Intelligent long-acting gradient self-repairing material, preparation method and application thereof

Abstract

The application discloses a kind of intelligent long-acting gradient self-repairing materials and preparation method and application thereof, including quick response type self-repairing agent 3-10 parts, medium speed sustained microcapsule 8-20 parts, super long-acting microorganism capsule 5-15 parts, cement-based cementing material 100-200 parts, fine aggregate 200-400 parts, water reducing agent 1-5 parts and water 60-120 parts by weight fraction.The application integrates complexation crystallization, microcapsule slow-release and microbial mineralization triple synergistic repair mechanism, realizes the dual matching of spatial distribution and response timing;At the same time, through three-layer gradient protection shell structure design, effectively resist the erosion of high alkaline environment of concrete, guarantee the long-term activity of microorganism, and then give concrete crack repeated self-repairing ability, significantly improve the durability and safety of service structure.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to an intelligent long-lasting gradient self-healing material, its preparation method, and its application. Background Technology

[0002] Concrete, as the most widely used building material, is inherently a porous and brittle system. During long-term service, under the combined effects of multiple factors such as temperature stress, external loads, shrinkage deformation, and uneven settlement, concrete structures are highly susceptible to the formation of microcracks, which gradually expand into macroscopic cracks. The formation of cracks not only provides rapid penetration channels for corrosive media such as moisture, chloride ions, and sulfate ions, leading to a deterioration in the structure's impermeability, but also accelerates the corrosion process of internal steel reinforcement, seriously threatening the safety, durability, and service life of infrastructure. Therefore, endowing concrete materials with intelligent self-healing capabilities that can autonomously sense and repair cracks has become a core research direction in the field of building materials to ensure the long-term safety of critical infrastructure.

[0003] Waterproof concrete, a widely used structural self-waterproofing material in underground engineering, water conservancy facilities, tunnels, and marine engineering, directly impacts the long-term reliability of structures under complex service environments due to its self-healing crack repair capabilities. In recent years, with the implementation of the national standard GB / T 18445—2025 "Cement-based Penetrating Crystalline Waterproofing Materials," the technical requirement for "self-healing capability" in rigid waterproofing materials for concrete structures has been explicitly stated at the national level for the first time. This signifies an accelerated shift in waterproofing technology from the traditional "passive barrier" to "active repair," providing clear policy guidance and evaluation criteria for the technological upgrading of rigid waterproofing materials. Against this backdrop, developing waterproof concrete materials with efficient, stable, and long-lasting crack self-healing functions has become a research hotspot and a key technological breakthrough in this field.

[0004] Currently, the main technical routes covered are as follows: (1) Chemical self-healing system based on polymer complexation, such as the impermeable concrete disclosed in CN121913739A, which uses polyacrylic acid and polyaspartic acid as calcium ion complexing carriers, which migrate to the cracks through concentration gradient, and react with silicate and carbonate in the pore fluid to generate hydrated calcium silicate and calcium carbonate precipitates to fill the cracks; (2) Bio-self-healing system based on microbial-induced calcium carbonate deposition, such as the composite microbial gradient slow-release self-healing method disclosed in CN122212583A, which uses PLA-HA composite membrane to construct a double-layer protective structure to achieve gradient slow release of bacterial powder, and C The self-healing particles of Bacillus pasteurellii loaded on modified fibers disclosed in N119100637A all belong to this technology branch; (3) Physical self-healing systems based on the release of repair agents by the rupture of two-component microcapsules, such as the waterproof repair resin material disclosed in CN114790088A, which uses epoxy resin microcapsules and cement microcapsules to release repair components when the capsule wall ruptures due to external stress; (4) Rigid waterproofing systems based on the penetration crystallization reaction, such as the cement-based penetration crystallization self-healing waterproof material disclosed in CN114656211A, which uses alkali metal salts and silicate metal salts as active components and relies on crystallization precipitation to block capillary channels.

[0005] However, the above-mentioned existing technologies still have several common and individual technical defects in practical applications: (1) Chemical precipitation system is only effective for microcracks below 0.2 mm. Microbial mineralization repair is slow and a single mechanism is difficult to achieve cross-scale repair from micron-level initiation cracks to millimeter-level expansion cracks; (2) The consumption rate of repair agent in the existing system is uncontrollable. After a large amount of repair agent is consumed in the early cracks, the repair ability will be significantly reduced in the later stage, and the complete time-series coverage of "rapid response - medium speed continuous - ultra-long duration" is not achieved; (3) The current self-healing functional components are mostly uniformly distributed in the concrete matrix. The functional gradient configuration is not based on the differences in the initiation time and width characteristics of cracks in different depth areas, resulting in low repair efficiency and resource utilization; (4) Existing microbial protection methods mostly rely on a single shell. During long-term service in the high alkaline environment of concrete, the microorganisms will face the risk of inactivation after the shell degrades; (5) Most existing technologies are only for one-time or limited repair. After the repair components are exhausted, the material loses its self-healing ability and does not have a cyclic self-healing function similar to the "damage-repair-re-damage-re-repair" cycle of organisms.

[0006] To address the aforementioned technical bottlenecks, there is an urgent need to develop a novel self-healing waterproof concrete system that integrates multi-mechanism synergistic response, time-controlled release, spatial gradient configuration, and long-term cyclic repair capabilities, so as to fully meet the pressing needs of modern infrastructure for the intelligent self-healing performance of concrete materials. Summary of the Invention

[0007] Based on the shortcomings of the existing technologies, this invention provides an intelligent long-lasting gradient self-healing material, its preparation method, and its application. This material integrates a triple synergistic repair mechanism of complexation crystallization, microcapsule sustained release, and microbial mineralization, achieving a dual match between spatial distribution and response timing. At the same time, through the three-layer gradient protective shell structure design, it effectively resists the erosion of the highly alkaline environment of concrete, ensures the long-term activity of microorganisms, and thus endows concrete cracks with the ability to repeatedly self-repair, significantly improving the durability and safety of the service structure.

[0008] The technical solution adopted by the present invention to solve the above-mentioned technical problem is as follows: The present invention discloses a smart long-lasting gradient self-healing material comprising, by weight, 3-10 parts of a fast-response self-healing agent, 8-20 parts of a medium-speed sustained-release microcapsule, and 5-15 parts of an ultra-long-lasting microbial capsule.

[0009] Preferably, the rapid-response self-healing agent is a complex crystalline type, comprising, by weight, 20-40 parts sodium silicate, 10-20 parts glycine, 20-40 parts calcium ion supplement, and 5-15 parts reaction promoter; the calcium ion supplement includes calcium hydroxide or calcium lactate.

[0010] Preferably, the medium-speed sustained-release microcapsule comprises a capsule wall and a capsule core; the capsule wall is a semi-permeable polymer material, including ethyl cellulose or polylactic acid, with a wall thickness of 3-8 μm and an average particle size of 100-300 μm; the capsule core material comprises, by weight, 30-50 parts of polyacrylic acid, 20-40 parts of polyaspartic acid, 10-20 parts of calcium ion supplement, and 5-10 parts of reaction promoter, wherein the calcium ion supplement includes calcium lactate or calcium acetate, and the reaction promoter includes one or more of diisopropanolamine monoethanolamine, diisopropanolamine monoethanolamine, or zinc salt.

[0011] Preferably, the ultra-long-lasting microbial capsule has a three-layer gradient protective shell structure, consisting of a nutrient protection layer, a pH buffer layer, and a strength layer from the inside out. The nutrient protection layer is composed of nutrients, a calcium source, and urea, and has a thickness of 10–20 μm. The pH buffer layer is composed of sodium silicate and calcium carbonate composite, and has a thickness of 15–30 μm. The strength layer is a polylactic acid-glycolic acid copolymer or a polylactic acid-caprolactone copolymer, and has a thickness of 20–40 μm. The nutrient protection layer contains a core, which is a lyophilized microbial powder, comprising 5–15 parts by weight, including lyophilized Pseudomonas aeruginosa or lyophilized Bacillus pasteurellii.

[0012] The present invention relates to the application of a smart long-lasting gradient self-healing material in concrete, wherein the concrete comprises, by weight, 16-45 parts of the smart long-lasting gradient self-healing material, 100-200 parts of cement, 200-400 parts of fine aggregate, 1-5 parts of water-reducing agent, and 60-120 parts of water.

[0013] Preferably, the cement is PO 42.5 grade silicate cement.

[0014] Preferably, the fine aggregate is medium sand with a fineness modulus of 2.5 to 2.7.

[0015] Preferably, the water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent.

[0016] Another technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned intelligent long-lasting gradient self-healing material, comprising the following steps: S01. Preparation of rapid response self-healing agent: Weigh sodium silicate, glycine, calcium ion supplement and reaction promoter according to the ratio, put them into a high-speed mixer, mix for 10 to 20 minutes at a speed of 300 to 500 r / min until uniform, pass through a 200 mesh sieve to obtain rapid response self-healing agent, seal and package for later use. S02, Preparation of medium-speed continuous microcapsules: Ethyl cellulose or polylactic acid is dissolved in dichloromethane to form an oil phase, and polyacrylic acid, polyaspartic acid, calcium ion supplement and reaction promoter are dissolved in water to form an aqueous phase. The medium-speed continuous microcapsules are prepared by oil-aqueous phase emulsification-solvent evaporation method with a stirring rate of 400-600 r / min. S03. Preparation of ultra-long-lasting microbial capsules: Bacillus cereus or Bacillus pasteurellii are inoculated onto a culture medium, and nutrients, calcium source, and urea are added. After culturing at 35℃ for 24 hours, a bacterial solution is obtained. The bacterial solution is collected and freeze-dried to obtain a lyophilized microbial powder. Using the sharp-pore method or layer-by-layer self-assembly technology, a nutrient protection layer, a pH buffer layer, and a strength layer are sequentially coated to obtain ultra-long-lasting microbial capsules. S04. Weigh cement, fine aggregate, water-reducing agent and water according to the design mix ratio, and mix them into a uniform concrete matrix. Premix the fast-response self-healing agent, medium-speed continuous microcapsules and ultra-long-lasting microbial capsules with the matrix concrete according to the gradient distribution in the thickness direction of the concrete section. Pour the concrete in layers in sequence, and vibrate and compact each layer and smooth it. The interval between each layer should not exceed 30 minutes. After natural curing for 28 days, the gradient-response long-lasting self-healing waterproof concrete is obtained.

[0017] In S04, the gradient distribution in the thickness direction of the concrete section includes a surface layer, a middle layer, and a core layer. The surface layer has a thickness of 0–30 mm, the middle layer has a thickness of 30–70 mm, and the core layer has a thickness of 70 mm or more. The layers are connected by a transition layer with a thickness of 10–20 mm.

[0018] Compared with the prior art, the advantages of the present invention are: This invention utilizes a triple mechanism of complexation crystallization, microencapsulation sustained release, and microbial mineralization to synergistically cover cracks with a width ranging from 0.05 to 1.0 mm, significantly outperforming the coverage of single mechanisms. Through a three-stage release sequence design, the repair effect lasts for over 90 days after crack appearance, covering the entire process of concrete crack initiation and expansion. A differentiated gradient distribution process enables rapid and immediate repair of surface cracks, while the core layer provides a continuous self-repair reserve for decades of service life. A three-layer gradient protective shell structure—a nutrient layer, a pH buffer layer, and a strength layer—ensures the long-term survival of microorganisms in the highly alkaline environment of concrete, overcoming the shortcomings of existing technologies where microorganisms are easily inactivated. A smart response mechanism of water-awakening and drying-dormant allows the material to continue functioning in multiple cycles of cracking-water-repair, achieving true intelligent and long-lasting self-repair. Detailed Implementation

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

[0020] This invention discloses an intelligent, long-lasting gradient self-healing material for use in concrete. By weight, it comprises 3-10 parts of a fast-response self-healing agent, 8-20 parts of a medium-speed sustained-release microcapsule, 5-15 parts of an ultra-long-lasting microbial capsule, 100-200 parts of cement, 200-400 parts of fine aggregate, 1-5 parts of a water-reducing agent, and 60-120 parts of water. Wherein: raw materials The rapid-response self-healing agent is a complex crystalline type, comprising, by weight, 20-40 parts sodium silicate, 10-20 parts glycine or aminoacetic acid, 20-40 parts calcium ion supplement, and 5-15 parts reaction promoter; the calcium ion supplement includes calcium hydroxide or calcium lactate. Upon contact with water, the active substances are rapidly activated, penetrating along the capillary pores of the concrete and continuously reacting with calcium ions in the concrete to generate calcium carbonate and CSH gel crystals, automatically filling and sealing microcracks within 0.6 mm. This reaction is completed rapidly within 0-7 days after the crack appears, achieving rapid and immediate crack repair.

[0021] The medium-speed sustained-release microcapsule comprises a capsule wall and a core. The capsule wall is a semi-permeable polymer material, including ethyl cellulose or polylactic acid, with a wall thickness of 3–8 μm and an average particle size of 100–300 μm. The core material, by weight, comprises 30–50 parts of polyacrylic acid with a molecular weight of 2000–5000, 20–40 parts of polyaspartic acid with a molecular weight of 3000–6000, 10–20 parts of calcium ion supplement, and 5–10 parts of reaction promoter. The calcium ion supplement includes calcium lactate or calcium acetate, and the reaction promoter includes one or more of diisopropanolamine, monoisopropanolamine, or zinc salt. After cracks appear, water seeps into the cracks and comes into contact with the microcapsules. The polylactic acid or ethyl cellulose in the capsule wall gradually forms permeation channels under the swelling effect of water. The complexed polymers in the capsule core, such as polyacrylic acid and polyaspartic acid, migrate directionally to the depth of the cracks driven by the concentration gradient. They undergo substitution reactions with silicate and carbonate ions in the pore fluid to generate hydrated calcium silicate and calcium carbonate precipitates that fill the cracks. At the same time, the polymers are released again to enter the next cycle, achieving continuous slow-release repair within 7 to 28 days.

[0022] The ultra-long-lasting microbial capsule features a three-layer gradient protective shell structure. From the inside out, it consists of an inner nutrient protection layer, a middle pH buffer layer, and an outer strength layer, each 10–20 μm thick. The nutrient protection layer comprises nutrients, a calcium source, and urea. The nutrients are beef extract and peptone, and the calcium source is calcium acetate or calcium lactate, providing the necessary nutrient matrix for microbial germination and mineralization. The pH buffer layer, composed of sodium silicate and calcium carbonate, is 15–30 μm thick and can consume OH- in the highly alkaline pH 12–13 environment of concrete. - Ions create a localized pH 8-10 microenvironment around the microcapsules, protecting microbial activity. The strength layer is made of polylactic acid-glycolic acid copolymer (PLGA) or polylactic acid-caprolactone copolymer, with a thickness of 20-40 μm. Inside the protective shell is a core, which, by weight, comprises 5-15 parts of lyophilized microbial powder, 10-30 parts of nutrients, 5-15 parts of calcium source, and 10-30 parts of urea, providing mechanical strength protection. The nutrient protective layer also contains a core, which, by weight, comprises 5-15 parts of mineralizing lyophilized microbial powder, 10-30 parts of nutrients, 5-15 parts of calcium source, and 10-30 parts of urea. The lyophilized microbial powder is either *Bacillus anthracis* or *Bacillus pasteurellis*. If cracks appear more than 28 days later, the outer strength layer ruptures as the cracks propagate, exposing the middle pH buffer layer to the concrete pore fluid, which then depletes OH-. - Ions create a suitable microenvironment for microbial survival. Microbial spores in the inner nutrient protective layer are awakened upon contact with water, begin to proliferate, and secrete urease. This urease catalyzes the hydrolysis of urea to produce carbonate ions, which combine with calcium ions to form calcium carbonate precipitate, continuously filling the cracks. After drying, the microorganisms enter a dormant state again, only to be awakened once more upon contact with water, achieving ultra-long-term cyclical repair.

[0023] The cement is PO 42.5 grade Portland cement.

[0024] The fine aggregate is medium sand with a fineness modulus of 2.5 to 2.7.

[0025] The water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent.

[0026] Preparation method Includes the following steps: S01. Preparation of rapid response self-healing agent: Weigh sodium silicate, glycine, calcium ion supplement and reaction promoter according to the ratio, put them into a high-speed mixer, mix for 10 to 20 minutes at a speed of 300 to 500 r / min until uniform, pass through a 200 mesh sieve to obtain rapid response self-healing agent, seal and package for later use. S02, Preparation of medium-speed continuous microcapsules: Ethyl cellulose or polylactic acid is dissolved in dichloromethane to form an oil phase, and polyacrylic acid, polyaspartic acid, calcium ion supplement and reaction promoter are dissolved in water to form an aqueous phase. The medium-speed continuous microcapsules are prepared by oil-aqueous phase emulsification-solvent evaporation method with a stirring rate of 400-600 r / min. S03. Preparation of ultra-long-lasting microbial capsules: Bacillus cereus or Bacillus pasteurellii are inoculated onto a culture medium, and nutrients, calcium source, and urea are added. After culturing at 35℃ for 24 hours, a bacterial solution is obtained. The bacterial solution is collected and freeze-dried to obtain a lyophilized microbial powder. Using the sharp-pore method or layer-by-layer self-assembly technology, a nutrient protection layer, a pH buffer layer, and a strength layer are sequentially coated to obtain ultra-long-lasting microbial capsules. S04. Weigh cement, fine aggregate, water-reducing agent and water according to the design mix ratio, and mix them into a uniform concrete matrix. Premix the fast-response self-healing agent, medium-speed continuous microcapsule and ultra-long-lasting microbial capsule with the matrix concrete according to the gradient ratio of each layer. Use a layered pouring process to pour the core layer concrete, the middle layer concrete and the surface layer concrete in sequence. Each layer is vibrated to compact and smoothed. The interval between pouring layers shall not exceed 30 minutes. After natural curing for 28 days, the gradient-response long-lasting self-healing waterproof concrete is obtained.

[0027] This invention employs a layered material distribution process during concrete pouring to achieve a gradient distribution of three self-healing functional components along the thickness of the concrete cross-section. These components include a surface layer, a middle layer, and a core layer. The surface layer has a thickness of 0–30 mm, the middle layer 30–70 mm, and the core layer over 70 mm. Surface cracks appear earliest and are the widest, requiring rapid and immediate repair capabilities; therefore, a rapid-response type should constitute the largest proportion. Core layer cracks appear latest, requiring ultra-long-term self-healing capacity reserves; therefore, ultra-long-lasting microbial capsules should constitute the largest proportion. Each layer is connected by a transition layer with a thickness of 10–20 mm to avoid interfacial performance mismatches caused by abrupt component changes.

[0028] The three repair components, released at different times after cracks appear, form a continuous and complementary repair process. The fast-response self-healing agent has an effective crack width of 0.05–0.6 mm, an activation period of 0–7 days, and a fast repair speed; the medium-speed sustained-release microcapsule has an effective crack width of 0.05–0.5 mm, an activation period of 7–28 days, and a medium repair speed; the ultra-long-lasting microbial capsule has an effective crack width of 0.1–0.8 mm, an activation period of more than 28 days, and a slow repair speed.

[0029] The combined effect of spatial and temporal gradients achieves a spatial and temporal match in the concrete repair process. The high-concentration, fast-response surface layer ensures rapid repair of cracks as soon as they appear; the balanced configuration in the middle layer provides a continuous transition of repair capabilities; and the high-concentration, ultra-long-lasting microbial capsules in the core layer provide a continuous reserve of self-healing capabilities for the decades-long service life of the concrete.

[0030] For the following examples and comparative examples, the fast-response self-healing agent was prepared using sodium silicate, glycine, and calcium lactate; the medium-speed sustained-release microcapsules were prepared using ethyl cellulose capsules with an average particle size of 200 μm; the ultra-long-lasting microbial capsules used a PLGA three-layer shell with an average particle size of 300 μm, the nutrient protection layer used beef extract, peptone, calcium lactate, and urea, the pH buffer layer used sodium silicate and calcium carbonate, and the strength layer used PLGA; the cement was PO 42.5 grade silicate cement; the fine aggregate was medium sand with a fineness modulus of 2.6; the water-reducing agent was a polycarboxylate-based high-efficiency water-reducing agent; and the water was tap water. Example 1

[0031] 6 parts of fast-response self-healing agent, 14 parts of medium-speed continuous microcapsule, 10 parts of ultra-long-lasting microbial capsule, 150 parts of cement, 300 parts of fine aggregate, 2 parts of water-reducing agent, and 75 parts of water.

[0032] A layered material placement process is adopted during concrete pouring to achieve a gradient distribution of the three self-healing functional components along the thickness of the concrete section, including a surface layer, a middle layer, and a core layer. The gradient distribution scheme is as follows: Surface layer (0-30mm): 3.6 parts of fast-response self-healing agent, 4.2 parts of medium-speed continuous microcapsule, and 1.0 part of ultra-long-lasting microbial capsule; Middle layer (30-70mm): 1.5 parts of fast-response self-healing agent, 7.0 parts of medium-speed continuous microcapsules, and 2.5 parts of ultra-long-lasting microbial capsules; Core layer (70mm and above): 0.9 parts of fast-response self-healing agent, 2.8 parts of medium-speed continuous microcapsule, and 6.5 parts of ultra-long-lasting microbial capsule.

[0033] The preparation method is as follows: (1) Preparation of rapid response self-healing agent: Weigh sodium silicate, glycine, calcium lactate and reaction promoter according to the ratio, put them into a high-speed mixer, mix for 15 minutes at 400 r / min until uniform, pass through a 200 mesh sieve, seal and package for later use.

[0034] (2) Preparation of medium-speed continuous microcapsules: Ethyl cellulose was dissolved in dichloromethane to form an oil phase, and polyacrylic acid with a molecular weight of 3500, polyaspartic acid with a molecular weight of 4500, calcium lactate and reaction promoter were dissolved in water to form an aqueous phase. The medium-speed continuous microcapsules were prepared by oil-aqueous phase emulsification-solvent evaporation method with a stirring rate of 500 r / min.

[0035] (3) Preparation of ultra-long-lasting microbial capsules: Bacillus cereus was inoculated onto a culture medium, and nutrients, calcium source and urea were added. After culturing at 35°C for 24 hours, the bacterial solution was collected and freeze-dried to obtain microbial freeze-dried powder. The inner nutrient protection layer, the middle pH buffer layer and the outer strength layer were sequentially coated by the sharp-pore method to obtain ultra-long-lasting microbial capsules.

[0036] (4) Preparation of gradient-responsive long-lasting self-healing concrete: Weigh cement, fine aggregate, water-reducing agent and water according to the design mix ratio and mix them into a uniform concrete matrix. Premix the three self-healing components with the matrix concrete according to the gradient mix ratio of each layer. Use a layered pouring process: first pour the core layer concrete with a thickness of 80mm and vibrate it to make it dense; then pour the middle layer concrete with a thickness of 40mm and vibrate it to make it dense; finally pour the surface layer concrete with a thickness of 30mm, vibrate it to make it dense and smooth it. The interval between each layer pouring is 20min. After natural curing for 28 days, the performance is tested. Example 2

[0037] This embodiment provides a formulation suitable for scenarios with high impermeability requirements: 8 parts of a fast-response self-healing agent, 16 parts of a medium-speed sustained-release microcapsule, 12 parts of an ultra-long-lasting microbial capsule, 180 parts of silicate cement, 280 parts of fine aggregate, 3 parts of water-reducing agent, and 80 parts of water. The gradient distribution scheme and preparation method are the same as in Embodiment 1.

[0038] Comparative Example 1: This was set up to verify the coupling effect between gradient distribution and functional response rate. The total dosage of Comparative Example 1 was the same as that of Example 1, with 10 parts of each of the three self-healing components: fast-response self-healing agent, medium-speed sustained-release microcapsule, and ultra-long-lasting microbial capsule, which were uniformly distributed in concrete. The layered gradient distribution process was not used, and the other components and preparation methods were strictly consistent with those of Example 1.

[0039] Comparative Example 2: This was set up to verify the necessity of the three-stage release sequence. In Comparative Example 2, the fast-response self-healing agent and the ultra-long-lasting microbial capsules were removed, and only the medium-speed sustained-release microcapsules were retained, with a dosage of 30 parts. The remaining components and preparation methods were strictly consistent with those in Example 1.

[0040] Comparative Example 3: This was set up to verify the effectiveness of the three-layer gradient protective shell in protecting microbial activity. In Comparative Example 3, the ultra-long-lasting microbial capsules were replaced with an equal weight proportion of unprotected, lyophilized microbial powder, which was directly incorporated into the concrete. All other components and preparation methods were strictly consistent with those in Example 1.

[0041] The self-healing waterproof concretes prepared in Examples 1-2 and Comparative Examples 1-3 were subjected to performance tests according to standards, and the results are summarized in Table 1.

[0042] Table 1 lists the performance test results of Examples 1-2 and Comparative Examples 1-3.

[0043]

[0044] A comparison of Example 1 and Comparative Example 1 shows that in the uniform distribution mode of Comparative Example 1, the surface repair agent concentration is insufficient, resulting in an inability to respond quickly after cracks appear, with a 7-day repair rate of only 42%; the internal repair agent is consumed prematurely, leading to a decrease in long-term repair capability, with a 90-day repair rate of only 70%. In contrast, in the gradient distribution mode of Example 1, the high concentration of fast-response self-healing agent on the surface ensures rapid response, achieving a 7-day repair rate of 78%, while the high concentration of ultra-long-lasting microbial capsules inside guarantees long-term repair capability, with a 90-day repair rate of 94%. This demonstrates that the coupled configuration of spatial gradient and response rate is key to achieving rapid surface response and long-term internal reserve.

[0045] A comparison of Example 1 and Comparative Example 2 shows that, under the single medium-rate slow-release mechanism of Comparative Example 2, the amount of repair agent released in the early stage of crack appearance is insufficient, with a repair rate of only 25% after 7 days, limited crack width coverage (maximum 0.3 mm), and a limited number of repair attempts. In contrast, under the three-stage release sequence of Example 1, the rapid-response type provides a rapid response within 0–7 days, the medium-rate sustained-release type provides continuous action within 7–28 days, and the ultra-long-lasting type provides long-term effectiveness for more than 28 days, covering cracks of all sizes from 0.05 to 1.0 mm. This demonstrates that the three-stage release sequence of rapid—medium-rate—ultra-long-lasting effect is the core of achieving gradient repair of cracks throughout their entire life cycle.

[0046] A comparison of Example 1 and Comparative Example 3 shows that exposed microorganisms without a protective layer rapidly deactivate in the highly alkaline environment of concrete, with a survival rate of only 10% after 28 days and virtually no repair capability after 90 days. In contrast, the microbial capsule with a three-layer gradient protective shell in Example 1 maintained an 85% survival rate after 28 days and a 94% repair rate after 90 days. This demonstrates that a three-layer gradient protective shell consisting of a nutrient layer, a pH buffer layer, and a strength layer is a necessary technical means to ensure the long-term activity of microorganisms.

[0047] Data from Examples 1 and 2 show that all performance indicators of the present invention are significantly better than those of the comparative example. The repair rate is not less than 78% in 7 days, not less than 90% in 28 days, and not less than 94% in 90 days. The maximum repairable crack width is 1.0 mm. The recovery rate of impermeability pressure after repair is not less than 85%. The number of repeated repairs is not less than 5 times. This confirms its high applicability and reliability as a gradient-responsive long-lasting self-healing material for waterproof concrete.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A smart, long-lasting gradient self-healing material, characterized in that: The ingredients are 3-10 parts by weight of a fast-response self-healing agent, 8-20 parts of a medium-speed sustained-release microcapsule, and 5-15 parts of an ultra-long-lasting microbial capsule.

2. The intelligent long-lasting gradient self-healing material according to claim 1, characterized in that: The rapid-response self-healing agent is a complex crystalline type, comprising, by weight, 20-40 parts sodium silicate, 10-20 parts glycine, 20-40 parts calcium ion supplement, and 5-15 parts reaction promoter; the calcium ion supplement includes calcium hydroxide or calcium lactate, and the reaction promoter includes one or more of diisopropanolamine monoethanolamine, diisopropanolamine monoethanolamine, or zinc salt.

3. The intelligent long-lasting gradient self-healing material according to claim 1, characterized in that: The medium-speed sustained-release microcapsule comprises a capsule wall and a capsule core; the capsule wall is a semi-permeable polymer material, including ethyl cellulose or polylactic acid, with a wall thickness of 3-8 μm and an average particle size of 100-300 μm; the capsule core material comprises, by weight, 30-50 parts of polyacrylic acid, 20-40 parts of polyaspartic acid, 10-20 parts of calcium ion supplement and 5-10 parts of reaction promoter, wherein the calcium ion supplement includes calcium lactate or calcium acetate.

4. The intelligent long-lasting gradient self-healing material according to claim 1, characterized in that: The ultra-long-lasting microbial capsule has a three-layer gradient protective shell structure, consisting of a nutrient protection layer, a pH buffer layer, and a strength layer from the inside out. The nutrient protection layer is composed of nutrients, a calcium source, and urea, with a thickness of 10–20 μm. The pH buffer layer is composed of sodium silicate and calcium carbonate composite, with a thickness of 15–30 μm. The strength layer is a polylactic acid-glycolic acid copolymer or a polylactic acid-caprolactone copolymer, with a thickness of 20–40 μm. The nutrient protection layer contains a core, which is a lyophilized microbial powder, with a weight ratio of 5–15 parts. The lyophilized microbial powder includes lyophilized Pseudomonas aeruginosa or lyophilized Bacillus pasteurellii.

5. The application of the intelligent long-lasting gradient self-healing material according to any one of claims 1-4 in concrete, characterized in that: The concrete comprises, by weight, 16-45 parts of intelligent long-lasting gradient self-healing material, 100-200 parts of cement, 200-400 parts of fine aggregate, 1-5 parts of water-reducing agent, and 60-120 parts of water.

6. The application of the intelligent long-lasting gradient self-healing material according to claim 5 in concrete, characterized in that: The cement is PO 42.5 grade silicate cement.

7. The application of the intelligent long-lasting gradient self-healing material according to claim 5 in concrete, characterized in that: The fine aggregate is medium sand with a fineness modulus of 2.5 to 2.

7.

8. The application of the intelligent long-lasting gradient self-healing material according to claim 5 in concrete, characterized in that: The water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent.

9. A method for preparing a smart, long-lasting gradient self-healing material according to any one of claims 1 to 4, characterized in that... Includes the following steps: S01. Preparation of rapid response self-healing agent: Weigh sodium silicate, glycine, calcium ion supplement and reaction promoter according to the ratio, put them into a high-speed mixer, mix for 10 to 20 minutes at a speed of 300 to 500 r / min until uniform, pass through a 200 mesh sieve to obtain rapid response self-healing agent, seal and package for later use. S02, Preparation of medium-speed continuous microcapsules: Ethyl cellulose or polylactic acid is dissolved in dichloromethane to form an oil phase, and polyacrylic acid, polyaspartic acid, calcium ion supplement and reaction promoter are dissolved in water to form an aqueous phase. The medium-speed continuous microcapsules are prepared by oil-aqueous phase emulsification-solvent evaporation method with a stirring rate of 400-600 r / min. S03. Preparation of ultra-long-lasting microbial capsules: Bacillus cereus or Bacillus pasteurellii are inoculated onto a culture medium, and nutrients, calcium source, and urea are added. After culturing at 35℃ for 24 hours, a bacterial solution is obtained. The bacterial solution is collected and freeze-dried to obtain a lyophilized microbial powder. Using the sharp-pore method or layer-by-layer self-assembly technology, a nutrient protection layer, a pH buffer layer, and a strength layer are sequentially coated to obtain ultra-long-lasting microbial capsules. S04. Weigh cement, fine aggregate, water-reducing agent and water according to the design mix ratio, and mix them into a uniform concrete matrix. Premix the fast-response self-healing agent, medium-speed continuous microcapsules and ultra-long-lasting microbial capsules with the matrix concrete according to the gradient distribution in the thickness direction of the concrete section. Pour the concrete in layers in sequence, and vibrate and compact each layer and smooth it. The interval between each layer should not exceed 30 minutes. After natural curing for 28 days, the gradient-response long-lasting self-healing waterproof concrete is obtained.

10. The method for preparing a smart long-lasting gradient self-healing material according to claim 9, characterized in that: In S04, the gradient distribution in the thickness direction of the concrete section includes a surface layer, a middle layer, and a core layer. The surface layer has a thickness of 0–30 mm, the middle layer has a thickness of 30–70 mm, and the core layer has a thickness of 70 mm or more. The layers are connected by a transition layer with a thickness of 10–20 mm.

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