A concrete nano-penetrating sealing agent and its construction method

Abstract

This invention relates to the technical field of engineering sealants, and more particularly to a concrete nano-penetrating sealant and its construction method, comprising physically isolated components A and B; component A is a solvent-based penetrating anchoring agent, comprising, by weight percentage: 1%~5% carboxyl-functionalized nano-silica; 8%~20% isobutyltriethoxysilane; 2%~5% octyltriethoxysilane; 2%~8% propylene glycol methyl ether; 0.05%~0.2% dibutyltin dilaurate; the remainder being isopropanol; component B is a water-based functional repair agent, comprising, by weight percentage: 2%~10% cationic nanocapsules; 0.1%~0.5% pH adjuster; 0.2%~1% nonionic surfactant; 0.1%~0.3% preservative; the remainder being deionized water. The carboxyl-functionalized nano-silica in component A carries a negative charge, and the cationic nanocapsules in component B carry a positive charge; the two components are used sequentially during construction to form a composite penetrating sealant with self-healing function, solving the defect of traditional penetrating agents being easily lost with water migration.

Description

Technical Field

[0001] This invention relates to the technical field of engineering sealants, and more specifically, to a nano-penetrating sealant for concrete and its application method. Background Technology

[0002] Concrete structures are widely used in infrastructure such as bridges, tunnels, docks, factories, and roads due to their excellent compressive strength, ease of construction, and cost-effectiveness. However, with the extension of structural service life and the deterioration of environmental conditions (such as freeze-thaw cycles, salt damage, chloride ion corrosion, carbonation, and wear), the durability of concrete structures is becoming increasingly prominent.

[0003] The cement-based paste structure in concrete contains a large number of capillary pores, microcracks and interconnected pore networks. Its porosity, pore size distribution and channel connectivity are affected by the water-cement ratio, type and dosage of admixtures, compaction, curing conditions and degree of hydration at different ages.

[0004] These pores provide pathways for the intrusion of harmful media such as moisture, gases (oxygen, carbon dioxide), chloride ions, and sulfate ions, thereby triggering the following typical damage mechanisms:

[0005] Water / air / ion permeation: includes diffusion (driven by concentration gradient), seepage (saturated liquid migrates through pores), and capillary action (unsaturated liquid is drawn into capillary channels).

[0006] Steel corrosion: Chloride ions penetrate, and oxygen and moisture react with steel bars to produce rust products. Expansion stress causes concrete to peel off.

[0007] Freeze-thaw cycle damage: Under freeze-thaw conditions, the volume of water-saturated concrete changes and generates expansion stress, causing cracks in the concrete to expand, peel off, and break apart.

[0008] Carbonation / sulfate erosion / chlorination expansion: Carbonation reduces alkalinity protection, while chlorination and sulfidation reactions generate expanding salts (such as oxychlorides) that damage the slurry structure.

[0009] Therefore, in concrete protection engineering, controlling the intrusion of moisture and ions, enhancing structural density, blocking crack propagation, and delaying durability deterioration have become important directions.

[0010] To address the aforementioned durability issues, sealant technology has emerged. Based on their mechanism of action, sealants can be categorized into film-forming sealants and penetrating sealants.

[0011] Film-type sealants form one or more layers of a thin film on the concrete surface, primarily relying on the film's waterproof, stain-resistant, and barrier functions. These products easily form a visual coating and are often used for decoration, pollution prevention, and anti-slip modification. However, they also have significant drawbacks: the film is prone to wear, peeling, and failure; once the film is damaged, the substrate is exposed; and the coating may hinder the evaporation of moisture from inside the concrete, leading to accelerated freeze-thaw damage due to saturation.

[0012] Penetrating sealants penetrate into the capillary pores of concrete through a low-viscosity solution, reacting or depositing with cementitious materials to form a dense gel, hydrophobic coating, or low-porosity network, thereby reducing the penetration of moisture, salt, and gases. Mainstream penetrating sealant chemical systems include alkoxysilanes, siloxanes, and silicates / silicides. Penetrating sealants can extend the time before concrete reaches its critical saturation state, thus reducing the risk of freeze-thaw damage and chloride ion attack.

[0013] Although penetrating sealants have achieved some success in practical applications, several problems still need to be solved:

[0014] Multi-penetrating agents can only penetrate a few micrometers into the concrete surface, rather than reaching deep into the concrete interior.

[0015] Traditional sealants mainly target pore filling and hydrophobicity, while paying less attention to crack initiation, propagation, and self-healing capabilities.

[0016] The moisture content, temperature, absorption rate, and surface condition of concrete have a significant impact on the penetration effect.

[0017] Against this backdrop, there is an urgent need in research and engineering to further improve the penetration depth of sealants, enhance interfacial bonding with the substrate, actively repair cracks, and improve the overall structural durability. Summary of the Invention

[0018] Therefore, the purpose of this invention is to provide a concrete nano-penetrating sealant and its construction method, forming a composite penetrating sealant with self-healing function, thus solving the defect of traditional penetrants being easily lost with water migration.

[0019] To achieve the above objectives, the present invention provides the following technical solution:

[0020] A concrete nano-permeable sealant comprising physically isolated component A and component B;

[0021] Component A is a solvent-based penetrating anchoring agent, comprising, by weight percentage:

[0022] Carboxyl-functionalized nano-silica: 1%~5%;

[0023] Isobutyltriethoxysilane: 8%~20%;

[0024] Octyltriethoxysilane: 2%~5%;

[0025] Propylene glycol methyl ether: 2%~8%;

[0026] Dibutyltin dilaurate: 0.05%~0.2%;

[0027] Isopropanol: Balance;

[0028] Component B is a water-based functional repair agent, comprising, by weight percentage:

[0029] Cationic nanocapsules: 2%~10%;

[0030] pH adjuster: 0.1%~0.5%;

[0031] Nonionic surfactants: 0.2%~1%;

[0032] Preservatives: 0.1%~0.3%;

[0033] Deionized water: Balance.

[0034] The present invention is further configured such that the average particle size range of the carboxyl-functionalized nano-silica in component A is 5 nm to 20 nm.

[0035] The present invention is further configured such that the average particle size of the cationic nanocapsules in component B is in the range of 50 nm to 100 nm.

[0036] The present invention is further configured such that: the shell of the cationic nanocapsule is made of chitosan, and its core material is an isocyanate prepolymer.

[0037] The present invention is further configured such that the preparation method of component A includes the following steps:

[0038] S1, Amination: The weight ratio of nano-silica particles to anhydrous alcohol solvent is 1:5 to 1:20 on a dry weight basis. Under nitrogen protection, (3-aminopropyl)triethoxysilane is slowly added dropwise. After the addition is complete, the system is heated to 60°C to 80°C and refluxed at this temperature for 4 to 8 hours.

[0039] S2, Carboxylation: Cool the reaction solution from step S1 to 20°C~30°C, and slowly add a succinic anhydride solution dissolved in anhydrous alcohol under vigorous stirring; after the addition is complete, continue stirring the reaction at this temperature for 10~15 hours.

[0040] S3. Purification: The product from step S2 is centrifuged at a force of 8000-12000g. The supernatant is discarded, and the precipitate is washed 2-3 times with anhydrous alcohol to obtain purified carboxyl-functionalized nano-silica.

[0041] S4. Compounding: In a dry reaction vessel purged with nitrogen, first add isopropanol and propylene glycol methyl ether, and mix evenly to obtain the base solution;

[0042] Start high-speed shear stirring at 1000~3000 rpm, slowly add the purified carboxyl-functionalized nano silica to the base solution, and continue shearing for 1~2 hours until a uniform, non-agglomerated nano dispersion is formed.

[0043] Reduce the stirring speed to a slow 200 to 500 rpm, add isobutyltriethoxysilane and octyltriethoxysilane in sequence, and continue stirring for 30 minutes to completely dissolve them;

[0044] After ensuring the system is fully mixed, dibutyltin dilaurate is slowly added to the system and stirred for 15-30 minutes to ensure complete dispersion. Then it is sealed and packaged to obtain component A.

[0045] The present invention is further configured such that the preparation method of component B includes the following steps:

[0046] (1) Preparation of aqueous phase: Add chitosan to deionized water containing pH adjuster, heat to 50°C~70°C and stir for 1~2 hours until completely dissolved to form a clear solution, and then cool to room temperature;

[0047] (2) Preparation of the oil phase: The core material raw materials are premixed;

[0048] (3) Pre-emulsification: The oil phase from step (2) is added to the aqueous phase from step (1), and a high-shear disperser is used to shear at a rate of 5000~10000 rpm for 10~20 minutes to form an O / W type crude emulsion;

[0049] (4) High pressure homogenization: Immediately pump the crude emulsion from step (3) into a high pressure homogenizer with a cooling circulation jacket, and homogenize it for 3 to 5 times under a pressure of 500 to 1000 bar to obtain a cationic nanocapsule dispersion.

[0050] (5) Preparation: Add nonionic surfactant and preservative to the dispersion in step (4) and mix for 30 minutes under slow stirring at 200~500 rpm to obtain component B.

[0051] The present invention is further configured such that: during the high-pressure homogenization process in step (4), the temperature of the emulsion is controlled between 15°C and 40°C by a cooling circulation jacket to prevent the core material from reacting prematurely due to local overheating.

[0052] The present invention is further configured such that: component A also contains a pH color indicator, which changes color when it comes into contact with the alkaline environment of concrete, for visual confirmation of the construction area.

[0053] A method for applying a sealant, comprising the following sequential steps:

[0054] Apply component A to the surface of the concrete substrate;

[0055] Apply component B within 5 to 60 minutes after applying component A.

[0056] Compared with the shortcomings of the prior art, the beneficial effects of the present invention are as follows:

[0057] The carboxyl-functionalized nano-silica in component A carries a negative charge, while the cationic nanocapsules in component B carry a positive charge. The two components are used sequentially during construction, allowing component B to be anchored in the pores of the concrete pretreated by component A through an electrostatic adsorption mechanism, forming a composite penetrating seal with self-healing function. This solves the defect of traditional penetrants that are easily lost with the migration of water, ensuring the long-term residence and efficient repair capability of the self-healing unit throughout the entire life cycle of the concrete. Attached Figure Description

[0058] Figure 1 This is a process flow diagram of the present invention;

[0059] Figure 2 This is a comparison chart of the capillary water absorption test results of the control group in this invention;

[0060] Figure 3 This is a comparison chart of the water absorption and desorption (air permeability) test results of the control group of this invention;

[0061] Figure 4 This is a comparison chart of the air (gas) permeability index test results of the control group in this invention;

[0062] Figure 5 This is a comparison chart of the freeze-thaw (FT) test results of the control group of this invention;

[0063] Figure 6 This is a product image showing the results of a freeze-thaw (FT) test on the control group of this invention. Detailed Implementation

[0064] Reference Figures 1 to 6 The embodiments of the present invention will be further described below.

[0065] The concrete nano-permeable sealant of the present invention comprises physically isolated component A and component B.

[0066] Component A is a solvent-based penetrating anchoring agent. Its main purpose is to form a dense, highly hydrophobic layer beneath the surface of the concrete substrate through penetration and reaction, preventing the intrusion of water and harmful ions. By weight percentage, Component A comprises: carboxyl-functionalized nano-silica, 1%–5%; isobutyltriethoxysilane, 8%–20%; octyltriethoxysilane, 2%–5%; propylene glycol methyl ether, 2%–8%; dibutyltin dilaurate, 0.05%–0.2%; and isopropanol as a solvent, constituting the balance. The average particle size of the carboxyl-functionalized nano-silica ranges from 5 nm to 20 nm. These nano-silica particles have a large number of carboxyl groups (-COOH) on their surface, giving them a negative charge. Their introduction is intended to improve permeability through their nanoscale structure and provide active sites to enhance the adsorption of subsequent component B. Isobutyltriethoxysilane and octyltriethoxysilane are hydrophobic silane coupling agents. They undergo a condensation reaction with hydroxyl groups (-OH) on the surface of concrete substrates via their triethoxy chains, forming Si-O-Si bonds. This introduces hydrophobic organic groups (isobutyl and octyl) into the concrete structure, thereby endowing the concrete with excellent hydrophobicity and weather resistance. Due to the steric hindrance effect of the isobutyl group, isobutyltriethoxysilane can form a denser hydrophobic layer, while octyltriethoxysilane provides good hydrophobicity. Dibutyltin dilaurate acts as a catalyst, accelerating the hydrolysis and condensation reactions of the silane coupling agents, improving curing speed and film-forming effect. Propylene glycol methyl ether acts as an auxiliary solvent, adjusting the evaporation rate and solubility of the system, and improving the uniformity of construction. Isopropanol, as the main solvent, dissolves other components and controls the penetration depth and evaporation rate.

[0067] The preparation of component A involves four main steps: amination, carboxylation, purification, and compounding. First, in the amination step, nano-silica particles are mixed with anhydrous alcohol solvent at a dry weight ratio of 1:5 to 1:20. Under nitrogen protection, (3-aminopropyl)triethoxysilane is slowly added dropwise. The mixture is then heated to 60°C–80°C and refluxed for 4–8 hours, allowing the amino group of (3-aminopropyl)triethoxysilane to react with the hydroxyl group on the surface of the nano-silica, introducing an amino group (-NH2) at the ethoxy terminus of the silane. Nitrogen protection is used to prevent oxidation of the reactants at high temperatures. Next, in the carboxylation step, the reaction solution is cooled to 20°C–30°C, and a succinic anhydride solution dissolved in anhydrous alcohol is slowly added dropwise with vigorous stirring. After the addition is complete, the reaction is continued with stirring for 10–15 hours, allowing the amino group to react with the succinic anhydride and introducing a carboxyl group (-COOH). This process introduces a negatively charged carboxyl functional group. In the subsequent purification step, the supernatant was discarded by centrifugation (8000~12000g), and the precipitate was washed 2~3 times with anhydrous alcohol to remove unreacted raw materials and byproducts, obtaining purified carboxyl-functionalized nano-silica to ensure product purity. Finally, in the compounding step, isopropanol and propylene glycol methyl ether were first added to a dry, nitrogen-purged reactor and mixed thoroughly to form a base solution. High-speed shear stirring (1000~3000 rpm) was started, and the purified carboxyl-functionalized nano-silica was slowly added, continuing shearing for 1~2 hours until a uniform, non-agglomerated nano-dispersion was formed, ensuring the silica particles were evenly dispersed in the solvent. Then, the stirring speed was reduced to 200~500 rpm, and isobutyltriethoxysilane and octyltriethoxysilane were added sequentially, continuing stirring for 30 minutes to ensure complete dissolution. Finally, after the system was thoroughly mixed, dibutyltin dilaurate was slowly added, and stirring was continued for 15~30 minutes to ensure complete dispersion. The entire process was carried out under nitrogen protection to prevent excessive hydrolysis of silane, and finally sealed and encapsulated to obtain component A.

[0068] Component B is a water-based functional repair agent. Its purpose is to anchor positively charged nanocapsules within the micropores of concrete treated with Component A via electrostatic adsorption. The isocyanate prepolymer within the nanocapsules reacts with moisture within the concrete substrate, further sealing and repairing micro-cracks in the concrete, thus achieving self-healing properties. By weight percentage, Component B comprises: cationic nanocapsules (2%–10%); pH adjuster (0.1%–0.5%); nonionic surfactant (0.2%–1%); preservative (0.1%–0.3%); and deionized water as a solvent, constituting the balance. The average particle size of the cationic nanocapsules ranges from 50 nm to 100 nm. These nanocapsules have a positively charged surface, a shell composed of chitosan (which itself carries a positive charge), and a core material of isocyanate prepolymer. The isocyanate prepolymer exhibits high reactivity, reacting with moisture in the concrete to form polyurea, thereby providing filling and repair functions. Chitosan, acting as a shell, stabilizes the dispersed phase and provides a cationic surface, enabling electrostatic adsorption during construction of negatively charged carboxyl-functionalized nano-silica in component A and negatively charged regions (such as silanol anions) on the concrete surface. A pH adjuster stabilizes the system's pH, ensuring the stability of component B. Nonionic surfactants reduce the system's surface tension, improving its spreadability and wettability on the concrete surface. Preservatives inhibit microbial growth, extending the product's shelf life.

[0069] The preparation method of component B includes five steps: preparation of the aqueous phase, preparation of the oil phase, pre-emulsification, high-pressure homogenization, and formulation. First, in the preparation of the aqueous phase, chitosan is added to deionized water containing a pH adjuster, heated to 50°C–70°C, and stirred for 1–2 hours until the chitosan is completely dissolved to form a clear solution, which is then cooled to room temperature. This step prepares an aqueous solution of chitosan with cationic groups. Next, in the preparation of the oil phase, the core material raw material (isocyanate prepolymer) is premixed. Then, in the pre-emulsification step, the oil phase is added to the aqueous phase and sheared at 5000–10000 rpm for 10–20 minutes using a high-shear disperser to form an O / W type crude emulsion, dispersing the oil phase into tiny oil droplets. Subsequently, in the high-pressure homogenization step, the crude emulsion is pumped into a high-pressure homogenizer equipped with a cooling circulation jacket and homogenized 3–5 times at a pressure of 500–1000 bar. High-pressure homogenization further refines oil droplets to the nanoscale, forming nanocapsules with chitosan shells. Maintaining the emulsion temperature between 15°C and 40°C using a cooling circulating jacket prevents premature polymerization or decomposition of the core material (isocyanate prepolymer) due to localized overheating, ensuring its stability. Finally, in the formulation step, nonionic surfactants and preservatives are added to the prepared cationic nanocapsule dispersion, and the mixture is stirred slowly at 200-500 rpm for 30 minutes to obtain a homogeneous and stable component B.

[0070] Component A also contains a pH color indicator. This indicator changes color when it comes into contact with the alkaline environment of concrete (pH value is usually above 12.5), turning red or blue when exposed to alkali. This is used to visually confirm the construction area, which helps operators to intuitively judge whether the sealant has been evenly applied to the target area, thereby improving construction quality and efficiency.

[0071] A construction method for applying the sealant of this invention includes the following sequential steps: First, component A is applied to the surface of a concrete substrate. Because component A contains a hydrophobic silane coupling agent, it penetrates into the pores of the concrete and reacts chemically with the hydroxyl groups on the concrete surface to form a hydrophobic filling layer. Simultaneously, the carboxyl-functionalized nano-silica in component A is adsorbed onto the concrete surface with its negative charge. Subsequently, within 5 to 60 minutes after applying component A, component B is applied. At this time, the cationic nanocapsules (carrying a positive charge) in component B are strongly anchored to the micropores of the concrete pretreated with component A and the negatively charged carboxyl-functionalized nano-silica surface through an electrostatic adsorption mechanism. Upon contact with trace amounts of moisture in the concrete, the isocyanate prepolymer core material undergoes a polymerization reaction, further filling and repairing the micro-cracks in the concrete, forming a dense, self-healing composite penetrating sealant. This two-step construction method allows components A and B to interact with the concrete substrate in a controlled and regional manner, ensuring that their respective functions are maximized and achieving synergistic effects between them.

[0072] Example 1: Preparation method of component A:

[0073] Amination: 3% of nano-silica particles (dry weight) were mixed with anhydrous alcohol solvent at a weight ratio of 1:10. Under nitrogen protection, the reaction temperature was controlled at 70.0°C, and 14% of (3-aminopropyl)triethoxysilane was slowly added dropwise. The mixture was refluxed for 6.0 hours.

[0074] Carboxylation: The amination product was cooled to 25.0°C, and a succinic anhydride solution dissolved in anhydrous alcohol was slowly added dropwise with vigorous stirring. The reaction was continued for 12.0 hours with stirring.

[0075] Purification: The supernatant was discarded after centrifugation at 10,000g, and the precipitate was washed three times with anhydrous alcohol to obtain purified 3% carboxyl-functionalized nano-silica.

[0076] Compounding: In a nitrogen-protected reactor, isopropanol and 5% propylene glycol methyl ether were mixed to form a base solution. High-speed shear stirring at 2000 rpm was initiated, and 3% purified carboxyl-functionalized nano-silica was slowly added, with continuous shearing for 1.5 hours to form a homogeneous dispersion. Subsequently, the stirring speed was reduced to 300 rpm, and 14% isobutyltriethoxysilane and 3.5% octyltriethoxysilane were added sequentially, stirring for 30 minutes. Finally, 0.125% dibutyltin dilaurate was slowly added, and stirring was continued for another 20 minutes. The mixture was then sealed and packaged to obtain component A.

[0077] Component B has the following composition: 6% cationic nanocapsules (average particle size 75nm), 0.3% pH adjuster, 0.6% nonionic surfactant, 0.2% preservative, and the remainder is deionized water.

[0078] Preparation of the aqueous phase: Chitosan was added to deionized water containing 0.3% pH adjuster, heated to 60.0°C and stirred for 1.5 hours until dissolved, and then cooled to 25.0°C.

[0079] Preparation of the oil phase: premixed 6% isocyanate prepolymer core material.

[0080] Pre-emulsification: The oil phase is added to the aqueous phase and sheared for 15 minutes at a rate of 8000 rpm using a high-shear disperser to form an O / W crude emulsion.

[0081] High-pressure homogenization: The crude emulsion was pumped into a high-pressure homogenizer and homogenized 4 times under a pressure of 800 bar. The jacket cooling temperature was controlled at 25.0°C to obtain a cationic nanocapsule dispersion with an average particle size of 75 nm.

[0082] Preparation: Add 0.6% nonionic surfactant and 0.2% preservative to the dispersion, and stir slowly at 300 rpm for 30 minutes to obtain component B.

[0083] This invention provides a concrete nano-penetrating sealant. By physically isolating a solvent-based hydrophobic silane coupling agent system (component A) and a water-based cationic nano-repair capsule system (component B) and applying them sequentially during construction, the following beneficial effects are achieved: First, the silane coupling agent in component A can effectively penetrate the pores of concrete and react chemically with the concrete substrate to form a hydrophobic barrier on the surface, improving the impermeability and durability of the concrete. Simultaneously, the presence of carboxyl-functionalized nano-silica provides active sites for the subsequent adsorption of component B. Second, the cationic nanocapsules in component B, due to the positive charge provided by the chitosan shell, can electrostatically adsorb with the negatively charged nano-silica in component A and the negatively charged regions on the concrete surface, thereby achieving deep anchoring and penetration. The capsule core material (isocyanate prepolymer) reacts with moisture in the concrete, filling and repairing micro-cracks, endowing the concrete with self-healing capabilities, and significantly improving the overall repair effect and service life of the sealant. Finally, the two components are used sequentially, ensuring the penetration and reaction of component A, and the effective adsorption and repair of component B. This avoids system instability or uncontrolled reaction that might result from direct mixing, ensuring the stability and final effect of the sealant. Compared to single-component sealants, this invention significantly improves the waterproofing, corrosion resistance, durability, and self-healing capabilities of concrete through synergistic effects, achieving a comprehensive performance enhancement.

[0084] To further demonstrate the beneficial effects of the present invention, particularly the synergistic effect between component A (penetrating anchoring agent) and component B (functional repair agent), and the superiority of the present invention over the prior art, the following series of comparative tests were conducted.

[0085] Concrete specimens from the same batch were selected and subjected to no treatment, serving as a control group;

[0086] Concrete specimens from the same batch were selected, and a commercially available high-performance solvent-based silane sealant with a solid content of 40% was applied as control group 2.

[0087] Concrete specimens from the same batch were selected, and only component B of this invention was applied to them as control group 3;

[0088] Concrete specimens from the same batch were selected, and only component A of this invention was applied to them as control group 4;

[0089] The product prepared in Example 1 was set as control group 5.

[0090] The specific experiment is as follows:

[0091] The capillary water absorption test (initial conditions and UV aging resistance) was conducted according to EN 13057. The coated surfaces of five groups of specimens were placed in shallow water, and the water absorption depth *i* was measured at different time points (t), and curves were plotted. The slope of the curve represents the water absorption rate; the lower the slope, the better the protection.

[0092] UV aging: Another batch of 5 groups of specimens were placed in the QUV ultraviolet aging test chamber to simulate 1000 hours of accelerated aging, and then the above capillary water absorption test was repeated.

[0093] like Figure 2 As shown:

[0094] Initial conditions (left figure): Control group 5 has the lowest curve slope, showing the best initial waterproof performance, superior to all control groups. Control group 4 is next. Control group 2 has a moderate slope. Control groups 1 and 3 have the highest slopes and the worst waterproof performance, proving that component B must rely on component A for anchoring.

[0095] After UV testing (right figure): The curve slope of control group 2 increased sharply, indicating that its silane structure was degraded by UV and its durability was poor. The curve slope of control group 5 remained almost unchanged, showing extremely high resistance to UV aging, which is attributed to the UV shielding effect of nano-silica in component A and the synergistic protection of nanocapsules in component B.

[0096] Water absorption and desorption (air permeability) test: Five groups of specimens were completely immersed in water for 3 days, and the mass change was recorded; then they were taken out and placed in a standard laboratory environment to air dry for 11 days, and the mass change was recorded.

[0097] like Figure 3 As shown:

[0098] Water absorption phase (0-3 days): Control group 5 had the lowest total water absorption, significantly lower than all other control groups.

[0099] Desorption phase (3-14 days): Control group 5 showed a good drying rate, proving that while waterproofing, the present invention still retains the "breathing" function (breathability) of concrete, and will not seal moisture inside like film-forming coatings.

[0100] Air (gas) permeability index test: The air permeability index (k) of 5 groups of specimens was tested using a gas permeameter. The lower the index, the better the pore sealing.

[0101] like Figure 4 As shown:

[0102] Control group 5 had the lowest air permeability index. This demonstrates that the nano-silica (5-20 nm) of component A and the nanocapsules (50-100 nm) of component B achieved "multi-scale pore filling," forming the densest permeable seal. Control group 4 (A only) was second best, and also superior to control group 2, proving the advanced nature of the nano-filling of component A in this invention.

[0103] Freeze-thaw (FT) cycle test (active self-healing verification)

[0104] This is a key experiment to verify the core innovation of this invention (active self-healing).

[0105] Test method: Five groups of specimens were subjected to freeze-thaw cycles according to ASTM C672 standard.

[0106] Test 1: Internal Damage (mDcrack) Monitoring:

[0107] like Figure 5 As shown, during the cyclic process, the `mDcrack` values ​​(representing the saturation of internal microcracks caused by freeze-thaw cycles) of controls 1, 2, 3, and 4 all increased significantly with the number of cycles. However, the `mDcrack` curve of control group 5 remained close to zero throughout.

[0108] This result irrefutably proves the active self-healing function of the present invention. At the moment when microcracks are generated by the freeze-thaw cycle, the nanocapsules of component B rupture and release the core material (isocyanate). The core material polymerizes upon contact with water vapor, repairing the microcracks in situ and preventing the accumulation of damage and the vicious cycle.

[0109] Test 2: Visual rating of surface scaling:

[0110] like Figure 6 As shown:

[0111] Control group 1 and control group 3: rating 4.5-5.0 (severe peeling).

[0112] Control group 2: Rating 3.5 (moderate to severe exfoliation).

[0113] Control group 4: Rating 1.5 (minor spalling). Component A provided good passive protection but could not repair new cracks.

[0114] Control group 5: rating 0.5 (very slight / nearly no peeling).

[0115] Based on the above test results, control group 5 significantly outperformed all other control groups in all key performance indicators. This invention not only provides superior and more durable basic waterproofing and impermeability compared to conventional technologies (as demonstrated by UV and air penetration tests), but also (through FT cycle testing) proves it possesses an "active self-healing" capability completely absent in existing technologies. This superior performance stems from the electrostatic adsorption anchoring and synergistic protection mechanism between component A (negative charge anchor points) and component B (positive charge repair capsules).

[0116] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any ordinary changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A nano-penetrating sealant for concrete, characterized in that, It contains physically isolated components A and B; Component A is a solvent-based penetrating anchoring agent, comprising, by weight percentage: Carboxyl-functionalized nano-silica: 1%~5%; Isobutyltriethoxysilane: 8%~20%; Octyltriethoxysilane: 2%~5%; Propylene glycol methyl ether: 2%~8%; Dibutyltin dilaurate: 0.05%~0.2%; Isopropanol: Balance; Component B is a water-based functional repair agent, comprising, by weight percentage: Cationic nanocapsules: 2%~10%; pH adjuster: 0.1%~0.5%; Nonionic surfactants: 0.2%~1%; Preservatives: 0.1%~0.3%; Deionized water: Balance.

2. The concrete nano-penetrating sealant according to claim 1, characterized in that, The average particle size range of the carboxyl-functionalized nano-silica in component A is 5 nm to 20 nm.

3. The concrete nano-penetrating sealant according to claim 2, characterized in that, The average particle size range of the cationic nanocapsules in component B is 50 nm to 100 nm.

4. The concrete nano-penetrating sealant according to claim 3, characterized in that, The shell of the cationic nanocapsule is made of chitosan, and its core material is an isocyanate prepolymer.

5. The concrete nano-penetrating sealant according to claim 1, characterized in that, The preparation method of component A includes the following steps: S1, Amination: The weight ratio of nano-silica particles to anhydrous alcohol solvent is 1:5 to 1:20 on a dry weight basis. Under nitrogen protection, (3-aminopropyl)triethoxysilane is slowly added dropwise. After the addition is complete, the system is heated to 60°C to 80°C and refluxed at this temperature for 4 to 8 hours. S2, Carboxylation: Cool the reaction solution from step S1 to 20°C~30°C, and slowly add a succinic anhydride solution dissolved in anhydrous alcohol under vigorous stirring; after the addition is complete, continue stirring the reaction at this temperature for 10~15 hours. S3. Purification: The product from step S2 is centrifuged at a force of 8000-12000g. The supernatant is discarded, and the precipitate is washed 2-3 times with anhydrous alcohol to obtain purified carboxyl-functionalized nano-silica. S4. Compounding: In a dry reaction vessel purged with nitrogen, first add isopropanol and propylene glycol methyl ether, and mix evenly to obtain the base solution; Start high-speed shear stirring at 1000~3000 rpm, slowly add the purified carboxyl-functionalized nano silica to the base solution, and continue shearing for 1~2 hours until a uniform, non-agglomerated nano dispersion is formed. Reduce the stirring speed to a slow 200 to 500 rpm, add isobutyltriethoxysilane and octyltriethoxysilane in sequence, and continue stirring for 30 minutes to completely dissolve them; After ensuring the system is fully mixed, dibutyltin dilaurate is slowly added to the system and stirred for 15-30 minutes to ensure complete dispersion. Then, the system is sealed and packaged to obtain component A.

6. The concrete nano-penetrating sealant according to claim 1, characterized in that, The preparation method of component B includes the following steps: (1) Preparation of aqueous phase: Add chitosan to deionized water containing pH adjuster, heat to 50°C~70°C and stir for 1~2 hours until completely dissolved to form a clear solution, and then cool to room temperature; (2) Preparation of the oil phase: The core material raw materials are premixed; (3) Pre-emulsification: The oil phase from step (2) is added to the aqueous phase from step (1), and a high-shear disperser is used to shear at a rate of 5000~10000 rpm for 10~20 minutes to form an O / W type crude emulsion; (4) High pressure homogenization: Immediately pump the crude emulsion from step (3) into a high pressure homogenizer with a cooling circulation jacket, and homogenize it for 3 to 5 times under a pressure of 500 to 1000 bar to obtain a cationic nanocapsule dispersion. (5) Preparation: Add nonionic surfactant and preservative to the dispersion in step (4) and mix for 30 minutes under slow stirring at 200~500 rpm to obtain component B.

7. A concrete nano-penetrating sealant according to claim 6, characterized in that, During the high-pressure homogenization process in step (4), the temperature of the emulsion is controlled between 15°C and 40°C by a cooling circulation jacket to prevent the core material from reacting prematurely due to local overheating.

8. The concrete nano-penetrating sealant according to claim 1, characterized in that, Component A also contains a pH color indicator that changes color when it comes into contact with the alkaline environment of concrete, for visual confirmation of the construction area.

9. A construction method using the sealant according to claim 1, characterized in that, Includes the following timing steps: Apply component A to the surface of the concrete substrate; Apply component B within 5 to 60 minutes after applying component A.

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