High-strength concrete and preparation method and application thereof

Abstract

This invention relates to a high-strength concrete, its preparation method, and its application, belonging to the field of building materials technology. It comprises 1300-1340 parts coarse aggregate, 820-860 parts fine aggregate, 320-360 parts cement, 130-140 parts fly ash, 1.2-2.5 parts quaternized amylopectin, 0.2-0.5 parts malic acid, 70-90 parts steel fiber, 2.5-3 parts water-reducing agent, 0.25-0.45 parts crosslinking synergist, and 120-130 parts water. The crosslinking synergist includes polyacrylic acid-grafted polyethylene glycol and potassium hydrogen tartrate. The polyacrylic acid-grafted polyethylene glycol and quaternized amylopectin form a polyelectrolyte complex, improving the uniformity of steel fiber dispersion. Potassium hydrogen tartrate creates a pH buffer environment on the surface of cement particles, enhancing the esterification and crosslinking efficiency of starch and malic acid. This results in high-strength concrete possessing high strength, crack resistance, toughness, and long-term durability.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a high-strength concrete, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] High-strength concrete (HSC) possesses high compressive strength, strong resistance to deformation, high density, and low porosity, making it widely used in high-rise building structures, long-span bridge structures, and special structures. It is of great significance for improving engineering quality and reducing life-cycle costs. Its mechanical properties are highly dependent on the integrity of the hydration process and the compactness of the microstructure. However, the rapid hydration reaction of HSC easily induces the generation and propagation of microcracks, and uneven hydration can cause internal defects and damage, leading to early cracking and threatening structural durability and long-term safety.

[0004] Existing technologies mostly employ temperature control and internal curing to mitigate early cracking, but both have drawbacks: temperature control is complex to implement and prone to heat accumulation or cooling errors that could damage early strength; internal curing introduces high-moisture lightweight aggregates or highly absorbent polymers, which can create excess pores in the matrix, reducing mechanical properties, and the water absorption process is difficult to precisely control, making it difficult to balance volume stability and high strength. Furthermore, while existing temperature control and internal curing technologies can alleviate shrinkage and temperature rise to some extent, they cannot simultaneously regulate the crosslinking efficiency of organic polymer components in a strongly alkaline environment, nor can they solve the problems of uniform dispersion of steel fibers in highly viscous slurries and chemical anchoring at the matrix interface. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a high-strength concrete, its preparation method, and its application. By compounding quaternized amylopectin and organic acids, and through the synergistic mechanism of "organic acid regulating the hydration process" and "quaternized amylopectin optimizing the microstructure," the hydration reaction and microstructure of high-strength concrete are optimized from both "time" and "space" dimensions, ultimately achieving a significant improvement in mechanical properties, especially flexural strength and toughness.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: Firstly, a high-strength concrete comprises the following components in parts by weight: The composition includes: 1300-1350 parts coarse aggregate, 830-870 parts fine aggregate, 330-370 parts cement, 140-150 parts fly ash, 1.2-2.5 parts quaternized amylopectin, 0.3-0.5 parts malic acid, 70-90 parts steel fiber, 2.5-3 parts water-reducing agent, 0.15-0.45 parts crosslinking synergist, and 120-130 parts water. The crosslinking synergist comprises polyacrylic acid grafted with polyethylene glycol and potassium hydrogen tartrate in a mass ratio of 1:(0.7~1.1).

[0007] Secondly, the above-mentioned method for preparing high-strength concrete includes the following steps: Prepare malic acid solution, quaternized amylopectin dispersion and crosslinking synergist dispersion. Dry mix cement, fly ash, fine aggregate and coarse aggregate to obtain dry mix. Add malic acid solution, quaternized amylopectin dispersion, crosslinking synergist, residual water and water-reducing agent to dry mix. After stirring, add steel fiber to obtain slurry. Pour and cure for a set time.

[0008] Thirdly, the application of the aforementioned high-strength concrete.

[0009] The beneficial effects of this invention are as follows: This invention employs quaternized amylopectin as a toughening agent, introducing a microfiber network and self-curing mechanism into high-strength concrete: quaternized amylopectin gelles under alkaline conditions, forming a viscous gel with a three-dimensional network structure. This gel bridges microcracks through in-situ fiberization, enhancing the fracture toughness and deformation capacity of the concrete. This gel network locks in free water, forming an "internal curing core" that continuously supplies water during the critical hydration period, significantly reducing self-drying shrinkage and plastic shrinkage. The quaternary ammonium groups impart a positive charge to the starch, resulting in electrostatic interaction with the negative charge of cement particles, improving dispersion and interfacial bonding. Furthermore, the steric hindrance effect promotes uniform dispersion of ultrafine powders, optimizes pore structure, and reduces the proportion of harmful pores. This invention further introduces a crosslinking synergist composed of polyethylene glycol-grafted polyacrylic acid and potassium hydrogen tartrate: the former, polyethylene glycol-grafted polyacrylic acid, forms a polyelectrolyte complex with quaternized amylopectin, shielding against excessive thickening and improving the uniformity of steel fiber dispersion; the latter, potassium hydrogen tartrate, creates a pH buffer environment on the surface of cement particles, enhancing the esterification and crosslinking efficiency of starch and malic acid, forming a dense coating layer, and improving interfacial bonding strength. The combined effect of these properties gives high-strength concrete high strength, crack resistance, toughness, and long-term durability.

[0010] In the key components of this invention, the organic acid and quaternized amylopectin are both derived from natural and renewable biomass raw materials. The polyacrylic acid grafted polyethylene glycol (PAA-g-PEG) and potassium hydrogen tartrate in the crosslinking synergist are both industrially mature products. The addition amount is low and the cost is controllable, which makes this invention not only improve performance but also conform to the development direction of green and sustainable building materials. Attached Figure Description

[0011] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0012] Figure 1 This is a statistical chart of the compressive strength and flexural strength of the embodiments and comparative examples in this invention.

[0013] Figure 2 This is a statistical chart of drying shrinkage rate and chloride ion diffusion coefficient in the embodiments and comparative examples of this invention. Detailed Implementation

[0014] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0015] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0016] The chemical substances involved in the following specific embodiments include the following: Malic acid, specifically DL-malic acid, CAS number 6915-15-7, molecular formula C4H6O5, is a white crystalline solid with no odor or a slightly characteristic odor, melting point of 131-133 ℃, and density of 1.609 g / cm³. 3 .

[0017] 3-Chloro-2-hydroxypropyltrimethylammonium chloride, CAS number 3327-22-8, is an etherifying agent.

[0018] Polyacrylic acid grafted with polyethylene glycol (PAA-g-PEG) was purchased from Xi'an Qiyue Biotechnology Co., Ltd. Among the components, the CAS number of PEG is 25322-68-3, and the CAS number of PAA is 9003-01-4. It is a white to pale yellow powder, hydrophilic, with a purity ≤ 100%.

[0019] Potassium hydrogen tartrate, CAS number 868-14-4, is a colorless crystal or white crystalline powder with a density of 1.954 g / mL at 25℃ (lit.).

[0020] One or more embodiments of the present invention provide high-strength concrete comprising the following components in parts by weight: The composition includes 1300-1340 parts coarse aggregate, 820-860 parts fine aggregate, 320-360 parts cement, 130-140 parts fly ash, 1.2-2.5 parts quaternized amylopectin, 0.2-0.5 parts malic acid, 70-90 parts steel fiber, 2.5-3 parts water-reducing agent, 0.25-0.45 parts crosslinking synergist, and 120-130 parts water. The crosslinking synergist comprises polyacrylic acid grafted with polyethylene glycol (PAA-g-PEG) and potassium hydrogen tartrate in a mass ratio of 1:(0.7~1.1).

[0021] Malic acid and quaternized amylopectin achieve synergistic effects: In terms of time, the retarding effect of malic acid provides a critical window for the full gelatinization of quaternized amylopectin and the construction of a uniform three-dimensional network; in the mid-to-late stages, the internal wet curing environment provided by starch promotes continuous hydration guided by the slow-release ions of organic acids. In terms of spatial structure, the dense, rigid hydration product skeleton generated by malic acid intertwines with the flexible, toughened three-dimensional gel network constructed by starch, forming a composite system that combines rigidity and flexibility. The cross-linking synergist components include potassium hydrogen tartrate and polyethylene glycol-grafted polyacrylic acid, which can precisely cause esterification cross-linking to occur during the peak of hydration heat through local pH regulation, achieving molecular-level interpenetration between the flexible network and the rigid skeleton at the microscale; at the same time, it improves the dispersion and anchoring of steel fibers, extending the fiber reinforcement effect to the microscopic interface, ultimately forming a ternary synergistic mechanism of "flexible gel network - rigid hydration products - steel fiber reinforcement", fundamentally solving the problems of high strength concrete's high brittleness and easy cracking, making it possess both high strength, excellent toughness, and volume stability.

[0022] The process by which local pH regulation influences the timing of esterification and crosslinking reactions includes: during dry or wet mixing, potassium bitartrate particles adhere to the surface of cement particles due to electrostatic interaction or mechanical mixing. Under the influence of the zeta potential on the cement particle surface, potassium ions and bitartrate ions preferentially distribute in areas with the highest hydration activity (such as C3S and C3A surfaces); upon contact with the pore liquid, potassium bitartrate begins to dissolve, releasing H₂. + Because the hydration reaction near the surface of cement particles consumes OH- - (For example, Ca²⁺ is released when C₃S hydrates to form CSH) + At the same time, OH is consumed - (Maintaining charge balance), the OH in this region - The concentration itself is lower than that of the bulk solution. Potassium hydrogen tartrate releases H₂... + Further neutralize the remaining OH - This causes the pH to drop rapidly to 5.5-6.5. Simultaneously, the hydrogen tartrate ion (HC4H4O6)...- ) and its conjugate base (C4H4O6²) - This forms a buffer pair to resist drastic pH fluctuations; as the hydration reaction proceeds, localized OH groups on the surface of cement particles... - It is constantly consumed (for example, the hydration of C3A to form ettringite requires a large amount of OH). - Potassium hydrogen tartrate continues to dissolve and replenish H+. + This buffering effect stabilizes the pH at 5.5–6.5; this buffering effect continues until the potassium bitartrate is depleted or the esterification cross-linking reaction is complete (approximately 2–6 hours); when the exothermic hydration raises the temperature to 50–60°C, the solubility of potassium bitartrate further increases, while the esterification reaction further enhances its effect on H+. + The consumption of potassium tartrate also accelerates, forming a "buffer-reaction" coupling mechanism. During this process, potassium tartrate does not change the overall pH of the system, but rather, through its own acidic dissociation equilibrium on the surface of cement particles and in the adjacent micron-sized region, it forms a local buffer microzone with a pH of 5.5–6.5. The spatial scale of this microzone is equivalent to the particle size of the cement particles or the thickness of the interfacial transition zone, and the temporal scale extends from the initial mixing stage to the hydration heating stage (approximately 2–6 hours). This "local" rather than "global" regulation avoids the excessive inhibition of overall hydration by traditional retarders, while providing a precise microenvironment for specific chemical reactions (starch-malic acid esterification crosslinking). This regulatory direction differs from the "global acidification" of conventional retarders (such as sodium gluconate and citric acid), which chelate Ca²⁺. + It may adsorb onto the surface of C3S, causing a slight decrease in the pH of the entire system (e.g., from 12.5 to 11.5), but it cannot reach weakly acidic conditions, nor can it form a stable low-pH micro-region locally. Potassium hydrogen tartrate only "creates" an acidic reaction island on the surface of the most actively hydrated cement particles without affecting the high alkalinity of the bulk slurry, thus precisely controlling the esterification and crosslinking reaction. In the crosslinking synergist, polyacrylic acid grafted polyethylene glycol (PAA-g-PEG) and other components are the main raw materials of the water-reducing agent. However, at this time, its role is to form a polyelectrolyte complex with quaternized amylopectin. In the early stage of mixing, it temporarily shields the excessive thickening and premature crosslinking of starch molecular chains through electrostatic complexation. The effect is to inhibit the adverse effect of starch on the fluidity of the slurry, create a low viscosity window for the uniform dispersion of steel fibers, and realize the sequential release of starch with the dissociation of the complex during the hydration heating period. This is different from the continuous dispersion effect of water-reducing agents and the effect of simply reducing water consumption. Among them, potassium hydrogen tartrate and other components are the main raw materials of retarder, but at this time their role is to create a buffer environment of pH 5.5~6.5 in the micro-regions on the surface of cement particles, precisely control the esterification and cross-linking reaction process of malic acid and quaternized amylopectin, improve the cross-linking efficiency, and make the cross-linking network preferentially form a dense anchoring layer on the surface of steel fiber, which is different from the global delay of hydration and the effect of delaying the exothermic peak of retarder.

[0023] Optionally, the cement is silicate cement or ordinary silicate cement of strength grade 42.5 or 42.5R, which is the core cementitious component used to bind aggregates and other components into a solid whole.

[0024] Optionally, the fine aggregate is basalt with a particle size of 0.15~4.75mm and an elastic modulus of 30-70 GPa; it is used to form mortar together with cement paste, to coat the coarse aggregate, and to ensure the volume stability, strength and impermeability of concrete.

[0025] Optionally, the coarse aggregate is basalt with a particle size of 5~25mm and an elastic modulus of 30-70 GPa; it is used to form the main skeleton of concrete, bear pressure, and ensure the elastic modulus and volume stability of concrete.

[0026] Optionally, the raw materials for preparing quaternized amylopectin include amylopectin and an etherifying agent, with a molar ratio of glucose units of the two being (4~6):1. Amylopectin has a high molecular weight, complex structure, high viscosity, large steric hindrance, and good stability. It can provide physical cross-linking and hydrogen bonding in cement-based materials, prevent aggregate and fiber segregation and water bleeding in the mixture, enhance the bonding force between cement particles, and thus potentially improve the compressive and flexural strength of concrete.

[0027] Optionally, the etherifying agent is 3-chloro-2-hydroxypropyltrimethylammonium chloride.

[0028] Optionally, the steel fiber is a straight brass-galvanized steel fiber; it is a reinforcing and toughening component that prevents the propagation of microcracks inside the concrete.

[0029] Optionally, the water-reducing agent is a polycarboxylate-based high-performance water-reducing agent, used to improve the fluidity of fresh concrete and reduce the water-cement ratio.

[0030] One or more embodiments of the present invention provide a method for preparing the above-mentioned high-strength concrete, comprising the following steps: Prepare malic acid solution and quaternized amylopectin dispersion. Dry mix cement, fly ash, fine aggregate and coarse aggregate to obtain dry mix. Add malic acid solution, quaternized amylopectin dispersion, crosslinking synergist, residual water and water-reducing agent to dry mix. After stirring, add steel fiber to obtain slurry. Pour and cure for a set time.

[0031] In the above process, dry mix is ​​first obtained, and then malic acid and quaternized amylopectin are added sequentially. Malic acid is adsorbed on the surface of cement particles, delaying early hydration; quaternary ammonium groups are adsorbed on the particle surface through electrostatic interaction, fully extending the branched structure, promoting powder dispersion and optimizing porosity. The two work synergistically to improve concrete performance.

[0032] Optionally, dry mixing methods include low-speed mixing; medium-speed mixing before adding steel fibers; and high-speed mixing after adding steel fibers.

[0033] One or more embodiments of the present invention provide the application of the above-mentioned high-strength concrete.

[0034] Optional applications include bridges, submarine tunnels, high-rise buildings, or offshore structures; specifically including: lining structures of submarine tunnels, densely reinforced shear walls or core tubes of high-rise buildings, and complex components of bridges or offshore structures.

[0035] The present invention will be further described below with reference to specific embodiments.

[0036] Preparation Example A quaternized amylopectin is prepared from amylopectin and an etherifying agent. The amylopectin is prepared from corn starch and 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) is used as the etherifying agent. The molar ratio of CHPTAC to glucose unit AGU is 5:1.

[0037] Preparation methods include: Weigh 10g of corn starch, add anhydrous ethanol to disperse and moisten the corn starch sample, add 350 mL of 0.5 mol / L NaOH solution, stir in a boiling water bath for 10 min until the liquid is clear, transparent and free of clumps; cool the obtained liquid and freeze to -18℃, centrifuge at 8000 r / min for 10 min, separate the centrifuged liquid, neutralize the centrifuged liquid with hydrochloric acid to neutral, add 100 mL of butanol-isoamyl alcohol mixture (butanol and isoamyl alcohol volume ratio of 3:1), heat and stir in a boiling water bath for 10 min, cool to room temperature, stand in a refrigerator at 2℃ for 24 h, take it out and freeze to -18℃, centrifuge at 8000 r / min for 10 min, the precipitate obtained is crude amylose, and the centrifuged liquid contains crude amylopectin.

[0038] The centrifuged liquid was allowed to separate into layers in a separatory funnel. The lower layer of latex solution was collected, and 40 mL of a butanol-isoamyl alcohol mixture (butanol and isoamyl alcohol volume ratio of 1:1) was added. The mixture was heated and stirred in a boiling water bath for 10 min, then cooled to room temperature and allowed to stand in a refrigerator at 2°C for 48 h. After removal, it was frozen to -18°C and centrifuged at 8000 r / min for 10 min. After centrifugation, the centrifuged liquid was separated. Twice the volume of anhydrous ethanol was slowly added to the centrifuged liquid, and the mixture was allowed to stand in a refrigerator at 2°C for 24 h to obtain a precipitate. The precipitate was then dissolved in a 0.5 mol / L NaOH solution to complete one purification operation.

[0039] After repeating the purification process, the sample was washed with anhydrous ethanol and dried in a forced-air drying oven at 40°C for 8 hours to obtain pure amylopectin.

[0040] Pure amylose was moistened with anhydrous ethanol, and then NaOH solution was added at a molar ratio of NaOH to anhydrous glucose units of 8:1 (this catalyzes the reaction process of linking hydroxyl groups and quaternary ammonium groups through ether bonds; insufficient NaOH will lead to low reaction efficiency, while excessive NaOH may cause starch degradation), so that the starch content in the reaction system was 2% (w / v). The reaction system was stirred and heated in an 80°C water bath for 10 min to form a stable starch dispersion. CHPTAC was added to the starch dispersion at a molar ratio of CHPTAC to glucose units AGU of 5:1, and the reaction was stirred and heated in a 65°C water bath for 3 h. After the reaction was completed, the reaction solution was rapidly cooled and transferred to a 3500 Da dialysis bag for dialysis for 9 days to remove small molecule impurities, and then freeze-dried to obtain quaternized amylopectin.

[0041] The obtained quaternized amylopectin was a white, non-crystalline powder with a melting point of 160-166℃ and a density of 1.85 g / cm³. 3 .

[0042] Example 1 A high-strength concrete comprises the following components in parts by weight: 340 parts cement, 140 parts fly ash, 1.5 parts quaternized amylopectin obtained in the preparation example, 0.25 parts malic acid, 840 parts fine aggregate, 1320 parts coarse aggregate, 80 parts straight brass galvanized steel fiber, 125 parts water, 2.75 parts water-reducing agent and 0.25 parts crosslinking synergist; The crosslinking synergist polyacrylic acid grafted polyethylene glycol (PAA-g-PEG) and potassium hydrogen tartrate are composed of a mass ratio of 1:0.7.

[0043] The cement used is silicate cement with a strength grade of 42.5.

[0044] The specific surface area of ​​fly ash is greater than 450 m² 2 / kg, density is 2.31 g / cm³ 3 .

[0045] The fine aggregate consists of basalt particles with a diameter of 0.15–4.75 mm and a density of 3.1 g / cm³. 3 Its elastic modulus is 75 GPa and its Poisson's ratio is 0.25.

[0046] The coarse aggregate consists of basalt particles with a diameter of 5-25 mm and a density of 3.1 g / cm³.3 Its elastic modulus is 70 GPa and its Poisson's ratio is 0.25.

[0047] The straight, galvanized brass steel fiber has a length of 20 mm, a diameter of 0.22 mm, a tensile strength greater than 2800 MPa, an elastic modulus of 200 GPa, and a density of 7.9 g / cm³. 3 .

[0048] The water-reducing agent is a polycarboxylate-based high-performance water-reducing agent.

[0049] The preparation method includes the following steps.

[0050] A 0.1 M malic acid solution was prepared using water and malic acid. A 0.1 M quaternized amylopectin dispersion was prepared using water and quaternized amylopectin. A crosslinking synergist dispersion was prepared by mixing the crosslinking dispersant with 10 times its mass of water. Cement, fly ash, fine aggregate, and coarse aggregate were mixed and stirred at a low speed of 80 rpm to obtain a dry mix. The malic acid solution and quaternized amylopectin dispersion were added to the dry mix, and the mixture was stirred at a low speed for 4 minutes until homogeneous. The crosslinking synergist was added and stirred at a low speed for 4 minutes. The remaining water and water-reducing agent were added and stirred at a low speed for 4 minutes. Then, the mixture was stirred at a medium speed of 160 rpm until it had good fluidity. Steel fibers were slowly added through a square-hole sieve, and then the mixture was stirred at a high speed of 360 rpm for 2 minutes to obtain a casting grout. After casting, air bubbles in the matrix were removed using a vibrating device. The mixture was then cured at room temperature (temperature: 20±2 ℃, relative humidity: >95% RH) for 24 hours before demolding.

[0051] Of this, the total water volume of 123.5 parts includes the water used to prepare the malic acid solution and the quaternized amylopectin dispersion.

[0052] Example 2 A high-strength concrete comprises the following components in parts by weight: 340 parts cement, 140 parts fly ash, 1.5 parts quaternized amylopectin, 0.5 parts malic acid, 840 parts fine aggregate, 1320 parts coarse aggregate, 80 parts straight brass-galvanized steel fiber, 125 parts water, 2.75 parts water-reducing agent, and 0.15 parts crosslinking synergist; The crosslinking synergist is composed of polyacrylic acid grafted polyethylene glycol (PAA-g-PEG) and potassium hydrogen tartrate in a mass ratio of 1:0.8.

[0053] The requirements for each raw material and the preparation method are the same as in Example 1.

[0054] Example 3 A high-strength concrete comprises the following components in parts by weight: 340 parts cement, 140 parts fly ash, 2.5 parts quaternized amylopectin, 0.25 parts malic acid, 840 parts fine aggregate, 1320 parts coarse aggregate, 80 parts straight brass-galvanized steel fiber, 125 parts water, 2.75 parts water-reducing agent, and 0.25 parts crosslinking synergist; The crosslinking synergist is composed of polyacrylic acid grafted polyethylene glycol (PAA-g-PEG) and potassium hydrogen tartrate in a mass ratio of 1:0.9.

[0055] The requirements for each raw material and the preparation method are the same as in Example 1.

[0056] Example 4 A high-strength concrete comprises the following components in parts by weight: 340 parts cement, 140 parts fly ash, 2.5 parts quaternized amylopectin, 0.47 parts malic acid, 840 parts fine aggregate, 1320 parts coarse aggregate, 80 parts straight brass-galvanized steel fiber, 125 parts water, 2.75 parts water-reducing agent, and 0.25 parts crosslinking synergist; The crosslinking synergist is composed of polyacrylic acid grafted polyethylene glycol (PAA-g-PEG) and potassium hydrogen tartrate in a 1:1 mass ratio.

[0057] The requirements for each raw material and the preparation method are the same as in Example 1.

[0058] Example 5 A high-strength concrete comprises the following components in parts by weight: 330 parts cement, 140 parts fly ash, 1.2 parts quaternized amylopectin, 0.3 parts malic acid, 830 parts fine aggregate, 1300 parts coarse aggregate, 70 parts straight brass-galvanized steel fiber, 120 parts water, 2.5 parts water-reducing agent, and 0.45 parts crosslinking synergist; The crosslinking synergist is composed of polyacrylic acid grafted polyethylene glycol (PAA-g-PEG) and potassium hydrogen tartrate in a mass ratio of 1:1.1.

[0059] The requirements for each raw material and the preparation method are the same as in Example 1.

[0060] Example 6 A high-strength concrete comprises the following components in parts by weight: 370 parts cement, 150 parts fly ash, 2.5 parts quaternized amylopectin, 0.5 parts malic acid, 870 parts fine aggregate, 1350 parts coarse aggregate, 90 parts straight brass-galvanized steel fiber, 130 parts water, 3 parts water-reducing agent, and 0.25 parts crosslinking synergist. The crosslinking synergist is composed of polyacrylic acid grafted polyethylene glycol (PAA-g-PEG) and potassium hydrogen tartrate in a mass ratio of 1:0.9.

[0061] The requirements for each raw material and the preparation method are the same as in Example 1.

[0062] Comparative Example 1 A type of concrete comprises the following components in parts by weight: 340 parts cement, 140 parts fly ash, 840 parts fine aggregate, 1320 parts coarse aggregate, 80 parts straight brass-galvanized steel fibers, 125 parts water, and 2.75 parts water-reducing agent.

[0063] The difference from Example 1 is that quaternized amylopectin, malic acid and crosslinking synergist are not added, while the requirements for other raw materials and preparation methods are the same as in Example 1.

[0064] Comparative Example 2 A type of concrete comprises the following components in parts by weight: 340 parts cement, 140 parts fly ash, 0.25 parts malic acid, 840 parts fine aggregate, 1320 parts coarse aggregate, 80 parts straight brass-galvanized steel fiber, 125 parts water, and 2.75 parts water-reducing agent.

[0065] The difference from Example 1 is that quaternized amylopectin and crosslinking synergist are not added, while the requirements for other raw materials and preparation methods are the same as in Example 1.

[0066] Comparative Example 3 A concrete comprising the following components in parts by weight: 340 parts cement, 140 parts fly ash, 1.5 parts quaternized amylopectin obtained in the preparation example, 840 parts fine aggregate, 1320 parts coarse aggregate, 80 parts straight brass-galvanized steel fiber, 125 parts water, 2.75 parts water-reducing agent, and 0.25 parts crosslinking synergist; The crosslinking synergist is composed of polyacrylic acid grafted polyethylene glycol (PAA-g-PEG) and potassium hydrogen tartrate in a mass ratio of 1:0.7.

[0067] The difference from Example 1 is that malic acid is not added, but the requirements for other raw materials and preparation methods are the same as in Example 1.

[0068] Comparative Example 4 A type of concrete comprises the following components in parts by weight: 340 parts cement, 140 parts fly ash, 0.5 parts malic acid, 840 parts fine aggregate, 1320 parts coarse aggregate, 80 parts straight brass-galvanized steel fiber, 125 parts water, 2.75 parts water-reducing agent and 0.15 parts crosslinking synergist. The crosslinking synergist is composed of polyacrylic acid grafted polyethylene glycol (PAA-g-PEG) and potassium hydrogen tartrate in a mass ratio of 1:0.9.

[0069] The difference from Example 2 is that quaternized amylopectin is not added, but the requirements for other raw materials and preparation methods are the same as in Example 2.

[0070] Comparative Example 5 A type of concrete comprises the following components in parts by weight: 340 parts cement, 140 parts fly ash, 2.5 parts quaternized amylopectin, 840 parts fine aggregate, 1320 parts coarse aggregate, 80 parts straight brass-galvanized steel fiber, 125 parts water, and 2.75 parts water-reducing agent.

[0071] The difference from Example 3 is that malic acid and cross-linking synergist are not added, while the requirements for other raw materials and preparation methods are the same as in Example 3.

[0072] Comparative Example 6 A high-strength concrete comprises the following components in parts by weight: 340 parts cement, 140 parts fly ash, 2.5 parts unquaternized amylopectin obtained in the preparation example, 840 parts fine aggregate, 1320 parts coarse aggregate, 80 parts straight brass-galvanized steel fiber, 125 parts water, 2.75 parts water-reducing agent, and 0.25 parts crosslinking synergist; The crosslinking synergist is composed of polyacrylic acid grafted polyethylene glycol (PAA-g-PEG) and potassium hydrogen tartrate in a mass ratio of 1:0.9.

[0073] The difference from Example 3 is that the added starch was not quaternized and no malic acid was added; the requirements for other raw materials and the preparation methods are the same as in Example 3.

[0074] Test case The concrete in the above embodiments and comparative examples were subjected to performance tests, including compressive strength, modulus of elasticity, flexural strength, drying shrinkage, chloride ion diffusion coefficient, and carbonation depth. Among them, the mechanical performance test was conducted in accordance with the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" GB / T 50081-2019, and the durability performance test was conducted in accordance with the "Standard for Test Methods of Long-Term Performance and Durability of Concrete" GB / T50082-2024.

[0075] The results are shown in Table 1.

[0076] Table 1 Performance test results for each embodiment and comparative example

[0077] It can be seen that: Examples comparing different malic acid contents at the same quaternized amylopectin content, such as Comparative Example 2 (0 parts starch, 0.25 parts malic acid) and Comparative Example 4 (0 parts starch, 0.5 parts malic acid), show that with increasing malic acid content, the compressive and flexural strengths of Comparative Example 2 increased by 8.50% and 6.25% respectively compared to Comparative Example 1; while those of Comparative Example 4 increased by 11.46% and 15.29% respectively compared to Comparative Example 2. This is because malic acid reacts with Ca²⁺... +It forms a soluble complex, temporarily binds calcium ions, and then slowly releases them, promoting the formation of secondary CSH, making the slurry denser, and demonstrating the properties of malic acid in reducing microcracks and improving strength.

[0078] Comparing Comparative Example 3 (quaternized amylopectin) with Comparative Example 6 (non-quaternized amylopectin): Comparative Example 3 showed a 14.43% increase in compressive strength, a 10.22% increase in elastic modulus, and a 9.88% increase in flexural strength compared to Comparative Example 6; however, it also exhibited a 18.11% decrease in drying shrinkage, a 16.67% decrease in chloride ion diffusion coefficient, and a 12.73% decrease in carbonization depth. This is because the quaternary ammonium groups impart a positive charge to the starch, resulting in electrostatic interaction with the negative charge on the surface of cement particles, thus improving dispersion or enhancing interfacial bonding.

[0079] Comparing different amounts of quaternized amylopectin with the same malic acid content, such as Comparative Example 3 (0 parts malic acid, 1.5 parts starch) and Comparative Example 5 (0 parts malic acid, 2.5 parts starch), with increasing starch content, the compressive and flexural strengths of Comparative Example 3 increased by 20.07% and 11.25% respectively compared to Comparative Example 1; while the strengths of Comparative Example 5 increased by 17.86% and 17.50% respectively compared to Comparative Example 1. The mechanism is that after starch gelatinization, its branched structure acts as a fiber in the slurry, reducing shrinkage cracks and improving load-bearing capacity and durability; it also optimizes the pore structure, reduces permeability, and decreases the carbonization depth and chloride ion diffusion coefficient.

[0080] Of the various embodiments, Example 3 (2.5 parts starch, 0.25 parts malic acid) exhibited the best overall performance. Its compressive strength was 118.3 MPa, significantly higher than the 81.2 MPa of Comparative Example 1; its elastic modulus was the highest at 41.5 GPa; and its flexural strength was 12.8 kN. This was attributed to the interweaving of the dense hydration products induced by malic acid with the three-dimensional gel network constructed by starch, forming a composite structure combining a rigid framework and a flexible network. Regarding durability, the chloride ion diffusion coefficient was 1.4 × 10⁻⁶. - ¹² m² / s, carbonization depth 3.0 mm, drying shrinkage 226.1 με (lowest among all examples, significantly lower than Comparative Example 1's 471.12 με).

[0081] Comparing Comparative Example 5, Example 3, and Example 4: the strength initially increased and then decreased with increasing malic acid content, with Example 4 showing lower strength than Example 3. This is because the synergistic effect of the two substances needs to be within a certain proportional range; excessive malic acid disrupts the microstructure and pore distribution, weakening the strength.

[0082] Comparing Comparative Example 5 (2.5 parts starch, without malic acid and crosslinking synergist) and Example 3 (2.5 parts starch, with malic acid and crosslinking synergist): the compressive and flexural strengths of Example 3 were increased by 23.62% and 36.17% respectively compared to Comparative Example 5, while the drying shrinkage was reduced by 28.96%. This is attributed to the polyelectrolyte complex formed by the polyacrylic acid-grafted polyethylene glycol (PAA-g-PEG) in the crosslinking synergist and the quaternized amylopectin, which shields against excessive thickening in the initial mixing stage and improves the uniformity of steel fiber dispersion. Potassium hydrogen tartrate creates a pH buffer environment on the surface of cement particles, improving the esterification and crosslinking efficiency of starch and malic acid, allowing the crosslinking network to form a dense coating layer on the surface of the steel fibers, thus enhancing interfacial adhesion.

[0083] Overall, Example 3 exhibits the best comprehensive performance, demonstrating outstanding mechanical properties and durability, making it suitable for engineering applications with high requirements for strength, toughness, and durability.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-strength concrete, characterized in that, It includes the following components in parts by weight: The composition includes: 1300-1350 parts coarse aggregate, 830-870 parts fine aggregate, 330-370 parts cement, 140-150 parts fly ash, 1.2-2.5 parts quaternized amylopectin, 0.3-0.5 parts malic acid, 70-90 parts steel fiber, 2.5-3 parts water-reducing agent, 0.15-0.45 parts crosslinking synergist, and 120-130 parts water. The crosslinking synergist comprises polyacrylic acid grafted with polyethylene glycol and potassium hydrogen tartrate in a mass ratio of 1:(0.7~1.1).

2. The high-strength concrete as described in claim 1, characterized in that, The cement is silicate cement or ordinary silicate cement with a strength grade of 42.5 or 42.5R.

3. The high-strength concrete as described in claim 1, characterized in that, The fine aggregate is basalt with a particle size of 0.15~4.75mm; the coarse aggregate is basalt with a particle size of 5~25mm.

4. The high-strength concrete as described in claim 1, characterized in that, The raw materials for preparing the quaternized amylopectin include amylopectin and an etherifying agent, wherein the molar ratio of the etherifying agent to the glucose units of the amylopectin is (4~6):

1.

5. The high-strength concrete as described in claim 1, characterized in that, The etherifying agent is 3-chloro-2-hydroxypropyltrimethylammonium chloride.

6. The high-strength concrete as described in claim 1, characterized in that, The steel fiber is a straight brass-galvanized steel fiber.

7. The high-strength concrete as described in claim 1, characterized in that, The water-reducing agent is a polycarboxylate-based high-performance water-reducing agent.

8. A method for preparing high-strength concrete as described in any one of claims 1-7, characterized in that, Includes the following steps: Prepare malic acid solution, quaternized amylopectin dispersion, and crosslinking synergist dispersion. Dry mix cement, fly ash, fine aggregate, and coarse aggregate to obtain dry mix. Add malic acid solution, quaternized amylopectin dispersion, crosslinking synergist dispersion, remaining water, and water-reducing agent to the dry mix. After stirring, add steel fiber to obtain slurry. Pour and cure for a set time.

9. The method for preparing high-strength concrete as described in claim 8, characterized in that, Dry mixing methods include low-speed mixing; medium-speed mixing before adding steel fibers; and high-speed mixing after adding steel fibers.

10. An application of high-strength concrete as described in any one of claims 1-7.

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