ammonia, ethanol, and KH-550 impurities. Throughout the process, the sol-gel reaction achieves efficient encapsulation of the repair agent, KH-550 modification introduces the amino groups required for targeted grafting, and physical post-treatment ensures the stability of the dispersion. The process is consistent and suitable for industrial production. S104, heat to 40-50℃, adjust pH to 5-7, slowly add aqueous dispersion of hydroxyl-terminated polyethylene glycol-infused microspheres and aqueous dispersion of aminated drug-loaded nano-silica, keep the reaction at this temperature for 4-8 hours, pump into a spray dryer, control the inlet air temperature to 180-200℃, the outlet air temperature to 80-90℃, and the atomization pressure to 0.3-0.5MPa to obtain a composite high-efficiency water-reducing agent; First, in the preliminary steps, the carboxyl groups of the polycarboxylate superplasticizer are activated to form an active ester (R-COONHS, where R represents the polycarboxylate molecule backbone). The acyl carbon of this active ester is highly electrophilic and can undergo efficient covalent reactions with the active groups of the two types of functional units under mild conditions of 40-50℃ and pH 5-7, avoiding side reactions. The first step is the esterification grafting reaction (internal maintenance unit bonding): the hydroxyl groups (-OH) on the surface of the hydroxyl-terminated polyethylene glycol microspheres act as nucleophiles, attacking the acyl carbon of the active ester, undergoing a nucleophilic substitution reaction, breaking the ester bond (-COO-NHS) and forming a new ester bond (-COO-), covalently grafting the hydroxyl-terminated polyethylene glycol microspheres onto the polycarboxylic acid backbone, while simultaneously releasing N-hydroxysuccinimide (NHS) as a byproduct. The reaction formula is as follows:

[0010] In this reaction, a weakly acidic environment of pH 5-7 ensures the stability of the active ester and promotes the nucleophilic attack of hydroxyl groups, while 40-50℃ increases the reaction rate and avoids microsphere aggregation. The second step is the amidation grafting reaction (self-healing unit binding): The amino groups (-NH2) on the surface of the aminated drug-loaded nano-silica also act as nucleophiles, undergoing nucleophilic substitution reactions with the remaining active esters. The acyl groups of the active esters combine with the amino groups to form stable amide bonds (-CONH-), anchoring the aminated drug-loaded nano-silica onto the polycarboxylic acid backbone or the surface of the grafted microspheres, while simultaneously releasing NHS byproducts. The reaction formula is as follows:

[0011] Amino groups have higher nucleophilic activity than hydroxyl groups, allowing them to react efficiently with active esters. Furthermore, amide bonds exhibit strong stability in the alkaline environment of concrete, preventing the self-healing units from detaching. During the process, the aqueous dispersions of the two types of functional units are added slowly to ensure uniform contact between the active ester and the functional groups, and to avoid excessive local reaction leading to aggregation; the reaction is kept at a temperature of 4-8 hours to allow the grafting reaction to proceed fully, with a grafting rate of over 90%; After the reaction, the pH was adjusted to 7-8 with sodium hydroxide solution to neutralize the residual weak acidic substances in the system, terminate the reaction, and improve the storage stability of the composite high-efficiency water-reducing agent, ultimately obtaining an integrated additive with water-reducing, internal curing, and self-healing functions; the entire grafting process achieved a strong connection between the functional unit and the polycarboxylate main chain through covalent bonding, providing a structural basis for the subsequent multi-performance synergy of concrete. S2, Raw material premixing: Weigh the gel material and quartz sand aggregate according to the ratio, put them into the mixer and dry mix for 2-3 minutes. Add the polyester composite fiber and continue to stir for 1-2 minutes. Mix the composite high-efficiency water-reducing agent with deionized water evenly to make an aqueous solution. Slowly add the solution to the mixture and stir for 3-5 minutes. The roles of each component in finished concrete: Cementitious materials (Portland cement + silica fume): Portland cement is the core strength source, and the CSH gel and calcium hydroxide generated by the hydration reaction constitute the matrix skeleton of concrete; silica fume, as a highly active admixture, fills the pores of cement hydration products on the one hand, reducing the total porosity (3-6%), and on the other hand, participates in the secondary hydration reaction to generate more CSH gel, strengthen the matrix density, and improve compressive strength (≥140MPa) and weather resistance (100% performance retention rate after 300 freeze-thaw cycles). Quartz sand aggregate: As the core aggregate in a coarse aggregate-free system, it optimizes the particle packing state through gradient gradation of 0.1-0.3mm ultrafine quartz sand and 0.3-1.0mm white fine sand, achieving high packing density and reducing internal voids; its white matrix ensures the pure white appearance of the finished concrete, providing both mechanical support and aesthetic function; through optimized gradation and the synergistic dispersion effect of composite high-efficiency water-reducing agent, it enhances the physical interlocking tightness between the aggregate and the cementitious matrix, compensating for insufficient interfacial bonding due to unmodified aggregate, and ensuring the system's structural stability and mechanical properties. Polyester composite fiber (polyethylene terephthalate and basalt fiber in a mass ratio of 80:20, with a diameter of 0.15-0.3mm and a length of 10-15mm, modified with a silane coupling agent): The fiber is uniformly dispersed in the matrix. Under stress, it can effectively bridge microcracks, prevent crack propagation (avoid brittle fracture), and improve the flexural strength (≥15MPa), toughness, and impact resistance of concrete. At the same time, the fiber provides a supporting skeleton for the self-healing process, promotes the deposition of hydration products of the repair agent at the crack, and enhances the self-healing effect. Composite high-efficiency water-reducing agent (polycarboxylate-based water-reducing agent activated and grafted with terminal hydroxyl polyethylene glycol microspheres + aminated drug-loaded nano-silica): The core of this product offers multiple functions in one agent. Its water-reducing function lowers the water-cement ratio and reduces porosity through adsorption and dispersion. Its internal curing function uses the terminal hydroxyl polyethylene glycol microspheres to slowly release water, preventing early drying shrinkage and cracking. Its self-healing function releases a repair agent at the cracks through the aminated drug-loaded nano-silica, filling the cracks (self-healing rate ≥95% within 0.3mm). These three functions work synergistically to ensure the integrated high strength, high weather resistance, and self-healing properties of concrete. Deionized water: As a medium for hydration reaction, it provides the necessary conditions for the hydration of cement and silica fume, while dissolving the water-reducing agent and ensuring its full dispersion effect; the low water-cement ratio (0.1-0.12) design, combined with the efficient dispersion of the water-reducing agent, further reduces the internal porosity and enhances the density and durability of the matrix. The first step involves dry mixing the cementitious material and quartz sand aggregate for 2-3 minutes to optimize the bulk density and pre-contact interface through gradient gradation. The second step involves adding polyester composite fiber and stirring for 1-2 minutes to achieve uniform fiber dispersion and improve interfacial compatibility. The third step involves adding a composite high-efficiency water-reducing agent aqueous solution and stirring for 3-5 minutes. The water-reducing agent is adsorbed on the particle surface to form a double electric layer and steric hindrance, breaking the flocculation structure and releasing free water. S3. Casting and Curing: The mixture is poured into a mold, vibrated and shaped, and cured for 24 hours at 20±2℃ and relative humidity ≥90%. After demolding, it is placed in a steam environment at 80-90℃ and cured for 72 hours to obtain the finished concrete. When C3S and C2S in cement come into contact with water, they undergo hydrolysis-polymerization reactions, generating CSH gel (an amorphous gel-like substance), which is the core source of concrete strength. The gels intertwine to form a three-dimensional network skeleton. The byproduct Ca(OH)2 increases the alkalinity of the system, providing conditions for the secondary hydration of silica fume. The reaction between silica fume (highly active SiO2) and Ca(OH)2 consumes Ca(OH)2 and generates more CSH gel, which reduces the porosity of the matrix and strengthens the interfacial bonding between cementitious materials, aggregates, and fibers. The high-temperature environment of steam curing lowers the activation energy of the hydration reaction, accelerates the above reactions, shortens the strength development cycle, and ultimately forms a concrete product with high compressive strength and good density. The reactions that occur during the above process: 3CaO·SiO2+nH2O→xCaO·SiO2·yH2O+(3-x)Ca(OH)2 2CaO·SiO2+mH2O→xCaO·SiO2·yH2O+(2-x)Ca(OH)2 SiO2+Ca(OH)2+H2O→xCaO·SiO2·yH2O The core function of each step: Vibration molding: Vibration causes the concrete mixture particles to rearrange, expel internal air and excess moisture, eliminate voids, and increase the density of the mixture, laying the physical foundation for the formation of a uniform and dense matrix structure in the subsequent hydration reaction. High humidity curing at room temperature (20±2℃, RH≥90%, 24h): This stage initiates the hydration reaction of the cementitious material. The high humidity environment prevents the moisture in the mixture from evaporating and causing surface cracking. Under room temperature conditions, the hydration reaction proceeds slowly and evenly, initially generating hydration products to build the matrix skeleton and ensure structural stability during demolding. Steam curing (80-90℃, 72h): High temperature accelerates the hydration reaction rate, promotes the generation and interweaving of hydration products, further fills the pores, and strengthens the density and strength of the matrix; at the same time, silica fume participates in secondary hydration, improves the interfacial bonding force, and there are no new reaction types, only the reaction process is accelerated. Preferably, the preparation method of polyester composite fiber is as follows: polyethylene terephthalate and basalt fiber are placed in a mixed modification solution of γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water in a mass ratio of 1:10:3 at a mass ratio of 80:20. The mixture is stirred and soaked at 60-80℃ for 1 hour, and stirred once every 15 minutes to ensure that the fiber surface is uniformly in contact with the modification solution. After removal, the fiber is dried at 80-100℃ to constant weight. After cooling to room temperature, the fiber is passed through a 0.15mm sieve to remove agglomerated particles, thus obtaining polyester composite fiber.

[0012] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention employs an integrated design approach of activation of composite high-efficiency water-reducing agents and covalent grafting of dual-functional units. Combined with the carboxyl activation and covalent grafting mechanism of ester and amide bonds, it successfully integrates three functional units—water reduction, internal curing, and self-healing—into the molecular skeleton of polycarboxylate-based water-reducing agents. This fundamentally solves the core pain points of existing technologies, such as poor compatibility of functional additives and mutual interference between water reduction and curing / healing functions caused by the use of multiple agents. It achieves a synergistic effect of multiple functions in one agent, ensuring that the functional units do not fall off in the alkaline environment of concrete, simplifying the construction and batching process, and improving the stability of product performance.

[0013] 2. This invention employs a synergistic interface optimization method using polyester composite fibers, combined with the interfacial bridging mechanism of silane coupling agents, to solve the problems of weak interfacial bonding between fibers and cementitious matrix, easy formation of micropores and stress concentration points in the prior art. This significantly improves the integrity and structural density of the concrete matrix, resulting in a flexural strength of ≥15MPa and excellent impact resistance in the finished concrete. At the same time, it provides a stable support framework for the deposition of self-healing products, ensuring self-healing efficiency (self-healing rate of ≥95% for 0.3mm cracks).

[0014] 3. This invention employs a synergistic optimization approach using gradient gradation of quartz sand (0.1-0.3mm ultrafine sand + 0.3-1.0mm fine sand) and a low water-cement ratio (0.1-0.12), combined with the electrostatic repulsion and steric hindrance dispersion mechanism of the composite high-efficiency water-reducing agent. This solves the contradiction in existing technologies where reducing the water-cement ratio to pursue high strength easily leads to shrinkage cracking and a decrease in weather resistance. By optimizing the particle packing density to reduce the total porosity (3-6%), a synergistic improvement in high strength and high weather resistance is achieved, resulting in a finished concrete compressive strength ≥140MPa and a 100% performance retention rate after 300 freeze-thaw cycles, capable of withstanding extreme service environments such as coastal areas and frigid regions.

[0015] 4. This invention employs a segmented curing process of room temperature high humidity pre-curing followed by high temperature steam curing, combined with a staged control mechanism for the hydration reaction of cementitious materials. This solves the problems of uneven hydration reaction, slow strength development, or microcracks in the matrix caused by the single curing method in existing technologies. Room temperature pre-curing ensures a stable start-up of the hydration reaction and stable demolding structure. High temperature steam curing accelerates the generation and interweaving of hydration products, shortens the strength development cycle, and promotes the secondary hydration of silica fume to consume Ca(OH)2, further enhancing the density and corrosion resistance of the matrix. Attached Figure Description

[0016] Figure 1 The compressive strength curve of the concrete prepared according to this invention; Figure 2 The bending performance curve of the concrete prepared according to the present invention; Figure 3 The fatigue performance curve of the concrete prepared according to the present invention. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0018] Example 1: Preparation of Ultra-High Performance Concrete: S1. Preparation of composite high-efficiency water-reducing agent: S101. Dilute the polycarboxylate superplasticizer solution with deionized water to a solid content of 20%. Under ice-water bath cooling and stirring, add a carbodiimide condensing agent and N-hydroxysuccinimide. The amount of condensing agent is 1.1 times the number of carboxyl groups in the polycarboxylate superplasticizer, and the amount of N-hydroxysuccinimide is equivalent to that of the condensing agent. Stir and react at room temperature for 3 hours to obtain an activated polycarboxylate superplasticizer solution. S102. Mix 45 parts of polyethylene glycol, 6 parts of acrylic acid, and 0.4 parts of N,N'-methylenebisacrylamide evenly. Add 110 parts of liquid paraffin containing 4 parts of emulsifier, stir for 5 minutes, heat to 65°C, add 0.4 parts of potassium persulfate, and keep the reaction at this temperature for 2 hours. Filter while hot, wash twice with anhydrous ethanol, and dry to obtain an aqueous dispersion of hydroxyl-terminated polyethylene glycol internally conditioned microspheres. S103. Dissolve 13 parts of sodium silicate and 6 parts of lithium carbonate in 90 parts of deionized water to prepare an aqueous solution of the repair agent. Mix 22 parts of tetraethyl orthosilicate and 55 parts of ethanol evenly, and slowly add the aqueous solution of the repair agent. Stir for 30 minutes. Adjust the pH to 9.5 with ammonia water, raise the temperature to 45°C, and keep the reaction at this temperature for 4 hours. Add 4 parts of silane coupling agent KH-550 and continue the reaction for 2 hours. Allow the mixture to stand and separate into layers. Wash twice with deionized water and dry to obtain an aminated drug-loaded nano silica aqueous dispersion. S104, heat to 45℃, adjust pH to 6, slowly add aqueous dispersion of end-hydroxyl polyethylene glycol internally nourished microspheres and aqueous dispersion of aminated drug-loaded nano silica, keep the reaction at the temperature for 6 hours, pump into a spray dryer, control the inlet air temperature to 190℃, the outlet air temperature to 85℃, and the atomization pressure to 0.4MPa to obtain a composite high-efficiency water-reducing agent. S2, Raw material premixing: Weigh 1130 parts of gel material (Portland cement and silica fume compounded at a mass ratio of 85:28) and 1000 parts of quartz sand aggregate (ultrafine quartz sand and white fine sand mixed at a mass ratio of 11:80), put them into a mixer and dry mix for 2.5 minutes. Add 170 parts of polyester composite fiber and continue mixing for 1.5 minutes. Mix 15 parts of composite high-efficiency water-reducing agent with 180 parts of deionized water evenly to make an aqueous solution, and slowly add it to the mixture and stir for 4 minutes. S3. Casting and Curing: The mixture is poured into a mold, vibrated to form the final product, and cured for 24 hours at 20℃ and relative humidity ≥90%. After demolding, it is placed in a steam environment at 85℃ for 72 hours to obtain the finished concrete.

[0019] Example 2: Preparation of Ultra-High Performance Concrete: S1. Preparation of composite high-efficiency water-reducing agent: S101. Dilute the polycarboxylate superplasticizer solution with deionized water to a solid content of 20%. Under ice-water bath cooling and stirring, add a carbodiimide condensing agent and N-hydroxysuccinimide. The amount of condensing agent is 1.1 times the number of carboxyl groups in the polycarboxylate superplasticizer, and the amount of N-hydroxysuccinimide is equivalent to that of the condensing agent. Stir and react at room temperature for 3 hours to obtain an activated polycarboxylate superplasticizer solution. S102. Mix 45 parts of polyethylene glycol, 6 parts of acrylic acid, and 0.4 parts of N,N'-methylenebisacrylamide evenly. Add 110 parts of liquid paraffin containing 4 parts of emulsifier, stir for 5 minutes, heat to 65°C, add 0.4 parts of potassium persulfate, and keep the reaction at this temperature for 2 hours. Filter while hot, wash twice with anhydrous ethanol, and dry to obtain an aqueous dispersion of hydroxyl-terminated polyethylene glycol internally conditioned microspheres. S103. Dissolve 13 parts of sodium silicate and 6 parts of lithium carbonate in 90 parts of deionized water to prepare an aqueous solution of the repair agent. Mix 22 parts of tetraethyl orthosilicate and 55 parts of ethanol evenly, and slowly add the aqueous solution of the repair agent. Stir for 30 minutes. Adjust the pH to 9.5 with ammonia water, raise the temperature to 45°C, and keep the reaction at this temperature for 4 hours. Add 4 parts of silane coupling agent KH-550 and continue the reaction for 2 hours. Let the mixture stand to separate into layers, wash twice with deionized water, and dry to obtain an aminated drug-loaded nano-silica aqueous dispersion. S104, heat to 45℃, adjust pH to 6, slowly add aqueous dispersion of end-hydroxyl polyethylene glycol internally nourished microspheres and aqueous dispersion of aminated drug-loaded nano silica, keep the reaction at the temperature for 6 hours, pump into a spray dryer, control the inlet air temperature to 190℃, the outlet air temperature to 85℃, and the atomization pressure to 0.4MPa to obtain a composite high-efficiency water-reducing agent. S2, Raw material premixing: Weigh 1130 parts of gel material (Portland cement and silica fume compounded at a mass ratio of 85:28) and 1000 parts of quartz sand aggregate (ultrafine quartz sand and white fine sand mixed at a mass ratio of 11:80), put them into a mixer and dry mix for 2.5 minutes. Add 170 parts of polyester composite fiber and continue mixing for 1.5 minutes. Mix 25 parts of composite high-efficiency water-reducing agent with 180 parts of deionized water evenly to make an aqueous solution, and slowly add it to the mixture and stir for 4 minutes. S3. Casting and Curing: The mixture is poured into a mold, vibrated to form the final product, and cured for 24 hours at 20℃ and relative humidity ≥90%. After demolding, it is placed in a steam environment at 85℃ for 72 hours to obtain the finished concrete.

[0020] Example 3: Preparation of Ultra-High Performance Concrete: S1. Preparation of composite high-efficiency water-reducing agent: S101. Dilute the polycarboxylate superplasticizer solution with deionized water to a solid content of 20%. Under ice-water bath cooling and stirring, add a carbodiimide condensing agent and N-hydroxysuccinimide. The amount of condensing agent is 1.1 times the number of carboxyl groups in the polycarboxylate superplasticizer, and the amount of N-hydroxysuccinimide is equivalent to that of the condensing agent. Stir and react at room temperature for 3 hours to obtain an activated polycarboxylate superplasticizer solution. S102. Mix 45 parts of polyethylene glycol, 6 parts of acrylic acid, and 0.4 parts of N,N'-methylenebisacrylamide evenly. Add 110 parts of liquid paraffin containing 4 parts of emulsifier, stir for 5 minutes, heat to 65°C, add 0.4 parts of potassium persulfate, and keep the reaction at this temperature for 2 hours. Filter while hot, wash twice with anhydrous ethanol, and dry to obtain an aqueous dispersion of hydroxyl-terminated polyethylene glycol internally conditioned microspheres. S103. Dissolve 13 parts of sodium silicate and 6 parts of lithium carbonate in 90 parts of deionized water to prepare an aqueous solution of the repair agent. Mix 22 parts of tetraethyl orthosilicate and 55 parts of ethanol evenly, and slowly add the aqueous solution of the repair agent. Stir for 30 minutes. Adjust the pH to 9.5 with ammonia water, raise the temperature to 45°C, and keep the reaction at this temperature for 4 hours. Add 4 parts of silane coupling agent KH-550 and continue the reaction for 2 hours. Allow the mixture to stand and separate into layers. Wash twice with deionized water and dry to obtain an aminated drug-loaded nano silica aqueous dispersion. S104, heat to 45℃, adjust pH to 6, slowly add aqueous dispersion of end-hydroxyl polyethylene glycol internally nourished microspheres and aqueous dispersion of aminated drug-loaded nano silica, keep the reaction at the temperature for 6 hours, pump into a spray dryer, control the inlet air temperature to 190℃, the outlet air temperature to 85℃, and the atomization pressure to 0.4MPa to obtain a composite high-efficiency water-reducing agent. S2, Raw material premixing: Weigh 1130 parts of gel material (Portland cement and silica fume mixed at a mass ratio of 85:28) and 1000 parts of quartz sand aggregate (ultrafine quartz sand and white fine sand mixed at a mass ratio of 11:80), put them into a mixer and dry mix for 2.5 minutes. Add 170 parts of polyester composite fiber and continue mixing for 1.5 minutes. Mix 20 parts of composite high-efficiency water-reducing agent with 180 parts of deionized water evenly to make an aqueous solution, and slowly add it to the mixture and stir for 4 minutes. S3. Casting and Curing: The mixture is poured into a mold, vibrated to form the final product, and cured for 24 hours at 20℃ and relative humidity ≥90%. After demolding, it is placed in a steam environment at 85℃ and cured for 72 hours to obtain the finished concrete.

[0021] Example 4: Preparation of Ultra-High Performance Concrete: S1. Preparation of composite high-efficiency water-reducing agent: S101. Dilute the polycarboxylate superplasticizer solution with deionized water to a solid content of 20%. Under ice-water bath cooling and stirring, add a carbodiimide condensing agent and N-hydroxysuccinimide. The amount of condensing agent is 1.1 times the number of carboxyl groups in the polycarboxylate superplasticizer, and the amount of N-hydroxysuccinimide is equivalent to that of the condensing agent. Stir and react at room temperature for 3 hours to obtain an activated polycarboxylate superplasticizer solution. S102. Mix 45 parts of polyethylene glycol, 6 parts of acrylic acid, and 0.4 parts of N,N'-methylenebisacrylamide evenly. Add 110 parts of liquid paraffin containing 4 parts of emulsifier, stir for 5 minutes, heat to 65°C, add 0.4 parts of potassium persulfate, and keep the reaction at this temperature for 2 hours. Filter while hot, wash twice with anhydrous ethanol, and dry to obtain an aqueous dispersion of hydroxyl-terminated polyethylene glycol internally conditioned microspheres. S103. Dissolve 13 parts of sodium silicate and 6 parts of lithium carbonate in 90 parts of deionized water to prepare an aqueous solution of the repair agent. Mix 22 parts of tetraethyl orthosilicate and 55 parts of ethanol evenly, and slowly add the aqueous solution of the repair agent. Stir for 30 minutes. Adjust the pH to 9.5 with ammonia water, raise the temperature to 45°C, and keep the reaction at this temperature for 4 hours. Add 4 parts of silane coupling agent KH-550 and continue the reaction for 2 hours. Let the mixture stand to separate into layers, wash twice with deionized water, and dry to obtain an aminated drug-loaded nano-silica aqueous dispersion. S104, heat to 45℃, adjust pH to 6, slowly add aqueous dispersion of end-hydroxyl polyethylene glycol internally nourished microspheres and aqueous dispersion of aminated drug-loaded nano silica, keep the reaction at the temperature for 6 hours, pump into a spray dryer, control the inlet air temperature to 190℃, the outlet air temperature to 85℃, and the atomization pressure to 0.4MPa to obtain a composite high-efficiency water-reducing agent. S2, Raw material premixing: Weigh 1130 parts of gel material (Portland cement and silica fume compounded at a mass ratio of 85:28) and 1000 parts of quartz sand aggregate (ultrafine quartz sand and white fine sand mixed at a mass ratio of 11:80), put them into a mixer and dry mix for 2.5 minutes. Add 150 parts of polyester composite fiber and continue mixing for 1.5 minutes. Mix 20 parts of composite high-efficiency water-reducing agent with 180 parts of deionized water evenly to make an aqueous solution, and slowly add it to the mixture and stir for 4 minutes. S3. Casting and Curing: The mixture is poured into a mold, vibrated to form the final product, and cured for 24 hours at 20℃ and relative humidity ≥90%. After demolding, it is placed in a steam environment at 85℃ and cured for 72 hours to obtain the finished concrete.

[0022] Example 5: Preparation of Ultra-High Performance Concrete: S1. Preparation of composite high-efficiency water-reducing agent: S101. Dilute the polycarboxylate superplasticizer solution with deionized water to a solid content of 20%. Under ice-water bath cooling and stirring, add a carbodiimide condensing agent and N-hydroxysuccinimide. The amount of condensing agent is 1.1 times the number of carboxyl groups in the polycarboxylate superplasticizer, and the amount of N-hydroxysuccinimide is equivalent to that of the condensing agent. Stir and react at room temperature for 3 hours to obtain an activated polycarboxylate superplasticizer solution. S102. Mix 45 parts of polyethylene glycol, 6 parts of acrylic acid, and 0.4 parts of N,N'-methylenebisacrylamide evenly. Add 110 parts of liquid paraffin containing 4 parts of emulsifier, stir for 5 minutes, heat to 65°C, add 0.4 parts of potassium persulfate, and keep the reaction at this temperature for 2 hours. Filter while hot, wash twice with anhydrous ethanol, and dry to obtain an aqueous dispersion of hydroxyl-terminated polyethylene glycol internally conditioned microspheres. S103. Dissolve 13 parts of sodium silicate and 6 parts of lithium carbonate in 90 parts of deionized water to prepare an aqueous solution of the repair agent. Mix 22 parts of tetraethyl orthosilicate and 55 parts of ethanol evenly, and slowly add the aqueous solution of the repair agent. Stir for 30 minutes. Adjust the pH to 9.5 with ammonia water, raise the temperature to 45°C, and keep the reaction at this temperature for 4 hours. Add 4 parts of silane coupling agent KH-550 and continue the reaction for 2 hours. Let the mixture stand to separate into layers, wash twice with deionized water, and dry to obtain an aminated drug-loaded nano-silica aqueous dispersion. S104, heat to 45℃, adjust pH to 6, slowly add aqueous dispersion of end-hydroxyl polyethylene glycol internally nourished microspheres and aqueous dispersion of aminated drug-loaded nano silica, keep the reaction at the temperature for 6 hours, pump into a spray dryer, control the inlet air temperature to 190℃, the outlet air temperature to 85℃, and the atomization pressure to 0.4MPa to obtain a composite high-efficiency water-reducing agent. S2, Raw material premixing: Weigh 1130 parts of gel material (Portland cement and silica fume compounded at a mass ratio of 85:28) and 1000 parts of quartz sand aggregate (ultrafine quartz sand and white fine sand mixed at a mass ratio of 11:80), put them into a mixer and dry mix for 2.5 minutes. Add 190 parts of polyester composite fiber and continue mixing for 1.5 minutes. Mix 20 parts of composite high-efficiency water-reducing agent with 180 parts of deionized water evenly to make an aqueous solution, and slowly add it to the mixture and stir for 4 minutes. S3. Casting and Curing: The mixture is poured into a mold, vibrated to form the final product, and cured for 24 hours at 20℃ and relative humidity ≥90%. After demolding, it is placed in a steam environment at 85℃ and cured for 72 hours to obtain the finished concrete.

[0023] Comparative Example 1: Compared with Example 3, in Comparative Example 1, 30 parts of composite high-efficiency water-reducing agent were mixed with 180 parts of deionized water evenly, and other conditions remained unchanged.

[0024] Comparative Example 2: Compared with Example 3, 210 parts of polyester composite fiber were added to Comparative Example 2 during raw material premixing, while other conditions remained unchanged.

[0025] Comparative Example 3: Compared with Example 3, the polyester composite fibers in Comparative Example 3 were not treated with silane reagents, while the other conditions remained unchanged.

[0026] Comparative Example 4: Compared with Example 3, in Comparative Example 4, the composite high-efficiency water-reducing agent was replaced by "ordinary polycarboxylate superplasticizer, with equal amounts of terminal hydroxyl polyethylene glycol microspheres and drug-loaded nano-silica added separately", while the other conditions remained unchanged.

[0027] Comparative Example 5: Compared with Example 3, Comparative Example 5 replaced "room temperature pre-curing for 24 hours + steam curing at 85°C for 72 hours" with "room temperature curing for 4 days", while the other conditions remained unchanged.

[0028] Performance testing: According to the standard test methods in GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete", GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", and T / CECS 913-2021 "Standard for Test Methods of Self-Healing Performance of Cement Concrete", the concrete prepared in the above examples and comparative proportions was tested for compressive strength, flexural strength, splitting tensile strength, modulus of elasticity, Poisson's ratio, mass loss rate after freeze-thaw cycles, strength retention rate, chloride ion diffusion coefficient, impermeability grade, spread, initial setting, final setting, crack area repair rate, and strength recovery rate.

[0029] Table 1. Basic mechanical properties of the prepared concrete

[0030] Data Analysis: Figure 1The compressive strength curve of the concrete prepared for this invention is shown, with strain (%) on the x-axis and compressive stress (MPa) on the y-axis. The curve for ordinary concrete (dashed line) shows a rapid drop in stress at low strain, exhibiting brittle fracture characteristics under compressive stress and quickly losing its load-bearing capacity. In contrast, the curve for this invention (solid line) first rises rapidly to an extremely high stress peak, and as strain increases (approaching 2%), the stress remains at a high level without a sharp decline. This curve characteristic corresponds to the superior compressive strength of this invention, which is 4 to 8 times that of ordinary concrete. Furthermore, it exhibits a linear stress state without breakage before reaching maximum stress and can withstand significant deformation afterward, demonstrating both high strength and good deformation capacity.

[0031] Figure 2 The bending performance curve of the concrete prepared for this invention is shown on the horizontal axis as displacement (unit: micrometer) and the vertical axis as bending strength (unit: MPa). The curve of ordinary concrete drops rapidly to zero when the displacement is small, reflecting the brittle fracture characteristics under bending stress. The curve of this invention rises to the peak strength first and then slowly decreases, and can withstand a large displacement (up to about 1400 micrometers). This difference is due to the polyester composite fiber added in this invention: when the bending stress exceeds the elastic limit, the fiber will hold the microcracks, so that the material exhibits ductile properties rather than brittle fracture. Therefore, multiple microcracks can be generated during bending, avoiding local concentrated failure and exhibiting better bending toughness.

[0032] Figure 3 The fatigue performance curves of the concrete prepared according to this invention are shown. The horizontal axis represents crack opening displacement (COD, unit μm), and the vertical axis represents bending load (unit kN). The curves correspond to cyclic loading cycles ranging from 300 to 1.2 million. As can be seen from the figure, the curves for different cycle numbers show a highly consistent trend. The bending load increases with the increase of crack opening displacement, and the curves corresponding to each cycle number almost overlap. This indicates that under cyclic loading, even after 1.2 million cycles, the crack opening displacement of this concrete does not increase significantly, and there is no crack propagation, demonstrating excellent fatigue resistance and the ability to withstand cyclic loading for a long time while maintaining stable mechanical performance.

[0033] According to the basic mechanical property data of the concrete prepared in Table 1, Example 3 has the best comprehensive mechanical properties. The properties of Examples 1, 2, 4 and 5 fluctuate slightly around it, while the properties of each comparative example show significant attenuation to different degrees. The core difference stems from the compatibility of component dosage and the application of innovative technologies.

[0034] Example 1: Due to a lower dosage of the composite high-efficiency water-reducing agent than the standard example, the dispersion effect on cementitious materials and aggregates was slightly weaker, resulting in a slight decrease in the workability and structural density of the mixture. Mechanical strength, frost resistance, and self-healing rate all declined slightly compared to the standard example. Whiteness and fiber dispersion remained basically stable, confirming that the dosage of water-reducing agent needs to be maintained within a reasonable range to ensure functional synergy. Example 2: The dosage of water-reducing agent was higher than the standard example. Although it improved the fluidity of the mixture, the excessive water-reducing agent introduced a small amount of excess air bubbles, slightly increasing the porosity inside the matrix. Mechanical strength decreased slightly compared to the standard example, while workability and durability remained at a high level. This indicates that more water-reducing agent is not necessarily better; it needs to be compatible with other components. Example 4: The dosage of polyester composite fiber was lower than the standard example. The bridging effect of the fiber on microcracks was weakened, and the flexural strength, toughness, and self-healing support effect decreased slightly compared to the standard example. Other mechanical and durability properties remained basically the same, demonstrating the direct impact of fiber content on material toughness. Example 5 showed a higher fiber content than the standard example, resulting in a slight improvement in flexural strength and toughness. However, excessive fiber content could lead to localized agglomeration during mixing, affecting the fluidity and matrix density of the mixture. The compressive strength and durability were not further optimized, indicating that there is an optimal range for fiber content.

[0035] The performance degradation of each comparative example was more significant: Comparative Example 1 showed excessive water-reducing agent, with excess air bubbles significantly increasing the matrix porosity, resulting in decreased mechanical strength and weakened frost resistance and density, verifying that excessive water-reducing agent dosage would disrupt system stability; Comparative Example 2 showed excessive fiber leading to severe agglomeration, forming internal stress concentration points and pore defects, resulting in a significant decline in workability, mechanical strength, and durability, highlighting the need for strict control of fiber content to avoid negative impacts; Comparative Example 3 showed that the polyester composite fiber was not treated with silane reagent, resulting in weak interfacial bonding between the composite fiber and the cementitious matrix, failing to effectively transfer stress and bridge cracks, thus affecting flexural strength and toughness. The significant decrease in strength and self-healing rate confirms the crucial role of fiber surface modification in interfacial compatibility. Comparative Example 4, which uses ordinary water-reducing agent combined with individual functional units to replace composite high-efficiency water-reducing agent, suffers from poor multi-agent compatibility, hindered dispersion, and easy detachment of functional units, resulting in a sharp drop in strength, durability, and self-healing performance, highlighting the core advantage of "covalent grafting integration of functional units". Comparative Example 5, which uses single room temperature curing, shows insufficient hydration reaction of cementitious materials, difficulty in promoting secondary hydration of silica fume, insufficient matrix density, and a significant decline in mechanical strength, durability, and workability, confirming the importance of segmented curing process for controlling the hydration process.

[0036] Table 2 Durability data of the prepared concrete

[0037] Data Analysis: According to the durability performance data in Table 2, Example 3 showed the best performance. Example 1 had a higher total porosity than the standard example, a correspondingly lower expansion, increased freeze-thaw mass loss, and a slightly lower strength retention rate. This is because its composite high-efficiency water-reducing agent dosage was lower than the standard example, resulting in insufficient dispersion of the cementitious materials and aggregates, leading to increased pores within the matrix, weakened structural density, and consequently reduced freeze-thaw resistance. Example 2 had a slightly higher total porosity than the standard example, improved expansion, slightly lower freeze-thaw mass loss, and a strength retention rate close to the standard example level. The increased water-reducing agent dosage enhanced the dispersion effect and improved the fluidity of the mixture, but the micro-bubbles introduced by the excessive water-reducing agent slightly increased the porosity; however, overall, it still maintained good density and durability. Example 4 had a higher total porosity than the standard example, a slightly lower expansion, increased freeze-thaw mass loss, and a decreased strength retention rate. This was due to insufficient polyester composite fiber dosage, which weakened the support and crack bridging effect on the matrix structure, and slightly reduced dispersion uniformity, leading to increased porosity and weakened freeze-thaw resistance. Example 5 had a slightly higher total porosity than the standard example, a slightly lower expansion, and freeze-thaw related indicators that were close to those of the standard example. Although the increase in fiber content improved toughness, local agglomeration caused a slight increase in porosity, but it did not have a significant impact on overall density and durability.

[0038] The durability degradation was more pronounced in each comparative example: Comparative Example 1 showed increased total porosity and excessive spread, resulting in increased freeze-thaw mass loss and decreased strength retention, due to the excessive water-reducing agent introducing a large number of air bubbles, which damaged the matrix density and weakened freeze-thaw resistance; Comparative Example 2 showed increased total porosity and decreased spread, leading to a decline in freeze-thaw performance, caused by excessive fiber content leading to agglomeration, forming internal pores and stress concentration points, reducing the overall structural integrity; Comparative Example 3 showed increased total porosity and decreased spread, resulting in reduced freeze-thaw performance, due to the composite fibers not being treated with silane reagent. The weak bonding between the agent and the matrix interface, along with increased interfacial porosity, weakens the structural foundation for freeze-thaw resistance. Comparative Example 4 shows a significant increase in total porosity and a decrease in spread, resulting in a marked decline in freeze-thaw performance. This is due to the poor compatibility between the ordinary water-reducing agent and the individual functional units, insufficient dispersion, and easy detachment of the functional units, leading to a surge in matrix porosity. Comparative Example 5 shows an increase in total porosity and a decrease in spread, prolonged initial and final setting times, and a decline in freeze-thaw performance. This is due to insufficient hydration of the cementitious material caused by single room temperature curing, difficulty in promoting secondary hydration of silica fume, insufficient matrix density, and ultimately weakened durability.

[0039] Table 3 Workability data of the prepared concrete

[0040] Data Analysis: Table 3 shows the workability data of the prepared concrete. Example 3 showed the best overall performance, while the other examples and comparative examples had weaker overall performance than Example 3. Example 1 showed a slightly increased chloride ion diffusion coefficient, a slightly decreased impermeability grade, slightly lower self-healing rate and strength recovery rate, and a slight decrease in whiteness and fiber dispersion. This is because its composite high-efficiency water-reducing agent dosage was lower than the standard example, resulting in insufficient dispersion of the cementitious system, a slight increase in matrix porosity, and weakened impermeability and chloride ion penetration resistance. Simultaneously, the dispersion uniformity of the functional units was slightly poor, leading to a slight decline in self-healing related properties, and the whiteness also fluctuated slightly due to uneven component distribution.

[0041] In Example 2, the chloride ion diffusion coefficient decreased slightly, the impermeability grade remained one level below the standard example, the self-healing indicators were close to the standard example, and the whiteness and fiber dispersion increased slightly. The increased amount of water-reducing agent enhanced the dispersion effect and reduced local porosity, thus slightly reducing the risk of chloride ion penetration; however, the micro-bubbles introduced by the excessive water-reducing agent failed to further improve the impermeability grade, but the synergy of the functional units remained good, and the self-healing performance was not significantly affected.

[0042] In Example 4, the chloride ion diffusion coefficient increased slightly, the impermeability grade decreased slightly, the self-healing index was slightly lower, and the fiber dispersion decreased slightly. The amount of polyester composite fiber was lower than in the standard example, resulting in a weaker bridging and supporting effect on the matrix, slightly poorer fiber dispersion uniformity, a slight increase in matrix porosity, weakened impermeability and chloride ion penetration resistance, insufficient support framework at cracks during the self-healing process, and a slight decline in repair effect.

[0043] In Example 5, the chloride ion diffusion coefficient increased slightly, the impermeability grade decreased slightly, the self-healing index was close to that of the standard example, and the fiber dispersion decreased slightly. The fiber content was higher than that of the standard example, and slight agglomeration occurred in some areas, which slightly increased the porosity of the matrix. The impermeability and chloride ion penetration resistance did not reach the level of the standard example, but the overall fiber still maintained good dispersion, and the self-healing performance was not significantly affected.

[0044] The performance degradation of each comparative example was more pronounced: Comparative Example 1 showed a significant increase in chloride ion diffusion coefficient, a downgrade in impermeability, and a decline in self-healing indicators, whiteness, and fiber dispersion. This was due to the excessive water-reducing agent introducing a large number of air bubbles, which damaged the matrix density and interfered with the distribution of functional units. Comparative Example 2 showed excessive fiber usage leading to agglomeration, which not only weakened the impermeability and chloride ion penetration resistance but also damaged fiber dispersion, significantly reducing the bridging effect of self-healing. Comparative Example 3 showed that the polyester composite fiber was not treated with silane reagent, resulting in weak interfacial bonding, a surge in interfacial porosity, and severely insufficient density, leading to a significant reduction in impermeability, chloride ion penetration resistance, and self-healing effects. Comparative Example 4 showed that the use of ordinary water-reducing agent in combination with individual functional units resulted in poor compatibility, leading to dispersion failure, functional unit detachment, and a collapse in matrix density, causing a sharp drop in impermeability and self-healing properties. Comparative Example 5 showed that single room temperature curing resulted in insufficient hydration, hindered secondary hydration of silica fume, extremely poor matrix density, and a sharp decline in impermeability, carbonization resistance, and self-healing performance.

[0045] The above embodiments demonstrate that the component-adapted, functionally integrated water-reducing agent and segmented curing process of the present invention can achieve excellent properties in concrete, such as high strength, high weather resistance, and efficient self-healing. Comparative examples prove that each innovation is indispensable: the absence of a functional water-reducing agent, unmodified components, or the use of incorrect curing processes will significantly weaken strength, durability, and self-healing effects, highlighting the inventiveness and practicality of the present invention.

[0046] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-strength, weather-resistant, self-healing, ultra-high-performance concrete, characterized in that, The raw materials include the following proportions: Gel material: 930-1330 parts, wherein the gel material is composed of Portland cement and silica fume in a mass ratio of 70-101:23-32; Quartz sand aggregate: 760-1280 parts, wherein the quartz sand aggregate is composed of ultrafine quartz sand with a particle size of 0.1-0.3mm and white fine sand with a particle size of 0.3-1.0mm at a mass ratio of 0-23:76-105; Polyester composite fiber: 50-190 parts, wherein the polyester composite fiber is a blend of polyethylene terephthalate with basalt fiber in a mass ratio of 80:20 with a diameter of 0.15-0.3 mm and a length of 10-15 mm, and modified with a silane coupling agent; Composite high-efficiency water-reducing agent: 15-25 parts, wherein the composite high-efficiency water-reducing agent is made of commercially available polycarboxylate water-reducing agent as base material, activated, grafted hydroxyl-terminated polyethylene glycol internally nourished microspheres and aminated drug-loaded nano-silica; Water: 155-210 parts; Water / cementing material ratio: 0.1-0.

12.

2. The high-strength, weather-resistant, self-healing, ultra-high-performance concrete according to claim 1, characterized in that, The preparation method of the polyester composite fiber is as follows: polyethylene terephthalate and basalt fiber are placed in a mixed modification solution of γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water in a mass ratio of 1:10:3 at a mass ratio of 80:

20. The mixture is stirred and soaked at 60-80℃ for 1 hour, and stirred once every 15 minutes to ensure that the fiber surface is in uniform contact with the modification solution. After removal, the fiber is dried at 80-100℃ to constant weight. After cooling to room temperature, the fiber is passed through a 0.15mm sieve to remove agglomerated particles, thus obtaining the polyester composite fiber.

3. The high-strength, weather-resistant, self-healing, ultra-high-performance concrete according to claim 1, characterized in that, The preparation method of the composite high-efficiency water-reducing agent is as follows: S1, Carboxyl group activation in polycarboxylate superplasticizer: The polycarboxylate superplasticizer solution was diluted with deionized water to a solid content of 20%. Under ice-water bath cooling and stirring, a carbodiimide condensing agent and N-hydroxysuccinimide were added. The amount of condensing agent was 1.0-1.2 times the number of carboxyl groups in the polycarboxylate superplasticizer, and the amount of N-hydroxysuccinimide was equivalent to that of the condensing agent. The reaction was stirred at room temperature for 2-4 hours to obtain an activated polycarboxylate superplasticizer solution. S2, Functional Unit Grafting: The temperature is raised to 40-50℃, the pH is adjusted to 5-7, and aminated drug-loaded nano-silica containing hydroxyl-terminated polyethylene glycol microspheres is slowly added. The reaction is maintained at this temperature for 4-8 hours, and then pumped into a spray dryer. The inlet air temperature is controlled at 180-200℃, the outlet air temperature at 80-90℃, and the atomization pressure at 0.3-0.5MPa to obtain a composite high-efficiency water-reducing agent.

4. The high-strength, weather-resistant, self-healing, ultra-high-performance concrete according to claim 3, characterized in that, The method for preparing the aqueous dispersion of the hydroxyl-terminated polyethylene glycol internally maintained microspheres is as follows: Mix 45 parts of polyethylene glycol, 6 parts of acrylic acid, and 0.4 parts of N,N'-methylenebisacrylamide evenly, add 110 parts of liquid paraffin containing 4 parts of emulsifier, stir for 5 minutes, heat to 65°C, add 0.4 parts of potassium persulfate, and keep the reaction at this temperature for 2 hours; filter while hot, wash twice with anhydrous ethanol, and dry to obtain hydroxyl-terminated polyethylene glycol internally conditioned microspheres.

5. The high-strength, weather-resistant, self-healing, ultra-high-performance concrete according to claim 3, characterized in that, The method for preparing the aqueous dispersion of the aminated drug-loaded nano-silica is as follows: Dissolve 13 parts of sodium silicate and 6 parts of lithium carbonate in 90 parts of deionized water to prepare an aqueous repair agent solution. Mix 22 parts of tetraethyl orthosilicate and 55 parts of ethanol evenly, and slowly add the aqueous repair agent solution while stirring for 30 minutes. Adjust the pH to 9.5 with ammonia, raise the temperature to 45°C, and keep the reaction at this temperature for 4 hours. Add 4 parts of silane coupling agent KH-550 and continue the reaction for 2 hours. Allow the mixture to stand and separate into layers, wash twice with deionized water, and dry to obtain aminated drug-loaded nano-silica.

6. A method for preparing high-strength, weather-resistant, self-healing, ultra-high-performance concrete according to any one of claims 1-5, characterized in that, Includes the following steps (1) Weigh the gel material and quartz sand aggregate according to the proportion, and put them into the mixer and dry mix for 2-3 minutes; (2) Add polyester composite fibers to the mixture in step (1) and continue stirring for 1-2 minutes; (3) Mix the composite high-efficiency water-reducing agent with deionized water evenly to make an aqueous solution, and slowly add it to the mixture in step (2) and stir for 3-5 minutes; (4) Pour the mixture into the mold, vibrate to form, and cure for 24 hours at 20±2℃ and relative humidity ≥90%. After demolding, place it in a steam environment at 80-90℃ for 72 hours to obtain the finished concrete.

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