A volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material and its preparation method

Abstract

A volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material and its preparation method belong to the field of concrete material technology. The material is formulated from a base material (ordinary silicate cement, coarse aggregate, fine aggregate, and mineral admixtures), an intelligent functional phase, additives, a composite emulsion, and water. The intelligent functional phase includes a pore-embedded aminated aerogel-temperature-sensitive reversible swelling gel composite powder (the aminated aerogel has micropores and mesopores in hierarchical structure, and the temperature-sensitive gel is copolymerized with N-isopropylacrylamide as the core monomer, growing in situ within the pores), chromium-modified nickel-titanium shape memory alloy fibers, and a nano-reinforcing phase. The gel reversibly swells / shrinks with temperature changes, compensating for the volume deformation of concrete due to temperature changes, sealing micropores and microcracks, and dynamically releasing internal temperature stress. The chromium-modified nickel-titanium shape memory alloy fibers, combined with the nano-reinforcing phase, multi-component additives, and the composite emulsion, synergistically enhance and toughen the concrete, effectively adapting to complex and harsh service environments such as extreme cold and large diurnal temperature variations.

Description

Technical Field

[0001] This invention belongs to the field of concrete material technology and relates to an intelligent crack-resistant concrete material with volume-stress temperature-sensitive self-regulation and its preparation method. It is suitable for concrete structures under severe temperature changes and complex stress, and can effectively solve the cracking problem caused by volume deformation of concrete due to temperature changes, thereby improving the durability and service life of concrete structures. Background Technology

[0002] Concrete, as the most widely used material in civil engineering, possesses numerous advantages such as readily available raw materials, stable mechanical properties, low cost, and strong plasticity, making it a core substrate for infrastructure construction in fields such as buildings, transportation, water conservancy, and municipal engineering. However, concrete itself has inherent defects such as high brittleness, poor crack resistance, and insufficient temperature stability. Under the influence of natural environmental temperature cycles, it is highly susceptible to volumetric expansion and contraction deformation and internal temperature stress accumulation, which in turn triggers the initiation and propagation of microcracks, eventually forming through cracks. This severely reduces the integrity, durability, and service life of concrete structures, increases maintenance costs, and even threatens project safety.

[0003] In low-temperature and frigid environments, the moisture inside concrete is prone to freeze-thaw phase transitions, while the overall matrix shrinks and deforms significantly, leading to concentrated internal shrinkage stress. This is the core cause of concrete cracking and damage. Conversely, as temperatures rise, the concrete matrix expands rapidly, and the residual stress accumulated in the early stages cannot be effectively released, easily resulting in secondary cracking, interface debonding, and other defects. Traditional concrete crack-resistant technologies often employ single modification methods, such as adding expansive agents, crack-resistant fibers, or mineral admixtures. These methods only achieve passive crack resistance and cannot adapt to the volume deformation and stress fluctuations caused by dynamic changes in ambient temperature, exhibiting significant technical limitations.

[0004] To address the problem of concrete cracking, existing technologies mainly focus on three aspects: material modification, structural design, and construction process optimization. Regarding material modification, common methods include incorporating fibers, expansive agents, and mineral admixtures to improve the tensile strength and toughness of concrete and inhibit crack initiation and propagation. However, these methods have several shortcomings. For example, ordinary organic and inorganic crack-resistant fibers can only inhibit crack propagation through physical reinforcement and cannot actively counteract temperature shrinkage stress, resulting in limited low-temperature crack resistance. Furthermore, fibers are prone to agglomeration and have poor compatibility with the cement matrix interface, easily introducing internal defects. Single expansive agents can only achieve early micro-expansion compensation and cannot dynamically control the expansion amount with temperature. Under temperature change cycles, the compensation effect fails, and shrinkage rebound easily occurs in the later stages.

[0005] With the development of smart materials technology, temperature-sensitive and force-sensitive intelligent responsive materials are gradually being applied in the field of concrete crack prevention. Temperature-sensitive materials can undergo reversible changes in physical or chemical properties according to changes in ambient temperature, thereby controlling the volume deformation of concrete; force-sensitive materials can sense changes in internal stress of the structure and disperse stress and inhibit crack propagation by adjusting their own shape or properties. Currently, some research reports on temperature-sensitive or force-sensitive concrete have emerged in related fields. For example, Chinese patent application CN114702867 A discloses an aerogel-based thermal insulation and decorative water-based coating, its preparation method, and its application. This coating mitigates the impact of temperature changes on concrete through the thermal insulation properties of aerogel. However, this material only provides passive thermal insulation and cannot actively regulate volume deformation. Furthermore, its mechanical properties are limited, resulting in poor crack resistance. Chinese patent application CN117105614 A discloses a low thermal conductivity aerogel slurry-modified coral sand concrete and its preparation method. This coating utilizes the ultra-low thermal conductivity of aerogel to reduce temperature stress in concrete. However, aerogel tends to agglomerate in concrete, has poor compatibility with the matrix, and does not address stress response regulation, making it unable to cope with stress concentration cracking under load. Chinese patent application CN120138989... Chinese patent application A discloses a carbon nanotube-aerogel-aluminum silicate superhydrophobic anti-icing material and its preparation method, which has certain heat insulation and moisture-proof properties, but it is not applied to concrete crack prevention and lacks temperature-sensitive and stress-sensitive self-regulating functions. Chinese patent application CN116606407A discloses a temperature-sensitive emulsifier, its preparation method, and its application in emulsion polymerization self-demulsification, which can be used in emulsion polymerization, but does not involve the volume-stress self-regulating crack prevention application in concrete materials. Chinese patent application CN121850482A discloses a gradient temperature-controlled self-healing crack-resistant concrete and its preparation method, using three types of microcapsules with different melting points to form a gradient heat-absorbing structure and reduce the temperature difference of hydration heat. It is mainly suitable for large-volume cast-in-place concrete, but the phase change material is a simple blend with general compatibility with the matrix. It can only weaken temperature fluctuations and cannot actively compensate for cracking problems caused by the superposition of volume deformation and temperature changes. It is also not optimized for extreme environments such as severe cold and large temperature differences, has general weather resistance, and a narrow range of applicable scenarios. Chinese patent application CN 121948994 A discloses a self-healing aerogel, its preparation method, and its applications. Specifically designed for deep-space construction scenarios, it utilizes a self-healing SiO2 aerogel used in lunar construction and relies on a Ni-Ti shape memory alloy framework and a polyimide microcapsule repair system to achieve self-repair, heat insulation, and radiation resistance. However, this technology only focuses on damage repair and does not achieve intelligent temperature and stress control. Furthermore, it uses aerogel as the substrate and is not part of the concrete system.Chinese patent applications CN106278030A and CN106316192A disclose the application of thermosensitive hydrogels in concrete. Both involve directly incorporating N-isopropylacrylamide-based thermosensitive hydrogels into concrete, with a critical phase transition temperature of approximately 30°C. Internal curing is achieved through water release during gel phase transition. However, the thermosensitive hydrogels, using a simple physical blending method, are prone to uneven dispersion and long-term loss, and are also ill-suited for cracking caused by temperature stress, making them unsuitable for extreme temperature environments. Chinese patent application CN121974624A discloses a cement-based composite material based on multi-level toughening and intelligent repair, and its preparation method. It utilizes a multi-scale toughening system constructed from PP and PVA fibers, modified nickel-titanium shape memory alloy short fibers, and elastic polymer microspheres, combined with pre-absorbent SAP microspheres to achieve internal curing and inhibit shrinkage, primarily for building structure repair. However, the functional components in this patent application are all directly blended, resulting in problems such as agglomeration and weak interfacial bonding. It lacks a dual-system for synergistic volume and stress regulation, making it unable to proactively address cracking damage under the coupled effects of temperature changes and loads. Chinese patent application CN 121517134 A discloses a high-crack-resistant concrete based on a sheath-core phase change composite fiber and its preparation method. It employs a core-shell structure with porous metal fibers loaded with a phase change material as the core and a thermo-shrinkable polymer as the sheath. The core material's phase change absorbs heat to reduce hydration heat and internal / external temperature differences, while the sheath's cooling and shrinkage generates pre-compression stress to offset shrinkage tensile stress, thus inhibiting cracking through a dual mechanism. However, this technology cannot achieve dynamic regulation of temperature and stress across the entire range, making it unsuitable for complex working conditions with extreme temperature differences. It also lacks supporting systems such as nano-reinforcement, UV resistance, and interfacial strengthening, resulting in insufficient weather resistance. Chinese patent application CN 121872710 A discloses an organic-inorganic composite gradient temperature-domain phase change regulated crack-resistant temperature-controlled cementitious material and its preparation method. This material utilizes an organic-inorganic composite gradient temperature-domain phase change unit and a thermally conductive reinforcement network for temperature-controlled crack resistance design. The gradient phase change system continuously absorbs and slowly releases temperature during hydration, effectively reducing the risk of temperature stress concentration and thermal crack formation. It is mainly applied to large-volume concrete engineering. Chinese patent application CN 105505350 A discloses a thermosensitive shape memory polymer-based elastic-toughness cement slurry system and its preparation method. By incorporating shape memory polymer particles and fibers with a phase change temperature of 50-80℃, and relying on the polymer's thermal deformation recovery characteristics, it reduces the elastic modulus of cement paste and improves toughness and impact resistance. However, this technology's thermosensitive polymer phase change temperature is adapted to the high-temperature downhole environment, lacks a low-temperature volume compensation design, and does not construct a dual intelligent temperature and stress control system, thus failing to solve the problems of concrete volume deformation and stress concentration cracking under low-temperature and large-temperature-difference conditions.

[0006] Existing temperature-sensitive and force-sensitive concrete technologies still have many shortcomings: ① Single-function response: Most materials can only achieve single-volume control and have limited crack prevention effects, lacking stress dispersion and active crack repair capabilities, and failing to achieve coordinated control of volume deformation and structural stress; ② Low response accuracy: The phase transition temperature of temperature-sensitive materials does not match the service environment temperature of concrete, and the response threshold of force-sensitive materials is too high, making it impossible to detect and control minute deformations and stresses in a timely manner; ③ Poor compatibility: The bonding between the intelligent functional phase and the concrete matrix is ​​weak, easily agglomerating and debonding, failing to fully realize its function; ④ Difficulty in balancing mechanical properties and intelligent response performance: The incorporation of intelligent materials usually reduces the compressive / tensile strength of concrete, failing to meet actual engineering needs; ⑤ Complex preparation process, high cost, and difficulty in large-scale application.

[0007] Furthermore, existing concrete crack-resistant materials are mostly passive crack-resistant, unable to actively and reversibly self-regulate according to changes in ambient temperature and structural stress. When the ambient temperature fluctuates drastically or the structural stress exceeds a threshold, cracking will still occur. Therefore, there is an urgent need to develop an intelligent crack-resistant concrete material that can achieve intelligent self-regulation of volume-stress temperature sensitivity, has good compatibility with the concrete matrix, excellent mechanical properties, strong weather resistance, and a simple preparation process. This would address the industry pain points of traditional concrete, such as temperature-induced cracking, poor durability, and insufficient intelligent responsiveness, and meet the long-term service requirements of concrete structures under harsh environments. Summary of the Invention

[0008] Technical Problem Solved: Addressing the shortcomings of existing concrete crack-resistant materials, such as single-function response, low response accuracy, poor component compatibility, difficulty in balancing mechanical properties and intelligent response performance, and complex preparation processes, this invention provides a volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material and its preparation method. Through innovative design of intelligent functional phases, synergistic optimization of components, and improvement of the preparation process, the prepared material can actively regulate volume deformation according to changes in ambient temperature and adaptively disperse stress according to the structural stress state, synergistically solving cracking problems caused by temperature-induced volume deformation and stress concentration. Simultaneously, it possesses excellent mechanical properties and durability, and the preparation process is simple. This invention can be applied on a large scale to various concrete projects, ensuring structural safety, reducing operation and maintenance costs, and extending the service life of projects, resulting in significant economic and social benefits.

[0009] Technical solution: The first objective of this invention is to provide a volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material, which is prepared by mixing base material, intelligent functional phase, additives, composite emulsion and water in a mass ratio of (90~125):(8~20):(2~7):(9~20):(6~12);

[0010] Of which, by weight,

[0011] The base material includes 35-50 parts of ordinary Portland cement, 25-40 parts of coarse aggregate, 20-30 parts of fine aggregate, and 4-10 parts of mineral admixture;

[0012] The intelligent functional phase comprises 4-12 parts of pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder, 3-6 parts of chromium-modified nickel-titanium shape memory alloy fiber, and 0.5-2 parts of nano-reinforcing phase.

[0013] The pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder is formed by in-situ polymerization of thermosensitive reversible swelling gel within the pores of aminated aerogel.

[0014] The aminated aerogel has a hierarchical pore structure consisting of 2-10 nm micropores and 50-100 nm mesopores.

[0015] The thermosensitive reversible swelling gel is copolymerized from N-isopropylacrylamide as the core monomer, combined with N-tert-butylacrylamide, n-butyl methacrylate, and the crosslinking agent N,N'-methylenebisacrylamide. The molar ratio of N-isopropylacrylamide, N-tert-butylacrylamide, and n-butyl methacrylate is (70~85):(10~20):(5~10). The amount of crosslinking agent added is 0.1~0.5% of the total mass of the monomers, i.e., the total mass of N-isopropylacrylamide, N-tert-butylacrylamide, and n-butyl methacrylate.

[0016] The chromium-modified nickel-titanium shape memory alloy fiber has an elemental composition of 50-55 at% Ni, 44-49 at% Ti, and 0.2-1 at% Cr. The phase transition temperature is controlled to -5-10℃ by doping with Cr to replace part of the Ni.

[0017] This invention employs a "dual intelligent core + nano-reinforcement" composite system, which is the core for achieving volume-stress temperature-sensitive self-regulation. Through the volume temperature-sensitive adaptive compensation of the temperature-sensitive reversible swelling gel and the stress self-regulation synergy of chromium-modified nickel-titanium shape memory alloy fibers, the concrete performance is enhanced through the nano-reinforcement phase. The three work together to achieve temperature response, crack self-repair, and structural strengthening functions.

[0018] The pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder is a volume-temperature-sensitive self-regulating core component. It is formed by in-situ polymerization of thermosensitive reversible swelling gel within the hierarchical pores of aminated aerogel, creating a hierarchical porous aerogel framework-swelling gel embedded interlocking composite structure. It combines the porous thermal insulation properties of aerogel with the reversible swelling properties of thermosensitive swelling gel.

[0019] The thermosensitive reversible swelling gel has a phase transition temperature of 0-5 ℃ through precise monomer ratio control. At 5 ℃, the swelling ratio is 25-50 times its own mass, and the shrinkage rate is ≥85% at 20 ℃. It can achieve ≥100 reversible swelling-shrinkage cycles. N-isopropylacrylamide has excellent thermosensitive reversible swelling properties, and its low critical solution temperature (LCST) can be controlled to a range that matches the service environment temperature of concrete by compounding monomers. N-tert-butylacrylamide and n-butyl methacrylate can also improve the compatibility between the gel and aerogel and enhance the interaction between amino groups on the surface of the gel and aerogel. The addition of crosslinking agent can control the swelling degree and mechanical strength of the gel, and avoid excessive swelling or shrinkage of the gel, which would lead to stress concentration inside the concrete.

[0020] This invention presents a pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder. It innovatively employs an in-situ polymerization embedding process to anchor the thermosensitive reversible gel within the multi-level pores of the aminated aerogel, completely solving the problems of easy agglomeration, easy loss, and poor matrix compatibility of traditional thermosensitive gels. The aerogel possesses ultra-high porosity and specific surface area, providing a stable load-bearing framework for the thermosensitive gel. Simultaneously, its porous structure optimizes the internal pore structure of concrete and improves structural density. The pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder exhibits excellent temperature-response reversible characteristics: when the ambient temperature is lower than the LCST of the thermosensitive gel, the gel swells. On one hand, it fills the capillary pores and early micro-cracks of the concrete, blocking the freeze-thaw penetration path of water and improving the concrete's freeze-thaw resistance and impermeability; on the other hand, through a controllable micro-expansion effect, it actively counteracts the low-temperature shrinkage volume deformation and shrinkage stress of the concrete, inhibiting shrinkage cracking from the source. When the ambient temperature is higher than LCST, the gel undergoes reversible shrinkage, actively releasing the residual temperature stress accumulated inside the concrete, avoiding stress concentration that could induce secondary cracks, and achieving active and reversible control of volume deformation under temperature cycling.

[0021] This invention achieves volume-stress temperature-sensitive self-regulating crack prevention through the synergistic effect of its components, while ensuring the mechanical properties and durability of the concrete. The intelligent crack-resistant concrete material provided by this invention is prepared through an innovative integrated process of component-oriented modification, stepwise compounding, ultrasonic / mechanical synergistic dispersion, and colloid milling. This process achieves uniform dispersion and synergistic effect of dual intelligent cores, providing long-term crack resistance and impermeability under temperature cycling from -15℃ to 25℃, adapting to various environmental application requirements.

[0022] Preferably, the particle size of the pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder is 5~20 μm, and the specific surface area is ≥800 m². 2 / g, porosity ≥95%, surface amino grafting rate ≥85% (modified by aminopropyltriethoxysilane), providing a three-dimensional porous anchoring skeleton for the thermosensitive reversible swelling gel; the thermosensitive reversible swelling gel has a swelling ratio (based on the total composite powder) of 25~50 times its own mass at 5℃, a shrinkage rate ≥85% at 20℃, and a reversible swelling-shrinkage cycle count ≥100 times.

[0023] The pore-embedded aminated aerogel is an aminated silica aerogel prepared using a template-induced sol-gel-supercritical drying process. It possesses a hierarchical pore structure with 2-10 nm micropores and 50-100 nm mesopores. This hierarchical structure provides ample pore space for loading a temperature-sensitive reversible swelling gel, while simultaneously achieving excellent thermal insulation performance (thermal conductivity ≤0.012 W / (m·K)), mitigating the impact of temperature changes on concrete. Surface amino grafting enhances the chemical bonding between the aerogel and the temperature-sensitive gel, ensuring stable gel growth within the aerogel pores and improving the compatibility between the aerogel and the concrete matrix. The composite powder has a pore embedding rate ≥90% and an aerogel pore utilization rate ≥85%. Its aerogel skeleton-swelling gel embedded structure achieves a synergistic triple function of thermal insulation, intelligent sealing, and mechanical stability.

[0024] Preferably, the chromium-modified nickel-titanium shape memory alloy fiber has a diameter of 80~250 μm, a length of 8~18 mm (length-to-diameter ratio 32~225), a tensile strength ≥1150 MPa, an elongation at break ≥8%, an elastic modulus retention rate ≥90% at -5 ℃, a shape memory recovery rate ≥90%, and a phase transformation temperature of -5~10 ℃. The surface of the fiber is modified by soaking in an ethanol solution of 1~2 wt% silane coupling agent KH-550 (γ-aminopropyltriethoxysilane) at 25~30 ℃ for 1~2 h, followed by drying. The surface amino grafting rate is ≥80%, the interfacial bonding strength with cement-based materials is ≥2.5 MPa, and the volume ratio of ethanol to water in the ethanol solution is 90:10.

[0025] The chromium-modified nickel-titanium shape memory alloy fiber is a stress-temperature-sensitive self-regulating core component. Modification is achieved by replacing part of the Ni with Cr, optimizing its phase transformation temperature and mechanical properties to achieve adaptive stress dispersion and active crack suppression. Cr doping regulates the phase transformation temperature of the shape memory alloy to -5~10 ℃, matching the service temperature of concrete in frigid regions. Excellent mechanical and shape memory properties ensure that the fiber effectively disperses stress and bridges cracks within the concrete. In the low-temperature phase transformation range, the fiber undergoes martensitic phase transformation and shrinkage, actively generating uniform pre-tension stress to counteract the tensile stress generated by the low-temperature shrinkage of the concrete matrix, inhibiting crack initiation. When the concrete is subjected to external forces or temperature changes, resulting in micro-cracks, the fiber, with its ≥95% ultra-high shape memory recovery rate, quickly restores its shape, providing a dual effect of "bridging constraint + compression closure" to effectively inhibit crack propagation and limit crack width growth. Simultaneously, the amino-modified surface treatment of the fiber significantly enhances its interfacial adhesion to the cement matrix, ensuring efficient stress transfer and preventing interfacial debonding failure.

[0026] Preferably, the nano-reinforcing phase is composed of nano-titanium boride and graphene oxide in a mass ratio of (3:1) to (2:1), wherein the nano-titanium boride has a particle size of 30-60 nm, and the graphene oxide sheet thickness is 1-5 nm with a sheet diameter of 0.5-2 μm. Both have a purity >95%, constructing a microscopic nano-reinforcing network. Nano-titanium boride has excellent hardness and wear resistance (Mohs hardness ≥9.0), which can enhance the compressive and tensile strength of concrete; graphene oxide provides two-dimensional sheet barrier and stress transmission functions, and has ultra-high specific surface area and mechanical properties, which can form a three-dimensional network structure inside the concrete, playing a bridging and reinforcing role, and inhibiting the generation and propagation of cracks. The combination of the two can exert a synergistic reinforcing effect, which can improve the mechanical properties of concrete and the dispersion of intelligent functional phases, synergistically enhance the crack prevention effect, and increase the tensile strength of cement-based materials by more than 25%; at the same time, the surface activity of graphene oxide can promote the uniform dispersion of intelligent functional phases in the concrete matrix and avoid agglomeration.

[0027] Preferably, the ordinary silicate cement has a strength grade ≥42.5 and a sieve residue of ≥5% on a 45 μm square-hole sieve. High-strength cement ensures that the concrete has good basic compressive and tensile strength, providing a stable carrier for the function of the intelligent functional phase. Controlling the sieve residue on the 45 μm square-hole sieve within a reasonable range optimizes the cement particle size distribution, improves the hydration reaction efficiency, and enhances the density of the concrete. The coarse aggregate has a particle size of 5~12 mm, continuous gradation, thermal conductivity ≤2.0 W / (m·K), mud content ≤0.5%, and loose bulk density of 1450~1550 kg / m³. 3Continuously graded coarse aggregates can reduce interparticle voids, improving the density and mechanical properties of concrete; low thermal conductivity can reduce the rate of temperature conduction, alleviating temperature stress; low mud content can avoid the adverse effects of impurities on concrete strength and interfacial bonding performance; fine aggregate particle size is 0.15~4.75 mm, with 30% being 0.15~0.60 mm, 40% being 0.60~1.18 mm, and 30% being 1.18~4.75 mm; thermal conductivity ≤1.8 W / (m·K); mud content ≤1.0%; and loose bulk density 1500~1600 kg / m³. 3 A reasonable fine aggregate gradation can form a good packing structure with coarse aggregate, fill the voids between coarse aggregate, and improve the density and crack resistance of concrete; a low thermal conductivity can further optimize the temperature sensitivity of concrete and reduce internal stress caused by temperature gradient; the mineral admixture is composed of metakaolin and silica fume mixed in a mass ratio of (2:1) to (3:1), wherein the specific surface area of ​​metakaolin is ≥550m². 2 / kg, 7d activity index ≥115%, silica ash purity ≥96%, specific surface area ≥25000m² 2 / kg, pozzolanic activity index ≥120%. Metakaolin and silica fume both have high pozzolanic activity, which can undergo secondary hydration reaction with cement hydration products to generate more CSH gel, fill the internal pores of concrete, and improve the density, strength and durability of concrete; at the same time, the addition of mineral admixtures can reduce the heat of hydration of concrete and reduce temperature cracks caused by the heat of hydration.

[0028] Preferably, the composite emulsion is composed of 6-12 parts of fluorocarbon modified styrene-acrylic emulsion, 3-7 parts of acrylate-butadiene copolymer emulsion, and 0.4-1 parts of film-forming aid; the aid is composed of 0.5-1.5 parts of polycarboxylate superplasticizer, 0.02-0.1 parts of air-entraining agent, 1.5-4 parts of composite expanding agent, and 0.3-1 parts of UV-resistant composite agent.

[0029] The composite emulsion is used to improve the interfacial bonding performance, toughness, and impermeability of concrete, and to assist in the dispersion and fixation of the intelligent functional phase. Fluorocarbon-modified styrene-acrylic emulsion has excellent weather resistance, water resistance, and stain resistance, which can improve the surface protection performance of concrete and enhance the interfacial bonding force between the intelligent functional phase and the concrete matrix; acrylate-butadiene copolymer emulsion has good flexibility and elasticity, which can improve the toughness and crack resistance of concrete and alleviate stress concentration.

[0030] Furthermore, the film-forming aid is propylene glycol methyl ether acetate, which can lower the film-forming temperature of the emulsion, ensuring that the emulsion can still form a film normally at low temperatures, while improving the stability and compatibility of the emulsion.

[0031] Preferably, the composite expansive agent is composed of ettringite and magnesium oxide in a mass ratio of 2:1, with a 7-day restricted expansion rate ≥0.035% and a 28-day restricted expansion rate ≥0.020%. ettringite can generate moderate expansion in the early stages of concrete, compensating for early shrinkage; magnesium oxide can generate slow expansion in the later stages of concrete, compensating for later shrinkage. The combination of these two agents works synergistically with the concrete hydration process to achieve full-age shrinkage compensation and inhibit shrinkage cracking. A reasonable expansion rate avoids excessive expansion leading to internal stress, ensuring the structural stability of the concrete. The UV-resistant composite agent is composed of nano-ZnO, nano-CeO2, and nano-TiO2 in a mass ratio of 3:2:1, with a UV shielding rate ≥90%. The UV-resistant composite agent can absorb and reflect ultraviolet rays, preventing UV irradiation from causing aging and cracking of the concrete surface, while protecting intelligent functional phases (such as thermosensitive gels and shape memory alloy fibers) from UV damage, thus improving the durability of concrete and the long-term stability of intelligent functions.

[0032] The polycarboxylate superplasticizer selected is a comb-shaped product with a side chain length of 12-18 carbon atoms, exhibiting a water reduction rate ≥30% and a slump change ≤50 mm over 1 hour. The comb-shaped polycarboxylate superplasticizer can disperse cement particles and intelligent functional phases through steric hindrance, improving the workability of concrete, reducing water consumption, and lowering the water-cement ratio, thereby enhancing the density and mechanical properties of the concrete. The high water reduction rate ensures that the concrete maintains good fluidity even at low water-cement ratios, meeting construction requirements.

[0033] The air-entraining agent is an alkylphenol polyoxyethylene ether with an air content of 5%~8%, an average bubble diameter ≤100 μm, and an air content change of ≤1.0% over 1 hour. This air-entraining agent introduces uniformly distributed microbubbles into the concrete. These bubbles act as a buffer, mitigating stresses caused by temperature changes and loads, while improving the concrete's frost resistance and impermeability. The microbubbles prevent excessively large bubbles from causing a decrease in concrete strength, and the stable air content ensures consistent concrete workability.

[0034] The above-mentioned additives are used to optimize the workability, expansion compensation performance, mechanical properties and durability of concrete, assist the intelligent functional phase to play its role, and improve the environmental adaptability of the material.

[0035] Preferably, the pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder is prepared by a method comprising the following steps:

[0036] Step 1: Aerogel Preparation: Tetraethyl orthosilicate (TES) was used as the silicon source, Pluronic F127 as the template agent, and aminopropyltriethoxysilane as the amino modifier. The mixture was prepared by mixing silicon source:template agent:amino modifier:ethanol:water in a molar ratio of 1:(0.05~0.1):(0.1~0.2):(10~15):(2~3), and stirred at 30~40℃ for 4~6 h to form a sol. The sol was then allowed to stand for 24~36 h for aging. Subsequently, it was freeze-dried at -50~-40℃ for 12~16 h, and then calcined at 500~550℃ for 2~3 h to remove the template agent, resulting in silica-aminated aerogel particles with a hierarchical porous structure, ensuring a microporous-mesoporous hierarchical distribution and surface amino activity. The template agent Pluronic F127 can induce the formation of a hierarchical porous structure, and the amino modifier can graft amino groups onto the aerogel surface, providing binding sites for in-situ polymerization of the thermosensitive gel.

[0037] Step 2: Aerogel carrier pretreatment: The aminated aerogel particles prepared in Step 1 were added to anhydrous ethanol and dispersed using a gradient ultrasonic method, i.e., first dispersed at 40 kHz for 15 min, then dispersed at 50 kHz for 15 min, with an ultrasonic power density of 1.5 W / cm³. 2 This forms a uniform aerogel suspension with a mass concentration of 5-8%. Gradient ultrasound can prevent aerogel particles from agglomerating, ensuring that the aerogel pores are fully open and exposed, creating conditions for monomer permeation.

[0038] Step 3: Monomer Infiltration of Thermosensitive Reversible Swelling Gel: Controlling the mass ratio of aerogel to thermosensitive reversible swelling gel monomers to be (3:1)~(2:1), N-isopropylacrylamide, N-tert-butylacrylamide, n-butyl methacrylate, and the crosslinking agent N,N'-methylenebisacrylamide are mixed and dissolved in deionized water to prepare a monomer solution with a solid content of 20%~30%. The monomer solution is injected into the aerogel suspension and placed in a vacuum tank. It is immersed for 2~3 hours under a vacuum of -0.08~-0.09 MPa and 25℃, with the vacuum released for 10 seconds every 30 minutes and then re-pressurized. The hydrogen bonding between the amino groups and the monomers promotes deep penetration of the monomers into the hierarchical pores, preventing pore blockage. Vacuum immersion removes air from the aerogel pores, ensuring that the monomers fully fill the pores, laying the foundation for in-situ polymerization.

[0039] Step 4: In-situ polymerization and curing: After releasing the vacuum, add the initiator-reduction composite solution and stir at 100-150 r / min at 35-45 ℃ for 3-5 h. This allows the thermosensitive reversible swelling gel to polymerize in-situ within the hierarchical pores of the aerogel, forming an embedded interlocking structure and preventing hydrogel detachment. The mass ratio of ammonium persulfate to sodium bisulfite in the initiator-reduction composite solution is 1:1.2-1:1.5, and the total added mass of the two solids is 0.8-1.2 wt% of the total monomer mass. The initiator-reduction composite solution lowers the polymerization temperature, ensuring a gentle and uniform polymerization reaction, preventing gel agglomeration on the aerogel surface, and forming a stable embedded structure.

[0040] Step 5, Post-processing: Filter the product and wash it 3-5 times with deionized water with a conductivity ≤20 μS / cm to remove free, temperature-sensitive, reversibly swollen gel from the surface. Then, freeze-dry it at a vacuum ≤10 Pa and -40 to -30℃ for 12-16 h. After pulverizing, sieve it through a 400-500 mesh sieve to obtain a composite powder with a particle size of 5-20 μm. Freeze-drying avoids structural damage caused by gel swelling and shrinkage, and sieving ensures uniform particle size of the composite powder, facilitating dispersion in concrete.

[0041] The composite powder preparation process solves the problems of poor aerogel dispersion, easy aggregation of swollen gels, and weak interfacial bonding in traditional physical mixing by gradient ultrasonic dispersion, vacuum circulation infiltration, low-temperature in-situ polymerization, and freeze drying.

[0042] Preferably, the preparation method of the chromium-modified nickel-titanium shape memory alloy fiber adopts a process route of alloy smelting, billet preparation, phase transformation temperature control, and surface modification to ensure that the fiber has excellent shape memory properties, mechanical properties, and compatibility with the concrete matrix. The specific steps are as follows:

[0043] Step 1: Alloy smelting and billet preparation: Weigh out pure metal raw materials of Ni, Ti, and Cr with a purity ≥ 99% according to the elemental ratio, and place them under a vacuum of ≤ 5 × 10⁻⁶. -3 In a vacuum arc furnace at 1500–1600 °C, the alloy is melted 3–4 times, with the ingot being turned over after each melting to ensure uniform composition. The resulting chromium-modified nickel-titanium alloy ingot is then homogenized by holding at 900–1000 °C for 4–6 h to eliminate casting stress. Subsequently, it is hot-rolled 3–4 times at 800–850 °C with a reduction of 25–35% per pass, followed by 3–5 cold-rolled at room temperature with a reduction of 20–30% per pass, to produce fiber blanks with a diameter of 80–250 μm. Vacuum melting avoids metal oxidation and ensures uniform alloy composition; homogenization eliminates casting defects and improves the mechanical properties of the alloy; multiple hot and cold rolling refines the grains, further enhancing the strength and toughness of the fibers.

[0044] Step 2, Phase Transformation Temperature Control: The fiber preform is solution treated at 500~550℃ for 1~2 h, followed by ice-water quenching at a cooling rate of ≥100℃ / min to obtain a martensitic structure. A stepped aging treatment is then performed: first, holding at 300℃ for 1 h, then at 320℃ for 0.5 h, and finally at 350℃ for 0.5 h. Through the doping effect of chromium, the phase transformation temperature is precisely controlled to -5~10℃. Solution treatment allows for complete dissolution of alloying elements, quenching yields a martensitic structure, and stepped aging treatment precisely controls the phase transformation temperature of the shape memory alloy, matching it to the service environment temperature of concrete, while simultaneously improving the shape memory recovery rate.

[0045] Step 3, Surface Modification: Fibers cut to the specified length are placed in a 1-2 wt% silane coupling agent KH-550 ethanol solution (ethanol:deionized water volume ratio = 90:10, pH adjusted to 4-5 to promote hydrolysis), and soaked at 25-30℃ for 1-2 hours with a stirring rate of 50-80 r / min to ensure full adsorption of the coupling agent. Subsequently, they are dried at 100-110℃ for 2-3 hours to form chromium-modified nickel-titanium shape memory alloy fibers covered by a modified film with a thickness of 50-100 nm. After drying, the surface amino grafting rate is ≥80%, and the interfacial bonding strength with the cementitious matrix is ​​≥2.5 MPa. The amino groups of the silane coupling agent can chemically bond with the hydration products in the concrete matrix, enhancing the interfacial adhesion between the fiber and the matrix. Simultaneously, the modified film improves the fiber's corrosion resistance and extends its service life. Surface modification with silane coupling agent can improve the compatibility and interfacial bonding strength between shape memory alloy fibers and cement matrix, prevent fiber debonding from matrix, ensure that fiber can effectively transfer stress, improve fiber corrosion resistance, and extend its service life.

[0046] The preparation process of shape memory alloy fibers ensures the uniformity of alloy composition and the accuracy of phase transformation temperature through the synergistic process of "multi-stage melting - chromium doping control - step aging - directional modification". Ni-Ti-Cr shape memory alloy fibers optimize phase transformation characteristics through Cr element doping, and the shape memory recovery rate at low temperature is ≥90%. At the same time, the chemical bonding interface is constructed through surface modification, and the bonding strength with cement-based interfaces is increased by more than 40%, which significantly improves the compatibility with cement-based materials.

[0047] The second objective of this invention is to provide a method for preparing a volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material, as described above. This method employs a multi-stage dynamic mixing process involving mortar pre-preparation, additive coating, intelligent functional phase dispersion, shape memory alloy fiber dispersion, and fusion of composite emulsion and coarse aggregate. This ensures uniform dispersion of all components, good interfacial bonding, and the synergistic effect of both volume regulation and stress regulation. The steps are as follows:

[0048] Step 1: Mortar Pre-preparation: Weigh the ordinary Portland cement, fine aggregate, and mineral admixtures from the base material. Under conditions of ambient humidity ≤60%, add them to a twin-shaft mixer and dry mix at 25~30 r / min for 3~5 min until the mixture is uniform in color. Then add 60 wt% water, with the water temperature controlled at 5~20℃, adjust the mixer speed to 30~35 r / min, and mix for 2~3 min to prepare a uniform mortar with a slump ≥200 mm. Dry mixing can ensure that the components of the base material are mixed evenly and avoid local clumping. Controlling the water temperature can prevent the hydration reaction from being too fast, which would reduce the fluidity of the mortar and ensure that the mortar has good workability.

[0049] Step 2, Additive Coating: Add the additive to the mortar and stir at 25~30 r / min for 1~2 min to allow the additive molecules to be evenly adsorbed on the surface of each particle in the mortar, forming a particle-additive coating structure, which improves the efficiency of the additive. The additive coating allows its function to be fully exerted and avoids interference with subsequent functional phases; at the same time, it can make the additive evenly distributed in the mortar, avoiding local concentrations that are too high or too low.

[0050] Step 3: Dispersion of the intelligent core functional phase: First, add the pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder and stir at 30~35 r / min for 1~2 min. Then, add the nano-reinforcing phase and continue stirring for 1~2 min. By utilizing the synergistic effect of the surface activity of nanoparticles and the amino groups on the aerogel surface, the composite powder is promoted to be uniformly dispersed, ensuring that there are no obvious agglomerates. The stepwise addition of the intelligent functional phase can avoid mutual interference between different components, ensure that each component is uniformly dispersed, and give full play to its intelligent regulation function.

[0051] Step 4: Dispersion of Chromium-Modified Nickel-Titanium Shape Memory Alloy Fibers: Add chromium-modified nickel-titanium shape memory alloy fibers, increase the rotation speed to 35~40 r / min, and simultaneously introduce a power density of 2.0 W / cm³ at a frequency of 40~50 kHz. 2 Ultrasonic-assisted dispersion is applied for 2-3 minutes, with the stirring direction reversed every 1 minute to prevent fiber entanglement and agglomeration. Ultrasonic-assisted dispersion is applied while stirring, which can effectively break up fiber agglomeration. Reversing the stirring direction can prevent the fiber from oriented and ensure that the fiber is evenly distributed in the concrete with a uniformity of ≥90%, forming a three-dimensional interwoven support network.

[0052] Step 5: Blending of Composite Emulsion and Coarse Aggregate: Add the composite emulsion, the remaining 40 wt% water, and the coarse aggregate from the base material. Stir and mix, adjusting the speed to 30-35 r / min and stirring for 2-3 minutes. Then, stir at a frequency of 35-45 kHz and a power density of 1.5 W / cm³. 2An ultrasonic homogenizer is used to homogenize the mixture for 1-2 minutes, maintaining a rotation speed of 35-40 r / min during this period to ensure thorough integration of the phases, ultimately resulting in intelligent crack-resistant concrete with volume-stress temperature-sensitive self-regulation. Ultrasonic homogenization further improves the dispersion uniformity of each component, enhances interfacial bonding, and ensures that the concrete possesses excellent mechanical properties and intelligent response performance.

[0053] The innovation of the volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material and its preparation method described in this invention lies in:

[0054] (1) This invention innovates the structure of ammoniated hierarchical porous silica aerogel. Through the pioneering hierarchical porous structure + surface ammoniation dual modification design, it breaks through the limitations of traditional single-pore aerogels. The hierarchical porous (micropores 2~10nm + mesopores 50~100nm) design increases the porosity to 90%, providing sufficient anchoring space for the swelling gel and optimizing the heat transfer path. The ultra-low thermal conductivity of the aerogel (≤0.012W / (m·K)) forms a thermal insulation barrier, reducing the temperature difference between the inside and outside of the concrete (the temperature difference is reduced by more than 40%). Surface ammoniation (grafting rate ≥85%) promotes the deep penetration and in-situ polymerization of hydrogel monomers through hydrogen bonding, increasing the interfacial bonding strength to ≥3.5MPa. This solves the problem of weak interfacial bonding between traditional aerogels and swelling gels, while enhancing the compatibility of aerogels with cementitious materials, ensuring no peeling or detachment during long-term service.

[0055] (2) This invention proposes a design of a porous embedded aerogel-thermosensitive reversible swelling gel composite system, breaking through the traditional physical mixing composite mode. It is the first to create an embedded structure of aerogel skeleton-swelling gel embedded in situ polymerization. The aerogel provides a three-dimensional porous anchor skeleton for the thermosensitive reversible swelling gel. The porous structure has both heat insulation and carrier functions. The thermosensitive swelling gel is grown in the pores of the aerogel through gradient ultrasonic dispersion-vacuum circulation infiltration-low temperature in situ polymerization-freeze drying process. Gradient ultrasonic (40 / 50 kHz) ensures that the pores of the aerogel are open. Vacuum circulation infiltration (-0.08~-0.09 MPa) allows the gel monomer to deeply penetrate into the deep pores of the aerogel. Then, low temperature in situ polymerization forms a stable embedded structure, which solves the problems of poor aerogel dispersion, easy agglomeration and loss of swelling gel and weak interfacial bonding in traditional physical mixing. The composite powder has both the heat insulation of aerogel and the intelligent responsiveness of hydrogel.

[0056] (3) This invention can achieve volume-stress temperature-sensitive synergistic self-regulation, and innovatively constructs a two-dimensional temperature-sensitive synergistic self-regulation system of pore-embedded aminated aerogel-temperature-sensitive reversible swelling gel composite powder + chromium-modified nickel-titanium shape memory alloy fiber. The two intelligent core components work together and complement each other to achieve dual active and reversible regulation of concrete volume deformation and stress concentration, forming a full-cycle dynamic crack-resistant closed loop. Specifically, 1) Innovatively adopting in-situ polymerization embedding process, the temperature-sensitive reversible gel is anchored inside the multi-level pores of aminated aerogel. The aerogel has ultra-high porosity and specific surface area, providing a stable load-bearing skeleton for the temperature-sensitive gel. At the same time, its own porous structure can optimize the internal pore structure of concrete and improve the structural density. The temperature-sensitive reversible swelling gel has excellent temperature response reversible characteristics. It rapidly swells in the low temperature range of 0~5℃, filling the capillary pores and microcracks of concrete, blocking the water penetration path, and improving the concrete's antifreeze and anti-seepage ability. At the same time, the controllable micro-expansion effect generated by swelling actively offsets the low-temperature shrinkage volume deformation and shrinkage stress of concrete, inhibiting shrinkage cracking from the source. When the ambient temperature rises to the normal temperature range of 10~20 ℃, the gel reversibly shrinks, actively releasing the residual temperature stress accumulated inside, avoiding stress concentration that leads to new cracks, and achieving dynamic and precise compensation for volume deformation under temperature cycling. 2) By precisely controlling the phase transformation temperature to the core low-temperature service range of concrete (-5~10 ℃) through Cr element doping, within the low-temperature phase transformation range, the fiber undergoes martensitic phase transformation shrinkage, actively generating uniform pre-tension stress to offset the tensile stress generated by the low-temperature shrinkage of the concrete matrix and inhibit crack initiation; when the concrete is subjected to external force or temperature change and micro-cracks are generated, the fiber, relying on its ultra-high shape memory recovery rate of ≥95%, quickly restores its shape, forming a dual effect of "bridging constraint + compression closure" on the crack, effectively inhibiting crack propagation and limiting crack width growth. The two intelligent components work together to significantly improve the crack resistance of concrete.

[0057] (4) This invention proposes a shape memory alloy fiber-nano phase interface strengthening technology, using chromium-modified nickel-titanium shape memory alloy fibers. By doping with Cr, the alloy phase transformation characteristics are optimized, improving the shape memory recovery rate (≥90%) and elastic modulus retention rate (≥90%) at low temperatures. At the same time, the fiber surface is modified with KH-550 silane coupling agent to form a chemical bond with the cement-based slurry, increasing the interfacial bonding strength by more than 40%. Combined with the nano-reinforcing phase (nano-titanium boride + graphene oxide), its high hardness and high interfacial bonding strength characteristics form a three-dimensional reinforcing network of macro-fiber bridging, micro-nano reinforcement, and embedded structure anchoring inside the cement matrix. This not only improves the overall tensile strength and toughness of the material, but also inhibits the initiation of interfacial cracks, solving the key bottleneck of poor compatibility between traditional alloy fibers and cement matrix and easy interface peeling.

[0058] (5) This invention has carried out multi-component synergistic optimization. Through the synergistic proportioning of base material, intelligent functional phase, additives and composite emulsion, the balance between the mechanical properties and intelligent response performance of concrete is achieved. The fluorocarbon modified composite emulsion system can form a rigid-flexible cross-linked polymer film inside the concrete, fill the matrix pores, optimize the interface structure, and improve the toughness, impermeability and crack resistance of concrete; mineral admixtures and composite emulsion improve the density and interfacial adhesion of concrete; the nano-reinforcing phase composed of nano-titanium boride and graphene oxide can fill the nano-scale micropores of concrete, refine the matrix microstructure, improve the density and mechanical strength of concrete, and at the same time disperse micro-stress and inhibit the propagation of micro-defects; the multi-component additives synergistically optimize the mixing fluidity, volume stability and durability of concrete; the components work together to ensure that the concrete has both excellent crack resistance and meets the mechanical and durability requirements of engineering practice.

[0059] (6) This invention achieves an innovative multi-stage dynamic mixing process for concrete, proposing a gradient speed control + ultrasonic-mechanical bidirectional dispersion mode. First, the temperature-sensitive composite powder is uniformly dispersed through medium-speed stirring combined with amino adsorption. Then, high-speed stirring + ultrasonic assistance solves the problem of fiber entanglement in chromium-modified nickel-titanium shape memory alloy. Finally, the composite emulsion is fused with coarse aggregate. This multi-stage dynamic mixing process completely solves industry problems such as agglomeration of intelligent functional phases, fiber entanglement, uneven component dispersion, and weak interfacial bonding, ensuring that the dual cores of volume control and stress control work synergistically. Furthermore, by precisely limiting the raw material parameters, proportion range, and preparation process parameters of each component, the controllable and stable preparation of intelligent concrete material performance is achieved. The final prepared concrete material has comprehensive advantages such as accurate temperature-sensitive response, excellent crack resistance, high mechanical strength, good toughness, freeze-thaw resistance, UV aging resistance, and strong durability, making it suitable for various harsh environmental engineering applications.

[0060] The beneficial effects of this invention are:

[0061] (1) The intelligent crack-resistant concrete material prepared by this invention has excellent crack resistance performance and can break through the bottleneck of traditional single passive crack resistance technology. Based on the synergy of dual intelligent core and gradient structure, it realizes volume-stress temperature-sensitive synergistic self-regulation, which can effectively cope with the cracking problem caused by temperature change volume deformation and stress concentration. The material's ultimate tensile value is ≥300μɛ, and the freeze-thaw resistance grade reaches F400. It can stably cope with stress accumulation cracking caused by repeated temperature changes. After 25 temperature change cycles (-15℃~25℃), no cracks are generated. The crack resistance performance of the concrete is improved by more than 80% compared with traditional concrete.

[0062] (2) The intelligent crack-resistant concrete material prepared by this invention has outstanding mechanical properties. Through the synergistic toughening and reinforcement of nano-reinforcing phase and composite emulsion, the micro-pore structure of concrete is refined, the matrix density is improved, and the compressive and tensile strengths of the concrete are significantly improved. At the same time, it has excellent elastic deformation capacity and can effectively disperse external stress. The compressive strength of the concrete is ≥60 MPa and the tensile strength is ≥4.5 MPa, which is 15%~40% higher than that of traditional crack-resistant concrete, and can meet the load-bearing requirements of various projects.

[0063] (3) The intelligent crack-resistant concrete material prepared by this invention has outstanding intelligent response performance. It adopts an in-situ embedded thermosensitive gel structure of aminated aerogel. Through the dual action of chemical bonding and physical interlocking, it completely solves the problems of aggregation, loss, poor compatibility and response failure of traditional thermosensitive gels. Moreover, the temperature response range of volume thermosensitive control matches the service environment temperature of concrete, and the response threshold of stress thermosensitive control is low. It can promptly sense and control small deformations and stresses, with fast response speed and stable control effect. By precisely doping Cr to modify shape memory alloy fibers, matching the low temperature phase transformation range of concrete, and with surface aminated modification, the bonding strength and stress transmission efficiency of the fiber-matrix interface are greatly improved. After 400 freeze-thaw cycles, the shape memory recovery rate of the shape memory alloy fibers is still ≥90%, and there is no functional failure phenomenon during long-term service.

[0064] (4) The intelligent crack-resistant concrete material prepared by the present invention has good compatibility and durability. The intelligent functional phase is firmly bonded to the concrete matrix interface without agglomeration or debonding. The concrete has excellent freeze-thaw resistance, impermeability and UV aging resistance. After 400 freeze-thaw cycles, the tensile strength and elastic modulus retention rate is ≥90%. It is also resistant to UV aging and its service life is significantly extended compared with traditional concrete.

[0065] (5) The intelligent crack-resistant concrete material prepared by this invention has strong environmental adaptability and rich application scenarios. It is not only suitable for severe cold and extreme environments, but also meets the needs of conventional engineering scenarios. It has excellent compatibility with existing concrete substrates (bond strength ≥2.5MPa). It is applicable to both new construction projects and the repair of old projects. It is suitable for construction needs in different climate regions and can be widely used in concrete projects such as building main structures, bridge box girders, tunnel linings, hydraulic dams, and open-air structures that are susceptible to temperature changes, freeze-thaw cycles, and ultraviolet aging. It effectively solves the pain points of cracking and damage of concrete structures and insufficient durability under harsh environments, significantly reduces engineering operation and maintenance costs, extends the service life of structures, and has significant economic and social benefits.

[0066] (6) The preparation process proposed in this invention is precise, controllable, economical, and environmentally friendly. It adopts a multi-stage gradient stirring + ultrasonic-assisted dispersion process to disperse different functional components step by step, effectively avoiding problems such as fiber entanglement, nanoparticle agglomeration, and uneven distribution of functional components. The process parameters are precise and controllable, the operation is simple, and the stability is strong. No complex equipment is required. All raw materials are commercially available and readily available products, and the preparation process of key components is mature. It can be directly adapted to the existing industrialized concrete mixing and pouring construction process, resulting in high construction efficiency and controllable costs. It has extremely strong engineering promotion value. All components meet environmental protection requirements and have no harmful release of formaldehyde, heavy metals, etc., which is in line with the development trend of green building materials. Attached Figure Description

[0067] Figure 1 The results of the concrete temperature stress test are shown in (a) temperature history curve and (b) stress development curve.

[0068] Figure 2 The images are of concrete after 400 freeze-thaw cycles. (a) and (b) are Comparative Example 2, and (c) and (d) are Example 2.

[0069] Figure 3 The results of the concrete slab cracking test are as follows: (a) air curing, (b) crack observation, (c) Comparative Example 1, (d) Comparative Example 2, (e) Example 2, (f) Example 4. Detailed Implementation

[0070] To more clearly describe the technical solution of the present invention, the following detailed and complete description of the technical solution of the present invention is provided in conjunction with preferred embodiments, comparative examples, and corresponding performance test data. This embodiment is based on the implementation of the technical solution of the present invention. The detailed implementation methods and operating procedures are only used to explain the present invention and are not intended to limit the scope of protection of the present invention. All similar embodiments listed based on the present invention should fall within the scope of protection of the present invention.

[0071] Unless otherwise specified, all raw materials described in this invention can be obtained through publicly available means.

[0072] In the examples described in this specification, the ordinary silicate cement strength grade is ≥42.5, and the residue on a 45 μm square-hole sieve is ≥5%.

[0073] The coarse aggregate has a particle size of 5~12 mm, continuous gradation, thermal conductivity ≤2.0 W / (m·K), mud content ≤0.5%, and loose bulk density of 1450~1550 kg / m³. 3 Continuously graded coarse aggregate can reduce the voids between particles and improve the density and mechanical properties of concrete.

[0074] The fine aggregate has a particle size of 0.15~4.75 mm, with 30% being 0.15~0.60 mm, 40% being 0.60~1.18 mm, and 30% being 1.18~4.75 mm. Its thermal conductivity is ≤1.8 W / (m·K), mud content is ≤1.0%, and loose bulk density is 1500~1600 kg / m³. 3 ;

[0075] The mineral admixture is composed of metakaolin and silica fume mixed in a mass ratio of (2:1) to (3:1), wherein the specific surface area of ​​the metakaolin is ≥550m². 2 / kg, 7d activity index ≥115%, silica ash purity ≥96%, specific surface area ≥25000m² 2 / kg, volcanic ash activity index ≥120%;

[0076] The nano-reinforcing phase is composed of nano-titanium boride and graphene oxide in a mass ratio of (3:1) to (2:1). The nano-titanium boride has a particle size of 30 to 60 nm, the graphene oxide has a sheet thickness of 1 to 5 nm and a sheet diameter of 0.5 to 2 μm, and both have a purity of >95%.

[0077] Polycarboxylate superplasticizers are comb-shaped products with side chain lengths of 12-18 carbon atoms, with a water reduction rate of ≥30% and a slump change of ≤50 mm over 1 hour.

[0078] The air-entraining agent is an alkylphenol polyoxyethylene ether with an air content of 5%~8%, an average bubble diameter of ≤100 μm, and an air content change of ≤1.0% over 1 hour.

[0079] The composite expansion agent is composed of ettringite and magnesium oxide in a mass ratio of 2:1. The composite expansion agent has a 7-day restricted expansion rate of ≥0.035% and a 28-day restricted expansion rate of ≥0.020%.

[0080] The UV-resistant composite agent is composed of nano ZnO, nano CeO2 and nano TiO2 in a mass ratio of 3:2:1, and has a UV shielding rate of ≥90%.

[0081] The film-forming aid is propylene glycol methyl ether acetate.

[0082] The preparation of the porous-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder in the embodiments of this specification adopts the process route of aerogel preparation - carrier pretreatment - monomer infiltration - in-situ polymerization - post-treatment. The specific steps are as follows: Tetraethyl orthosilicate is used as the silicon source, Pluronic F127 is used as the template agent, and aminopropyltriethoxysilane is used as the amino modifier. They are mixed in a molar ratio of silicon source: template agent: amino modifier: ethanol: water = 1:0.08:0.15:12:2.5, stirred at 35 ℃ for 5 h to form a sol, and allowed to stand for aging for 30 h; then freeze-dried at -45 ℃ for 14 h, and then calcined at 500 ℃ for 2.5 h to remove the template agent, to obtain silica aminated aerogel particles with hierarchical pore structure (porous-embedded aminated aerogel particles without thermosensitive gel); the aminated aerogel particles are added to anhydrous ethanol and dispersed using a gradient ultrasonic method, that is, first dispersed at 40 kHz for 15 min, and then dispersed at 50 kHz for 15 min. min, ultrasonic power density 1.5 W / cm 2 A 6 wt% aerogel suspension was prepared. The mass ratio of aerogel to thermosensitive swelling gel monomers was controlled at 2.5:1. The molar ratio of N-isopropylacrylamide:N-tert-butylacrylamide:n-butyl methacrylate was 80:12:8. 0.2% of the total monomer mass of the crosslinking agent N,N'-methylenebisacrylamide was dissolved in deionized water to prepare a 25% solids monomer solution. The solution was soaked in a vacuum of -0.08 MPa at 25 ℃ for 2.5 h, with the vacuum released for 10 s every 30 min and then re-pressurized. The hydrogen bonding between the amino groups and the monomers promoted deep penetration of the monomers into the hierarchical pores. After releasing the vacuum, 1.0 wt% of the total monomer mass of an ammonium persulfate-sodium bisulfite solution (mass ratio of ammonium persulfate to sodium bisulfite was 1:1.2) was added, and the mixture was stirred at 40 ℃ and 130 r / min for 4 h. The product was washed 3-5 times with deionized water and then freeze-dried at -35 ℃ under a vacuum of ≤10 Pa for 14 hours. h, after being crushed and passed through a 500-mesh sieve, a composite powder with a particle size of 5~20 μm is obtained.

[0083] The preparation of chromium-modified nickel-titanium shape memory alloy fibers adopts an alloy smelting-bulk preparation-phase transformation temperature control-surface modification process. The specific steps are as follows: Weigh out pure metal raw materials with a purity ≥99% (Ni 51at%, Ti 48.5at%, Cr 0.5at%) according to the elemental ratio, and place them under a vacuum of ≤5×10 -3The ingot was smelted three times in a vacuum arc furnace at 1500 ℃ and Pa, with the ingot turned over after each smelting to ensure uniform composition. Then, a chromium-modified nickel-titanium alloy ingot was cast. The ingot was homogenized by holding at 950 ℃ for 5 h to eliminate casting stress. It was then hot-rolled four times at 850 ℃ (reduction 25-35% / pass) and cold-rolled five times at room temperature (reduction 20-30% / pass) to produce a 150 μm diameter fiber preform. The preform was solution-treated at 550 ℃ for 1.5 h, then quenched in ice water, and subsequently subjected to a stepped aging treatment: holding at 300 ℃ for 1 h, 320 ℃ for 0.5 h, and 350 ℃ for 0.5 h. The fibers were cut to 12 mm in length and immersed in a 2 wt% KH-550 ethanol solution (ethanol to water volume ratio 90:10) at 30 ℃ for 2 h with a stirring rate of 60 r / min, and then dried at 105 ℃ for 2.5 h. h, forming a modified film with a thickness of 50~100 nm, to obtain modified alloy fibers.

[0084] The preparation of a volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material employs a multi-stage dynamic mixing process: mortar pre-preparation, additive coating, intelligent functional phase dispersion, shape memory alloy fiber dispersion, and composite emulsion fusion with coarse aggregate. The specific steps are as follows: Ordinary silicate cement, fine aggregate, and mineral admixtures are weighed and added to a twin-shaft mixer. Under ambient humidity ≤60%, the mixture is dry-mixed at 25 r / min for 3 min. 60 wt% water is added and the temperature is controlled to 10℃. The mixture is then stirred at 30 r / min for 2 min to prepare a uniform mortar. Additives are then added, and the mixture is stirred at 30 r / min for 1.5 min to complete the coating. Next, pore-embedded aminated aerogel-temperature-sensitive reversible swelling gel composite powder and nano-reinforcing phase are added sequentially, each stirred at 30 r / min for 1 min to achieve uniform dispersion. Finally, chromium-modified nickel-titanium shape memory alloy fibers are added, and a 45 kHz power density of 2.0 W / cm³ is applied simultaneously while stirring at 35 r / min. 2 The mixture was ultrasonically dispersed for 3 min, with reverse stirring every 1 min; finally, the composite emulsion, the remaining 40 wt% water, and the coarse aggregate were added, and stirred at 35 r / min for 2 min at 35 kHz with a power density of 1.5 W / cm³. 2 After ultrasonic homogenization for 2 minutes, the phases are fully integrated to obtain intelligent crack-resistant concrete.

[0085] The specific implementation method is as follows:

[0086] Example 1

[0087] In this embodiment, the intelligent crack-resistant concrete material is prepared by mixing base material, intelligent functional phase, additives, composite emulsion and water in a mass ratio of 110:12:4.35:14.5:8. The base material, by weight, consists of 44 parts of P·O 42.5 cement, 32 parts of coarse aggregate, 26 parts of fine aggregate, and 8 parts of mineral admixture (meta-kaolin: silica fume mass ratio = 3:1); the intelligent functional phase consists of 6 parts of pore-embedded amino-aerogel-thermosensitive reversible swelling gel composite powder, 4.5 parts of chromium-modified nickel-titanium shape memory alloy fiber, and 1.5 parts of nano-reinforcing phase (titanium boride: graphene oxide mass ratio = 2:1); the additives consist of 0.8 parts of polycarboxylate superplasticizer, 0.05 parts of air-entraining agent, 3 parts of composite expansion agent, and 0.5 parts of UV-resistant composite agent; the composite emulsion consists of 10 parts of fluorocarbon-modified styrene-acrylic emulsion, 4 parts of acrylate-butadiene copolymer emulsion, and 0.5 parts of film-forming aid.

[0088] Example 2

[0089] In this embodiment, the intelligent crack-resistant concrete material is prepared by mixing base material, intelligent functional phase, additives, composite emulsion and water in a mass ratio of 106:12:4.35:14.7:8. The base material, by weight, consists of 42 parts of P·O 52.5 cement, 32 parts of coarse aggregate, 26 parts of fine aggregate, and 6 parts of mineral admixture (meta-kaolin: silica fume mass ratio = 2:1); the intelligent functional phase consists of 6 parts of pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder, 4.5 parts of chromium-modified nickel-titanium shape memory alloy fiber, and 1.5 parts of nano-reinforcing phase (titanium boride: graphene oxide mass ratio = 3:1); the additives consist of 0.8 parts of polycarboxylate superplasticizer, 0.05 parts of air-entraining agent, 3 parts of composite expansion agent, and 0.5 parts of UV-resistant composite agent; the composite emulsion consists of 9 parts of fluorocarbon-modified styrene-acrylic emulsion, 5 parts of acrylate-butadiene copolymer emulsion, and 0.7 parts of film-forming aid.

[0090] Example 3

[0091] In this embodiment, the intelligent crack-resistant concrete material is prepared by mixing base material, intelligent functional phase, additives, composite emulsion, and water in a mass ratio of 106:16:4.35:14.7:8. Specifically, by mass, the intelligent functional phase consists of 8 parts of pore-embedded amino-aerogel-thermosensitive reversible swelling gel composite powder, 6 parts of chromium-modified nickel-titanium shape memory alloy fiber, and 2 parts of nano-reinforcing phase (titanium boride:graphene oxide mass ratio = 3:1); the additives consist of 1.2 parts of polycarboxylate-based water-reducing agent, 0.05 parts of air-entraining agent, 3 parts of composite expansion agent, and 0.5 parts of UV-resistant composite agent; the composite emulsion consists of 10 parts of fluorocarbon-modified styrene-acrylic emulsion, 4 parts of acrylate-butadiene copolymer emulsion, and 0.7 parts of film-forming aid; the remaining components and proportions are the same as in Example 2.

[0092] Example 4

[0093] In this embodiment, the intelligent crack-resistant concrete material is prepared by mixing base material, intelligent functional phase, additives, composite emulsion, and water in a mass ratio of 106:8.5:4.35:14.7:8. Specifically, by mass, the intelligent functional phase consists of 4 parts of pore-embedded amino-aerogel-thermosensitive reversible swelling gel composite powder, 3 parts of chromium-modified nickel-titanium shape memory alloy fiber, and 1.5 parts of nano-reinforcing phase (titanium boride:graphene oxide mass ratio = 3:1); the additives consist of 0.7 parts of polycarboxylate superplasticizer, 0.05 parts of air-entraining agent, 3 parts of composite expansion agent, and 0.5 parts of UV-resistant composite agent; the remaining components and proportions are the same as in Example 2.

[0094] Example 5

[0095] In this embodiment, the intelligent crack-resistant concrete material is prepared by mixing base material, intelligent functional phase, additives, composite emulsion, and water in a mass ratio of 106:12:4.35:14.7:8. Specifically, by mass, the intelligent functional phase consists of 4 parts of pore-embedded amino-aerogel-thermosensitive reversible swelling gel composite powder, 6 parts of chromium-modified nickel-titanium shape memory alloy fiber, and 2 parts of nano-reinforcing phase (titanium boride:graphene oxide mass ratio = 3:1); the remaining components and proportions are the same as in Example 2.

[0096] To facilitate comparison of the actual effects of the volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material in the examples, several sets of comparative examples are set as follows:

[0097] Comparative Example 1

[0098] The ordinary C50 fiber concrete mix proportion is as follows: by weight, 40 parts P·O 52.5 cement, 9 parts fly ash, 3 parts silica fume, 0.1 parts polypropylene fiber, 136 parts coarse aggregate, 58 parts fine aggregate, 16 parts water, and 0.8 parts water-reducing agent. It does not contain the intelligent functional phase, additives, or composite emulsion of this invention.

[0099] Comparative Example 2

[0100] Same as Example 2, except that it does not contain any smart functional phase. The concrete material is prepared by mixing base material, additives, composite emulsion and water in a mass ratio of 106:4.35:14.7:8. Among them, by mass parts, the additives consist of 0.6 parts of polycarboxylate superplasticizer, 0.05 parts of air-entraining agent, 3 parts of composite expansion agent and 0.5 parts of UV-resistant composite agent; the remaining components and proportions are the same as in Example 2.

[0101] Comparative Example 3

[0102] Similar to Example 2, except that no pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder is added. The intelligent crack-resistant concrete material is prepared by mixing base material, intelligent functional phase, additives, composite emulsion and water in a mass ratio of 106:6:4.35:14.7:8. Among them, by mass parts, the intelligent functional phase consists of 4.5 parts of chromium-modified nickel-titanium shape memory alloy fiber and 1.5 parts of nano-reinforcing phase (titanium boride:graphene oxide mass ratio = 3:1); the remaining components and proportions are the same as in Example 2.

[0103] Comparative Example 4

[0104] Similar to Example 2, except that chromium-modified nickel-titanium shape memory alloy fibers are not added. The intelligent crack-resistant concrete material is prepared by mixing base material, intelligent functional phase, additives, composite emulsion and water in a mass ratio of 106:7.5:4.35:14.7:8. Among them, by mass parts, the intelligent functional phase consists of 6 parts of pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder and 1.5 parts of nano-reinforcing phase (titanium boride:graphene oxide mass ratio = 3:1); the remaining components and proportions are the same as in Example 2.

[0105] Comparative Example 5

[0106] Same as Example 2, except that the porous-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder is replaced with porous-embedded aminated aerogel powder without thermosensitive gel. The intelligent crack-resistant concrete material is prepared from base material, intelligent functional phase, additives, composite emulsion, and water in a mass ratio of 106:12:4.35:14.7:8. Specifically, by mass, the intelligent functional phase consists of 6 parts of porous-embedded aminated aerogel powder without thermosensitive gel, 4.5 parts of chromium-modified nickel-titanium shape memory alloy fiber, and 1.5 parts of nano-reinforcing phase (titanium boride:graphene oxide mass ratio = 3:1); the remaining components and proportions are the same as in Example 2.

[0107] To ensure the scientific validity, accuracy, and verifiability of the test data, all performance tests strictly adhered to current national standards and industry specifications. The specific test methods are as follows:

[0108] The temperature in the laboratory is controlled at (20±2)℃ and the relative humidity is not less than 50%. Concrete is mixed according to the material ratio and process.

[0109] Compressive strength test: Referring to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete" 5 Compressive strength test section, 150 mm × 150 mm × 150 mm cube specimens were formed. After standard curing for 28 days, the compressive strength of concrete was tested using a pressure testing machine with a loading rate of 0.5~0.8 MPa / s. The arithmetic mean of 3 specimens was used as the measured value.

[0110] Axial tensile test: Referring to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete" 11 Axial tensile test section, prism specimens with a molding size of 100 mm × 100 mm × 515 mm were formed. After standard curing for 28 days, the axial tensile strength and ultimate tensile value of the concrete were tested using a tensile testing machine. The arithmetic mean of 4 specimens was used as the test result.

[0111] Crack resistance testing: A concrete temperature-stress testing machine was used to cast dumbbell-shaped specimens with an effective total length of 1500 mm and a cross-section of 150 mm × 150 mm. The crack resistance at a specific temperature history was evaluated through uniaxial restraint testing (temperature history curve shown in Figure 1). Figure 1 (a) shows the crack resistance of concrete under approximately 100% constraint, and the stress development curve is as follows: Figure 1 As shown in (b), the internal temperature, strain, stress, and other indicators of the concrete were monitored over time from the start of pouring to the hydration and hardening process. The crack resistance of the concrete was evaluated using the comprehensive index of cracking temperature drop (the difference between the highest temperature and the cracking temperature). For air curing and crack observation, please refer to [references to be inserted here]. Figure 3 (a) and (b).

[0112] Freeze-thaw resistance test: A rapid freeze-thaw tester for concrete was used. According to the rapid freezing method in Part 4 of GB / T 50082-2024 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", 100 mm × 100 mm × 400 mm prism specimens were formed and cured under standard conditions for 28 days. The freeze-thaw resistance of the concrete was tested. The specimens were frozen at (-18±2)℃ for 4 hours and thawed at (5±2)℃ for 4 hours. Each cycle lasted 8 hours. The relative dynamic modulus of elasticity and mass loss rate were measured every 100 cycles. A total of 400 cycles were performed. The average value of the measurements of three specimens in one set was taken as the test result.

[0113] Temperature cycling test: A high and low temperature cycling test chamber was used to simulate temperature cycling conditions from -15℃ to 25℃. The heating / cooling rate was 4℃ / h, and the temperature was held at the target temperature for 2 hours. The duration of a single cycle was 24 hours. Referring to Part 9 of GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", early crack resistance test, concrete was poured into a flat thin-plate mold of 800mm×600mm×100mm, with a pre-installed crack inducer. Fan ventilation was started within 30 minutes of pouring. After 25 temperature cycles, the total crack area per unit area of ​​the concrete was observed and counted using a 100x reading microscope. Figure 3 As shown in (a) and (b);

[0114] Temperature-induced cyclic shape memory recovery rate test: Referring to the non-contact method in section 8.1 of GB / T 50082-2024 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", part 8 shrinkage test, the initial gauge length L0 was measured after the specimen was cured for 28 days. After 25 cycles of high and low temperature, the length L1 after deformation was measured in the -15℃ constant temperature stage, and the length L2 after recovery was measured in the 25℃ constant temperature stage. The temperature-induced cyclic shape memory recovery rate was calculated according to the formula: shape memory recovery rate (%) = (L1-L2) / (L1-L0)×100%. The average value of 3 parallel specimens in each group was taken.

[0115] Temperature-induced cyclic tensile strength retention rate and elastic modulus retention rate test: Referring to GB / T 50081-2019, prism specimens with a molding size of 100mm×100mm×515mm were subjected to 25 temperature-induced cyclic cycles after 28 days of standard curing. The tensile strength and tensile elastic modulus of the concrete were tested before and after each cycle, and the temperature-induced cyclic tensile strength retention rate and elastic modulus retention rate were calculated. The results are shown in Table 1 below.

[0116] Table 1. Concrete properties of intelligent crack-resistant concrete materials

[0117]

[0118] The results of Examples 1 and 2 show that Example 1 used low-grade P·O 42.5 cement, while Example 2 used the optimal mix ratio of this invention (high-grade P·O 52.5 cement). The compositions of the two sets of intelligent functional phases, additives, and emulsions, as well as the preparation processes, are consistent; the main differences are in the base material components and the cement grade. Data shows that compared to Example 1, Example 2 exhibits the following improvements: compressive strength increased by 19.5%, tensile strength increased by 24.4%, and ultimate tensile strength increased by 21.9%; the cracking temperature drop increased from 61.4℃ to 73.2℃, significantly enhancing the concrete's resistance to temperature cracking; after 400 freeze-thaw cycles, the specimens remained smooth and intact, without any peeling (e.g., ...). Figure 2 As shown in (c) and (d), the mass loss rate decreased from 2.15% to 1.43%, the relative dynamic modulus of elasticity increased from 85.4% to 92.5%, and the freeze-thaw resistance was significantly improved; the unit crack area under temperature change cycling decreased from 5 mm 2 / m 2 Reduced to 0 (e.g.) Figure 3 (as shown in (e)), the shape memory recovery rate, strength, and modulus retention rate are simultaneously improved. The hydration reaction of P·O 52.5 high-grade cement is more complete, the hydration product CSH gel structure is more dense, the matrix porosity is lower, and the overall stiffness and structural stability are stronger. The volume compensation, stress regulation, and crack bridging functions of the intelligent functional phase all rely on the concrete matrix to exert their effectiveness.

[0119] Comparing Examples 2-4, it can be seen that, with all component ratios fixed and only the total amount of intelligent functional phase changed: Example 2 represents the optimal amount of this invention, Example 3 represents a high amount, and Example 4 represents a low amount. In Example 3, after increasing the total amount of intelligent functional phase, the compressive and tensile strengths decreased slightly, the cracking temperature drop decreased to 69.7℃, and the freeze-thaw mass loss rate increased to 1.62%, but the shape memory recovery rate increased slightly. When the intelligent powder content is too high, the particle specific surface area is large, and local agglomeration is prone to occur during mixing, forming micro-interface defects inside the matrix, weakening the mechanical properties and resistance to thermal cracking; however, the total amount of volume compensation and stress control sites in the system is sufficient, so zero cracking can still be achieved, and the shape memory performance is slightly improved. In Example 4, the intelligent functional phase content is slightly insufficient, and various properties show a cliff-like decline, with a cracking temperature drop of only 62.3℃, far lower than the optimal group; a small number of cracks appeared in the early plate test under temperature change cycling conditions (e.g. Figure 3 (f)), the unit crack area reaches 36mm. 2 / m 2 The mass loss rate after 400 freeze-thaw cycles reached 2.64%, and the shape memory recovery rate and strength retention rate both declined significantly under temperature change cycles. This is because the intelligent functional phase is the core of this invention for achieving volume-stress synergistic regulation. Insufficient dosage leads to a severe lack of effective sites for low-temperature volume compensation, internal stress dispersion, and crack bridging, failing to suppress cracking and damage caused by temperature changes and freeze-thaw cycles at the source. Therefore, the intelligent functional phase of this invention has a clearly defined optimal dosage threshold; excessive dosage easily leads to powder agglomeration and internal defects; insufficient dosage renders the intelligent regulation function essentially ineffective.

[0120] Comparing Examples 2 and 5, Example 5, which uses a low-dosage pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder and a high-dosage chromium-modified nickel-titanium shape memory alloy fiber, shows that compared to Example 2, the cracking temperature drop in Example 5 decreased from 73.2℃ to 67.5℃, a reduction of 5.7℃; the unit cracking area increased from 0 to 12mm. 2 / m 2The mass loss rate after 400 freeze-thaw cycles increased to 1.85%, indicating a significant weakening of the freeze-thaw resistance. However, the shape memory recovery rate only decreased slightly, and the reduction in tensile strength and modulus retention was limited. The core function of the pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder is low-temperature volume compensation, capillary pore sealing, and seepage prevention and freeze-thaw resistance. It relies on the reversible swelling / shrinkage of the thermosensitive gel to offset the low-temperature shrinkage deformation of concrete and block the water penetration path, which is the key to resisting freeze-thaw and temperature-induced shrinkage. The core function of the chromium-modified nickel-titanium shape memory alloy fiber is stress offsetting, crack bridging, and shape memory. It relies on low-temperature phase transformation to generate pre-tension stress, while simultaneously forming bridging-compression constraints on microcracks, giving the material shape memory characteristics. In Example 5, reducing the amount of pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder and increasing the amount of chromium-modified nickel-titanium shape memory alloy fiber weakened the volume compensation and pore-blocking capabilities, highlighting low-temperature shrinkage and moisture penetration issues, directly leading to a decrease in thermal crack resistance and freeze-thaw resistance. However, the sufficient amount of shape memory fiber ensured that stress regulation and shape memory functions were well preserved. This demonstrates that the dual intelligent components must maintain a balanced ratio; an imbalance in a single component will disrupt the synergistic closed loop of volume regulation and stress regulation. The optimal ratio defined in this invention—6 parts pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder + 4.5 parts chromium-modified nickel-titanium shape memory alloy fiber—maximizes the synergy of both functions.

[0121] Comparative Examples 2-4 show that Comparative Example 2, lacking any intelligent components, exhibits reduced compressive and tensile strengths to 52.7 MPa and 4.3 MPa, respectively, compared to Example 2; its ultimate tensile strength is only 126 μɛ, indicating poor matrix toughness; the cracking temperature drop is only 45.8℃, and numerous cracks appear in the early plate test under temperature change cycling conditions (e.g., ...). Figure 3 (d)), the unit crack area is as high as 400 mm 2 / m 2 The mass loss rate after 400 freeze-thaw cycles reached 4.11%, with a relative dynamic elastic modulus of only 70.8%. The strength and modulus retention rates under temperature change cycles were less than 55%, and the shape memory recovery rate was only 32.4%. After losing its three core functions of volume compensation, stress offsetting, and crack bridging, concrete reverted to a traditional matrix material, with inherent defects such as temperature shrinkage, stress concentration, and freeze-thaw damage fully exposed. This also verifies that the intelligent functional phase is the core carrier for achieving active crack prevention in this invention. Comparative Example 3, retaining only memory fibers and nano-reinforcing phases, still achieved a shape memory recovery rate of 70.8%, indicating that the shape memory and stress bridging functions of the memory fibers were normal; however, the crack area increased to 212 mm². 2 / m 2The freeze-thaw mass loss rate was 3.12%, and the resistance to thermal cracking and freeze-thaw damage plummeted. Relying solely on shape memory fibers can only offset some stress and bridge existing cracks, but it cannot compensate for the low-temperature volume shrinkage of concrete, nor can it seal capillary pores or prevent moisture intrusion; therefore, low-temperature cracking and freeze-thaw damage remain unresolved. Comparative Example 4, retaining only the temperature-sensitive composite phase and the nano-reinforcing phase, saw its shape memory recovery rate drop to 47.4%, with a crack area per unit area as high as 255 mm². 2 / m 2 After temperature changes, the tensile strength and modulus retention rate were less than 70%. Thermosensitive composite powder can achieve volume compensation and pore sealing, but it cannot offset internal temperature stress; after microcracks initiate, the lack of fiber bridging constraint causes the cracks to continue to propagate. The results show that both the pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder and the chromium-modified nickel-titanium shape memory alloy fiber are indispensable; the absence of a single component will cause the corresponding function to completely fail, fully verifying the core innovation of the volume-stress dual thermosensitive synergistic self-regulating system of this invention.

[0122] Comparing Example 2 and Comparative Example 5, it can be seen that Comparative Example 5, which replaced the pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder with ordinary aminated aerogel (without embedded thermosensitive gel), while keeping the other proportions and processes completely identical, showed that compared to Example 2, its compressive and tensile strengths decreased to 55.8 MPa and 4.1 MPa, respectively; the cracking temperature drop was only 48.2℃, a decrease of 25.0℃ compared to the optimal group; and the unit cracking area reached as high as 128 mm². 2 / m 2 The shape memory recovery rate dropped to 76.2%, and the stability under freeze-thaw cycles and temperature changes deteriorated significantly. This invention employs an interlocking structure embedded within the aerogel pores. Through in-situ polymerization, the thermosensitive gel is fixed within the multi-level pores of the aminated aerogel. Relying on a combination of chemical bonding and physical confinement, the gel is prevented from detaching or leaking during mixing, freeze-thaw cycles, and high / low temperature cycling, ensuring long-term stability of the thermosensitive response. The in-situ polymerization process and interlocking microstructure are key technologies for ensuring the long-term stable function of the pore-embedded aminated aerogel-thermally sensitive reversible swelling gel composite powder, and are also important innovations that distinguish this invention from traditional blended thermosensitive materials.

[0123] Comparative Example 1 uses C50 polypropylene fiber reinforced concrete, a commonly used engineering material. It is a traditional passive crack-resistant material, relying solely on the physical reinforcement of polypropylene fibers to delay crack propagation without any intelligent control function. Comparing Example 2 and Comparative Example 1, Example 2 shows a 41.5% increase in compressive strength, a 51.4% increase in tensile strength, and an ultimate tensile strength 3.12 times that of traditional concrete, significantly improving matrix toughness. Traditional concrete exhibits only a 41.2℃ temperature drop upon cracking, and under temperature cycling conditions, it shows more cracks in early plate tests (e.g., ...). Figure 3 (c)), with a crack area of ​​up to 348 mm². 2 / m2 The material of this invention achieves zero cracking (e.g. Figure 3 (e) shows an order-of-magnitude improvement in resistance to thermal cracking; after 400 freeze-thaw cycles, traditional concrete generally exhibits spalling and exposed aggregate (e.g.) Figure 2 As shown in (a) and (b), the mass loss rate is 3.85% and the relative dynamic elastic modulus is 62.3%, which is far inferior to the material of this invention. The strength retention rate of traditional concrete after temperature change is only 50.8%, and it has no shape memory capability. Traditional polypropylene fiber concrete is a passive crack-resistant material, which can only delay the propagation of cracks after they occur, but cannot eliminate the cracking causes caused by temperature change and freeze-thaw. The intelligent concrete of this invention relies on a dual intelligent collaborative system to achieve active perception and active control, suppressing cracking from the two major sources of volume deformation and internal stress, and completing the technical upgrade from "passive protection" to "active intelligent control".

[0124] Based on the above group experiments, data comparisons, and mechanism analysis, the technical superiority of this invention in four dimensions—component design, proportion optimization, microstructure, and preparation process—can be fully verified: ① The optimal range is defined by the total amount of intelligent functional phases, the balanced ratio of pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder and chromium-modified nickel-titanium shape memory alloy fiber, with the two types of intelligent components complementing each other. ② The volume-stress dual thermosensitive synergistic system composed of pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder (volume compensation, sealing and seepage prevention) + chromium-modified nickel-titanium shape memory alloy fiber (stress offset, crack bridging, shape memory) constructs a full-cycle active crack-resistant closed loop, fundamentally solving the industry pain points of concrete temperature change and freeze-thaw cracking, demonstrating significant technical advantages. ③ Compared to traditional simple blending processes, the in-situ polymerization structure embedded in the aerogel effectively solves the problems of easy detachment and failure of thermosensitive gel, significantly improving the stability of intelligent components under long-term temperature change and freeze-thaw conditions, and extending the service life of materials. ④ Multi-stage dynamic mixing and ultrasonic-assisted dispersion processes can effectively avoid powder agglomeration and fiber entanglement, ensuring uniform distribution of each component; the process is simple to operate and can be directly integrated with existing concrete preparation processes. ⑤ Compared with traditional polypropylene fiber concrete and ordinary modified concrete, the intelligent crack-resistant concrete of this invention achieves comprehensive improvements in mechanical strength, resistance to thermal cracking, resistance to freeze-thaw cycles, resistance to temperature changes, and shape memory.

[0125] In summary, this invention, through technological innovation and process optimization, has successfully developed an intelligent crack-resistant concrete material with self-regulating temperature-stress dual response capabilities. It also proposes a refined multi-stage preparation process, providing an effective technical solution to address industry challenges such as temperature-induced cracking, poor stability, and poor durability in traditional concrete. This technology can be widely applied to concrete engineering projects in cold regions, including buildings, bridges, tunnels, and hydraulic structures, offering significant economic and social benefits and promising broad application prospects. Future research can further explore the intelligent control mechanism of the intelligent components, develop an intelligent response system that adapts to environmental changes, optimize the preparation process to reduce production costs, expand application areas, and promote the industrialization of intelligent concrete technology.

[0126] This invention verifies the optimal fit range of each distribution ratio and process parameter through multiple sets of orthogonal gradient tests. Each parameter is synergistic and indispensable; exceeding the limits of this invention will lead to varying degrees of degradation in intelligent response performance, mechanical properties, and durability. The raw material curing, on-site construction, and post-concrete curing processes not detailed in this invention are all existing conventional standardized concrete processes, which can be adapted and adjusted by those skilled in the art according to current engineering specifications.

[0127] The above embodiments are merely preferred embodiments for illustrating the content of this invention and do not constitute a limitation on the content of this invention. It should be noted that for those skilled in the art, any modifications, equivalent substitutions, optimizations, and improvements made based on the core technical principles and innovative concepts of this invention shall fall within the protection scope of this invention.

Claims

1. A volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material, characterized in that, It is formulated from base material, intelligent functional phase, additives, composite emulsion and water in a mass ratio of 90~125:8~20:2~7:9~20:6~12; Of which, by weight, The base material includes 35-50 parts of ordinary Portland cement, 25-40 parts of coarse aggregate, 20-30 parts of fine aggregate, and 4-10 parts of mineral admixture; The intelligent functional phase comprises 4-12 parts of pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder, 3-6 parts of chromium-modified nickel-titanium shape memory alloy fiber, and 0.5-2 parts of nano-reinforcing phase. The pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder is formed by in-situ polymerization of thermosensitive reversible swelling gel within the pores of aminated aerogel. The aminated aerogel has a hierarchical pore structure consisting of 2-10 nm micropores and 50-100 nm mesopores. The thermosensitive reversible swelling gel is copolymerized with N-isopropylacrylamide as the core monomer, compounded with N-tert-butylacrylamide, n-butyl methacrylate, and crosslinking agent N,N'-methylenebisacrylamide. The molar ratio of N-isopropylacrylamide, N-tert-butylacrylamide, and n-butyl methacrylate is 70~85:10~20:5~10. The amount of crosslinking agent added is 0.1~0.5% of the total mass of the monomers, i.e., the total mass of N-isopropylacrylamide, N-tert-butylacrylamide, and n-butyl methacrylate. The chromium-modified nickel-titanium shape memory alloy fiber has an elemental composition of 50-55 at% Ni, 44-49 at% Ti, and 0.2-1 at% Cr, and is modified by doping Cr to replace part of the Ni.

2. The volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material according to claim 1, characterized in that, The pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder has a particle size of 5~20 μm and a specific surface area ≥800 m². 2 / g, porosity ≥95%, surface amino grafting rate ≥85%; the thermosensitive reversible swelling gel has a swelling ratio of 25~50 times its own mass at 5℃, a shrinkage rate of ≥85% at 20℃, and a reversible swelling-shrinkage cycle count of ≥100 times.

3. The volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material according to claim 1, characterized in that, The chromium-modified nickel-titanium shape memory alloy fiber has a diameter of 80~250 μm, a length of 8~18 mm, a tensile strength ≥1150MPa, an elongation at break ≥8%, a shape memory recovery rate ≥90%, and a phase transformation temperature of -5~10 ℃. The surface of the fiber is immersed in a 1~2wt% silane coupling agent KH-550 ethanol solution at 25~30 ℃ for 1~2h, and then dried. The surface amino grafting rate is ≥80%, the interfacial bonding strength with cement-based materials is ≥2.5 MPa, and the volume ratio of ethanol to water in the ethanol solution is 90:

10.

4. The volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material according to claim 1, characterized in that, The nano-reinforcing phase is composed of nano-titanium boride and graphene oxide in a mass ratio of 3:1 to 2:1, wherein the nano-titanium boride has a particle size of 30 to 60 nm, and the graphene oxide sheet has a thickness of 1 to 5 nm and a sheet diameter of 0.5 to 2 μm.

5. The volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material according to claim 1, characterized in that, The ordinary silicate cement has a strength grade ≥42.5 and a residue of ≥5% on a 45 μm square-hole sieve; the coarse aggregate has a particle size of 5~12 mm, continuous gradation, and a thermal conductivity ≤2.0 W·m. -1 ·K -1 The mud content is ≤0.5%, and the loose bulk density is 1450~1550 kg / m³. 3 The fine aggregate particle size is 0.15~4.75 mm, with 30% being 0.15~0.60 mm, 40% being 0.60~1.18 mm, and 30% being 1.18~4.75 mm. The thermal conductivity is ≤1.8 W·m. -1 ·K -1 The mud content is ≤1.0%, and the loose bulk density is 1500~1600 kg / m³. 3 The mineral admixture is composed of metakaolin and silica fume mixed in a mass ratio of 2:1 to 3:1, wherein the metakaolin has a specific surface area ≥550m². 2 / kg, 7d activity index ≥115%, silica ash purity ≥96%, specific surface area ≥25000m² 2 / kg, volcanic ash activity index ≥120%.

6. The volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material according to claim 1, characterized in that, The composite emulsion is composed of 6-12 parts of fluorocarbon modified styrene-acrylic emulsion, 3-7 parts of acrylate-butadiene copolymer emulsion, and 0.4-1 parts of film-forming aid; the aid consists of 0.5-1.5 parts of polycarboxylate water-reducing agent, 0.02-0.1 parts of air-entraining agent, 1.5-4 parts of composite expanding agent, and 0.3-1 parts of UV-resistant composite agent.

7. The volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material according to claim 6, characterized in that, The composite expanding agent is composed of ettringite and magnesium oxide in a mass ratio of 2:

1. The composite expanding agent has a 7-day restricted expansion rate of ≥0.035% and a 28-day restricted expansion rate of ≥0.020%. The UV-resistant composite agent is composed of nano ZnO, nano CeO2 and nano TiO2 in a mass ratio of 3:2:

1. The UV shielding rate is ≥90%.

8. The volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material according to claim 1, characterized in that, The pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder is prepared by a method including the following steps: Step 1: Using tetraethyl orthosilicate as the silicon source, Pluronic F127 as the template agent, and aminopropyltriethoxysilane as the amino modifier, mix them in a molar ratio of silicon source: template agent: amino modifier: ethanol: water = 1:0.05~0.1:0.1~0.2:10~15:2~3, stir at 30~40℃ for 4~6 h to form a sol, and let it stand for aging for 24~36 h; then freeze-dry at -50~-40℃ for 12~16 h, and then calcine at 500~550℃ for 2~3 h to remove the template agent, to obtain silica amino aerogel particles with hierarchical pore structure; Step 2: Add the aminated aerogel particles prepared in Step 1 to anhydrous ethanol and disperse them using a gradient ultrasonic method, i.e., disperse at 40 kHz for 15 min, then disperse at 50 kHz for 15 min, with an ultrasonic power density of 1.5 W / cm³. 2 This forms a uniform aerogel suspension with a mass concentration of 5-8%. Step 3: Control the mass ratio of aerogel to thermosensitive reversible swelling gel monomers to be 3:1~2:

1. Mix and dissolve N-isopropylacrylamide, N-tert-butylacrylamide, n-butyl methacrylate and crosslinking agent N,N'-methylenebisacrylamide in deionized water to prepare a monomer solution with a solid content of 20%~30%. Inject the monomer solution into the aerogel suspension and place it in a vacuum tank. Immerse it for 2~3 hours under vacuum conditions of -0.08~-0.09 MPa and 25℃. During this period, release the vacuum for 10 seconds every 30 minutes and then re-pressurize. Utilize the hydrogen bonding between amino groups and monomers to promote the deep penetration of monomers into the hierarchical pores. Step 4: After releasing the vacuum, add the initiation-reduction composite solution and stir at 100-150 r / min at 35-45℃ for 3-5 h to allow the thermosensitive reversible swelling gel to polymerize in situ within the hierarchical pores of the aerogel, forming an embedded interlocking structure. The mass ratio of ammonium persulfate to sodium bisulfite in the initiation-reduction composite solution is 1:1.2-1:1.5, and the total added mass of the two solids is 0.8-1.2 wt% of the total monomer mass. Step 5: Filter the product and wash it 3-5 times with deionized water with a conductivity ≤20 μS / cm to remove the free temperature-sensitive reversible swelling gel on the surface; then freeze-dry it at a vacuum degree ≤10 Pa and -40~-30℃ for 12-16 h, pulverize it and sieve it through a 400~500 mesh to obtain the composite powder.

9. The volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material according to claim 1, characterized in that, The specific steps for preparing the chromium-modified nickel-titanium shape memory alloy fiber are as follows: Step 1: Weigh out pure metal raw materials of Ni, Ti, and Cr with a purity ≥ 99% according to the elemental ratio, and place them in a vacuum of ≤ 5 × 10⁻⁶. -3 In a vacuum arc furnace with a strength of Pa, the ingot is melted 3-4 times at 1500-1600℃, with the ingot being turned over after each melting to ensure uniform composition. The resulting chromium-modified nickel-titanium alloy ingot is then homogenized by holding it at 900-1000℃ for 4-6 hours to eliminate casting stress. Subsequently, it is hot rolled 3-4 times at 800-850℃ with a reduction of 25-35% per pass, and then cold rolled 3-5 times at room temperature with a reduction of 20-30% per pass to produce fiber preforms with a diameter of 80-250 μm. Step 2: Solution treat the fiber preform at 500~550℃ for 1~2 h, then quench it with ice water at a cooling rate of ≥100 ℃ / min to obtain a martensitic structure; then perform step aging treatment, first holding at 300℃ for 1 h, then at 320℃ for 0.5 h, and finally at 350℃ for 0.5 h. Step 3: Place the fibers cut to the specified length in a 1-2 wt% silane coupling agent KH-550 ethanol solution and soak at 25-30℃ for 1-2 h, stirring at a rate of 50-80 r / min during the process to ensure full adsorption of the coupling agent; then dry at 100-110℃ for 2-3 h to form chromium-modified nickel-titanium shape memory alloy fibers covered by a modified film with a thickness of 50-100 nm.

10. The method for preparing a volume-stress temperature-sensitive self-regulating intelligent crack-resistant concrete material according to claim 1, characterized in that, The steps are as follows: Step 1: Weigh the ordinary Portland cement, fine aggregate, and mineral admixtures from the base material. Under conditions of ambient humidity ≤60%, add them to the mixer and dry mix at 25~30 r / min for 3~5 min until the mixture is uniform in color. Then add 60 wt% water, with the water temperature controlled at 5~20℃, adjust the mixer speed to 30~35 r / min, and mix for 2~3 min to prepare a uniform mortar with a slump ≥200 mm. Step 2: Add additives to the mortar and stir at 25-30 r / min for 1-2 min to allow the additive molecules to be uniformly adsorbed onto the surface of each particle in the mortar, forming a particle-additive coating structure. Step 3: First, add the pore-embedded aminated aerogel-thermosensitive reversible swelling gel composite powder and stir at 30~35 r / min for 1~2 min. Then add the nano-reinforcing phase and continue stirring for 1~2 min. Utilize the synergistic effect of the surface activity of nanoparticles and the amino groups on the aerogel surface to promote uniform dispersion of the composite powder and ensure no obvious agglomerates. Step 4: Add chromium-modified nickel-titanium shape memory alloy fibers, increase the rotation speed to 35~40 r / min, and simultaneously apply a power density of 2.0 W / cm² at a frequency of 40~50 kHz. 2 Ultrasonic-assisted dispersion for 2-3 minutes, with the stirring direction reversed every 1 minute to prevent fiber entanglement and aggregation; Step 5: Add the composite emulsion, the remaining 40 wt% water, and the coarse aggregate from the base material. Stir and mix, adjusting the speed to 30-35 r / min and stirring for 2-3 minutes. Then, stir at a frequency of 35-45 kHz and a power density of 1.5 W / cm³. 2 The mixture is homogenized by an ultrasonic homogenizer for 1-2 minutes, during which the rotation speed is maintained at 35-40 r / min to ensure that the phases are fully integrated, and finally intelligent crack-resistant concrete with volume-stress temperature-sensitive self-regulation is obtained.

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