Whisker reinforced cement-based anticorrosive paint and preparation method thereof

Abstract

The invention discloses a whisker reinforced cement-based anticorrosive coating and a preparation method thereof. The anticorrosive paint is prepared from the following raw materials: sulphoaluminate cement, graded quartz sand, water, silica fume, metakaolin, barium sulfate, a polycarboxylate superplasticizer and modified zinc oxide whiskers. The anticorrosive paint has the advantages of low cost, high curing speed, high temperature stability, high environmental aging resistance and high adaptability to a humid environment, and can obviously improve the apparent flatness of a concrete structure; meanwhile, through the combination of a silica fume-metakaolin-barium sulfate compound system and a zinc oxide whisker three-dimensional enhancement technology, the bonding strength and durability of the coating are greatly improved, the surface of the coating is endowed with the self-antibacterial characteristic, and the coating is low in construction requirement, can be directly constructed on a wet base plane, does not release VOC in the construction process, is healthy and friendly to constructors, and has good application prospects. Therefore, the corrosion inhibitor can be widely applied to corrosion prevention of surfaces of concrete substrates of various sewage treatment structures in sewage treatment plants, and durability of the substrates is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of anti-corrosion materials for sewage treatment structures, and particularly to a whisker-reinforced cement-based anti-corrosion coating and a preparation method thereof. Background Art

[0002] With the increasing demand for urban sewage treatment, the corresponding sewage treatment facilities are constantly aging, which poses higher requirements for the durability of various sewage treatment structures. In sewage treatment plants, main structures such as inlet pump houses, fine screens, biochemical tanks, and secondary sedimentation tanks are all subject to the flow abrasion of sewage, corrosive gases, and solid particles, as well as the scouring of sewage for a long time. These structures generally adopt reinforced concrete structures. Therefore, their durability performance will face many challenges, including chemical corrosion by acid-base sewage and gases, scouring by water flow and solid particles, physical damage caused by temperature change stress, and microbial corrosion caused by bacteria and algae.

[0003] Currently, the coatings widely used in the anti-corrosion field are mainly polymer organic materials, such as polyurethane anti-corrosion coatings. However, the long-term stability of such materials is relatively poor, and there are large differences in mechanical properties and temperature incompatibility with substrates such as concrete. It is easy to have inconsistent deformation under the action of long-term physical scouring and temperature changes, resulting in the peeling off of the anti-corrosion layer. In addition, polymer organic coatings may release toxic gases during the construction process, posing a threat to the health of construction workers in relatively enclosed limited spaces.

[0004] Cement-based anti-corrosion coatings have excellent durability and are easy to manufacture. Compared with the elastic modulus of organic anti-corrosion coatings (1 - 3 GPa), the elastic modulus of cement-based anti-corrosion coatings is closer to the elastic modulus of concrete substrates (20 - 40 GPa), and the stress and deformation of the substrate and the anti-corrosion coating under the action of stress and temperature are more coordinated. Moreover, the general construction thickness of cement-based anti-corrosion coatings is 5 - 20 mm, which is thicker than that of organic anti-corrosion coatings (generally 0.3 - 0.6 mm). After implementation, it can improve the apparent flatness of the concrete structure. However, ordinary cement-based anti-corrosion materials have insufficient self-adhesion and strength, and are still prone to cracking and peeling from the base layer in the complex environment of sewage treatment structures. Summary of the Invention

[0005] To solve the problems existing in the prior art, the present invention provides a whisker-reinforced cement-based anti-corrosion coating and a preparation method thereof.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A whisker-reinforced cement-based anticorrosive coating, the composition of its raw materials is as follows by weight percentage: 35-45% of sulfoaluminate cement, 20-30% of graded quartz sand, 8-12% of water, 8-10% of silica fume, 6-8% of metakaolin, 5-6% of barium sulfate, 1.5-2.5% of polycarboxylate water reducer, 1-1.5% of modified zinc oxide whiskers, and the sum of the weight percentages of each raw material is 100%.

[0007] Further, the sulfoaluminate cement is a low-alkalinity sulfoaluminate cement, the content of C4A3S in its mineral composition is ≥55%, its specific surface area is 350-450 m² / kg, and the initial setting time is ≤45 minutes.

[0008] Further, the graded quartz sand is mixed with a double grading, among which the quartz sand of 40-80 mesh accounts for 60-70% of the total weight, the quartz sand of 80-120 mesh accounts for 30-40% of the total weight, its bulk density is ≥1.6 g / cm³, and the mud content is ≤0.3%.

[0009] Further, the content of SiO2 in the silica fume is ≥95%, and the particle size is 0.1-0.2 μm.

[0010] Further, the polycarboxylate water reducer is a high-performance water reducer with a comb-shaped structure copolymerized from monomers containing unsaturated olefins, carboxyl groups, and EO and PO with a certain degree of polymerization.

[0011] Further, the modified zinc oxide whiskers are prepared by mixing zinc oxide whiskers and silane coupling agent KH-550 in a mass ratio of 1:0.015 and refluxing in absolute ethanol at 75°C for 4 hours.

[0012] Furthermore, the zinc oxide whiskers have a four-needle structure, the length of a single whisker is 10-50 μm, and the aspect ratio is ≥15:1.

[0013] The preparation method of the whisker-reinforced cement-based anticorrosive coating includes the following steps: 1) Dry powder premixing: Mix sulfoaluminate cement, graded quartz sand, silica fume, metakaolin, and barium sulfate by stirring; 2) Wet mixing: Add water and polycarboxylate water reducer to the mixed dry powder obtained in step 1), and continue to stir and mix; 3) Component addition: Under stirring conditions, add the modified zinc oxide whiskers to the mixture in step 2) in three times to obtain the whisker-reinforced cement-based anticorrosive coating.

[0014] Further, the rotation speed of the stirring and mixing in step 1) is 200-300 rpm, and the mixing time is 8-12 min.

[0015] Further, the rotation speed of the stirring and mixing in step 2) is 500 - 600 rpm, and the mixing time is 3 - 5 min.

[0016] Further, the rotation speed of the stirring in step 3) is 150 - 200 rpm.

[0017] Further, the time interval for each addition of the modified zinc oxide whiskers in step 3) is 1 min.

[0018] The using method of the cement - based anticorrosive coating is that during construction, the cement - based anticorrosive coating is spray - coated on the concrete substrate in multiple passes by a airless spraying process.

[0019] Further, the thickness of each coating layer is 3 - 5 mm, and the total thickness of the coating is controlled within 5 - 15 mm.

[0020] Further, the interval time between each spraying is 2 - 4 h.

[0021] The present invention uses a double - graded quartz sand with 40 - 80 mesh accounting for 60 - 70%, 80 - 120 mesh accounting for 30 - 40%, and a bulk density ≥ 1.6 g / cm 3 By optimizing the gradation of coarse sand and fine sand, the compactness and particle wrapping property of the coating are improved, the capillary porosity is significantly reduced, and the penetration path of corrosive media is blocked.

[0022] The present invention adds silica fume and ultrafine active mineral admixture of barium sulfate, which play a role in filling voids and lubricating. Barium sulfate is chemically inert and has a high density, and can form a physical shielding layer in acid solution, improving the denseness and acid - corrosion resistance of the coating, further blocking the physical penetration path of corrosive media, and at the same time improving the wear resistance of the coating.

[0023] The present invention uses metakaolin to replace traditional fly ash. Through the reaction of its high pozzolanic activity with the aluminum phase, the chloride ion permeability resistance and sulfate erosion resistance of the coating are improved, and the risk of volume instability caused by free calcium oxide is reduced.

[0024] In addition, the compound system of silica fume - metakaolin - barium sulfate can also fill the voids in the material at different scales to optimize the microstructure of the coating, improve the compactness and strength of the material, and produce a good synergistic effect. This compound system enhances the overall strength and toughness of the coating, and at the same time improves the chemical corrosion resistance and weather resistance of the coating.

[0025] The present invention adds tetrapod - shaped zinc oxide whiskers. Zinc oxide whiskers have a certain antibacterial ability, and their unique three - dimensional network structure can effectively disperse the internal stress in the coating, significantly improving the toughness of the coating. At the same time, the zinc ions (Zn 2+ in the zinc oxide whiskers and the calcium ions (Ca 2+) can undergo a replacement reaction, accelerate the formation of ettringite (AFt) crystals, and further enhance the structural stability of the material. In addition, the present invention uses silane coupling agent KH-550 to perform surface modification on zinc oxide whiskers, which significantly enhances the interface bonding strength between the whiskers and the cement matrix and improves the overall mechanical properties of the coating.

[0026] Polycarboxylic acid water reducers have the characteristics of high water reduction rate (maximum water reduction rate can reach 40%), good water retention performance, low pollution, low dosage, excellent collapse retention performance, etc. The present invention adopts polycarboxylic acid water reducers to reduce the water-binder ratio of cement-based coatings, thereby significantly improving the strength of cement-based materials.

[0027] The present invention reduces the porosity of the cement-based coating and the pore size through the chemical reaction between the raw materials, further optimizes the pore structure inside the coating, and thus significantly improves the mechanical strength of the material.

[0028] The significant advantages of the present invention are: (1) The anticorrosive coating of the present invention effectively overcomes the shortcomings of polymer organic anticorrosive coatings in terms of thermal stability, long-term chemical stability, and incompatibility with structural deformation. At the same time, through the silica fume-metakaolin-barium sulfate composite system and zinc oxide whisker three-dimensional reinforcement technology, the strength and bonding properties of cement-based anticorrosive coatings are greatly improved, and the coating also has a self-inhibitory function, which can inhibit the formation of sulfate-reducing bacteria in sewage. Therefore, the coating is very suitable for anticorrosion treatment of the surface of reinforced concrete structures in sewage environments. It has excellent durability, good bonding properties, and economic benefits, and can effectively extend the service life of the structure and reduce maintenance costs.

[0029] (2) The cement-based anti-corrosion coating of the present invention has significant advantages in terms of cost, which is far lower than that of traditional polymer organic anti-corrosion coatings. At the same time, the construction requirements are relatively low. It can be directly constructed on a damp base surface. No VOC is released during the construction process, which is convenient for construction personnel to operate and apply, greatly improving construction efficiency and cost control. DETAILED DESCRIPTION

[0030] A whisker-reinforced cement-based anticorrosive coating, the preparation method of which comprises the following steps: 1) Modification of zinc oxide whiskers: zinc oxide whiskers and silane coupling agent KH-550 were mixed at a mass ratio of 1:0.015, and refluxed in anhydrous ethanol at 75°C for 4 hours to obtain modified zinc oxide whiskers; 2) Dry powder premixing: Add sulphoaluminate cement, graded quartz sand, silica fume, metakaolin and barium sulfate into a mixer and mix them in a closed mixer at a speed of 200-300 rpm for 8-12 minutes; 3) Wet mixing: Add water and polycarboxylate water reducer to the mixed dry powder obtained in step 2), and continue to stir and mix at a speed of 500 - 600 rpm for 3 - 5 min; 4) Component addition: Add the modified zinc oxide whiskers to the mixture in step 3) in three portions at a stirring speed of 150 - 200 rpm, with an interval of 1 min each time, to obtain the whisker-reinforced cement-based anticorrosive coating.

[0031] In the obtained whisker-reinforced cement-based anticorrosive coating, the composition of each raw material is as follows by weight percentage: sulfoaluminate cement 35 - 45%, graded quartz sand 20 - 30%, water 8 - 12%, silica fume 8 - 10%, metakaolin 6 - 8%, barium sulfate 5 - 6%, polycarboxylate water reducer 1.5 - 2.5%, modified zinc oxide whiskers 1 - 1.5%, and the sum of the weight percentages is 100%.

[0032] To make the content of the present invention easier to understand, the technical solutions of the present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0033] The zinc oxide whiskers used in the examples have a four-needle structure, the length of a single whisker is 10 - 50 μm, and the aspect ratio ≥ 15:1.

[0034] The sulfoaluminate cement used in the examples is a low-alkalinity sulfoaluminate cement, the C4A3S content in its mineral composition ≥ 55%, its specific surface area is 350 - 450 m² / kg, and the initial setting time ≤ 45 minutes.

[0035] The graded quartz sand used in the examples is mixed with a double grading, where the quartz sand of 40 - 70 mesh accounts for 60% of the total weight, and the quartz sand of 70 - 110 mesh accounts for 40% of the total weight, its bulk density ≥ 1.6 g / cm³, and the mud content ≤ 0.3%.

[0036] The silica fume used in the examples has a SiO2 content ≥ 95% and a particle size of 0.1 - 0.2 μm.

[0037] The water reduction rate of the polycarboxylate water reducer used in the examples ≥ 25%.

[0038] Example 1 1) Modification of zinc oxide whiskers: Mix zinc oxide whiskers and silane coupling agent KH-550 at a mass ratio of 1:0.015, and reflux in absolute ethanol at 75 °C for 4 h to obtain modified zinc oxide whiskers; 2) Dry powder premixing: Add sulfoaluminate cement, graded quartz sand, silica fume, metakaolin, and barium sulfate to a mixer, and stir and mix tightly at a speed of 200 rpm for 10 min; 3) Wet mixing: Add water and polycarboxylate water reducer to the mixed dry powder obtained in step 2), and continue to stir and mix at a speed of 500 rpm for 5 min; 4) Component addition: Under a stirring speed of 150 rpm, add the modified zinc oxide whiskers to the mixture in step 3) in three portions at intervals of 1 min each to obtain a whisker-reinforced cement-based anticorrosive coating. By weight percentage, the sulfoaluminate cement accounts for 40%, the graded quartz sand accounts for 25%, the water accounts for 10%, the silica fume accounts for 10%, the metakaolin accounts for 6%, the barium sulfate accounts for 5%, the polycarboxylate water reducer accounts for 2.5%, and the modified zinc oxide whiskers account for 1.5%.

[0039] Example 2 1) Modification of zinc oxide whiskers: Mix zinc oxide whiskers with silane coupling agent KH-550 at a mass ratio of 1:0.015, and reflux in absolute ethanol at 75 °C for 4 h to obtain modified zinc oxide whiskers; 2) Dry powder premixing: Add sulfoaluminate cement, graded quartz sand, silica fume, metakaolin, and barium sulfate to a mixer, and stir and mix hermetically at a speed of 200 rpm for 10 min; 3) Wet mixing: Add water and polycarboxylate water reducer to the mixed dry powder obtained in step 2), and continue to stir and mix at a speed of 500 rpm for 5 min; 4) Component addition: Under a stirring speed of 200 rpm, add the modified zinc oxide whiskers to the mixture in step 3) in three portions at intervals of 1 min each to obtain a whisker-reinforced cement-based anticorrosive coating. By weight percentage, the sulfoaluminate cement accounts for 42%, the graded quartz sand accounts for 22%, the water accounts for 10%, the silica fume accounts for 9%, the metakaolin accounts for 8%, the barium sulfate accounts for 5%, the polycarboxylate water reducer accounts for 2.5%, and the modified zinc oxide whiskers account for 1.5%.

[0040] Comparative Example 1 Use 10% fly ash instead of 10% silica fume, and the remaining operations are the same as in Example 1.

[0041] Comparative Example 2 Use 5% calcium carbonate instead of 5% barium sulfate, and the remaining operations are the same as in Example 1.

[0042] Comparative Example 3 Use 6% fly ash instead of 6% metakaolin, and the remaining operations are the same as in Example 1.

[0043] Comparative Example 4 Use 1.5% zinc oxide whiskers instead of 1.5% modified zinc oxide whiskers, and the remaining operations are the same as in Example 1.

[0044] Comparative Example 5 Use the modified calcium carbonate whiskers prepared by the same method at 1.5% to replace the use of 1.5% modified zinc oxide whiskers, and the remaining operations are the same as those in Example 1.

[0045] Carry out the performance test of the cement-based anti-corrosion coatings prepared in the examples and comparative examples according to JGS 153-2015 "Durability Design Standard for Water Transportation Engineering Structures".

[0046] Table 1 Performance comparison of the cement-based anti-corrosion coatings obtained in the examples and comparative examples

[0047] As can be seen from Table 1, compared with the comparative example, the cement-based anti-corrosion coating prepared in the example has higher compressive strength, tensile bond strength, dynamic elastic modulus, antibacterial rate and lower acid resistance loss rate.

[0048] In summary, compared with traditional polymer organic anti-corrosion coatings, the cement-based anti-corrosion coating provided by the present invention has low cost, fast curing, good temperature stability, strong anti-environmental aging ability, strong adaptability to humid environments, and can improve the apparent flatness of concrete structures; compared with ordinary cement-based bonding materials, its bonding strength and durability are greatly improved, and the coating surface is given self-antibacterial characteristics. Therefore, it effectively solves the problems of poor long-term stability of polymer organic materials, mismatch with substrates, poor adhesion and easy peeling of ordinary cement-based anti-corrosion coatings, and can be widely used in the anti-corrosion of concrete substrate surfaces in sewage treatment structures such as intake pump houses, fine grids, biochemical tanks, and secondary sedimentation tanks in sewage treatment plants.

[0049] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims

1. A whisker-reinforced cement-based anticorrosive coating, characterized in that: The raw material composition is as follows by weight percentage: 35-45% of sulfoaluminate cement, 20-30% of graded quartz sand, 8-12% of water, 8-10% of silica fume, 6-8% of metakaolin, 5-6% of barium sulfate, 1.5-2.5% of polycarboxylate superplasticizer, and 1-1.5% of modified zinc oxide whiskers. The sum of the weight percentages of all raw materials is 100%.

2. The whisker-reinforced cement-based anti-corrosion coating according to claim 1, characterized in that: In the mineral composition of the sulfoaluminate cement, the content of C4A3S is ≥55%, its specific surface area is 350-450 m² / kg, and the initial setting time is ≤45 minutes.

3. The whisker-reinforced cement-based anti-corrosion coating according to claim 1, characterized in that: The graded quartz sand is mixed with a double grading, where the quartz sand of 40-80 mesh accounts for 60-70% of the total weight, and the quartz sand of 80-120 mesh accounts for 30-40% of the total weight. Its bulk density is ≥1.6 g / cm³, and the mud content is ≤0.3%.

4. The whisker-reinforced cement-based anti-corrosion coating according to claim 1, wherein: The content of SiO2 in the silica fume is ≥95%, and the particle size is 0.1-0.2 μm.

5. The whisker-reinforced cement-based anti-corrosion coating according to claim 1, characterized in that: The modified zinc oxide whiskers are prepared by mixing zinc oxide whiskers and silane coupling agent KH-550 at a mass ratio of 1:0.015 and refluxing in absolute ethanol at 75°C for 4 h.

6. The whisker-reinforced cement-based anticorrosive coating according to claim 5, characterized in that: The zinc oxide whiskers have a four-needle structure, the length of a single whisker is 10-50 μm, and the aspect ratio is ≥15:

1.

7. A preparation method of a whisker-reinforced cement-based anticorrosive coating as described in claim 1, characterized in that: It includes the following steps: 1) Dry powder premixing: Mix sulfoaluminate cement, graded quartz sand, silica fume, metakaolin, and barium sulfate by stirring. 2) Wet mixing: Add water and polycarboxylate superplasticizer to the mixed dry powder obtained in step 1) and continue to stir and mix. 3) Component addition: Under stirring conditions, add the modified zinc oxide whiskers to the mixture in step 2) in three portions to obtain the whisker-reinforced cement-based anticorrosive coating.

8. The preparation method of a whisker-reinforced cement-based anti-corrosion coating according to claim 7, characterized in that: The stirring speed in step 1) is 200-300 rpm, and the mixing time is 8-12 min; the stirring speed in step 2) is 500-600 rpm, and the mixing time is 3-5 min; the stirring speed in step 3) is 150-200 rpm.

9. The preparation method of a whisker-reinforced cement-based anticorrosive coating according to claim 7, characterized in that: In step 3), the time interval for each addition of the modified zinc oxide whiskers is 1 min.

10. A method for using a whisker-reinforced cement-based anti-corrosion coating as described in claim 1, characterized in that: During construction, the cement-based anticorrosive coating is spray-coated in multiple passes using the airless spraying process. The thickness of each coating is 3-5 mm, and the total thickness of the coating is controlled within 5-15 mm; the interval time between each spraying is 2-4 h.

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