High-toughness anti-cracking concrete and preparation method thereof

Abstract

This invention discloses a high-toughness crack-resistant concrete and its preparation method, relating to the field of building materials technology. The high-toughness crack-resistant concrete includes cementitious materials, aggregates, water, admixtures, and reinforcing components. The reinforcing components include a multi-scale hybrid fiber system and a time-compensated shrinkage system. The multi-scale hybrid fiber system includes micro-scale high-modulus fibers and macro-scale crack-resistant fibers. The micro-scale high-modulus fibers are used to inhibit the initiation of cracks in the concrete matrix and induce crack refinement. In this invention, by setting up a multi-scale hybrid fiber system and utilizing the synergistic effect of micro-scale high-modulus fibers and macro-scale crack-resistant fibers, the entire process of concrete cracking is controlled. Due to their small diameter and large specific surface area, the micro-scale high-modulus fibers can be uniformly distributed in the concrete matrix, effectively inhibiting crack initiation and inducing crack refinement after crack formation.

Description

Technical Field

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

[0002] Concrete, as the most widely used building material in the world, directly affects the safety and service life of construction projects due to its durability. However, concrete itself has an inherent characteristic: low tensile strength, high brittleness, and susceptibility to cracking. In actual engineering projects, cracks in concrete structures caused by factors such as shrinkage deformation, temperature stress, and load are very common. These cracks not only affect the aesthetics of the structure but, more importantly, accelerate steel corrosion, reduce the structural load-bearing capacity, shorten service life, and even lead to safety accidents.

[0003] Currently, research on the crack resistance of concrete mainly focuses on the following aspects: first, using admixtures such as water-reducing agents to lower the water-cement ratio and increase the density of concrete; second, adding mineral admixtures such as silica fume and slag powder to improve the microstructure of concrete; and third, adding fiber materials to prevent crack propagation through the bridging effect of fibers. Fiber-reinforced concrete is one of the most widely researched and applied crack-resistant technologies. Commonly used fibers include steel fibers, basalt fibers, polypropylene fibers, and polyvinyl alcohol fibers. However, single fiber types have obvious limitations: while low-modulus fibers can effectively inhibit crack initiation, their ability to prevent crack propagation is limited; while high-modulus fibers can improve the strength and stiffness of concrete, their effect on inhibiting early-stage cracks is not significant.

[0004] Furthermore, shrinkage cracking in concrete is a persistent problem in the engineering field. During the hardening process, concrete undergoes various shrinkage deformations, including drying shrinkage, temperature shrinkage, and autogenous shrinkage. When these shrinkages are constrained, tensile stress is generated. When this tensile stress exceeds the tensile strength of the concrete, cracks will form. While traditional expansion agents can compensate for concrete shrinkage to some extent, controlling the timing of expansion is a technical challenge: if expansion occurs when the concrete strength is low, it can easily lead to structural damage; if expansion occurs after most of the concrete has shrunk, it cannot effectively suppress the formation of shrinkage cracks. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a high-toughness crack-resistant concrete and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a high-toughness, crack-resistant concrete, comprising: The high-toughness crack-resistant concrete comprises cementitious materials, aggregates, water, admixtures, and reinforcing components. The reinforcing components include a multi-scale hybrid fiber system and a time-compensated shrinkage system; The multi-scale hybrid fiber system includes microscale high-modulus fibers and macroscale crack-resistant fibers. The microscale high-modulus fibers are used to inhibit the initiation of cracks in the concrete matrix and induce the refinement of multiple cracks. The macroscale crack-resistant fibers are used to bridge cracks and provide energy-dissipating constraints during the crack propagation stage. The time-compensated shrinkage system includes a compensating shrinkage component with delayed hydration characteristics. The compensating shrinkage component undergoes restricted expansion after the early hardening of concrete and during the microcrack formation stage. Under the constraint of the multi-scale hybrid fiber system, it produces a directional closing effect on the microcracks to inhibit shrinkage cracking of concrete.

[0007] As a further description of the above technical solution: The microscale high-modulus fibers are selected from polyethylene fibers, polyvinyl alcohol fibers, or combinations thereof, and have a length of 6–12 mm and a diameter of 10–40 μm.

[0008] As a further description of the above technical solution: The macroscale crack-resistant fibers are selected from basalt fibers, steel fibers, or combinations thereof, and their length is 18–30 mm.

[0009] As a further description of the above technical solution: The total volumetric content of the multi-scale hybrid fiber system is 0.5 to 2.0% of the total concrete volume, wherein the volume ratio of microscale high-modulus fibers to macroscale crack-resistant fibers is 1:0.5 to 1:2.

[0010] As a further description of the above technical solution: The time-compensating shrinkage system includes CaO-type expansion components, CSA-type expansion components, or a combination of both. The compensating shrinkage components are coated or composite-treated to delay their hydration reaction in the early hardening stage of concrete.

[0011] As a further description of the above technical solution: The shrinkage compensation component is coated or compounded using mineral micropowder, porous inorganic materials, or polymer materials.

[0012] As a further description of the above technical solution: The high-toughness crack-resistant concrete exhibits significantly improved flexural toughness under standard curing conditions, and its early shrinkage crack width is controlled below 0.20 mm.

[0013] As a further description of the above technical solution: A method for preparing high-toughness, crack-resistant concrete, comprising the following steps: The additives are mixed with mineral powder to prepare a uniform pre-dispersion system; Add cementitious materials and water to the pre-dispersed system to form a concrete matrix; The multi-scale hybrid fiber system is added to the concrete matrix in stages, wherein micro-scale high-modulus fibers are added first, followed by macro-scale crack-resistant fibers. After the multi-scale hybrid fiber system is dispersed, the time-compensated shrinkage system is added to ensure its uniform distribution in the concrete.

[0014] As a further description of the above technical solution: The mineral powder in the pre-dispersed system is selected from silica fume, slag powder, fly ash or a combination thereof, and the additive is a water-reducing agent or a composite system of water-reducing agent and dispersant.

[0015] As a further description of the above technical solution: The time interval between the addition of microscale high-modulus fibers and macroscale crack-resistant fibers is 30–180 s.

[0016] The present invention has the following beneficial effects: 1. In this invention, a multi-scale hybrid fiber system is first established, utilizing the synergistic effect of microscale high-modulus fibers and macroscale crack-resistant fibers to achieve control over the entire process of concrete cracking. Microscale high-modulus fibers, due to their small diameter and large specific surface area, can be uniformly distributed in the concrete matrix, effectively inhibiting crack initiation and inducing cracks to develop towards multi-crack refinement after they occur. Macroscale crack-resistant fibers, due to their longer length and higher modulus, can effectively bridge cracks during the crack propagation stage, preventing further crack opening, and dissipating energy through interfacial bonding between the fiber and the matrix, thereby improving the fracture toughness of the concrete. This dual-scale synergistic reinforcement mechanism significantly improves the crack resistance of concrete.

[0017] 2. In this invention, a time-compensated shrinkage system is established, utilizing a shrinkage-compensating component with delayed hydration characteristics to match its expansion timing with the formation timing of shrinkage cracks in concrete. After the early hardening of the concrete and during the microcrack formation stage, the shrinkage-compensating component begins to undergo a hydration reaction and expand. Since the concrete already possesses a certain strength at this point, it can restrain the expansion, thereby generating pre-compression stress within the concrete, effectively offsetting the shrinkage tensile stress. Simultaneously, the multi-scale hybrid fiber system restrains the expansion deformation, concentrating the expansion effect at the microcrack location, producing a directional closure effect, further inhibiting crack propagation.

[0018] 3. In this invention, by synergistically setting up a multi-scale hybrid fiber system and a time-compensated shrinkage system, an organic combination of "crack prevention" and "crack control" is achieved. The bridging and energy-dissipating effects of the fiber system provide a constrained framework for the directional expansion of the expansive agent, while the expansion effect of the expansive agent further enhances the crack-preventing effect of the fibers. The two reinforce each other, jointly improving the toughness and crack resistance of concrete. Compared with the prior art, the high-toughness crack-resistant concrete prepared by this invention exhibits significantly improved flexural toughness under standard curing conditions, and the width of early shrinkage cracks can be controlled below 0.20 mm, demonstrating excellent durability. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] One embodiment of the present invention provides a high-toughness crack-resistant concrete, comprising: cementitious materials, aggregates, water, admixtures, and reinforcing components; the reinforcing components comprising a multi-scale hybrid fiber system and a time-compensating shrinkage system; the multi-scale hybrid fiber system comprising micro-scale high-modulus fibers and macro-scale crack-resistant fibers, wherein the micro-scale high-modulus fibers are used to inhibit the initiation of cracks in the concrete matrix and induce crack refinement; the macro-scale crack-resistant fibers are used to bridge cracks and provide energy-dissipating constraints during crack propagation; the time-compensating shrinkage system comprises a shrinkage-compensating component with delayed hydration characteristics, wherein the shrinkage-compensating component undergoes restricted expansion after early hardening of the concrete and during the micro-crack formation stage, and under the constraint of the multi-scale hybrid fiber system, it exerts a directional closing effect on the micro-cracks to inhibit shrinkage cracking of the concrete.

[0021] High-toughness, crack-resistant concrete mainly consists of the following components: cementitious materials, aggregates, water, admixtures, and reinforcing components. Among these, the reinforcing components are a multi-scale hybrid fiber system and a time-compensated shrinkage system, which is key to achieving the technical effects of this invention.

[0022] Cementitious materials can be general-purpose Portland cement, including but not limited to ordinary Portland cement, slag Portland cement, fly ash Portland cement, pozzolanic Portland cement, and their composite cements. Cementitious materials play a primary role in binding aggregates and building strength in concrete. Their dosage is determined based on the concrete strength grade and project requirements, typically ranging from 350 to 550 kg / m³. 3 .

[0023] Aggregates include coarse aggregates and fine aggregates. Coarse aggregates can be crushed stone or pebbles, with a maximum particle size not exceeding 25mm; fine aggregates can be natural sand or manufactured sand, and the gradation should meet the requirements of relevant standards. Aggregates play a skeleton and filler role in concrete, and their quality directly affects the strength and durability of concrete.

[0024] Clean drinking water or water that meets the standards for concrete mixing water should be used. The amount of water used is determined according to the workability requirements of the concrete and the water-cement ratio, which is usually controlled within the range of 0.30 to 0.50.

[0025] Admixtures include water-reducing agents, retarders, and accelerators, which are added as needed. Water-reducing agents can be polycarboxylate-based, naphthalene-based, or lignin-based, and their main function is to reduce the water-cement ratio and improve the workability and strength of concrete.

[0026] The reinforcing components include a multi-scale hybrid fiber system and a time-compensated shrinkage system, which is the core innovation of this invention.

[0027] The multi-scale hybrid fiber system consists of two different scales of fibers: microscale high-modulus fibers and macroscale crack-resistant fibers. The two fibers work together to achieve full-process control of cracks.

[0028] The primary function of microscale high-modulus fibers is to inhibit crack initiation in concrete matrices and induce crack refinement. These fibers have small diameters, typically ranging from 10 to 40 μm, and lengths from 6 to 12 mm. Due to their large specific surface area, they can be uniformly dispersed in the concrete matrix, forming a three-dimensional network structure at the interface between cement paste and aggregate. When concrete is subjected to shrinkage or temperature stress, these microfibers can effectively withstand early-inducing tensile stress, preventing the formation and propagation of microcracks. Simultaneously, the presence of microfibers can disperse stress concentration, inducing single cracks to develop into multiple, refined cracks, thereby reducing crack width and depth.

[0029] In a preferred embodiment of the present invention, the microscale high-modulus fiber is selected from polyethylene fiber or polyvinyl alcohol fiber. Polyethylene fiber has advantages such as high strength, high modulus, corrosion resistance, and wear resistance; its elastic modulus can reach 5–15 GPa, and its tensile strength can reach 500–1500 MPa. Polyvinyl alcohol fiber has good hydrophilicity and bonding properties; its elastic modulus can reach 10–40 GPa, and its tensile strength can reach 800–2000 MPa. These two fibers can be used alone or in combination to achieve better results.

[0030] The primary function of macroscale crack-inhibiting fibers is to bridge cracks and provide energy-dissipating constraints during crack propagation. These fibers are relatively long, typically ranging from 18 to 30 mm, and have a relatively large diameter. When cracks begin to propagate in concrete, these macrofibers can cross the cracks on both sides, providing mechanical bridging and preventing further crack opening. Simultaneously, the interfacial bonding between the fibers and the matrix dissipates energy during crack propagation, absorbing fracture energy and improving the fracture toughness of the concrete.

[0031] In a preferred embodiment of the present invention, the macroscale crack-resistant fiber is selected from basalt fiber or steel fiber. Basalt fiber is a new type of high-performance fiber with excellent properties such as high strength, high modulus, high temperature resistance, and corrosion resistance. Its elastic modulus can reach 80-110 GPa, and its tensile strength can reach 2000-3000 MPa. Steel fiber is the most traditional reinforcing fiber, characterized by high strength and high elastic modulus, and its tensile strength can reach 600-2000 MPa. Both fibers can be used alone or in combination.

[0032] The dosage of multi-scale hybrid fibers is a key parameter affecting concrete performance. In this invention, the total volumetric dosage of the multi-scale hybrid fiber system is controlled within the range of 0.5% to 2.0% of the total concrete volume. If the dosage is too low, the fiber's reinforcing and crack-resistant effect is not significant; if the dosage is too high, it will affect the workability of the concrete and the dispersibility of the fibers, increasing construction difficulty.

[0033] Meanwhile, the volume ratio of microscale high-modulus fibers to macroscale crack-resistant fibers is also an important parameter, controlled within the range of 1:0.5 to 1:2. This ratio ensures that the two types of fibers can fully utilize their respective advantages and achieve a synergistic reinforcement effect. If the proportion of microscale fibers is too high, the crack-resistant ability during the crack propagation stage will be insufficient; if the proportion of macroscale fibers is too high, the suppression effect on the crack initiation stage will be poor.

[0034] The time-compensated shrinkage system is another core innovation of this invention. Its design concept is to match the expansion timing of the expansion agent with the formation timing of shrinkage cracks in concrete, thereby achieving effective control of shrinkage cracks.

[0035] The time-compensated shrinkage system includes a shrinkage-compensating component with delayed hydration properties. During the hardening process of concrete, the early stage is dominated by cement hydration, during which the concrete strength increases rapidly, but significant shrinkage deformation also occurs. If traditional expansive agents undergo hydration expansion at this stage, the expansion stress cannot be effectively restrained due to the low concrete strength, potentially leading to structural damage. The shrinkage-compensating component of this invention is specially treated to delay its hydration reaction beyond the early hardening stage of concrete, expanding only after the early hardening process and during the microcrack formation stage.

[0036] At this point, the concrete has already acquired a certain strength, effectively restraining expansion. The shrinkage-compensating components undergo hydration reactions and expand, generating pre-compression stress within the concrete. This pre-compression stress effectively counteracts the tensile stress caused by drying shrinkage, temperature shrinkage, and autogenous shrinkage, thereby reducing or eliminating shrinkage cracks. Simultaneously, the presence of the multi-scale hybrid fiber system restrains expansion deformation, concentrating the expansion effect at micro-crack locations and producing a directional closure effect.

[0037] In a preferred embodiment of the present invention, the shrinkage-compensating component is selected from CaO-based expansion components, CSA-based expansion components, or a combination of both. The main component of the CaO-based expansion component is calcium oxide, which undergoes a hydration reaction to produce calcium hydroxide, resulting in volume expansion. The CSA-based expansion component is a sulfoaluminate expansion agent, which undergoes a hydration reaction to produce ettringite, also resulting in volume expansion. These two expansion components each have their own characteristics: the CaO-based expansion component has a fast expansion rate and large expansion amount, but its expansion stability is relatively poor; the CSA-based expansion component has a moderate expansion rate and good expansion stability, but its expansion amount is relatively small. Using both in combination can leverage their respective strengths and compensate for their weaknesses, achieving a better shrinkage-compensating effect.

[0038] To compensate for the delayed hydration characteristics of the shrinkage component, it is necessary to coat or composite it. In a preferred embodiment of the present invention, mineral micropowders, porous inorganic materials, or polymer materials are used for coating or compositing. Mineral micropowders can be selected from silica fume, slag powder, fly ash, etc.; porous inorganic materials can be selected from expanded perlite, zeolite powder, etc.; polymer materials can be selected from polyvinyl alcohol, polyacrylate, etc. These coatings or composite materials can, to a certain extent, block the contact between moisture and the expanding component, delaying the initiation time of the hydration reaction, thereby achieving precise control of the expansion timing.

[0039] The coating or composite process can be physical coating, chemical composite, or microencapsulation. Physical coating involves mixing the expanding agent particles with the coating material and then using ball milling or stirring to make the coating material adhere to the surface of the expanding agent. Chemical composite involves combining the expanding agent and the coating material through chemical bonding. Microencapsulation involves encapsulating the expanding agent inside a shell material to form core-shell structured microcapsule particles.

[0040] A method for preparing high-toughness crack-resistant concrete includes the following steps: mixing admixtures with mineral micropowders to prepare a uniform pre-dispersion system; adding cementitious materials and water to the pre-dispersion system to form a concrete matrix; adding the multi-scale hybrid fiber system to the concrete matrix in stages, wherein micro-scale high-modulus fibers are added first, followed by macro-scale crack-resistant fibers; after the dispersion of the multi-scale hybrid fiber system is completed, adding the time-compensated shrinkage system to ensure its uniform distribution in the concrete.

[0041] A method for preparing high-toughness, crack-resistant concrete includes the following steps: The first step is to mix the additives with the mineral powder to prepare a uniform pre-dispersion system.

[0042] In this step, water-reducing agents, dispersants, and other admixtures are first mixed evenly with mineral powder. The mineral powder can be silica fume, slag powder, fly ash, or a combination thereof. Silica fume is a byproduct of the ferrosilicon alloy industry; its main component is SiO2, which has extremely high activity and specific surface area, effectively improving the microstructure of concrete and enhancing its strength and durability. Slag powder is a byproduct of the steel industry; its main components are CaO, SiO2, and Al2O3, possessing potential hydraulic properties. Fly ash is a byproduct of coal-fired power plants; its main components are also SiO2 and Al2O3, exhibiting certain activity. These mineral powders not only serve as auxiliary components of cementitious materials, participating in hydration reactions and improving the microstructure of concrete, but also act as fiber dispersion carriers, helping fibers to disperse evenly in the concrete.

[0043] The admixtures selected are water-reducing agents or a composite system of water-reducing agents and dispersants. The main function of water-reducing agents is to reduce the water-cement ratio and improve the workability and strength of concrete; the main function of dispersants is to help fibers disperse evenly in concrete and prevent fiber agglomeration.

[0044] Pre-mixing admixtures with mineral powders allows the admixtures to be fully dispersed on the surface of the mineral powders, forming a uniform pre-dispersion system. This pre-dispersion system, when mixed with cementitious materials, enables the admixtures and mineral powders to be more evenly distributed in the concrete, maximizing their effectiveness.

[0045] The second step is to add cementitious materials and water to the pre-dispersed system to form a concrete matrix.

[0046] The pre-dispersed system prepared in the first step is mixed with the cementitious material, and then an appropriate amount of water is added and stirred to form a homogeneous concrete matrix. This step can be carried out using conventional concrete mixing equipment. The mixing time is determined according to the equipment capacity and the amount of concrete to ensure that the cementitious material is fully hydrated and forms a homogeneous paste.

[0047] The third step involves adding a multi-scale hybrid fiber system to the concrete matrix in stages, first adding micro-scale high-modulus fibers and then adding macro-scale crack-resistant fibers.

[0048] This is a key step in the preparation method of this invention. The fibers are added in stages, rather than all at once, to ensure that both types of fibers are evenly dispersed in the concrete and can fully exert their respective functions.

[0049] First, add the microscale high-modulus fibers. Because these fibers have a small diameter and short length, if added simultaneously with the macroscale crack-resistant fibers, they are prone to entanglement and aggregation during mixing, affecting the dispersion effect. Adding them in stages avoids this problem.

[0050] After adding the microscale high-modulus fibers, continue stirring for a period of time to ensure uniform dispersion in the concrete matrix. The stirring time is determined based on the fiber dosage and dispersion, and is generally 30–60 seconds.

[0051] Then, macroscale crack-blocking fibers are added. Because macroscale crack-blocking fibers are relatively long, direct addition can easily lead to clumping. They must be added after the microscale high-modulus fibers have been uniformly dispersed to reduce fiber entanglement.

[0052] The time interval between the addition of the two fibers is 30 to 180 seconds. This time interval ensures that the first fiber is fully dispersed without excessively prolonging the mixing time and affecting the workability of the concrete.

[0053] In another implementation, macroscale crack-blocking fibers can be added first, followed by microscale high-modulus fibers, but the effect is slightly worse. This is because the macroscale crack-blocking fibers are relatively long, and if they are added first, they may disturb the microscale high-modulus fibers when they are added, affecting the dispersion effect.

[0054] The fourth step is to add a time-compensated shrinkage system after the multi-scale hybrid fiber system has been dispersed, so that it is evenly distributed in the concrete.

[0055] The shrinkage compensation component must be added after the fiber dispersion is complete. Adding the shrinkage compensation component before or at the same time as the fiber may affect the fiber dispersion effect and also affect the integrity of the swelling agent coating layer.

[0056] After adding the shrinkage-compensating component, continue stirring until homogeneous. Do not stir for too long to avoid damaging the expansion agent particles.

[0057] The final product is high-toughness, crack-resistant concrete. The workability of this concrete should meet construction requirements, with a slump generally between 180 and 220 mm. Appropriate curing, especially early curing, should be carried out after concrete pouring to fully utilize the effects of fibers and expanding agents.

[0058] The high-toughness, crack-resistant concrete prepared by this invention exhibits significantly improved flexural toughness. Due to the synergistic reinforcing effect of the multi-scale hybrid fiber system, the concrete, when subjected to flexural loads, can absorb more fracture energy through fiber bridging and energy dissipation mechanisms, thus significantly improving flexural toughness. Compared with ordinary concrete without fibers, the flexural toughness of the concrete prepared by this invention can be increased by 2 to 5 times.

[0059] The width of early shrinkage cracks is controlled below 0.20 mm. Due to the precise matching between the time-compensated shrinkage system and the timing of concrete shrinkage, the prestress generated by expansion can effectively offset the shrinkage tensile stress. At the same time, the constraint effect of the fibers concentrates the expansion at the micro-crack locations, producing a directional closure effect. Under standard curing conditions, the width of early shrinkage cracks can be controlled below 0.20 mm, meeting durability requirements.

[0060] Excellent crack resistance. The synergistic effect of the multi-scale hybrid fiber system and the time-compensated shrinkage system effectively inhibits the initiation and propagation of cracks throughout the entire process from early hardening to later use. Even under harsh environmental conditions, such as dryness, high temperature, and low temperature, the crack resistance of the concrete remains stable.

[0061] Improved durability. Due to effective crack control, durability issues such as steel corrosion, alkali-aggregate reaction, and freeze-thaw damage are significantly improved, extending the service life of concrete structures.

[0062] Example 1: This example describes the preparation of a high-toughness, crack-resistant concrete. The specific formula and process are as follows: Cementitious material: Ordinary Portland cement, dosage 450 kg / m³ 3 ; Aggregate: Natural sand with a fineness modulus of 2.8, at a dosage of 650 kg / m³ 3 Crushed stone with a particle size of 5-20mm, at a dosage of 1100kg / m³. 3 ; Water: Tap water, dosage 162 kg / m³ 3 Water-to-binder ratio: 0.36; Admixture: Polycarboxylate superplasticizer, dosage 8 kg / m³ 3 ; Multi-scale hybrid fiber system: polyvinyl alcohol microfibers, volume fraction 0.6%, length 8mm, diameter 20μm; basalt macrofibers, volume fraction 0.8%, length 25mm; total fiber volume fraction 1.4%, microfiber to macrofiber volume ratio 1:1.33; Time-compensated shrinkage system: CaO-CSA composite expansion agent, coated with silica fume, dosage 35 kg / m³. 3 ; Preparation method: The preparation is carried out in four steps according to the above method.

[0063] Performance test results: The compressive strength of the concrete cube reached 62MPa, the flexural toughness index increased to 3.2 times that of ordinary concrete, and no visible cracks were observed after 7 days of standard curing, with the crack width controlled below 0.15mm.

[0064] Example 2: This example describes the preparation of another type of high-toughness, crack-resistant concrete. The specific formula and process are as follows: Cementitious material: 400 kg / m³ ordinary Portland cement 3 Silica fume 30kg / m 3 Slag powder 60kg / m 3 ; Aggregate: Natural sand with a fineness modulus of 2.6, at a dosage of 620 kg / m³ 3 Crushed stone with a particle size of 5-25mm, at a dosage of 1050kg / m³. 3 ; Water: Tap water, dosage 168 kg / m³ 3 Water-to-binder ratio: 0.35; Admixture: A compound of polycarboxylate superplasticizer and polypropylene dispersant, at a dosage of 10 kg / m³. 3 ; Multi-scale hybrid fiber system: polyethylene microfibers, volume content 0.5%, length 10mm, diameter 25μm; steel fibers, volume content 1.0%, length 30mm; total fiber volume content 1.5%, microfiber to macrofiber volume ratio 1:2; Time-compensated shrinkage system: CSA expanding agent, coated with zeolite powder, dosage 40 kg / m³ 3 ; Preparation method: The preparation is carried out in four steps according to the above method.

[0065] Performance test results: The compressive strength of the concrete cube reached 68MPa, the flexural toughness index increased to 4.1 times that of ordinary concrete, and no visible cracks were observed after 7 days of standard curing, with the crack width controlled below 0.10mm.

[0066] Example 3: This example describes the preparation of a high-toughness, crack-resistant concrete suitable for large-volume concrete. The specific formula and process are as follows: Cementitious material: Ordinary Portland cement 350kg / m³ 3 fly ash 80kg / m³ 3 Slag powder 50kg / m 3 ; Aggregate: Natural sand with a fineness modulus of 2.4, at a dosage of 680 kg / m³ 3 Crushed stone with a particle size of 5–31.5 mm, at a dosage of 1000 kg / m³. 3 ; Water: Tap water, dosage 168 kg / m³ 3 Water-to-binder ratio: 0.38; Admixture: Polycarboxylate superplasticizer, dosage 7 kg / m³ 3 ; Multi-scale hybrid fiber system: polyvinyl alcohol microfiber, volume fraction 0.4%, length 6mm, diameter 15μm; basalt fiber, volume fraction 0.6%, length 18mm; total fiber volume fraction 1.0%, microfiber to macrofiber volume ratio 1:1.5; Time-compensated shrinkage system: CaO expansion agent, coated with polymer microcapsules, dosage 30 kg / m³ 3 ; Preparation method: The preparation is carried out in four steps according to the above method.

[0067] Performance test results: The compressive strength of the concrete cube reached 55MPa, the flexural toughness index increased to 2.8 times that of ordinary concrete, and no visible cracks were observed after 7 days of standard curing, with the crack width controlled below 0.18mm.

[0068] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-toughness, crack-resistant concrete, characterized in that, include: The high-toughness crack-resistant concrete comprises cementitious materials, aggregates, water, admixtures, and reinforcing components. The reinforcing components include a multi-scale hybrid fiber system and a time-compensated shrinkage system; The multi-scale hybrid fiber system includes microscale high-modulus fibers and macroscale crack-resistant fibers. The microscale high-modulus fibers are used to inhibit the initiation of cracks in the concrete matrix and induce the refinement of multiple cracks. Macroscale crack-blocking fibers are used to bridge cracks and provide energy-dissipating constraints during crack propagation. The time-compensated shrinkage system includes a compensating shrinkage component with delayed hydration characteristics. The compensating shrinkage component undergoes restricted expansion after the early hardening of concrete and during the microcrack formation stage. Under the constraint of the multi-scale hybrid fiber system, it produces a directional closing effect on the microcracks to inhibit shrinkage cracking of concrete.

2. The high-toughness crack-resistant concrete according to claim 1, characterized in that: The microscale high-modulus fibers are selected from polyethylene fibers, polyvinyl alcohol fibers, or combinations thereof, and have a length of 6–12 mm and a diameter of 10–40 μm.

3. The high-toughness crack-resistant concrete according to claim 1, characterized in that: The macroscale crack-resistant fibers are selected from basalt fibers, steel fibers, or combinations thereof, and their length is 18–30 mm.

4. The high-toughness crack-resistant concrete according to claim 1, characterized in that: The total volumetric content of the multi-scale hybrid fiber system is 0.5 to 2.0% of the total concrete volume, wherein the volume ratio of microscale high-modulus fibers to macroscale crack-resistant fibers is 1:0.5 to 1:

2.

5. The high-toughness crack-resistant concrete according to claim 1, characterized in that: The time-compensating shrinkage system includes CaO-type expansion components, CSA-type expansion components, or a combination of both. The compensating shrinkage components are coated or composite-treated to delay their hydration reaction in the early hardening stage of concrete.

6. The high-toughness crack-resistant concrete according to claim 5, characterized in that: The shrinkage compensation component is coated or compounded using mineral micropowder, porous inorganic materials, or polymer materials.

7. The high-toughness crack-resistant concrete according to claim 1, characterized in that: The high-toughness crack-resistant concrete exhibits significantly improved flexural toughness under standard curing conditions, and its early shrinkage crack width is controlled below 0.20 mm.

8. A method for preparing high-toughness crack-resistant concrete as described in any one of claims 1-7, characterized in that: The steps are as follows: The additives are mixed with mineral powder to prepare a uniform pre-dispersion system; Add cementitious materials and water to the pre-dispersed system to form a concrete matrix; The multi-scale hybrid fiber system is added to the concrete matrix in stages, wherein micro-scale high-modulus fibers are added first, followed by macro-scale crack-resistant fibers. After the multi-scale hybrid fiber system is dispersed, the time-compensated shrinkage system is added to ensure its uniform distribution in the concrete.

9. The method for preparing high-toughness crack-resistant concrete according to claim 8, characterized in that: The mineral powder in the pre-dispersed system is selected from silica fume, slag powder, fly ash or a combination thereof, and the additive is a water-reducing agent or a composite system of water-reducing agent and dispersant.

10. The method for preparing high-toughness crack-resistant concrete according to claim 8, characterized in that: The time interval between the addition of microscale high-modulus fibers and macroscale crack-resistant fibers is 30–180 s.