A protection system for improving the durability of coastal bridge concrete and a preparation method thereof

Abstract

This invention relates to a protective system and its preparation method for enhancing the durability of concrete in coastal bridges. The protective system is applied to concrete containing cementitious materials, aggregates, and water. The cementitious materials include functional admixtures, such as a proprietary composite modified core-shell powder, complexation reaction modified mineral powder, and zeolite powder-supported gypsum whisker composite powder. This invention utilizes a dual-response film-forming mechanism of "secretion-triggered ion complexation." When biological secretions come into contact with the concrete surface, the core-shell powder releases alkaline substances to neutralize organic acids. Simultaneously, the complexation reaction modified mineral powder undergoes a complexation reaction with metal ions in the secretions, forming an organic-inorganic interlocking protective film. This film then fuses with the subsequently grown shellfish shell to construct a dual protective structure. This invention provides stable protection, enhancing the concrete's resistance to chloride ion penetration and sulfate attack, effectively inhibiting steel corrosion, and extending the service life of concrete in coastal bridges.

Description

Technical Field

[0001] This invention relates to the field of concrete protective materials for coastal engineering, and in particular to a protective system for improving the durability of concrete in coastal bridges and its preparation method. Background Technology

[0002] The average salinity of seawater is as high as 3.5%, mainly consisting of sodium (Na₂O). + Mg 2+ Cl - SO4 2- The combined effects of plasma, salinity, and climate in marine environments create what is widely recognized as the harshest service environment for concrete. Common corrosion types include chemical corrosion and physical corrosion. The deterioration of concrete under chemical erosion mainly falls into two categories: one is due to the presence of magnesium in the marine environment... 2+ and SO4 2- One type can consume alkaline oxides in concrete, leading to a gradual decrease in the concrete's cementitious strength and even the detachment of the surface concrete, resulting in deterioration; another type is high concentrations of Cl... - Through surface penetration, it infiltrates the concrete, destroys the passivation film on the steel reinforcement surface, and forms corrosion cells, thereby causing steel reinforcement corrosion and concrete rust expansion and cracking. Physical corrosion mainly includes the long-term scouring effect of ocean waves and tides on concrete, the drying process of concrete being wetted by seawater and water evaporation caused by changes in seawater level and wave splash, concrete damage caused by salt precipitation, and concrete freeze-thaw damage.

[0003] Existing protective technologies suffer from drawbacks such as limited material modification, passive film-forming mechanisms, and crude dispersion processes, leading to the technical problem of coating detachment. Domestic and international research has found that marine mollusks attached to concrete surfaces can improve the concrete's impermeability and durability, with the protective effect increasing as the density of attachment points increases. However, after attachment, the organic acids and mucopolysaccharides secreted by these marine organisms can penetrate the concrete pores, disrupting hydration products, accelerating steel corrosion, and reducing structural durability. This contradiction of "both advantages and disadvantages in bioattachment" makes it difficult to achieve ideal comprehensive protective effects by simply inducing or preventing bioattachment.

[0004] Therefore, how to achieve the active synergy between "passivation of biological secretions" and "utilization of biological shells" and construct a protective system that can both neutralize the corrosion of secretions and induce biological directional attachment and integration is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The present invention aims to address the shortcomings of the prior art by providing a protective system for improving the durability of concrete in coastal bridges and its preparation method.

[0006] To achieve the above objectives, the present invention employs the following technical solution: a protective system for improving the durability of concrete in coastal bridges, wherein the protective system is applied to concrete, the concrete comprising cementitious materials, aggregates, and water, and the cementitious materials comprising functional admixtures; the functional admixtures include:

[0007] The proprietary composite modified core-shell powder has a core-shell structure of "alkaline inorganic core - bio-induced shell". Its surface is modified with organic compounds to release alkaline substances for neutralization reaction when in contact with marine organism secretions and to induce bioattachment.

[0008] Complexation reaction modified mineral powder is prepared by loading mineral powder with organophosphonic acid compounds that can undergo complexation reaction with metal ions. It is used to undergo complexation reaction with metal ions in biological secretions and metal ions produced by cement hydration.

[0009] Zeolite powder-supported gypsum whisker composite powder, which is made by supporting gypsum whiskers with porous zeolite powder, is used to slowly release calcium ions and provide physical sites for bioattachment.

[0010] Specifically, the dosage ranges of each component in the cementitious material, based on total mass, are as follows:

[0011] Ordinary Portland cement: 50%~55%;

[0012] Ultrafine mineral powder: 20%~25%;

[0013] Functional admixtures: 15%~20%, wherein the exclusive composite modified core-shell powder is 4%~6%, the complexation reaction modified mineral powder is 1%~2%, and the zeolite powder supported gypsum whisker composite powder is 6%~12%;

[0014] Polyacrylonitrile short-cut fibers: their volume content is 0.15%~0.2%;

[0015] And auxiliary components, including: 0.8%~1.2% polycarboxylate superplasticizer and 0.5% aliphatic organic amine rust inhibitor.

[0016] Specifically, the proprietary composite modified core-shell powder has a "magnesium hydroxide core-hydroxyapatite shell" structure, with a core particle size of 50~100nm, a shell thickness of 20~50nm, and an overall particle size of 70~150nm; the surface of the proprietary composite modified core-shell powder is modified by a combination of stearic acid and silane coupling agent, and the mass ratio of stearic acid to silane coupling agent is 1:1.

[0017] Specifically, the proprietary composite modified core-shell powder is prepared by a method comprising the following steps:

[0018] S1. Disperse magnesium hydroxide micro powder in anhydrous ethanol solution and ultrasonically disperse it at 20~30kHz for 5~8min to form a suspension;

[0019] S2. Add hydroxyapatite precursor solution to the suspension and react at a constant temperature of 70~80℃ for 1.5~2h to generate core-shell powder with a "magnesium hydroxide core-hydroxyapatite shell" structure;

[0020] S3. Add a composite modifier of stearic acid and silane coupling agent to the reaction system. The mass ratio of stearic acid to silane coupling agent is 1:1. Continue stirring at 60~80℃ for 2~3h to carry out surface modification.

[0021] S4. The modified product is vacuum dried at 80~90℃ for 4~6h and ground until the overall particle size is 70~150nm to obtain the exclusive composite modified core-shell powder.

[0022] The proprietary composite modified core-shell powder is used for neutralizing biological secretions, guiding in-situ film formation, and improving compatibility with cementitious matrices.

[0023] Specifically, the complexation reaction modified mineral powder is an aminotrimethylene phosphonic acid modified ultrafine mineral powder, wherein the loading of aminotrimethylene phosphonic acid is 3% to 5% of the mass of the ultrafine mineral powder.

[0024] Specifically, the complexation reaction modified mineral powder is prepared by a method comprising the following steps:

[0025] P1. Disperse ultrafine mineral powder in deionized water, and add aminotrimethylene phosphonic acid, wherein the amount of aminotrimethylene phosphonic acid added is 3% to 5% of the mass of the ultrafine mineral powder;

[0026] P2. Stir the mixture at 50~60℃ for 1~2h to fully load aminotrimethylenephosphonic acid onto the surface of the ultrafine mineral powder;

[0027] P3. The product after the reaction is dried and ground to obtain the complexation reaction modified mineral powder.

[0028] The complexation reaction modified mineral powder is used to undergo a complexation reaction with metal ions in biological secretions, participating in a dual-response film-forming mechanism.

[0029] Specifically, the zeolite powder-supported gypsum whisker composite powder is natural zeolite powder-supported α-hemihydrate gypsum whiskers, wherein the pore size of the natural zeolite powder is 0.5~2μm, and the loading of α-hemihydrate gypsum whiskers is 15%~20%.

[0030] Specifically, the zeolite powder-supported gypsum whisker composite powder is prepared by a method comprising the following steps:

[0031] N1. Natural zeolite powder is activated by acid treatment with 5%~8% hydrochloric acid solution for 2~3 hours, filtered and washed until neutral, and then dried to obtain activated zeolite powder.

[0032] N2. Immerse the activated zeolite powder in an α-hemihydrate gypsum whisker slurry with a mass concentration of 10%~15% and adsorb at a constant temperature of 40~50℃ for 4~6 hours to load the α-hemihydrate gypsum whiskers onto the pores and surface of the activated zeolite powder.

[0033] N3. Filter to separate the solid product, and dry it at 60~70℃ to constant weight to obtain the zeolite powder supported gypsum whisker composite powder.

[0034] The zeolite powder-loaded gypsum whisker composite powder is used to achieve precise synergy between calcium ion slow release and bio-attachment sites.

[0035] A method for preparing a protective system to improve the durability of concrete for coastal bridges includes the following steps:

[0036] A1. Graded premixing-ultrasound-assisted dispersion:

[0037] The exclusive composite modified core-shell powder is added to anhydrous ethanol solution and ultrasonically dispersed at 20-30 kHz and 300-500 W for 10-15 min. Then it is mixed with the polycarboxylate superplasticizer solution and mechanically stirred for 3-5 min until uniform to obtain core-shell powder premix.

[0038] The polyacrylonitrile short-cut fibers are premixed with a polyethylene glycol dispersant at a dosage of 2% to 3% of the mass of the polyacrylonitrile short-cut fibers. The fibers are then added in steps using a combination of mechanical stirring and airflow dispersion. The mechanical stirring speed is 300 to 500 r / min.

[0039] The zeolite powder-loaded gypsum whisker composite powder is mechanically premixed separately for 2-3 minutes and then set aside.

[0040] A2. Mixing and molding: Add aggregates, ordinary Portland cement, ultrafine mineral powder, all premixed functional materials obtained in step A1, and water in that order. The total mixing time shall not be less than 5 minutes. Then, vibrate and compact the mixture in layers to form the final product.

[0041] A3. Curing and application: After molding, place the precast concrete components in a constant temperature and humidity environment of 20±2℃ and ≥95% for 24 hours before demolding. Then, switch to the segmented curing mode. The total curing time shall not be less than 28 days, and finally form precast concrete components.

[0042] The precast concrete components are used in the concrete structures of coastal bridges to achieve active film-forming protection triggered by biological secretions.

[0043] The beneficial effects of this invention are:

[0044] 1. Active corrosion resistance: Through the dual-response film-forming mechanism of "secretion triggering-ion complexation", when marine organism secretions come into contact with the concrete surface, the core-shell powder is triggered to release alkaline substances to neutralize organic acids. At the same time, the complexation reaction modified mineral powder undergoes a complexation reaction with the metal ions in the secretions to form an organic-inorganic interlocking protective film. It does not require external energy to drive it and can still actively respond in the absence of light, providing stable and long-lasting protection.

[0045] 2. Superior performance: Improves the concrete's resistance to chloride ion penetration, reducing the chloride ion flux to 590~780C in 28 days, which is more than 60% higher than that of conventional concrete; significantly enhances the resistance to sulfate attack, with the 90-day sulfate attack strength loss rate controlled at 2.8%~4.5%, far lower than the industry standard (≤10%); effectively prevents steel corrosion, with the steel corrosion potential remaining stable in the no-corrosion-risk range of -130mV to -180mV.

[0046] 3. Composite protective structure: The hydroxyapatite shell is homologous to the shell composition of shellfish, which can induce directional attachment of organisms; zeolite powder provides stable attachment sites, and gypsum whiskers slowly release Ca. 2+ It promotes the growth of shellfish shells, ultimately forming a dual protective structure of "artificial protective film and biological shell", which increases the shellfish attachment induction efficiency by 53% to 75% compared with ordinary coastal concrete.

[0047] 4. Strong construction adaptability: The graded premixing-ultrasonic assisted dispersion process ensures uniform dispersion of functional admixtures in the concrete matrix, avoiding material agglomeration and functional interference; construction is convenient, no external coating is required, it can be adapted to the complex working conditions of coastal bridges, and extend the service life of the structure. Detailed Implementation

[0048] The present invention will be further described below with reference to embodiments:

[0049] A protective system for improving the durability of concrete in coastal bridges is disclosed. The protective system is applied to concrete containing cementitious materials, aggregates, and water, with a water-cement ratio ≤0.32. The cementitious materials include functional admixtures, which include proprietary composite modified core-shell powder, complexation reaction modified mineral powder, and zeolite powder-supported gypsum whisker composite powder.

[0050] The proprietary composite modified core-shell powder possesses a core-shell structure of "alkaline inorganic core - bio-induced shell," with its surface modified by organic compounds. It is used to release alkaline substances for neutralization upon contact with marine organism secretions and to induce bioattachment. Specifically, the proprietary composite modified core-shell powder has a "magnesium hydroxide core - hydroxyapatite shell" structure, with a core particle size of 50-100 nm, a shell thickness of 20-50 nm, and an overall particle size of 70-150 nm. The surface of the proprietary composite modified core-shell powder is modified with a combination of stearic acid and a silane coupling agent (KH550), with a stearic acid to silane coupling agent mass ratio of 1:1. The proprietary composite modified core-shell powder is prepared by a method including the following steps:

[0051] S1. Disperse magnesium hydroxide micro powder in anhydrous ethanol solution and ultrasonically disperse it at 20~30kHz for 5~8min to form a suspension;

[0052] S2. Add hydroxyapatite precursor solution to the suspension and react at a constant temperature of 70~80℃ for 1.5~2h to generate core-shell powder with a "magnesium hydroxide core-hydroxyapatite shell" structure;

[0053] S3. Add a composite modifier of stearic acid and silane coupling agent to the reaction system. The mass ratio of stearic acid to silane coupling agent is 1:1. Continue stirring at 60~80℃ for 2~3h to carry out surface modification.

[0054] S4. The modified product is vacuum dried at 80~90℃ for 4~6h and ground until the overall particle size is 70~150nm to obtain the exclusive composite modified core-shell powder.

[0055] The proprietary composite modified core-shell powder is used for neutralizing biological secretions, guiding in-situ film formation, and improving compatibility with cementitious matrices.

[0056] Complexation-modified mineral powder is prepared by loading mineral powder with organophosphonic acid compounds capable of complexing with metal ions. It is used to react with metal ions in biological secretions and metal ions generated during cement hydration. Specifically, the complexation-modified mineral powder is aminotrimethylene phosphonic acid (ATMP) modified ultrafine mineral powder, wherein the loading of aminotrimethylene phosphonic acid is 3%~5% of the mass of the ultrafine mineral powder. The complexation-modified mineral powder is prepared by a method including the following steps:

[0057] P1. Disperse ultrafine mineral powder in deionized water, and add aminotrimethylene phosphonic acid, wherein the amount of aminotrimethylene phosphonic acid added is 3% to 5% of the mass of the ultrafine mineral powder;

[0058] P2. Stir the mixture at 50~60℃ for 1~2h to fully load aminotrimethylenephosphonic acid onto the surface of the ultrafine mineral powder;

[0059] P3. The product after the reaction is dried and ground to obtain the complexation reaction modified mineral powder.

[0060] The complexation reaction modified mineral powder is used to undergo a complexation reaction with metal ions in biological secretions, participating in a dual-response film-forming mechanism.

[0061] The zeolite powder-supported gypsum whisker composite powder is prepared by supporting gypsum whiskers with porous zeolite powder. It is used for the slow release of calcium ions and to provide physical sites for bioattachment. Specifically, the zeolite powder-supported gypsum whisker composite powder is made of natural zeolite powder supporting α-hemihydrate gypsum whiskers, wherein the pore size of the natural zeolite powder is 0.5~2μm, and the loading of α-hemihydrate gypsum whiskers is 15%~20%. The zeolite powder-supported gypsum whisker composite powder is prepared by a method including the following steps:

[0062] N1. Natural zeolite powder is activated by acid treatment with 5%~8% hydrochloric acid solution for 2~3 hours, filtered and washed until neutral, and then dried to obtain activated zeolite powder.

[0063] N2. Immerse the activated zeolite powder in an α-hemihydrate gypsum whisker slurry with a mass concentration of 10%~15% and adsorb at a constant temperature of 40~50℃ for 4~6 hours to load the α-hemihydrate gypsum whiskers onto the pores and surface of the activated zeolite powder.

[0064] N3. Filter to separate the solid product, and dry it at 60~70℃ to constant weight to obtain the zeolite powder supported gypsum whisker composite powder.

[0065] The zeolite powder-loaded gypsum whisker composite powder is used to achieve precise synergy between calcium ion slow release and bio-attachment sites.

[0066] The dosage ranges of each component in the cementitious material, based on the total mass, are as follows:

[0067] Ordinary Portland cement: 50%~55%; the ordinary Portland cement is PO 42.5;

[0068] Ultrafine mineral powder: 20%~25%; the specific surface area of ​​the ultrafine mineral powder is ≥450m². 2 / kg, activity index (28d) ≥95%;

[0069] Functional admixtures: 15%~20%, wherein the exclusive composite modified core-shell powder is 4%~6%, the complexation reaction modified mineral powder is 1%~2%, and the zeolite powder supported gypsum whisker composite powder is 6%~10%;

[0070] Polyacrylonitrile chopped strands: volume fraction of 0.15%~0.2%; fiber length of 6mm; tensile strength ≥800MPa;

[0071] And auxiliary components, including: 0.8%~1.2% polycarboxylate superplasticizer and 0.5% aliphatic organic amine rust inhibitor; the polycarboxylate superplasticizer is a retarding type with a water reduction rate ≥25%.

[0072] A method for preparing a protective system to improve the durability of concrete for coastal bridges includes the following steps:

[0073] A1. Graded premixing-ultrasound-assisted dispersion:

[0074] The exclusive composite modified core-shell powder is added to anhydrous ethanol solution and ultrasonically dispersed at 20-30 kHz and 300-500 W for 10-15 min. Then it is mixed with the polycarboxylate superplasticizer solution and mechanically stirred for 3-5 min until uniform to obtain core-shell powder premix.

[0075] The polyacrylonitrile short-cut fibers are premixed with a polyethylene glycol dispersant at a dosage of 2% to 3% of the mass of the polyacrylonitrile short-cut fibers. The fibers are then added in steps using a combination of mechanical stirring and airflow dispersion. The mechanical stirring speed is 300 to 500 r / min.

[0076] The zeolite powder-loaded gypsum whisker composite powder is mechanically premixed separately for 2-3 minutes and then set aside.

[0077] A2. Mixing and molding: Add aggregates, ordinary Portland cement, ultrafine mineral powder, all premixed functional materials obtained in step A1, and water in that order. The total mixing time shall not be less than 5 minutes. Then, vibrate and compact the mixture in layers to form the final product.

[0078] A3. Curing and application: After molding, place the precast concrete components in a constant temperature and humidity environment of 20±2℃ and ≥95% for 24 hours before demolding. Then, switch to the segmented curing mode. The total curing time shall not be less than 28 days, and finally form precast concrete components.

[0079] The precast concrete components are used in the concrete structures of coastal bridges to achieve active film-forming protection triggered by biological secretions.

[0080] The core working mechanism of this invention is as follows:

[0081] 1. Exclusive Composite Modified Core-Shell Powder Design and Technical Effects: Utilizing a "magnesium hydroxide core-hydroxyapatite shell" structure, the surface is modified with a composite of stearic acid and KH550 (mass ratio 1:1) to form an exclusive core-shell powder. The magnesium hydroxide core efficiently neutralizes organic acids in marine organism secretions, preventing the erosion of concrete hydration products; the hydroxyapatite shell is homologous to the components of shellfish shells, inducing directional attachment and shell fusion; the composite modification layer not only solves the problem of poor compatibility between single modifying materials and the cement matrix but also promotes uniform dispersion of the core-shell powder in the matrix, enabling synergistic effects of neutralization, film formation, and adhesion induction.

[0082] 2. Preparation and Technical Effects of Zeolite Powder-Supported Gypsum Whisker Composite Powder: Supported composite powder was prepared using an acid activation-isothermal adsorption process. The porous structure of zeolite powder provides stable bioattachment sites while simultaneously adsorbing harmful chloride ions from seawater; the supported gypsum whiskers slowly release Ca... 2+ This avoids the problem of rapid dissolution of gypsum whiskers leading to sudden changes in calcium ion concentration, improves the efficiency of shellfish attachment induction, and achieves precise synergy between slow release of calcium ions and supply of attachment sites, thus solving the defects of functional conflict and insufficient synergistic effect of single materials.

[0083] 3. "Secretion-Triggered Ion Complexation" Dual-Response Film-Forming Mechanism and Technical Effects: An active film-forming mechanism is constructed. When biological secretions come into contact with the concrete surface, on the one hand, it triggers the release of ions from the core-shell powder, which neutralizes the organic acids in the secretions to form insoluble salts; on the other hand, ATMP-modified ultrafine mineral powder undergoes a complexation reaction with metal ions and cement hydration ions in the secretions, forming an organic-inorganic interlocking protective film. This mechanism does not require external energy to drive it and can still actively respond in the absence of light, increasing the density of the protective film by more than 60%. While blocking chloride ions, it can also seamlessly integrate with the shells of subsequently growing shellfish, forming dual protection.

[0084] 4. Staged Premixing-Ultrasonic Assisted Dispersion Process and its Effects: The dispersion process is optimized for the specific characteristics of the modified materials. The core-shell powder is dispersed ultrasonically (20~30kHz, 300~500W) before being mixed with the water-reducing agent. Fibers are dispersed using a mechanical-airflow composite method, and the loaded powder is premixed separately. This process avoids damage to the core-shell structure, fiber agglomeration, and interference between different functional materials, improving the uniformity of dispersion of functional admixtures in the concrete matrix. This ensures that each material fully performs its function and enhances the stability of the protective effect.

[0085] Example 1 (Intermediate Dosage of Functional Blend)

[0086] (1) Basic materials

[0087] Ordinary Portland cement: PO 42.5, conforming to GB 175-2007 standard;

[0088] Ultrafine mineral powder: specific surface area 480m² 2 / kg, 28d activity index 98%;

[0089] Aggregates: crushed stone (5-25mm continuous gradation, crushing value ≤10%), medium sand (fineness modulus 2.6, mud content ≤1%).

[0090] Polyacrylonitrile chopped short fibers: 6mm in length, tensile strength 850MPa;

[0091] Polycarboxylate superplasticizer: retarded type, water reduction rate 28%;

[0092] Aliphatic organic amine rust inhibitor: industrial grade;

[0093] Anhydrous ethanol and polyethylene glycol dispersants: qualified industrial-grade products;

[0094] Water: Meets the standards for water used in concrete mixing;

[0095] Artificial seawater: salinity 3.2%, pH 8.1, simulating the ionic composition of the actual coastal environment.

[0096] (2) Preparation of special modified materials

[0097] The preparation steps for the proprietary composite modified core-shell powder are as follows:

[0098] S1. Disperse magnesium hydroxide micro powder in anhydrous ethanol solution and then sonicate it at 25 kHz for 6 min to form a suspension.

[0099] S2. Add hydroxyapatite precursor solution to the suspension and react at a constant temperature of 75℃ for 1.8h to generate core-shell powder with a "magnesium hydroxide core-hydroxyapatite shell" structure.

[0100] S3. Add a composite modifier of stearic acid and silane coupling agent to the reaction system. The mass ratio of stearic acid to silane coupling agent is 1:1. Continue stirring at 70°C for 2.5 h to carry out surface modification.

[0101] S4. The modified product is vacuum dried at 85°C for 5 hours and then ground until the overall particle size is 90~120nm (core particle size 60~80nm, shell thickness 30~40nm), thus obtaining the exclusive composite modified core-shell powder.

[0102] The preparation steps of complexation reaction modified mineral powder are as follows:

[0103] P1. Disperse ultrafine mineral powder in deionized water and add aminotrimethylene phosphonic acid (ATMP), wherein the amount of aminotrimethylene phosphonic acid added is 4% of the mass of the ultrafine mineral powder;

[0104] P2. Stir the mixture at 55°C for 1.5 hours to ensure that aminotrimethylenephosphonic acid is fully loaded onto the surface of the ultrafine mineral powder.

[0105] P3. The product after the reaction is dried and ground to obtain the complexation reaction modified mineral powder.

[0106] The preparation steps for zeolite powder-supported gypsum whisker composite powder are as follows:

[0107] N1. Natural zeolite powder is activated by acid treatment with 6% hydrochloric acid solution for 2.5 hours, filtered and washed until neutral, and then dried to obtain activated zeolite powder.

[0108] N2. The activated zeolite powder is immersed in 12% (w / w) α-hemihydrate gypsum whisker slurry and is kept at 45°C for 5 hours to allow α-hemihydrate gypsum whiskers to be loaded onto the pores and surface of the activated zeolite powder.

[0109] N3. Filter to separate the solid product, dry at 65°C to constant weight, with a loading of 18%, to obtain the zeolite powder-supported gypsum whisker composite powder.

[0110] (3) Cementitious material composition and dosage (by total mass, water-cement ratio 0.30):

[0111] Ordinary Portland cement: 52%;

[0112] Ultrafine mineral powder: 23%;

[0113] Functional admixtures: 17%, of which the exclusive composite modified core-shell powder is 5%, the complexation reaction modified mineral powder is 1.5%, and the zeolite powder supported gypsum whisker composite powder is 10.5%;

[0114] Polyacrylonitrile short-cut fibers: their volume content is 0.18%;

[0115] And auxiliary components, including: 1% polycarboxylate superplasticizer and 0.5% aliphatic organic amine rust inhibitor;

[0116] Water: Add according to the water-to-binder ratio.

[0117] (4) The preparation steps of the protection system are as follows:

[0118] A1. Graded Premixing-Ultrasonic Assisted Dispersion: The proprietary composite modified core-shell powder is added to anhydrous ethanol solution and ultrasonically dispersed at 25 kHz and 400 W for 12 min. Then, it is mixed with the polycarboxylate superplasticizer solution and mechanically stirred for 4 min until homogeneous to obtain a core-shell powder premix. The polyacrylonitrile short-cut fibers are premixed with polyethylene glycol dispersant at a dosage of 2.5% of the mass of the polyacrylonitrile short-cut fibers. Then, they are added step by step using a combination of mechanical stirring and airflow dispersion at a mechanical stirring speed of 350 r / min. The zeolite powder-loaded gypsum whisker composite powder is mechanically premixed separately for 2.5 min and set aside.

[0119] A2. Mixing and molding: Add the aggregate, ordinary Portland cement, ultrafine mineral powder, all premixed functional materials obtained in step A1, and water in that order. The total mixing time is 6 minutes. Then, vibrate and compact the mixture in layers to form the final product.

[0120] A3. Curing and Application: After molding, place the mold in a constant temperature and humidity environment of 20±2℃ and 96% for 24 hours before demolding. Then, switch to a segmented curing mode (1-6 days of continuous moisturizing curing, 7-14 days of artificial seawater spraying to simulate tides, and 15-28 days of enhanced fusion). The curing process uses intermittent seawater spraying with 12 hours of immersion and 12 hours of exposure. The seawater salinity is 3.2%, the spraying pressure is 0.15MPa, and the total curing time is 28 days.

[0121] (5) Performance test results

[0122] 28-day chloride ion flux: 680C;

[0123] 90-day sulfate attack strength loss rate: 3.2%;

[0124] 90d steel reinforcement corrosion potential: -150mV;

[0125] Shellfish attachment induction efficiency: 62% higher than ordinary coastal concrete.

[0126] Example 2 (Proportion of High-Functional Components)

[0127] (1) Basic materials

[0128] Same as Example 1.

[0129] (2) Preparation of special modified materials

[0130] Same as Example 1.

[0131] (3) Cementitious material composition and dosage (by total mass, water-cement ratio 0.29):

[0132] Ordinary Portland cement: 50%;

[0133] Ultrafine mineral powder: 22%;

[0134] Functional admixtures: 20%, of which the exclusive composite modified core-shell powder is 6%, the complexation reaction modified mineral powder is 2%, and the zeolite powder supported gypsum whisker composite powder is 12%.

[0135] Polyacrylonitrile short-cut fibers: their volume content is 0.18%;

[0136] And auxiliary components, including: 1% polycarboxylate superplasticizer and 0.5% aliphatic organic amine rust inhibitor;

[0137] Water: Add according to the water-to-binder ratio.

[0138] (4) Preparation steps of the protection system

[0139] Same as Example 1.

[0140] (5) Performance test results

[0141] 28-day chloride ion flux: 590C;

[0142] 90-day sulfate attack strength loss rate: 2.8%;

[0143] 90d steel reinforcement corrosion potential: -130mV;

[0144] Shellfish attachment induction efficiency: 75% higher than ordinary coastal concrete.

[0145] Example 3 (Low functional admixture ratio)

[0146] (1) Basic materials

[0147] Same as Example 1.

[0148] (2) Preparation of special modified materials

[0149] Same as Example 1.

[0150] (3) Cementitious material composition and dosage (by total mass, water-cement ratio 0.32):

[0151] Ordinary Portland cement: 55%;

[0152] Ultrafine mineral powder: 25%;

[0153] Functional admixtures: 15%, of which the exclusive composite modified core-shell powder is 4%, the complexation reaction modified mineral powder is 1%, and the zeolite powder supported gypsum whisker composite powder is 10%;

[0154] Polyacrylonitrile short-cut fibers: their volume content is 0.18%;

[0155] And auxiliary components, including: 1% polycarboxylate superplasticizer and 0.5% aliphatic organic amine rust inhibitor;

[0156] Water: Add according to the water-to-binder ratio.

[0157] (4) Preparation steps of the protection system

[0158] Same as Example 1.

[0159] (5) Performance test results

[0160] 28-day chloride ion flux: 780C;

[0161] 90-day sulfate attack strength loss rate: 4.5%;

[0162] 90d steel reinforcement corrosion potential: -180mV;

[0163] Shellfish attachment induction efficiency: 53% higher than ordinary coastal concrete.

[0164] Comparative Example 1 (lacking proprietary composite modified core-shell powder)

[0165] (1) Basic materials

[0166] Same as Example 1.

[0167] (2) Preparation of special modified materials

[0168] The preparation of the complexation reaction modified mineral powder and zeolite powder loaded with gypsum whisker composite powder is the same as in Example 1; there is no dedicated composite modified core-shell powder.

[0169] (3) Cementitious material composition and dosage (by total mass, water-cement ratio 0.30):

[0170] Ordinary Portland cement: 57% (to make up for the missing proportion of exclusive composite modified core-shell powder);

[0171] Functional admixture: 12%, of which the complexation reaction modified mineral powder is 1.5% and the zeolite powder-supported gypsum whisker composite powder is 10.5%;

[0172] The remaining components and dosages are the same as in Example 1.

[0173] (4) Preparation steps of the protection system

[0174] The maintenance and application are the same as in Example 1; the preparation differences are as follows: there is no ultrasonic dispersion step for the exclusive composite modified core-shell powder. The complexed reaction modified mineral powder, zeolite powder loaded with gypsum whisker composite powder and polycarboxylate superplasticizer solution are directly mechanically stirred for 4 minutes. The remaining dispersion and stirring parameters are the same as in Example 1.

[0175] (5) Performance test results

[0176] 28-day chloride ion flux: 1250C;

[0177] 90-day sulfate erosion intensity loss rate: 11.8%;

[0178] 90d steel reinforcement corrosion potential: -320mV;

[0179] Shellfish attachment induction efficiency: 18% higher than ordinary coastal concrete.

[0180] Comparative Example 2 (no special modifying materials were used; conventional powders were employed)

[0181] (1) Basic materials

[0182] Same as Example 1.

[0183] (2) Selection of alternative powders

[0184] Replacement for proprietary composite modified core-shell powder: ordinary magnesium hydroxide powder (particle size 100~200nm).

[0185] Alternative complexation reaction modified mineral powder: unmodified ultrafine mineral powder;

[0186] Alternative zeolite powder-supported gypsum whisker composite powder: ordinary gypsum whiskers (length 50~100μm).

[0187] (3) Components and dosage of cementitious materials (water-cement ratio 0.30 by total mass)

[0188] Consistent with Example 1, except that the functional admixtures were replaced with alternative powders (5% ordinary magnesium hydroxide powder, 1.5% unmodified ultrafine mineral powder, and 10.5% ordinary gypsum whiskers).

[0189] (4) Preparation steps of the protection system

[0190] The maintenance application is the same as in Example 1; the preparation differences are as follows: conventional stirring process is used, all powders are directly added to the aggregate after mixing, without graded premixing-ultrasonic assisted dispersion step, the fiber is directly added without predispersion, and conventional mechanical stirring (300r / min, 5min) is used.

[0191] (5) Performance test results

[0192] 28-day chloride ion flux: 1420C;

[0193] 90-day sulfate attack intensity loss rate: 15.3%;

[0194] 90d steel reinforcement corrosion potential: -380mV;

[0195] Shellfish attachment induction efficiency: 12% higher than ordinary coastal concrete;

[0196] Comparative Example 3 (without using graded premixing-ultrasonic dispersion process)

[0197] The preparation methods and parameters of the basic materials and special modified materials are completely consistent with those in Example 1.

[0198] Preparation steps of the protective system: The curing and application are the same as in Example 1; the differences in preparation are as follows: all powders are directly added to the aggregate after mixing, without a graded premixing step, and the fibers are directly added without pre-dispersing with polyethylene glycol dispersant, using conventional mechanical stirring (300r / min, 5min).

[0199] Performance test results

[0200] 28-day chloride ion flux: 980C;

[0201] 90-day sulfate attack strength loss rate: 8.6%;

[0202] 90d steel reinforcement corrosion potential: -260mV;

[0203] Shellfish attachment induction efficiency: 35% higher than ordinary coastal concrete.

[0204] Table 1 summarizes the core performance data of Examples 1-3 and Comparative Examples 1-3 above:

[0205] Table 1 Summary of Core Performance Data

[0206]

[0207] Note: Key indicators interpretation: ① The lower the chloride ion flux, the stronger the resistance to penetration; ② The lower the sulfate corrosion intensity loss rate, the stronger the corrosion resistance; ③ The closer the steel corrosion potential is to 0 (>-200mV means no risk of corrosion), the better the protective effect; ④ The higher the shellfish attachment induction efficiency, the more fully the composite protective structure is formed.

[0208] As shown in Table 1, the electrical flux of Examples 1-3 was all below 800C, with Example 2 (high-functionality internal dopant) having the lowest at only 590C and Example 3 (low dopant) having the highest at 780C. Overall, they were at the low permeability level (≤1000C is considered excellent). Compared with Comparative Example 1 (core-shell powder lacking), the flux was reduced by 45.6%~60.0%; compared with Comparative Example 2 (conventional powder, ordinary process), the flux was reduced by 45.1%~58.4%; and compared with Comparative Example 3 (lacking optimized process), the flux was reduced by 20.4%~39.8%. This is because the uniform dispersion of the proprietary composite modified core-shell powder, the complexation effect of the complexation reaction modified mineral powder, and the chloride ion adsorption of the zeolite powder synergistically construct a dense protective membrane, blocking the chloride ion permeation pathway and verifying the technical effect of "ion complexation-membrane structure densification".

[0209] The strength loss rate in Examples 1-3 was ≤4.5%, while in Example 2 it was only 2.8%, far below the industry standard (generally required to be ≤10%). This represents a reduction of 64.4%~75.4% compared to Comparative Example 1; a reduction of 70.6%~81.7% compared to Comparative Example 2; and a reduction of 47.7%~67.4% compared to Comparative Example 3. This is because the magnesium hydroxide core neutralizes the organic acids in biological secretions, preventing sulfates from reacting with cement hydration products to form expansive products; and the gypsum whiskers slowly release Ca... 2+ Optimize the hydration structure; together, they inhibit the strength loss caused by sulfate erosion.

[0210] The corrosion potentials in Examples 1-3 were all >-200mV (Example 1: -150mV, Example 2: -130mV, Example 3: -180mV), falling within the "no corrosion risk" range. The potentials were 53.1%~59.4% higher than Comparative Example 1 (-320mV); 52.6%~65.8% higher than Comparative Example 2 (-380mV); and 30.8%~46.2% higher than Comparative Example 3 (-260mV). This is due to the triple effect of the aliphatic organic amine corrosion inhibitor, the protective film's barrier to chloride ions, and the complexation reaction-modified mineral powder's complexation of metal ions, which prevents the damage to the passivation film on the steel reinforcement surface and inhibits the formation of corrosion cells from the root.

[0211] Examples 1-3 showed an increase in induction efficiency of 53%~75%, while Example 2 (high-performance admixture) reached 75%, far exceeding that of conventional concrete. Compared to Comparative Example 1 (core-shell-deficient powder), the efficiency was increased by 194.4%~316.7%; compared to Comparative Example 2 (conventional powder), the efficiency was increased by 341.7%~525.0%; and compared to Comparative Example 3 (lacking optimized process), the efficiency was increased by 51.4%~114.3%. This is because the hydroxyapatite shell is homologous to the shell of shellfish, inducing directional attachment of organisms; zeolite powder provides stable attachment sites; and gypsum whiskers slowly release Ca. 2+ It promotes the growth of shellfish shells, eventually forming a dual protective structure of a protective membrane and a biological shell.

[0212] In Comparative Example 1, the performance of various components deteriorated significantly after the absence of the proprietary composite modified core-shell powder (chloride ion flux doubled, sulfate erosion loss rate exceeded 3 times, and induction efficiency was only 18%). This demonstrates the irreplaceable role of the proprietary composite modified core-shell powder in the process of "neutralizing organic acids - inducing adhesion - synergistic film formation".

[0213] Comparative Example 2 used ordinary magnesium hydroxide and unmodified mineral powder to replace the special materials, and without any optimized process, the performance was the worst (electric flux 1420C, erosion loss rate 15.3%), which verified that the functional targeting of the special modified materials (such as core-shell structure, ATMP modification, and supported whiskers) far exceeds that of conventional materials.

[0214] Comparative Example 3 uses the same materials as Example 1, but without the optimized process, resulting in a decrease in performance. This indicates that the process can avoid material clumping and functional interference, ensure uniform dispersion of the special materials, and fully leverage the synergistic effect.

[0215] Example 2 (high dosage: 20%) > Example 1 (intermediate dosage: 17%) > Example 3 (low dosage: 15%). All performance indicators are positively correlated, proving that the dosage of functional admixtures is linearly related to the protective effect and can be flexibly adjusted according to engineering needs.

[0216] This invention achieves four core effects through the synergistic design of "dedicated modified materials, dual-response film-forming mechanism, and optimized process":

[0217] 1. Resistance to seepage and corrosion: Resistance to chloride ion penetration is increased by more than 60%, and the loss rate of sulfate erosion is controlled within 5%, solving the core pain point of ion erosion in coastal environments;

[0218] 2. Reinforcing steel protection capability: The corrosion potential is kept stable within the risk-free range to avoid structural cracking caused by reinforcing steel corrosion;

[0219] 3. Highly efficient construction of composite protection: The efficiency of shellfish attachment induction is increased by more than 50%, forming a dual protection of "active film formation and biological shell" to enhance long-term stability;

[0220] 4. Extended service life: Combined with various performance improvements, and the fact that no external coating is required during construction, it is suitable for the complex working conditions of coastal bridges.

[0221] The data fully demonstrates that this protective system effectively solves the shortcomings of existing technologies, such as "passive film formation, easy coating peeling, and insufficient functional synergy," and possesses technological advantages and engineering value.

[0222] The present invention has been described above by way of example. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any improvements made by adopting the inventive concept and technical solution of the present invention, or direct application to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A protective system for improving the durability of concrete in coastal bridges, characterized in that, The protective system is applied to concrete, which contains cementitious materials, aggregates and water, and the cementitious materials contain functional admixtures. The functional admixtures include: The proprietary composite modified core-shell powder has a core-shell structure of "alkaline inorganic core - bio-induced shell". Its surface is modified with organic compounds to release alkaline substances for neutralization reaction when in contact with marine organism secretions and to induce bioattachment. Complexation reaction modified mineral powder is prepared by loading mineral powder with organophosphonic acid compounds that can undergo complexation reaction with metal ions. It is used to undergo complexation reaction with metal ions in biological secretions and metal ions produced by cement hydration. Zeolite powder-supported gypsum whisker composite powder, which is made by supporting gypsum whiskers with porous zeolite powder, is used to slowly release calcium ions and provide physical sites for bioattachment.

2. The protective system for improving the durability of concrete in coastal bridges according to claim 1, characterized in that, The dosage ranges of each component in the cementitious material, based on the total mass, are as follows: Ordinary Portland cement: 50%~55%; Ultrafine mineral powder: 20%~25%; Functional admixtures: 15%~20%, wherein the exclusive composite modified core-shell powder is 4%~6%, the complexation reaction modified mineral powder is 1%~2%, and the zeolite powder supported gypsum whisker composite powder is 6%~12%; Polyacrylonitrile short-cut fibers: their volume content is 0.15%~0.2%; And auxiliary components, including: 0.8%~1.2% polycarboxylate superplasticizer and 0.5% aliphatic organic amine rust inhibitor.

3. The protective system for improving the durability of concrete in coastal bridges according to claim 2, characterized in that, The proprietary composite modified core-shell powder has a "magnesium hydroxide core-hydroxyapatite shell" structure, with a core particle size of 50~100nm, a shell thickness of 20~50nm, and an overall particle size of 70~150nm. The surface of the proprietary composite modified core-shell powder is modified by a combination of stearic acid and silane coupling agent, with a mass ratio of stearic acid to silane coupling agent of 1:

1.

4. A protective system for improving the durability of concrete in coastal bridges according to claim 3, characterized in that, The proprietary composite modified core-shell powder is prepared by a method comprising the following steps: S1. Disperse magnesium hydroxide micro powder in anhydrous ethanol solution and ultrasonically disperse it at 20~30kHz for 5~8min to form a suspension; S2. Add hydroxyapatite precursor solution to the suspension and react at a constant temperature of 70~80℃ for 1.5~2h to generate core-shell powder with a "magnesium hydroxide core-hydroxyapatite shell" structure; S3. Add a composite modifier of stearic acid and silane coupling agent to the reaction system. The mass ratio of stearic acid to silane coupling agent is 1:

1. Continue stirring at 60~80℃ for 2~3h to carry out surface modification. S4. The modified product is vacuum dried at 80~90℃ for 4~6h and ground until the overall particle size is 70~150nm to obtain the exclusive composite modified core-shell powder. The proprietary composite modified core-shell powder is used for neutralizing biological secretions, guiding in-situ film formation, and improving compatibility with cementitious matrices.

5. A protective system for improving the durability of concrete in coastal bridges according to claim 2, characterized in that, The complexation reaction modified mineral powder is an aminotrimethylene phosphonic acid modified ultrafine mineral powder, wherein the loading of aminotrimethylene phosphonic acid is 3% to 5% of the mass of the ultrafine mineral powder.

6. A protective system for improving the durability of concrete in coastal bridges according to claim 5, characterized in that, The complexation reaction modified mineral powder is prepared by a method including the following steps: P1. Disperse ultrafine mineral powder in deionized water, and add aminotrimethylene phosphonic acid, wherein the amount of aminotrimethylene phosphonic acid added is 3% to 5% of the mass of the ultrafine mineral powder; P2. Stir the mixture at 50~60℃ for 1~2h to fully load aminotrimethylenephosphonic acid onto the surface of the ultrafine mineral powder; P3. The product after the reaction is dried and ground to obtain the complexation reaction modified mineral powder. The complexation reaction modified mineral powder is used to undergo a complexation reaction with metal ions in biological secretions, participating in a dual-response film-forming mechanism.

7. A protective system for improving the durability of concrete in coastal bridges according to claim 2, characterized in that, The zeolite powder-supported gypsum whisker composite powder is specifically natural zeolite powder-supported α-hemihydrate gypsum whiskers, wherein the pore size of the natural zeolite powder is 0.5~2μm, and the loading of α-hemihydrate gypsum whiskers is 15%~20%.

8. A protective system for improving the durability of concrete in coastal bridges according to claim 7, characterized in that, The zeolite powder-supported gypsum whisker composite powder is prepared by a method including the following steps: N1. Natural zeolite powder is activated by acid treatment with 5%~8% hydrochloric acid solution for 2~3 hours, filtered and washed until neutral, and then dried to obtain activated zeolite powder. N2. Immerse the activated zeolite powder in an α-hemihydrate gypsum whisker slurry with a mass concentration of 10%~15% and adsorb at a constant temperature of 40~50℃ for 4~6 hours to load the α-hemihydrate gypsum whiskers onto the pores and surface of the activated zeolite powder. N3. Filter to separate the solid product, and dry it at 60~70℃ to constant weight to obtain the zeolite powder supported gypsum whisker composite powder. The zeolite powder-loaded gypsum whisker composite powder is used to achieve precise synergy between calcium ion slow release and bio-attachment sites.

9. A method for preparing a protective system for improving the durability of concrete in coastal bridges as described in any one of claims 2-8, characterized in that, Includes the following steps: A1. Graded premixing-ultrasound-assisted dispersion: The exclusive composite modified core-shell powder is added to anhydrous ethanol solution and ultrasonically dispersed at 20-30 kHz and 300-500 W for 10-15 min. Then it is mixed with the polycarboxylate superplasticizer solution and mechanically stirred for 3-5 min until uniform to obtain core-shell powder premix. The polyacrylonitrile short-cut fibers are premixed with a polyethylene glycol dispersant at a dosage of 2% to 3% of the mass of the polyacrylonitrile short-cut fibers. The fibers are then added in steps using a combination of mechanical stirring and airflow dispersion. The mechanical stirring speed is 300 to 500 r / min. The zeolite powder-loaded gypsum whisker composite powder is mechanically premixed separately for 2-3 minutes and then set aside. A2. Mixing and molding: Add aggregates, ordinary Portland cement, ultrafine mineral powder, all premixed functional materials obtained in step A1, and water in that order. The total mixing time shall not be less than 5 minutes. Then, vibrate and compact the mixture in layers to form the final product. A3. Curing and application: After molding, place the precast concrete components in a constant temperature and humidity environment of 20±2℃ and ≥95% for 24 hours before demolding. Then, switch to the segmented curing mode. The total curing time shall not be less than 28 days, and finally form precast concrete components. The precast concrete components are used in the concrete structures of coastal bridges to achieve active film-forming protection triggered by biological secretions.

Images