Preparation method of marine concrete heavy anti-corrosion coating

Abstract

The invention relates to the technical field of building materials and ocean engineering protection, in particular to a preparation method of a marine concrete heavy anti-corrosion coating. Comprising the following steps: 1, preparing materials and carrying out dry mixing to obtain an inorganic dry powder base material; step 2, preparing and mixing wet materials, taking polymer emulsion, a silane coupling agent and water, and uniformly mixing the polymer emulsion, the silane coupling agent and the water; in a stirring state, slowly dropwise adding the mixed solution into the inorganic dry powder base material in the step 1; step 3, dispersion and defoaming: stirring is kept in the dropwise adding process, a defoaming agent is added, high-speed dispersion is performed until the slurry is in a uniform flow state and has no obvious bubbles, and heavy-duty cement-based composite coating slurry is obtained; 4, film forming construction is conducted, specifically, a concrete base surface is coated with the slurry obtained in the step 3 through a layered coating technology, and an anti-corrosion coating is formed after standing and curing. According to the invention, the physical compactness of the coating is greatly improved, the water absorption rate of the coating is obviously reduced, and the anti-permeability pressure is improved.

Description

Technical Field

[0001] This invention relates to the field of building materials and marine engineering protection technology, specifically to a method for preparing a heavy-duty anti-corrosion coating for marine concrete. Background Technology

[0002] Offshore concrete structures are exposed to harsh environments such as chloride ion erosion, wet-dry cycles, and seawater immersion for extended periods, placing extremely high demands on the durability of protective coatings. However, existing conventional cement-based anti-corrosion materials often lack effective micro-filling effects, resulting in insufficient structural density and difficulty in effectively blocking corrosive media such as chloride ions from penetrating through large capillary pores. Simultaneously, traditional inorganic materials or composite coatings with low polymer content typically suffer from brittleness, poor flexibility, and insufficient adhesion, failing to form a continuous and complete organic polymer film network between inorganic cement hydration products. This makes them prone to cracking and peeling when faced with substrate micro-deformation, dynamic loads, or temperature changes, thus negating the protective advantages of the interface-reinforced structure. Therefore, there is an urgent need for a heavy-duty anti-corrosion coating preparation scheme for offshore concrete that can combine excellent physical shielding performance and mechanical flexibility by constructing a high-density inorganic-organic interpenetrating network structure. This would effectively resist chloride ion penetration and adapt to substrate deformation in different environments such as splash zones and immersion zones, significantly improving impermeability and long-term service life. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a heavy-duty anti-corrosion coating for marine concrete. By constructing a high-density inorganic-organic interpenetrating network structure, it overcomes the shortcomings of existing conventional cement-based anti-corrosion materials, such as poor micro-filling effect and the brittleness and easy peeling of composite coatings. Furthermore, it achieves excellent physical shielding performance and mechanical flexibility, thereby effectively resisting chloride ion penetration and adapting to substrate deformation in harsh marine environments. Specifically, the technical solution of this invention is as follows:

[0004] A method for preparing a heavy-duty anti-corrosion coating for marine concrete includes the following steps:

[0005] Step 1: Material preparation and dry mixing. Weigh cement, ultrafine active filler, functional filler and fine sand according to the preset ratio; put the above dry powder materials into the mixer and mechanically stir until they are mixed evenly to obtain inorganic dry powder base material.

[0006] Step 2: Wet material preparation and mixing. Take the polymer emulsion, silane coupling agent and water, and mix them evenly. Under stirring, slowly add the mixture dropwise to the inorganic dry powder base material described in Step 1.

[0007] Step 3: Dispersion and defoaming. During the dripping process, keep stirring, add defoamer, and disperse at high speed until the slurry is uniformly flowing and has no obvious bubbles, thus obtaining the heavy-duty anti-corrosion cement-based composite coating slurry.

[0008] Step 4: Film formation construction. A layered coating process is used to apply the slurry obtained in Step 3 to the concrete substrate. After static curing, an anti-corrosion coating is formed.

[0009] Preferably, the mass ratio of the cement, ultrafine active filler, functional filler, fine sand, polymer emulsion, silane coupling agent and defoamer is (45-55):(8-12):(1-5):(3-7):(35-45):(0.1-0.5):(0.3-0.8).

[0010] Preferably, the polymer emulsion is selected from either silicone-acrylic emulsion or styrene-butadiene emulsion; the solid content of the polymer emulsion is 38%-42%.

[0011] Preferably, the ultrafine active filler is any one or a mixture of two of silica fume and nano silica; the functional filler is any one of graphite powder and zinc-aluminum composite anti-rust pigment.

[0012] Preferably, in step 2, the water-to-material ratio is controlled between 0.35 and 0.45; the water-to-material ratio refers to the ratio of the total amount of water added during wet material preparation to the total mass of the inorganic dry powder base material; during the mixing process of the polymer emulsion and the inorganic dry powder base material, continuous stirring is required to form a polymer-cement-based composite system.

[0013] Preferably, in step 3, the defoamer is 0.3-0.8 parts by mass; the dispersion process must ensure that there are no agglomerated particles in the slurry.

[0014] Preferably, in step 4, the layered coating process specifically involves: applying the coating using airless spraying or roller coating; repeating the coating operation at least twice, controlling the thickness of each layer, so that the total coating thickness reaches 1.8-2.2 mm.

[0015] Preferably, during the layered coating process, the application interval between two adjacent coating layers is 3-5 hours; before applying the next coating layer, it is necessary to confirm that the previous coating layer has basically cured.

[0016] Preferably, in step 4, the static curing includes: after the coating is applied, it is naturally cured at room temperature for at least 24 hours before demolding or subsequent treatment; the overall curing cycle is 6-8 days.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. This invention, by compounding ultrafine active fillers such as silica fume or nano-silica into an inorganic dry powder base, utilizes the micro-filling effect generated by their extremely small particle size and the pozzolanic reaction with calcium hydroxide to effectively fill the micro-capillary pores between cement hydration products, significantly improving the physical density of the coating; this technical feature directly solves the problem in the background art where existing conventional cement-based materials have a loose structure and are unable to block the penetration of corrosive media such as chloride ions due to the lack of effective micro-filling, significantly reducing the water absorption rate of the coating and improving its anti-seepage pressure;

[0019] 2. This invention uses a high-content polymer emulsion combined with cement aggregate, and through a specific wet material preparation and mixing process, constructs a continuous and complete inorganic-organic interpenetrating network structure inside the coating. The flexible network formed after polymer film formation interweaves with the rigid cement hydration products, effectively overcoming the defects of traditional inorganic coatings or low polymer content composite coatings in the background technology, which are brittle and have poor flexibility. This gives the coating excellent elongation at break and interfacial adhesion, so that it can remain intact when faced with micro-deformation of marine engineering substrate, dynamic load or temperature difference changes, and avoid cracking and peeling.

[0020] 3. This invention introduces graphite powder or zinc-aluminum composite anti-rust pigments as functional fillers into the formulation system. On the basis of providing physical shielding, it endows the coating with electrochemical cathodic protection performance for the zinc-aluminum composite anti-rust pigment system, or endows the coating with enhanced wear resistance and weather resistance for the graphite powder system. This multi-dimensional synergistic protection mechanism specifically solves the corrosion protection problem of marine concrete in extreme environments such as wet-dry cycles in the splash zone and seawater immersion, effectively delays the diffusion path of corrosive media, and significantly extends the service life of marine concrete structures in harsh service environments.

[0021] 4. This invention ensures the uniform flow of the slurry and effectively eliminates internal air bubbles and agglomerated particles by strictly controlling the water-to-material ratio, the timing of adding defoamer, and the construction process that combines high-speed dispersion with layered coating. The control of layered coating and interlayer interval avoids the risk of sagging or cracking caused by excessive thickness of a single coating, ensuring that the final anti-corrosion coating has a uniform thickness and is free of pinhole defects, thereby guaranteeing the stability and reliability of the overall protective performance of the coating. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1This is a flowchart of the preparation process of the present invention;

[0024] Figure 2 A schematic diagram of the microstructure of an inorganic-organic interpenetrating network containing silica fume micro-aggregates (based on Example 3);

[0025] Figure 3 This is a schematic diagram of the cross-sectional structure of a multi-layer anti-corrosion coating. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] Example 1:

[0028] This embodiment provides a method for preparing a heavy-duty anti-corrosion coating for marine concrete, including the following steps: Step 1: Material preparation and dry mixing. Weigh cement, ultrafine active filler, functional filler, and fine sand according to a preset ratio; put the above dry powder materials into a mixer and mechanically stir until they are uniformly mixed to obtain an inorganic dry powder base material; Step 2: Wet material preparation and mixing. Take polymer emulsion, silane coupling agent, and water, and mix them uniformly; while stirring, slowly add the mixture to the inorganic dry powder base material in Step 1; Step 3: Dispersion and defoaming. Keep stirring during the dripping process, add a defoamer, and disperse at high speed until the slurry is uniformly flowing and has no obvious bubbles, to obtain a heavy-duty anti-corrosion cement-based composite coating slurry; Step 4: Film formation and construction. Using a layered coating process, apply the slurry obtained in Step 3 to the concrete substrate, and after static curing, form an anti-corrosion coating;

[0029] The mass ratio of cement, ultrafine active filler, functional filler, fine sand, polymer emulsion, silane coupling agent, and defoamer is 45:8:1:3:35:0.1:0.3; the polymer emulsion is silicone-acrylic emulsion with a solid content of 38%; the ultrafine active filler is silica fume; the functional filler is graphite powder; in step 2, the water-to-material ratio is controlled at 0.35; in step 3, the defoamer in the above proportion is added; in step 4, the layered coating process is as follows: airless spraying is used for construction; the thickness of each layer is controlled to achieve a total coating thickness of 1.8 mm; the application interval between two adjacent layers is 3 hours; after natural curing at room temperature for 24 hours, the coating is demolded, and the overall curing period is 6 days.

[0030] This embodiment controls the ratio of cement to ultrafine active filler to the lower end of the mixing range, and combines it with 35 parts of silicone-acrylic emulsion. The pozzolanic effect of silica fume is used to fill the pores between cement hydration products, so that the formed anti-corrosion coating can ensure basic physical shielding performance while having good interfacial bonding force. It is suitable for the protection of marine non-submerged structures where coating thickness requirements are relatively sensitive, and effectively slows down the initial penetration of chloride ions.

[0031] Example 2:

[0032] This embodiment provides a method for preparing a heavy-duty anti-corrosion coating for marine concrete, including the following steps: Step 1: Material preparation and dry mixing. Weigh cement, ultrafine active filler, functional filler, and fine sand according to a preset ratio; put the above dry powder materials into a mixer and mechanically stir until they are uniformly mixed to obtain an inorganic dry powder base material; Step 2: Wet material preparation and mixing. Take polymer emulsion, silane coupling agent, and water, and mix them uniformly; while stirring, slowly add the mixture to the inorganic dry powder base material in Step 1; Step 3: Dispersion and defoaming. Keep stirring during the dripping process, add a defoamer, and disperse at high speed until the slurry is uniformly flowing and has no obvious bubbles, to obtain a heavy-duty anti-corrosion cement-based composite coating slurry; Step 4: Film formation and construction. Using a layered coating process, apply the slurry obtained in Step 3 to the concrete substrate, and after static curing, form an anti-corrosion coating;

[0033] The mass ratio of cement, ultrafine active filler, functional filler, fine sand, polymer emulsion, silane coupling agent, and defoamer is 50:10:3:5:40:0.3:0.55; the polymer emulsion is styrene-butadiene emulsion with a solid content of 40%; the ultrafine active filler is nano-silica; the functional filler is zinc-aluminum composite anti-rust pigment; in step 2, the water-to-material ratio is controlled at 0.40; in step 3, the amount of defoamer added is 0.5% of the total mass of the coating; in step 4, the layered coating process is as follows: the coating is applied by roller coating; the thickness of each layer is controlled so that the total coating thickness reaches 2.0 mm; the application interval between two adjacent layers is 4 hours; the coating is naturally cured at room temperature for 30 hours before demolding, and the overall curing period is 7 days.

[0034] In this embodiment, a mixture of 50 parts cement and 10 parts nano silica is used. The filling effect of the nanoparticles and the flexible polymer film formed by 40 parts styrene-butadiene emulsion are intertwined. The addition of zinc-aluminum composite anti-rust pigment further enhances the electrochemical protection capability of the coating. This anti-corrosion coating exhibits good weather resistance and crack resistance in the wet and dry cycle environment of the splash zone, reducing the risk of corrosion caused by microcracks in the substrate.

[0035] Example 3:

[0036] This embodiment provides a method for preparing a heavy-duty anti-corrosion coating for marine concrete, including the following steps: Step 1: Material preparation and dry mixing. Weigh cement, ultrafine active filler, functional filler, and fine sand according to a preset ratio; put the above dry powder materials into a mixer and mechanically stir until they are uniformly mixed to obtain an inorganic dry powder base material; Step 2: Wet material preparation and mixing. Take polymer emulsion, silane coupling agent, and water, and mix them uniformly; while stirring, slowly add the mixture to the inorganic dry powder base material in Step 1; Step 3: Dispersion and defoaming. Keep stirring during the dripping process, add a defoamer, and disperse at high speed until the slurry is uniformly flowing and has no obvious bubbles, to obtain a heavy-duty anti-corrosion cement-based composite coating slurry; Step 4: Film formation and construction. Using a layered coating process, apply the slurry obtained in Step 3 to the concrete substrate, and after static curing, form an anti-corrosion coating;

[0037] The mass ratio of cement, ultrafine active filler, functional filler, fine sand, polymer emulsion, silane coupling agent, and defoamer is 55:12:5:7:45:0.5:0.8. The polymer emulsion used is silicone-acrylic emulsion with a solid content of 42%. The ultrafine active filler is a mixture of silica fume and nano-silica. The functional filler is graphite powder. In step 2, the water-to-material ratio is controlled at 0.45. In step 3, the defoamer in the above-mentioned proportion is added. In step 4, the layered coating process is as follows: airless spraying is used for construction; the thickness of each layer is controlled to achieve a total coating thickness of 2.2 mm; the application interval between adjacent layers is 5 hours; after natural curing at room temperature for 36 hours, the coating is demolded, with an overall curing period of 8 days.

[0038] This embodiment constructs a high-density inorganic-organic interpenetrating network structure by increasing the proportions of cement to 55 parts, ultrafine active filler to 12 parts, and polymer emulsion to 45 parts. The 2.2mm thick coating provides a longer diffusion path for corrosive media, making it particularly suitable for concrete pile foundations that are submerged in seawater for extended periods. This significantly improves the coating's resistance to seepage pressure and its long-term service life.

[0039] Example 4:

[0040] This embodiment provides a method for preparing a heavy-duty anti-corrosion coating for marine concrete, including the following steps: Step 1: Material preparation and dry mixing. Weigh cement, ultrafine active filler, functional filler, and fine sand according to a preset ratio; put the above dry powder materials into a mixer and mechanically stir until they are uniformly mixed to obtain an inorganic dry powder base material; Step 2: Wet material preparation and mixing. Take polymer emulsion, silane coupling agent, and water, and mix them uniformly; while stirring, slowly add the mixture to the inorganic dry powder base material in Step 1; Step 3: Dispersion and defoaming. Keep stirring during the dripping process, add a defoamer, and disperse at high speed until the slurry is uniformly flowing and has no obvious bubbles, to obtain a heavy-duty anti-corrosion cement-based composite coating slurry; Step 4: Film formation and construction. Using a layered coating process, apply the slurry obtained in Step 3 to the concrete substrate, and after static curing, form an anti-corrosion coating;

[0041] The mass ratio of cement, ultrafine active filler, functional filler, fine sand, polymer emulsion, silane coupling agent, and defoamer is 48:9:2:4:38:0.2:0.4; the polymer emulsion is a silicone-acrylic emulsion with a solid content of 39%; the ultrafine active filler is silica fume; the functional filler is a zinc-aluminum composite anti-rust pigment; in step 2, the water-to-material ratio is controlled at 0.38; in step 3, the defoamer in the above proportion is added; in step 4, the layered coating process is specifically carried out by roller coating; the single layer is controlled... The coating thickness is set to a total coating thickness of 1.9 mm; the application interval between two adjacent coating layers is 3.5 hours; after natural curing at room temperature for 28 hours, the coating is demolded, and the overall curing period is 7 days. In this embodiment, by adjusting each component to the medium-low range, the fluidity and thixotropy of the slurry are balanced, resulting in a more uniform distribution of fine sand particles in the coating, reducing sagging during construction. The resulting coating has a low water absorption rate and good coverage and adaptability for complex marine engineering irregular surfaces.

[0042] Example 5:

[0043] This embodiment provides a method for preparing a heavy-duty anti-corrosion coating for marine concrete, including the following steps: Step 1: Material preparation and dry mixing. Weigh cement, ultrafine active filler, functional filler, and fine sand according to a preset ratio; put the above dry powder materials into a mixer and mechanically stir until they are uniformly mixed to obtain an inorganic dry powder base material; Step 2: Wet material preparation and mixing. Take polymer emulsion, silane coupling agent, and water, and mix them uniformly; while stirring, slowly add the mixture to the inorganic dry powder base material in Step 1; Step 3: Dispersion and defoaming. Keep stirring during the dripping process, add a defoamer, and disperse at high speed until the slurry is uniformly flowing and has no obvious bubbles, to obtain a heavy-duty anti-corrosion cement-based composite coating slurry; Step 4: Film formation and construction. Using a layered coating process, apply the slurry obtained in Step 3 to the concrete substrate, and after static curing, form an anti-corrosion coating;

[0044] The mass ratio of cement, ultrafine active filler, functional filler, fine sand, polymer emulsion, silane coupling agent, and defoamer is 52:11:4:6:42:0.4:0.7; the polymer emulsion is styrene-butadiene emulsion with a solid content of 41%; the ultrafine active filler is nano-silica; the functional filler is graphite powder; in step 2, the water-to-material ratio is controlled at 0.42; in step 3, the defoamer in the above proportion is added; in step 4, the layered coating process specifically involves: using airless spraying; controlling the thickness of each layer to ensure... The total coating thickness reaches 2.1 mm; the application interval between two adjacent coating layers is 4.5 hours; after natural curing at room temperature for 32 hours, the coating is demolded, and the overall curing cycle is 7.5 days. In this embodiment, 52 parts of cement and a relatively high proportion of 11 parts of nano-silica are used to enhance the filling effect of micropores. Combined with the toughness provided by 42 parts of styrene-butadiene emulsion, the anti-corrosion coating can still maintain the integrity of the structure when subjected to dynamic loads or basic deformation caused by temperature changes, reducing the propagation of microcracks. It is suitable for marine engineering exposure environments with large temperature differences.

[0045] In Examples 1-5 and Comparative Examples 1-2, the cement was P.O42.5 ordinary Portland cement, sourced from Anhui Conch Cement Co., Ltd.; the silica fume was from Shanghai Maclean Biochemical Technology Co., Ltd., CAS No.: 69012-64-2, with SiO2 content ≥92%; the nano silica was from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 7631-86-9, with an average particle size of 15-20nm, and was hydrophilic; the graphite powder was from Sinopharm Chemical Reagent Co., Ltd., CAS No.: 7782-42-5, with purity >99.85%; and the zinc-aluminum composite anti-rust pigment was from Hunan Jinzhu. The following materials were supplied by the company: New Materials Co., Ltd., product model ZAP-01; Modified silane coupling agent (γ-methacryloyloxypropyltrimethoxysilane, KH-570) from Nanjing Jiecheng Chemical Co., Ltd., CAS No.: 2530-85-0; Silicone-acrylic emulsion from Badifu Group Co., Ltd., model RS-3788; Styrene-butadiene emulsion from BASF (China) Co., Ltd., model SD-623; Defoamer from BYK Chemical, model BYK-024; Ordinary fly ash from Gongyi Fuda Water Purification Materials Co., Ltd., grade II; Fine sand was commercially available washed river sand, fineness modulus 1.6-2.2; All other products were commercially available.

[0046] Comparative Example 1:

[0047] This comparative example provides a method for preparing a heavy-duty anti-corrosion coating for marine concrete. The preparation steps are basically the same as those in Example 2, except that: no ultrafine active filler is added to the inorganic dry powder base material, but an equal mass of ordinary fly ash is used instead, and no functional filler is added; specifically, the mass ratio of cement, ordinary fly ash, fine sand, polymer emulsion and defoamer is 50:10:5:40:0.55; due to the lack of micro-filling effect and pozzolanic reaction of ultrafine active filler, the microstructure of the coating prepared in this comparative example is relatively poor. Although the polymer emulsion provides a certain film-forming property, in a high salt spray environment, chloride ions can easily penetrate through larger capillary pores, resulting in its impermeability and long-term anti-corrosion effect being inferior to that of Example 2. The water absorption test results show that its water absorption rate is significantly higher than that of Example 2.

[0048] Comparative Example 2:

[0049] This comparative example provides a method for preparing a heavy-duty anti-corrosion coating for marine concrete. The preparation steps are basically the same as in Example 2, except that the amount of polymer emulsion is significantly reduced and the amount of water is increased accordingly to maintain workability. Specifically, the mass ratio of cement, ultrafine active filler, fine sand, polymer emulsion, and defoamer is 65:10:5:10:0.55. Due to the low content of polymer emulsion, a continuous and complete organic polymer film network cannot be formed between the inorganic cement hydration products, resulting in obvious brittleness of the coating and a significant decrease in adhesion and flexibility. When the substrate undergoes wet-dry cycles or micro-deformation, the coating is prone to cracking and peeling, losing the protective advantages brought by the interface reinforcement structure and failing to meet the stringent requirements of heavy-duty anti-corrosion in marine engineering.

[0050] The heavy-duty anti-corrosion coatings for marine concrete prepared in Examples 1-5 and Comparative Examples 1-2 were tested accordingly, and the test results are shown below:

[0051] (1) Chloride ion diffusion coefficient test:

[0052] To evaluate the coating's ability to resist chloride ion penetration in marine environments, the chloride ion diffusion coefficients of the anti-corrosion coatings prepared in Examples 1-5 and Comparative Examples 1-2 were tested. The test method referred to the RCM method (unsteady-state chloride ion migration method) in the national standard GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete". The testing equipment used was the NEL-RCM type concrete chloride ion diffusion coefficient tester (Beijing NEL Instrument Equipment Co., Ltd., China).

[0053] The specific operation was as follows: the coated specimen (cut into cylinders with a diameter of 100mm ± 1mm ​​and a height of 50mm ± 2mm) after curing was placed in a vacuum saturation chamber for saturation treatment for 24 hours; then the specimen was installed in the rubber sleeve of the measuring instrument, 0.3mol / L NaOH solution was injected into the anode tank, and 10% NaCl solution was injected into the cathode tank; in an indoor environment of 20±2℃, a DC voltage of 60V was applied and continuously energized for 24 hours; after the test, the specimen was split along the axial direction, and 0.1mol / L AgNO3 solution was sprayed for color development, the chloride ion penetration depth was measured, and the unsteady chloride ion migration coefficient was calculated; to ensure the accuracy of the data, three parallel samples were prepared for each example and comparative example for repeated testing. After removing outliers, the arithmetic mean of the remaining data was taken as the final recorded result. The test results are shown in Table 1.

[0054] Table 1

[0055] As shown in Table 1, the heavy-duty anti-corrosion coatings for marine concrete prepared by this invention all exhibit extremely low chloride ion diffusion coefficients, demonstrating excellent resistance to chloride ion penetration. Among them, Example 3 shows the best barrier performance, with a chloride ion diffusion coefficient of only 1.24. ;

[0056] Trend analysis shows that the density of the coating is significantly improved with the optimization of the ratio of ultrafine active filler to polymer emulsion. Example 3 uses a compound system of silica fume and nano silica, combined with a high content of silicone-acrylic emulsion, to construct a dual shielding structure of inorganic-organic interpenetrating network + multi-scale micro-aggregate filling. The ultrafine particle size of nano silica effectively fills the micron-scale pores between cement hydration products and fine sand aggregate, while the pozzolanic effect of silica fume further consumes easily soluble calcium hydroxide and refines the pore size.

[0057] Comparative analysis revealed that the performance of Examples 1-5 was significantly better than that of Comparative Examples 1 and 2. Although Comparative Example 1 maintained a high polymer emulsion content, it used ordinary fly ash instead of ultrafine active filler. Due to the larger particle size and lower activity of fly ash compared to silica fume and nano silica, its early micro-filling effect and later secondary hydration reaction were weaker, resulting in more interconnected capillary channels inside the coating and a shorter chloride ion migration path, thus leading to a higher diffusion coefficient.

[0058] Comparative Example 2 had the worst performance, with a chloride ion diffusion coefficient as high as 5.89. This is because Comparative Example 2 significantly reduced the amount of polymer emulsion used, making it impossible to form a continuous and complete organic polymer film in the cement matrix. Without the flexible polymer film wrapping and bridging, the inorganic matrix is ​​prone to microcracks during curing and shrinkage, which become channels for rapid chloride ion intrusion. Furthermore, the addition of the zinc-aluminum composite anti-rust pigment in the examples further delayed the deep migration of the corrosive medium through physical shielding and sacrificial anode effects, while the absence of this component in Comparative Example 1 also led to a decrease in protective capability. In summary, the continuous film structure formed by the polymer emulsion and the dense filling effect of the ultrafine active filler are the key factors determining the coating's resistance to chloride ion penetration.

[0059] (2) Bond strength test:

[0060] To evaluate the interfacial bonding ability between the coating and the concrete substrate, tensile bond strength tests were conducted on the anti-corrosion coatings prepared in Examples 1-5 and Comparative Examples 1-2. The test method referred to the industry standard JG / T336-2011 "Polymer Cement Mortar for Repair of Concrete Structures", and the equipment used was an HC-6000C fully automatic pull-out tester (Haichuang High-Tech (Beijing) Technology Co., Ltd., China).

[0061] The specific operation is as follows: apply anti-corrosion coating to a standard concrete base block and cure it to the specified age; use epoxy resin to bond a 40mm diameter steel pull-out head to the coating surface, and after curing for 24 hours, cut the coating down to the substrate along the pull-out head; start the pull-out tester and apply a tensile force vertically upward at a loading rate of 0.05MPa / s until the coating is damaged or peeled off, and record the maximum failure load; record the failure mode as cohesive failure or interface failure; each group of samples is tested 5 times repeatedly, and after removing the maximum and minimum values, the arithmetic mean of the remaining 3 values ​​is taken. The test results are shown in Table 2.

[0062] Table 2

[0063] As shown in Table 2, the coatings prepared in Examples 1-5 exhibit extremely strong interfacial adhesion to the concrete substrate, with bond strengths exceeding 2.3 MPa, far surpassing the standard requirements for general marine coatings. Example 3 demonstrates the highest bond strength, attributed to the synergistic effect of its high polymer emulsion content and modified silane coupling agent. In-depth mechanistic analysis reveals that the KH-570 modified silane coupling agent acts as a molecular bridge in the system. The alkoxy group at one end, after hydrolysis, can undergo a condensation reaction with cement hydration products and hydroxyl groups on the substrate surface, forming chemical bonds. The organic functional group at the other end undergoes physical entanglement or chemical cross-linking with the polymer chains in the silicone-acrylic or styrene-butadiene emulsion. This chemical bonding significantly enhances the interfacial shear resistance.

[0064] Meanwhile, the continuous polymer film formed after the polymer emulsion dehydrates and breaks down not only penetrates into the capillaries of the substrate surface to form mechanical anchoring points, but also alleviates the interfacial stress caused by the difference in elastic modulus between the coating and the substrate through its own flexibility. In contrast, the bonding strength of Comparative Example 1 decreased to 1.85 MPa. Although its emulsion content was sufficient, the lack of functional fillers and optimized modification with modified silane coupling agents led to a reduction in chemical bonding points at the interface. Furthermore, the low reactivity of fly ash made the interfacial transition zone relatively loose, easily becoming a weak point for stress concentration. The bonding strength of Comparative Example 2 was... The strength was the lowest, only 1.12 MPa, and the failure mode was mainly interfacial delamination. This was due to the insufficient amount of polymer emulsion, which could not accumulate at the interface to form an effective adhesive layer. The high water-to-material ratio and low polymer-to-ash ratio increased the risk of slurry bleeding, forming a water film at the interface and leaving a large number of pores after curing, which severely weakened the mechanical interlocking force. In addition, the lack of sufficient polymer flexible components caused the coating to generate large internal stress during curing shrinkage, resulting in pre-damage to the interface. Therefore, the introduction of sufficient polymer emulsion and silane coupling agent is the fundamental guarantee to ensure that the coating does not fall off during long-term service.

[0065] (3) Water absorption test: In order to evaluate the waterproof performance of the coating under alternating wet and dry conditions, water absorption tests were conducted on each example and comparative example; the test method referred to the water absorption test method in JG / T230-2007 "Premixed Mortar"; the instruments used were an electric heating drying oven (DGG-9070A, Shanghai Senxin Experimental Instrument Co., Ltd., China) and an electronic balance (sensitivity 0.01g); the specific operation was as follows: the prism specimen with dimensions of 40mm×40mm×160mm was dried at 60℃ to constant weight. The specimen was then immersed in water at 20±2℃, with the water level 20mm above the top surface of the specimen. After soaking for 48 hours, it was removed, the surface moisture was wiped off with a wrung-out damp cloth, and it was weighed immediately. The formula for calculating water absorption rate is: The average value of three test blocks in each test group was taken as the final result. The test results are shown in Table 3.

[0066] Table 3

[0067] As shown in Table 3, Example 3 has the lowest water absorption rate, at only 0.85%, exhibiting excellent hydrophobic and impermeable properties. This is mainly due to the high-density microstructure and the hydrophobic properties of the organic components. Examples 2 and 5 contain nano-silica, whose large specific surface area promotes the formation of CSH gel, resulting in a significant reduction in porosity and thus blocking the capillary adsorption channels of water molecules.

[0068] Comparative analysis shows that the water absorption rate of Examples 1-5 was controlled below 1.3%, while the water absorption rate of Comparative Example 1 increased to 3.45%. Although the ordinary fly ash used in Comparative Example 1 has a certain morphological effect, it cannot fill the micropores at the tens of nanometer level like silica fume or nano silica. In addition, the absence of flake functional fillers such as graphite powder makes the diffusion path of water inside the coating straighter and shorter, increasing the amount of water intrusion.

[0069] Comparative Example 2 exhibited the highest water absorption rate, reaching 5.12%, which corroborates its high chloride ion diffusion coefficient and low adhesion strength. Due to the extremely low polymer emulsion content, a significant amount of hydrophilic inorganic components were exposed on the coating surface, resulting in high internal pore connectivity. More importantly, the lack of a polymer film barrier effect and pore blockage effect made it easy for external moisture to be drawn into the coating under capillary tension. Furthermore, Comparative Example 2 increased the amount of water used to maintain workability, i.e., the water-to-material ratio was increased. After the excess water evaporated, it left behind a large number of open pores, further deteriorating the waterproof performance.

[0070] In summary, the core mechanism for reducing the water absorption rate and improving the durability of heavy-duty anti-corrosion coatings for marine concrete is to achieve the densest packing by regulating the gradation of ultrafine active fillers and to seal the capillaries with hydrophobic polymer emulsions. The technical solution of this invention successfully balances the high strength of inorganic materials with the high impermeability of organic materials, solving the technical problems of easy cracking and easy penetration of traditional marine coatings.

[0071] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a marine concrete heavy-duty coating, characterized by, The method comprises the following steps: Step 1: material preparation and dry mixing, cement, ultra-fine active filler, functional filler and fine sand are weighed according to the preset ratio; the above dry powder materials are put into a mixer and mechanically stirred until uniformly mixed to obtain an inorganic dry powder base; Step 2: wet material preparation and mixing, polymer emulsion, silane coupling agent and water are mixed uniformly; under stirring, the mixed solution is slowly added to the inorganic dry powder base of step 1; Step 3: dispersion and defoaming, stirring is maintained during the addition process, defoaming agent is added, and high-speed dispersion is carried out until the slurry is uniformly fluid and has no obvious bubbles, to obtain a heavy-duty cement-based composite coating slurry; Step 4: film forming and construction, the slurry obtained in step 3 is applied to the concrete surface by layer-by-layer coating process, and an anticorrosion coating is formed after standing and curing.

2. The method for preparing a marine concrete heavy-duty coating according to claim 1, characterized in that, The mass fraction ratio of cement, ultra-fine active filler, functional filler, fine sand, polymer emulsion, silane coupling agent and defoaming agent is (45-55):(8-12):(1-5):(3-7):(35-45):(0.1-0.5):(0.3-0.8).

3. The method for preparing a marine concrete heavy-duty coating according to claim 1, characterized in that, The polymer emulsion is selected from any one of silicone-acrylic emulsion or styrene-butadiene emulsion; the solid content of the polymer emulsion is 38%-42%.

4. The method for preparing a marine concrete heavy-duty coating material according to claim 1, characterized in that, The ultra-fine active filler is any one or mixture of both of silica fume and nano-silicon dioxide; the functional filler is any one of graphite powder and zinc-aluminum composite anti-rust pigment.

5. The method for preparing a heavy-duty anti-corrosion coating for marine concrete according to claim 1, characterized in that, In step 2, the water-material ratio is controlled between 0.35-0.45; during the mixing process of polymer emulsion and inorganic dry powder base, continuous stirring is required to form a polymer-cement-based composite system.

6. The method for preparing a heavy-duty anti-corrosion coating for marine concrete according to claim 1, characterized in that, In step 3, the mass fraction of defoaming agent is 0.3-0.8 parts; during the dispersion process, it is necessary to ensure that there are no agglomerated particles in the slurry.

7. The method for preparing a heavy-duty anti-corrosion coating for marine concrete according to claim 1, characterized in that, In step 4, the layer-by-layer coating process is specifically: airless spraying or rolling is used for construction; the operation is repeated at least twice, the single-layer coating thickness is controlled, and the total coating thickness reaches 1.8-2.2 mm.

8. The method for preparing a heavy-duty anti-corrosion coating for marine concrete according to claim 7, characterized in that, During the layer-by-layer coating process, the interval time between adjacent two layers of coating is 3-5 hours; before the next coating, it is necessary to confirm that the previous coating has been substantially solidified.

9. The method for preparing a heavy-duty anti-corrosion coating for marine concrete according to claim 1, characterized in that, In step 4, the standing and curing includes: after the coating construction is completed, the mold is demolded or subsequent treatment is carried out after natural curing for at least 24 hours in a room temperature environment; the overall curing period is 6-8 days.

10. The method for preparing a heavy-duty anti-corrosion coating for marine concrete according to claim 1, characterized in that, The silane coupling agent is a silane coupling agent containing a methacryloyloxy functional group, preferably - methacryloyloxypropyltrimethoxysilane.

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