Concrete coating prepared from waste phosphorus-magnesium material as well as preparation method and application of concrete coating

Abstract

The invention relates to the technical field of building materials, in particular to a concrete coating prepared from a waste phosphorus-magnesium material and a preparation method and application thereof. The concrete coating is prepared from the following raw materials in parts by weight: 70-85 parts of a gelling agent, 1-3 parts of a retarder, 10-15 parts of a waste treated phosphorus-magnesium material, 3-5 parts of a composite modifier and 22-25 parts of mixing water. According to the invention, cyclic utilization of the waste phosphorus-magnesium material is realized, the preparation cost of the coating is reduced, and meanwhile, the mechanical property and the corrosion resistance of the coating are improved, so that the coating can better meet the corrosion-resistant application requirement of a concrete structure.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a concrete coating prepared from waste magnesium phosphate materials, its preparation method, and its application. Background Technology

[0002] Against the backdrop of the rapid development of the marine new energy industry, the basic structures of offshore facilities (such as pile foundations and platforms) are subjected to harsh environments of high salinity, high humidity, and chloride ion corrosion for extended periods. Meanwhile, concrete structures in land-based buildings also frequently face corrosion from atmospheric and water sources. This corrosion can lead to damage to the concrete itself and corrosion of internal reinforcing steel, thereby affecting the safety and durability of the structure. To address this issue, anti-corrosion coatings have become an important means of protecting concrete structures. Among these, water-based inorganic coatings have gradually become a research hotspot because they avoid the release of large amounts of volatile organic compounds (VOCs) during the production and construction of traditional organic coatings. Among various water-based inorganic coatings, magnesium phosphate-based coatings, with magnesium phosphate cement as the main cementing component, have already found some application in the field of concrete and steel structure corrosion protection due to their environmental friendliness, high bonding strength with concrete substrates, and excellent weather resistance.

[0003] Currently, relevant technologies have disclosed anti-corrosion coating systems based on magnesium phosphate cement. These systems mainly consist of magnesium phosphate cement, retarders, and other components, and are suitable for surface protection of concrete or steel structures. They form a continuous protective layer on the substrate surface to resist corrosion from media such as chloride ions and water. However, with the widespread application of magnesium phosphate-based anti-corrosion materials, the amount of waste magnesium phosphate materials generated during their production process and the amount of failed coatings after use are gradually increasing. These waste materials still contain a large number of unreacted active components, such as magnesium oxide and phosphates, which have potential for further utilization due to their mechanical properties. In existing technologies, the recycling and resource utilization technologies for such waste magnesium phosphate materials are not yet mature. Most waste materials are only stored or disposed of using conventional methods, failing to effectively explore their reuse value. At the same time, the preparation of existing magnesium phosphate-based coatings mostly relies on virgin magnesium phosphate cement raw materials, resulting in high raw material costs, which to some extent limits their wider market application. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a concrete coating prepared from waste magnesium phosphate materials, its preparation method, and its application. By specifically treating the waste magnesium phosphate materials and adjusting the ratio of composite modifiers and cementitious agents, the mechanical properties and anti-corrosion performance of the coating are improved, thereby better meeting the anti-corrosion application requirements of concrete structures, while achieving the recycling of waste magnesium phosphate materials and reducing the cost of coating preparation.

[0005] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions: A concrete coating prepared from waste magnesium phosphate material is composed of the following raw materials in parts by weight: 70-85 parts of cementitious agent, 1-3 parts of retarder, 10-15 parts of waste magnesium phosphate material, 3-5 parts of composite modifier, and 22-25 parts of mixing water.

[0006] Furthermore, the gelling agent comprises potassium dihydrogen phosphate and calcined magnesium oxide, wherein the mass ratio of calcined magnesium oxide to potassium dihydrogen phosphate is 2~3.5:1.

[0007] Furthermore, the composite modifier includes polyacrylic acid and citric acid, wherein the mass ratio of polyacrylic acid to citric acid is 0.25~2.5:1.

[0008] Furthermore, when the mass ratio of Mg to P in the waste magnesium phosphate material is 7 to 20, the mass ratio of polyacrylic acid to citric acid is 2 to 2.5:1, and the mass ratio of calcined magnesium oxide to potassium dihydrogen phosphate is 2 to 2.5:1.

[0009] Furthermore, when the mass ratio of Mg to P in the waste magnesium phosphate material is 1 to 6, the mass ratio of polyacrylic acid to citric acid is 0.25 to 1:1, and the mass ratio of calcined magnesium oxide to potassium dihydrogen phosphate is 3 to 3.5:1.

[0010] Furthermore, the waste magnesium phosphate material is one or more of magnesium phosphate slurry and anti-corrosion coating, the mass ratio of magnesium phosphate material in the waste magnesium phosphate material is not less than 80%, and the storage time does not exceed 2 years.

[0011] Furthermore, the retarder is one of borax, boric acid, and sodium citrate.

[0012] This invention also provides a method for preparing a concrete coating made from waste magnesium phosphate material as described above, comprising the following steps: Waste magnesium phosphate materials are processed by washing, drying, crushing, and grinding to a particle size of 400-500 mesh. The mass ratio of Mg to P in the treated waste magnesium phosphate material was measured. Based on the mass ratio of Mg to P, the mass ratio of polyacrylic acid to citric acid in the composite modifier is determined, and the mass ratio of calcined magnesium oxide to potassium dihydrogen phosphate in the gelling agent is determined. Citric acid is added to the mixing water and stirred to form a citric acid solution. The treated waste phosphorus and magnesium materials are then added and stirred to form a suspension. Polyacrylic acid is then added and stirred to form a composite modified suspension. Potassium dihydrogen phosphate, calcined magnesium oxide and retarder are mixed and stirred to obtain dry gelling agent powder; The dry powder of the gelling agent is added to the composite modified suspension and stirred to obtain the concrete coating.

[0013] Furthermore, after adding the treated waste magnesium phosphate material, stir at a speed of 200~300 r / min; after adding polyacrylic acid, stir at a speed of 200~300 r / min; after adding the dry gelling agent powder to the composite modified suspension, stir at a speed of 100~200 r / min.

[0014] This invention also provides an application of a concrete coating prepared from waste magnesium phosphate material, wherein the concrete coating described above is brushed onto the concrete surface to form an anti-corrosion coating.

[0015] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages: 1. In the concrete coating of this invention, waste magnesium phosphate material is used as a recycled component to replace virgin magnesium phosphate cement raw material, reducing production costs. A gelling agent, as the main film-forming substance, provides the matrix structure of the coating. A retarder regulates the setting time to prevent premature curing that could affect construction. A composite modifier enhances the interfacial adhesion and corrosion resistance of the coating. Mixing water controls the fluidity of the slurry, ensuring uniform application. The introduction of waste magnesium phosphate material reduces the use of virgin materials, meeting environmental protection requirements. The combination of gelling agent and composite modifier optimizes the microstructure of the coating, improving its density. This synergistic effect solves the problem of resource waste while maintaining the coating's workability and durability. While achieving the recycling of waste magnesium phosphate material and reducing coating preparation costs, it also improves the mechanical and anti-corrosion properties of the coating, making it better suited to the anti-corrosion application requirements of concrete structures.

[0016] 2. This invention analyzes the elemental composition of waste phosphate magnesium materials and rationally adjusts the M / P ratio of composite modifier components and gelling agent to achieve a more targeted and rational utilization of waste phosphate magnesium material components, thereby improving the performance and application effect of phosphate magnesium coatings.

[0017] 3. First, add the finely ground waste magnesium phosphate material to a citric acid solution. In waste magnesium phosphate materials with a low Mg / P ratio, there is a higher proportion of unreacted phosphate. After thorough stirring, this phosphate dissolves. At this point, increasing the concentration of the citric acid solution can slightly disrupt the struvite structure, dissolving ions. After fine grinding and heating with stirring, the waste magnesium phosphate material dissolves more easily in the citric acid solution, releasing more Mg. 2+ And phosphates participate in the hydration process of the gelling agent, while citric acid complexes part of the Mg. 2+ This prevents precipitation and acts as a slowing agent for coagulation. Furthermore, waste magnesium phosphate materials stored for too long often have some MgO carbonized into MgCO3. After treatment with citric acid solution, carbon dioxide is released, releasing MgO that can participate in hydration reactions. 2+ It increases the reactivity of the reaction.

[0018] 4. After treatment with citric acid solution, polyacrylic acid is added. The polyacrylic acid reacts with magnesium ions from the waste magnesium phosphate to form a mixed suspension. In this modified suspension, cross-linking polymerization forms a magnesium polyacrylate network structure. The carboxyl groups on the introduced polyacrylic acid chains bond with calcium and aluminum ions on the concrete surface, forming strong ionic bonds that tightly chemically bind the magnesium polyacrylate gel network to the concrete substrate, enhancing interfacial adhesion. In addition, polyacrylic acid can also form hydrogen bonds with the concrete surface, further strengthening adhesion. For magnesium phosphate materials with a low Mg / P ratio, MgO is usually in excess, primarily utilizing the large amount of unreacted MgO. Therefore, increasing the polyacrylic acid content allows for more efficient utilization of this process. Ultimately, the waste magnesium phosphate material is modified into an admixture with gelling capabilities. When incorporated into the cementitious material, the dissolved ions act as reactants, while the unreacted polyacrylic acid, the MgO in the cementitious material, and the already formed reactive magnesium polyacrylate network structure undoubtedly enhance the interfacial adhesion between the cementitious material and the concrete.

[0019] 5. The order of use of citric acid and polyacrylic acid in combination: First, use citric acid solution to react with waste magnesium phosphate material. The alkaline component MgO in the waste magnesium phosphate material gradually neutralizes the pH of the solution. Polyacrylic acid has better dispersibility under slightly higher pH conditions. Therefore, the order of use of the two and the addition of waste magnesium phosphate material allows these two acids to play a better role.

[0020] 6. The modified waste magnesium phosphate material not only participates in the hydration process of the coating, but also retains undissolved and intact struvite products. These hard hydration products can be ground into fine aggregates to fill pores, thereby improving mechanical properties and corrosion resistance.

[0021] Advantages of additional aspects of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. 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. The drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In addition, the dimensions or spacing between the components are exaggerated to show the position of each component, and the schematic diagrams are for illustrative purposes only.

[0023] Figure 1 This is a schematic diagram of the treated waste magnesium phosphate material provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the prepared coating sample provided in the embodiments of the present invention; Figure 3 This is a test diagram of the bond strength between the coating and concrete provided in an embodiment of the present invention; Figure 4 These are test blocks for the anti-corrosion performance of the coating provided in this embodiment of the invention, and images showing corrosion after immersion in simulated seawater. Detailed Implementation It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] This invention utilizes different proportions to treat waste phosphorus-magnesium materials (such as...) Figure 1 As shown, waste magnesium phosphate material is used as a raw material for anti-corrosion coating. By analyzing the composition of the waste magnesium phosphate material and adjusting the composition of the composite modifier and the binder, the cost can be reduced, the mechanical properties, workability and anti-corrosion performance can be improved, and the material can be better adapted to concrete anti-corrosion applications.

[0025] A concrete coating prepared from waste magnesium phosphate material is composed of the following raw materials in parts by weight: 70-85 parts of cementitious agent, 1-3 parts of retarder, 10-15 parts of waste magnesium phosphate material, 3-5 parts of composite modifier, and 22-25 parts of mixing water.

[0026] As the core gelling component of the coating, a dosage of 70-85 parts of gelling agent ensures sufficient gelling strength, providing a foundation for the subsequent formation of a dense protective layer. Adding 1-3 parts of retarder prevents the coating from setting too quickly, allowing ample working time for application. A dosage of 10-15 parts of waste magnesium phosphate material fully utilizes its unreacted magnesium oxide, phosphate, and other active components, reducing the consumption of new raw materials and lowering preparation costs, without causing a decline in overall coating performance due to excessive dosage. A composite modifier of 3-5 parts specifically improves the compatibility of waste magnesium phosphate material with other components, enhancing the coating's mechanical properties and anti-corrosion effect. 22-25 parts of mixing water ensures the raw materials form a slurry with suitable fluidity, meeting the requirements for brush application and preventing insufficient water from causing the slurry to dry and be difficult to apply, or excessive water from affecting the strength of the cured coating.

[0027] This raw material combination solves the problems of low resource utilization rate of waste phosphate magnesium materials and high cost of phosphate magnesium-based coatings in existing technologies. Through the synergistic effect of each component, the active components of waste phosphate magnesium materials can participate in the hydration reaction of the gelling agent, while the composite modifier helps to improve the fullness of the reaction and the adhesion of the coating. Ultimately, the coating can achieve the recycling of waste materials while maintaining good mechanical and anti-corrosion properties.

[0028] The gelling agent comprises potassium dihydrogen phosphate and calcined magnesium oxide, with a mass ratio of calcined magnesium oxide to potassium dihydrogen phosphate of 2-3.5:1. Calcined magnesium oxide provides an alkaline environment, while potassium dihydrogen phosphate acts as an acid source; the two react to produce gel products such as struvite. A ratio that is too high or too low will affect the reaction rate and product stability; a range of 2-3.5:1 ensures sufficient hydration and avoids excessive unreacted components that could degrade coating performance.

[0029] The composite modifier comprises polyacrylic acid and citric acid, with a mass ratio of polyacrylic acid to citric acid of 0.25–2.5:1. Citric acid first reacts with waste magnesium phosphate material, dissolving magnesium ions and phosphates, while simultaneously complexing the magnesium ions to prevent precipitation. Polyacrylic acid is then added, forming a magnesium acrylate network structure with the magnesium ions, enhancing the chemical bond between the coating and the concrete substrate. The 0.25–2.5:1 ratio ensures that the two acids work in stages, avoiding pH abrupt changes that could affect dispersibility.

[0030] When the mass ratio of Mg to P in the waste magnesium phosphate material is 7–20, the mass ratio of polyacrylic acid to citric acid is 2–2.5:1, and the mass ratio of recalcined magnesium oxide to potassium dihydrogen phosphate is 2–2.5:1. Increasing the proportion of polyacrylic acid in this case allows for more effective utilization of excess magnesium ions to form a gel network, while reducing the proportion of recalcined magnesium oxide to potassium dihydrogen phosphate in the gelling agent avoids an excessively alkaline environment, thus balancing the reaction system. This improves the coating's adhesion and corrosion resistance, fully utilizing the characteristics of the waste material.

[0031] When the mass ratio of Mg to P in the waste magnesium phosphate material is 1–6, the mass ratio of polyacrylic acid to citric acid is 0.25–1:1, and the mass ratio of recalcined magnesium oxide to potassium dihydrogen phosphate is 3–3.5:1. Increasing the proportion of citric acid helps dissolve more phosphates, promotes the hydration reaction, and simultaneously increases the proportion of recalcined magnesium oxide in the gelling agent to supplement the magnesium source, ensuring a complete reaction. This optimizes the ion release and complexation process, improving coating density and corrosion resistance.

[0032] The waste magnesium phosphate material being treated is one or more of magnesium phosphate slurry and anti-corrosion coatings. The magnesium phosphate material constitutes no less than 80% of the total mass of the waste magnesium phosphate material, and the storage time does not exceed 2 years. This ensures the content of active components in the waste material and avoids excessive carbonization or contamination. The treatment process includes washing, drying, crushing, and grinding to 400-500 mesh to increase the specific surface area and promote subsequent reactions. Controlling the storage time reduces the carbonization of MgO to MgCO3 and maintains reactivity.

[0033] The retarder is one of borax, boric acid, or sodium citrate, which effectively delays setting time without affecting final strength. Borax and boric acid inhibit hydration by adsorption on the particle surface, while sodium citrate delays the reaction through complexation. Each retarder works synergistically with citric acid in the composite modifier to further adjust pH and ion concentration, improving workability.

[0034] The present invention also provides a method for preparing a concrete coating made from waste magnesium phosphate material as described above, comprising the following steps: Waste magnesium phosphate materials are processed by washing, drying, crushing, and grinding to a particle size of 400-500 mesh. The mass ratio of Mg to P in the treated waste magnesium phosphate material was measured. Based on the mass ratio of Mg to P, the mass ratio of polyacrylic acid to citric acid in the composite modifier is determined, and the mass ratio of calcined magnesium oxide to potassium dihydrogen phosphate in the gelling agent is determined. Citric acid is added to the mixing water and stirred to form a citric acid solution. The treated waste phosphorus and magnesium materials are then added and stirred to form a suspension. Polyacrylic acid is then added and stirred to form a composite modified suspension. Potassium dihydrogen phosphate, calcined magnesium oxide and retarder are mixed and stirred to obtain dry gelling agent powder; The dry powder of the gelling agent is added to the composite modified suspension and stirred to obtain the concrete coating.

[0035] This preparation method, through its orderly step design, solves the problems of uneven mixing and insufficient reaction of waste magnesium phosphate materials with other components, ensuring the stable performance of each batch of coating, while giving full play to the synergistic effect of each component, thereby improving the mechanical properties and anti-corrosion effect of the coating.

[0036] Further, the treatment method for waste magnesium phosphate materials is as follows: First, wash the surface stains of the waste magnesium phosphate mortar or coating with pure water, then dry it at 80°C, pulverize it, grind it finely using a ball mill or pulverizer, and sieve it to a particle size of 400-500 mesh. Then, use X-ray fluorescence (XRF) or other microscopic methods to test the chemical composition and determine the ratio of Mg to P elements. The mass ratio of magnesium to phosphate components in conventionally prepared magnesium phosphate materials has a relatively large range (1-4). Therefore, in practical applications, the ratio of the two components of the composite modifier and the gelling agent needs to be adjusted according to the tested Mg / P element ratio. Furthermore, the preparation methods of the composite modifier and the composite modified suspension include the following steps: (S1) Based on the high Mg / P element mass ratio of 7~20 in the waste phosphate magnesium material obtained from the test, it is determined that the Mg content is high. The polyacrylic acid content in the composite modified material S2 is increased, and the mass ratio of polyacrylic acid and citric acid is adjusted to 2~2.5:1.

[0037] For waste magnesium phosphate mortar or coating with a low Mg / P element mass ratio of 1~6, it is determined that the phosphate content is relatively high. Therefore, the content of citric acid in the composite modifier is increased, and the mass ratio of polyacrylic acid and citric acid is adjusted to 0.25~1:1.

[0038] (S2) Add the citric acid in the proportion determined in (S1) to the mixing water, and stir at 100~150 r / min for 5 min at room temperature to form a citric acid solution.

[0039] (S3) Add the treated waste phosphorus magnesium material to a citric acid solution and stir at a constant temperature of 50°C and a speed of 200~300r / min for 20 minutes to form a suspension.

[0040] (S4) Then add a certain proportion of polyacrylic acid to the suspension and stir at 200~300 r / min for 5 min to form a composite modified suspension.

[0041] Furthermore, the preparation of the gelling agent includes the following steps: (1) When the Mg / P ratio of waste magnesium phosphate material is high, reduce the ratio of recalcined MgO to potassium dihydrogen phosphate in the gelling agent and adjust the mass ratio to 2~2.5:1. When the Mg / P ratio of waste magnesium phosphate material is low, increase the ratio of MgO to potassium dihydrogen phosphate in the gelling agent and adjust the mass ratio to 3~3.5:1.

[0042] (2) Weigh the dry powder materials such as potassium dihydrogen phosphate, calcined magnesium oxide and retarder according to the proportion, and then stir the dry powder materials for 5 minutes before use; (3) Add the prepared gelling agent dry powder to the composite modified suspension prepared in (S4), stir at 100~200r / min for 3min, and apply by brushing. The thickness of the brushed concrete is 1~2mm.

[0043] This invention also provides an application of a concrete coating prepared from waste magnesium phosphate material, which is brushed onto the concrete surface to form an anti-corrosion coating. During brushing, the coating thickness is typically controlled to 1-2 mm. This thickness ensures sufficient resistance to erosion, preventing chloride ions, water, and other corrosive media from penetrating the concrete, while preventing shrinkage cracking due to excessive thickness. The coating exhibits good adhesion to the concrete surface. On one hand, the polyacrylic acid in the composite modifier can form ionic and hydrogen bonds with calcium and aluminum ions on the concrete surface; on the other hand, the hydration products of the gelling agent can combine with the hydration products on the concrete surface, ensuring the coating is not easily detached. This application method fully utilizes the anti-corrosion performance of the coating, solving the problem of insufficient durability of concrete structures due to erosion and achieving long-term protection.

[0044] Example 1 A long-lasting anti-corrosion coating for concrete prepared from recycled waste magnesium phosphate materials includes the following steps: (1) Take waste magnesium phosphate material 1, rinse the surface stains with pure water, dry it at 80°C, crush it, grind it finely using a ball mill or pulverizer, and then sieve it to a particle size of 400~500 mesh. Use X-ray fluorescence (XRF) to test the chemical composition and determine that the Mg / P element mass ratio is 7~9. Weigh 15 parts of the treated magnesium phosphate material 1. (2) Weigh 5 parts of the composite modifier, in which the mass ratio of polyacrylic acid and citric acid is 2:1. Weigh 3.3 parts of polyacrylic acid and 1.6 parts of citric acid for later use.

[0045] (3) Weigh 22 portions of mixing water, add citric acid to the mixing water, stir at 100~150r / min for 5min at room temperature to form a 7.2% citric acid solution for later use.

[0046] (4) Add the treated waste phosphorus magnesium material 1 to citric acid solution, and stir at a constant temperature of 50°C and a speed of 200~300r / min for 20 minutes to form a suspension.

[0047] (5) Then add 3.3 parts of polyacrylic acid to the suspension and stir at 200~300r / min for 5min to form a composite modified suspension.

[0048] (6) Weigh 80 parts of gelling agent, including 26 parts of potassium dihydrogen phosphate, 53 parts of calcined magnesium oxide, and 3 parts of retarder, and then stir the dry powder for 5 minutes before use. (7) Add the weighed dry powder from (6) to the composite modified suspension prepared in (5), and stir at 100~200 r / min for 3 min to obtain the anti-corrosion coating (e.g. Figure 2 As shown in the figure, the thickness of the brushed concrete is 1-2 mm.

[0049] Performance testing: (1) The workability of cement paste was tested according to the cement paste test method. The setting time was 19 min and the fluidity was 210 mm. (2) Corrosion resistance test (e.g.) Figure 4 (As shown). Apply the coating to the Q235 steel sheet, seal the edges with epoxy, leaving a 1cm margin. 2 The working area was immersed in simulated seawater for 28 days, and the corrosion resistance of the anti-corrosion layer was tested using a CHI660E electrochemical workstation. The measured corrosion current density was 8.661 × 10⁻⁶. -7 A·cm -2 ; (3) Bond strength test with concrete (e.g.) Figure 3As shown in the figure, the adhesion strength of the prepared anti-corrosion coating was tested according to GB / T-5210-2006 "Paints and Varnishes - Pull-off Adhesion Test". The higher the value, the better the adhesion effect and the better the corrosion and peeling. The adhesion strength after 7 days of curing at room temperature was 4.50 MPa, and the adhesion strength after 28 days of immersion in seawater was 3.68 MPa.

[0050] Example 2 This embodiment reduces the amount of composite modifier compared to Embodiment 1.

[0051] A long-lasting anti-corrosion coating for concrete prepared from recycled waste magnesium phosphate materials includes the following steps: (1) Take waste magnesium phosphate material 1, rinse the surface stains with pure water, dry it at 80°C, crush it, grind it finely using a ball mill or pulverizer, and then sieve it to a particle size of 400~500 mesh. Use X-ray fluorescence (XRF) to test the chemical composition and determine that the Mg / P element mass ratio is 7~9. Weigh 10 parts of the treated magnesium phosphate material 1. (2) Weigh 3 parts of the composite modifier, in which the mass ratio of polyacrylic acid and citric acid is 2:1. Weigh 2 parts of polyacrylic acid and 1 part of citric acid for later use.

[0052] (3) Weigh 22 portions of mixing water, add citric acid to the mixing water, stir at 100~150r / min for 5min at room temperature to form a 4.5% citric acid solution for later use.

[0053] (4) Add the treated waste phosphorus magnesium material 1 to citric acid solution, and stir at a constant temperature of 50°C and a speed of 200~300r / min for 20 minutes to form a suspension.

[0054] (5) Then add 3 parts of polyacrylic acid to the suspension and stir at 200~300r / min for 5min to form a composite modified suspension.

[0055] (6) Weigh 80 parts of gelling agent, including 26 parts of potassium dihydrogen phosphate, 53 parts of calcined magnesium oxide, and 3 parts of retarder, and then stir the dry powder for 5 minutes before use. (7) Add the dry powder weighed in (6) to the composite modified suspension prepared in (5), and stir at 100~200r / min for 3min to obtain the anti-corrosion coating. The thickness of the concrete to be brushed is 1~2mm.

[0056] Performance testing: (1) Test its workability according to the cement paste test method. Setting time 20 min, fluidity 225 mm; (2) Corrosion resistance test. The coating is brushed onto a Q235 steel sheet, and the edges are sealed with epoxy, leaving a 1cm gap. 2 The working area was immersed in simulated seawater for 28 days, and the corrosion resistance of the anti-corrosion layer was tested using a CHI660E electrochemical workstation. The measured corrosion current density was 1.214 × 10⁻⁶. -6 A·cm -2 .

[0057] (3) Bond strength test with concrete: The bond strength of the prepared anti-corrosion coating was tested according to GB / T-5210-2006 "Paint and Varnish Adhesion Test by Pull-off Method". The higher the value, the better the bonding effect and the better the corrosion and peeling. The bond strength after 7 days of curing at room temperature was 3.85 MPa, and the bond strength after 28 days of immersion in seawater was 3.11 MPa.

[0058] Example 3 This embodiment reduces the total mass of waste magnesium phosphate material 1 compared to embodiment 1.

[0059] A long-lasting anti-corrosion coating for concrete prepared from recycled waste magnesium phosphate materials includes the following steps: (1) Take waste magnesium phosphate material 1, rinse the surface stains with pure water, dry it at 80°C, crush it, grind it finely using a ball mill or pulverizer, and then sieve it to a particle size of 400~500 mesh. Use X-ray fluorescence (XRF) to test the chemical composition and determine that the Mg / P element mass ratio is 7~9. Weigh 10 parts of the treated magnesium phosphate material; (2) Weigh 5 parts of the composite modifier, in which the mass ratio of polyacrylic acid and citric acid is 2:1. Weigh 3.3 parts of polyacrylic acid and 1.6 parts of citric acid for later use.

[0060] (3) Weigh 22 portions of mixing water, add citric acid to the mixing water, stir at 100~150r / min for 5min at room temperature to form a 7.2% citric acid solution for later use.

[0061] (4) Add the treated waste phosphorus magnesium material 1 to citric acid solution, and stir at a constant temperature of 50°C and a speed of 200~300r / min for 20 minutes to form a suspension.

[0062] (5) Then add 3.3 parts of polyacrylic acid to the suspension and stir at 200~300r / min for 5min to form a composite modified suspension.

[0063] (6) Weigh 80 parts of gelling agent, including 26 parts of potassium dihydrogen phosphate, 53 parts of calcined magnesium oxide, and 3 parts of retarder, and then stir the dry powder for 5 minutes before use. (7) Add the dry powder weighed in (6) to the composite modified suspension prepared in (5), and stir at 100~200r / min for 3min to obtain the anti-corrosion coating. The thickness of the concrete to be brushed is 1~2mm.

[0064] Performance testing: (1) Test its workability according to the cement paste test method. Setting time 20 min, fluidity 230 mm; (2) Corrosion resistance test. The coating is brushed onto a Q235 steel sheet, and the edges are sealed with epoxy, leaving a 1cm gap. 2 The working area was immersed in simulated seawater for 28 days, and the corrosion resistance of the anti-corrosion layer was tested using a CHI660E electrochemical workstation. The measured corrosion current density was 2.331 × 10⁻⁶. -6 A·cm -2 ; (3) Bond strength test with concrete: The bond strength of the prepared anti-corrosion coating was tested according to GB / T-5210-2006 "Paint and Varnish Adhesion Test by Pull-off Method". The higher the value, the better the bonding effect and the better the corrosion and peeling. The bond strength after 7 days of curing at room temperature was 3.44 MPa, and the bond strength after 28 days of immersion in seawater was 3.02 MPa.

[0065] Example 4 In this embodiment, waste magnesium phosphate material 2 is used instead of the material in embodiment 1.

[0066] A long-lasting anti-corrosion coating for concrete prepared from recycled waste magnesium phosphate materials includes the following steps: (1) Take waste magnesium phosphate material 2, rinse the surface stains with pure water, dry it at 80°C, crush it, grind it finely using a ball mill or pulverizer, and then sieve it to a particle size of 400~500 mesh. Use X-ray fluorescence (XRF) to test the chemical composition and determine that the Mg / P element mass ratio is 2~3. Weigh 15 parts of the treated magnesium phosphate material 1. (2) Weigh 5 parts of the composite modifier, in which the mass ratio of polyacrylic acid and citric acid is 1:2. Weigh 1.6 parts of polyacrylic acid and 3.3 parts of citric acid for later use.

[0067] (3) Weigh 22 portions of mixing water, add citric acid to the mixing water, stir at 100~150r / min for 5min at room temperature to form a 15% citric acid solution for later use.

[0068] (4) Add the treated waste phosphorus magnesium material 2 into citric acid solution, and stir at a constant temperature of 50°C and a speed of 200~300r / min for 20 minutes to form a suspension.

[0069] (5) Then add 3.3 parts of polyacrylic acid to the suspension and stir at 200~300r / min for 5min to form a composite modified suspension.

[0070] (6) Weigh 80 parts of gelling agent, including 18 parts of potassium dihydrogen phosphate, 62 parts of calcined magnesium oxide, and 3 parts of retarder, and then stir the dry powder for 5 minutes before use. (7) Add the dry powder weighed in (6) to the composite modified suspension prepared in (5), and stir at 100~200r / min for 3min to obtain the anti-corrosion coating. The thickness of the concrete to be brushed is 1~2mm.

[0071] Performance testing: (1) Test its workability according to the cement paste test method. Setting time 21 min, fluidity 215 mm; (2) Corrosion resistance test. The coating is brushed onto a Q235 steel sheet, and the edges are sealed with epoxy, leaving a 1cm gap. 2 The working area was immersed in simulated seawater for 28 days, and the corrosion resistance of the anti-corrosion layer was tested using a CHI660E electrochemical workstation. The measured corrosion current density was 4.052 × 10⁻⁶. -7 A·cm -2 ; (3) Bond strength test with concrete: The bond strength of the prepared anti-corrosion coating was tested according to GB / T-5210-2006 "Paint and Varnish Adhesion Test by Pull-off Method". The higher the value, the better the bonding effect and the better the corrosion and peeling. The bond strength after 7 days of curing at room temperature was 4.06 MPa, and the bond strength after 28 days of immersion in seawater was 3.48 MPa.

[0072] Example 5 This embodiment reduces the amount of composite modifier compared to Embodiment 4.

[0073] A long-lasting anti-corrosion coating for concrete prepared from recycled waste magnesium phosphate materials includes the following steps: (1) Take waste magnesium phosphate material 2, rinse the surface stains with pure water, dry it at 80°C, crush it, grind it finely using a ball mill or pulverizer, and then sieve it to a particle size of 400~500 mesh. Use X-ray fluorescence (XRF) to test the chemical composition and determine that the Mg / P element mass ratio is 2~3. Weigh 15 parts of the treated magnesium phosphate material 1. (2) Weigh 3 parts of the composite modifier, in which the mass ratio of polyacrylic acid and citric acid is 1:2. Weigh 1 part of polyacrylic acid and 2 parts of citric acid for later use.

[0074] (3) Weigh 22 portions of mixing water, add citric acid to the mixing water, stir at 100~150r / min for 5min at room temperature to form a 9% citric acid solution for later use.

[0075] (4) Add the treated waste phosphorus magnesium material 2 into citric acid solution, and stir at a constant temperature of 50°C and a speed of 200~300r / min for 20 minutes to form a suspension.

[0076] (5) Then add 3.3 parts of polyacrylic acid to the suspension and stir at 200~300r / min for 5min to form a composite modified suspension.

[0077] (6) Weigh 80 parts of gelling agent, including 18 parts of potassium dihydrogen phosphate, 62 parts of calcined magnesium oxide, and 3 parts of retarder, and then stir the dry powder for 5 minutes before use. (7) Add the dry powder weighed in (6) to the composite modified suspension prepared in (5), and stir at 100~200r / min for 3min to obtain the anti-corrosion coating. The thickness of the concrete to be brushed is 1~2mm.

[0078] Performance testing: (1) Test its workability according to the cement paste test method. Setting time: 18 min; Flowability: 210 mm; (2) Corrosion resistance test. The coating is brushed onto a Q235 steel sheet, and the edges are sealed with epoxy, leaving a 1cm gap. 2 The working area was immersed in simulated seawater for 28 days, and the corrosion resistance of the anti-corrosion layer was tested using a CHI660E electrochemical workstation. The measured corrosion current density was 8.810 × 10⁻⁶. -7 A·cm -2 ; (3) Bond strength test with concrete: The bond strength of the prepared anti-corrosion coating was tested according to GB / T-5210-2006 "Paint and Varnish Adhesion Test by Pull-off Method". The higher the value, the better the bonding effect and the better the corrosion and peeling. The bond strength after 7 days of curing at room temperature was 3.59 MPa, and the bond strength after 28 days of immersion in seawater was 3.22 MPa.

[0079] Example 6 This embodiment reduces the total mass of waste magnesium phosphate material 2 compared to embodiment 4.

[0080] A long-lasting anti-corrosion coating for concrete prepared from recycled waste magnesium phosphate materials includes the following steps: (1) Take waste magnesium phosphate material 2, rinse the surface stains with pure water, dry it at 80°C, crush it, grind it finely using a ball mill or pulverizer, and then sieve it to a particle size of 400~500 mesh. Use X-ray fluorescence (XRF) to test the chemical composition and determine that the Mg / P element mass ratio is 2~3. Weigh 10 parts of the treated magnesium phosphate material 1. (2) Weigh 5 parts of the composite modifier, in which the mass ratio of polyacrylic acid and citric acid is 1:2. Weigh 1.6 parts of polyacrylic acid and 3.3 parts of citric acid for later use.

[0081] (3) Weigh 22 portions of mixing water, add citric acid to the mixing water, stir at 100~150r / min for 5min at room temperature to form a 15% citric acid solution for later use.

[0082] (4) Add the treated waste phosphorus magnesium material 2 into citric acid solution, and stir at a constant temperature of 50°C and a speed of 200~300r / min for 20 minutes to form a suspension.

[0083] (5) Then add 1.6 parts of polyacrylic acid to the suspension and stir at 200~300r / min for 5min to form a composite modified suspension.

[0084] (6) Weigh 80 parts of gelling agent, including 18 parts of potassium dihydrogen phosphate, 62 parts of calcined magnesium oxide, and 3 parts of retarder, and then stir the dry powder for 5 minutes before use. (7) Add the dry powder weighed in (6) to the suspension prepared in (5), stir at 100~200r / min for 3min to obtain the anti-corrosion coating. The thickness of the concrete to be brushed is 1~2mm.

[0085] Performance testing: (1) Test its workability according to the cement paste test method. Setting time: 16 min; Flowability: 200 mm. (2) Corrosion resistance test. The coating is brushed onto a Q235 steel sheet, and the edges are sealed with epoxy, leaving a 1cm gap. 2 The working area was immersed in simulated seawater for 28 days, and the corrosion resistance of the anti-corrosion layer was tested using a CHI660E electrochemical workstation. The measured corrosion current density was 1.012 × 10⁻⁶. -6 A·cm -2 ; (3) Bond strength test with concrete: The bond strength of the prepared anti-corrosion coating was tested according to GB / T-5210-2006 "Paint and Varnish Adhesion Test by Pull-off Method". The higher the value, the better the bonding effect and the better the corrosion and peeling. The bond strength after 7 days of curing at room temperature was 3.44 MPa, and the bond strength after 28 days of immersion in seawater was 3.15 MPa.

[0086] Comparative Example 1 Compared to Example 1, this embodiment contains waste magnesium phosphate material 1, but does not include a composite modifier, and includes the following steps: (1) Take waste phosphorus magnesium material 1, rinse the surface stains with pure water, dry it at 80°C, crush it, grind it with a ball mill or pulverizer and then sieve it to a particle size of 400~500 mesh. Weigh 15 parts of the treated phosphorus magnesium material 1. (2) Weigh 22 portions of mixing water, add the treated waste phosphorus magnesium material 1 to the mixing water, and stir at 200~300r / min for 5min to form a suspension.

[0087] (3) Weigh 80 parts of gelling agent, including 18 parts of potassium dihydrogen phosphate, 62 parts of calcined magnesium oxide, and 3 parts of retarder, and then stir the dry powder for 5 minutes before use.

[0088] (4) Add the dry powder weighed in (3) to the suspension prepared in (2), stir at 100~200r / min for 3min to obtain the anti-corrosion coating. The thickness of the concrete to be brushed is 1~2mm.

[0089] Performance testing: (1) Test its workability according to the cement paste test method. Setting time 24 min, fluidity 205 mm; (2) Corrosion resistance test. The coating is brushed onto a Q235 steel sheet, and the edges are sealed with epoxy, leaving a 1cm gap. 2 The working area was immersed in simulated seawater for 28 days, and the corrosion resistance of the anti-corrosion layer was tested using a CHI660E electrochemical workstation. The measured corrosion current density was 9.866 × 10⁻⁶. -6 A·cm -2 ; (3) Bond strength test with concrete: The bond strength of the prepared anti-corrosion coating was tested according to GB / T-5210-2006 "Paint and Varnish Adhesion Test by Pull-off Method". The higher the value, the better the bonding effect and the better the corrosion and peeling. The bond strength after 7 days of curing at room temperature was 2.70 MPa, and the bond strength after 28 days of immersion in seawater was 1.98 MPa.

[0090] Comparative Example 2 Compared to Example 4, this embodiment contains waste magnesium phosphate material 2 but does not include a composite modifier, and includes the following steps: (1) Take waste phosphorus magnesium material 2, rinse the surface stains with pure water, dry it at 80°C, crush it, grind it with a ball mill or pulverizer and then sieve it to a particle size of 400~500 mesh. Weigh 15 parts of the treated phosphorus magnesium material 1. (2) Weigh 22 portions of mixing water, add the treated waste phosphorus magnesium material 2 to the mixing water, and stir at 200~300r / min for 5min to form a suspension.

[0091] (3) Weigh 80 parts of gelling agent, including 18 parts of potassium dihydrogen phosphate, 62 parts of calcined magnesium oxide, and 3 parts of retarder, and then stir the dry powder for 5 minutes before use.

[0092] (4) Add the dry powder weighed in (3) to the suspension prepared in (2), stir at 100~200r / min for 3min to obtain the anti-corrosion coating. The thickness of the concrete to be brushed is 1~2mm.

[0093] Performance testing: (1) Test its workability according to the cement paste test method. Setting time: 22 min; Flowability: 195 mm; (2) Corrosion resistance test. The coating is brushed onto a Q235 steel sheet, and the edges are sealed with epoxy, leaving a 1cm gap. 2 The working area was immersed in simulated seawater for 28 days, and the corrosion resistance of the anti-corrosion layer was tested using a CHI660E electrochemical workstation. The measured corrosion current density was 7.544 × 10⁻⁶. -6 A·cm -2 ; (3) Bond strength test with concrete: The bond strength of the prepared anti-corrosion coating was tested according to GB / T-5210-2006 "Paint and Varnish Pull-off Adhesion Test". The higher the value, the better the bonding effect and the better the corrosion and peeling. The bond strength after 7 days of curing at room temperature was 2.42 MPa, and the bond strength after 28 days of immersion in seawater was 1.66 MPa.

[0094] Comparative Example 3 The preparation method in this embodiment is the same as that in Example 1, except that the proportion of the gelling agent applied to the waste magnesium phosphate material 1 in step (6) is different: Weigh out 80 parts of gelling agent, including 20 parts of potassium dihydrogen phosphate, 60 parts of calcined magnesium oxide, and 3 parts of retarder, and then stir the dry powder for 5 minutes before use. Performance testing: (1) Test its workability according to the cement paste test method. Setting time 16 min, fluidity 190 mm; (2) Corrosion resistance test. The coating is brushed onto a Q235 steel sheet, and the edges are sealed with epoxy, leaving a 1cm gap. 2 The working area was immersed in simulated seawater for 28 days, and the corrosion resistance of the anti-corrosion layer was tested using a CHI660E electrochemical workstation. The measured corrosion current density was 6.588 × 10⁻⁶. -6 A·cm -2 ; (3) Bond strength test with concrete: The bond strength of the prepared anti-corrosion coating was tested according to GB / T-5210-2006 "Paint and Varnish Adhesion Test by Pull-off Method". The higher the value, the better the bonding effect and the better the corrosion and peeling. The bond strength after 7 days of curing at room temperature was 3.25 MPa, and the bond strength after 28 days of immersion in seawater was 2.18 MPa.

[0095] Comparative Example 4 This embodiment uses the same preparation method as Example 4, except that the proportion of the gelling agent applied to the waste magnesium phosphate material 2 in step (6) is different: Weigh out 80 parts of gelling agent, including 30 parts of potassium dihydrogen phosphate, 50 parts of calcined magnesium oxide, and 3 parts of retarder, and then stir the dry powder for 5 minutes before use. Performance testing: (1) Test its workability according to the cement paste test method. Setting time 24 min, fluidity 220 mm; (2) Corrosion resistance test. The coating is brushed onto a Q235 steel sheet, and the edges are sealed with epoxy, leaving a 1cm gap. 2 The working area was immersed in simulated seawater for 28 days, and the corrosion resistance of the anti-corrosion layer was tested using a CHI660E electrochemical workstation. The measured corrosion current density was 8.321 × 10⁻⁶. -6 A·cm -2 ; (3) Bond strength test with concrete: The bond strength of the prepared anti-corrosion coating was tested according to GB / T-5210-2006 "Paint and Varnish Adhesion Test by Pull-off Method". The higher the value, the better the bonding effect and the better the corrosion and peeling. The bond strength after 7 days of curing at room temperature was 3.34 MPa, and the bond strength after 28 days of immersion in seawater was 2.78 MPa.

[0096] A comparison of the above embodiments and comparative examples shows that: Both Example 1 and Comparative Example 1 target waste magnesium phosphate materials with a high Mg / P ratio. Comparative Example 1, however, uses no modifier, while maintaining the same proportions of other materials. In Example 1, the bond strength after 7 days is 4.50 MPa, and after immersion in seawater for 28 days, the bond strength is 3.68 MPa. The corrosion current density is 8.661 × 10⁻⁶. -7 A·cm -2 The setting time was 19 min, and the flowability was 210 mm. In contrast, in Comparative Example 1, the bond strength after 7 days without the composite modification was 2.70 MPa, and the bond strength after 28 days of immersion in seawater was 1.98 MPa. The measured corrosion current density was 9.866 × 10⁻⁶. -6 A·cm -2 The setting time was 24 min, and the flowability was 205 mm. Relatively speaking, with the addition of the composite modifier, the bond strength increased significantly by 66.6% after 7 days and by 85.8% after 28 days of corrosion, while the corrosion current also decreased, demonstrating enhanced corrosion resistance. Furthermore, the reduced setting time had little impact on flowability, indicating that it still maintained good workability.

[0097] Example 4 and Comparative Example 2 both target waste magnesium phosphate materials with low Mg / P ratios. Comparative Example 4, however, uses no modifier, while the proportions of other materials remain the same. In Example 4, the bond strength after 7 days is 4.06 MPa, and the bond strength after immersion in seawater for 28 days is 3.48 MPa. The corrosion current density is 4.052 × 10⁻⁶. -7 A·cm -2 The setting time was 21 min, and the flowability was 215 mm. In contrast, in Comparative Example 2, the bond strength after 7 days without the composite modification was 2.42 MPa, and the bond strength after immersion in seawater for 28 days was 1.66 MPa. The measured corrosion current density was 7.544 × 10⁻⁶. -6 A·cm -2 The setting time was 22 minutes, and the flowability was 195 mm. Relatively speaking, with the addition of the composite modifier, the bond strength increased significantly by 67.7% after 7 days and by 109.6% after 28 days of corrosion, while the corrosion current also decreased, demonstrating enhanced corrosion resistance. Apart from this, the setting time and flowability had little effect, indicating that it still maintained good workability.

[0098] Example 1 was prepared in the same way as Comparative Example 1, except that the proportion of the gelling agent used on waste magnesium phosphate material 2 was different. As mentioned above, when the Mg / P element ratio of the waste magnesium phosphate material is high, the proportion of calcined MgO and potassium dihydrogen phosphate in the gelling agent is reduced to a mass ratio of 2~2.5:1. In Example 1, there were 53 parts of calcined magnesium oxide and 26 parts of potassium dihydrogen phosphate, and the mass ratio was adjusted to 2.03:1. In Comparative Example 3, the ratio of recalcined MgO to potassium dihydrogen phosphate was 3:1 (60 parts recalcined MgO and 20 parts potassium dihydrogen phosphate). The bonding strength after 7 days was 3.25 MPa, which was 27.7% lower than that in Example 1. After immersion in seawater for 28 days, the bonding strength was 2.18 MPa, which was 40.7% lower than that in Example 1. The corrosion current density was also increased compared to Example 1, indicating that the anti-corrosion performance was correspondingly reduced.

[0099] As mentioned earlier, when the Mg / P element ratio of waste magnesium phosphate material is low, the ratio of recalcined MgO to potassium dihydrogen phosphate in the gelling agent is increased, and the mass ratio is adjusted to 3~3.5:1. In the four cases implemented, there were 62 parts of recalcined magnesium oxide and 18 parts of potassium dihydrogen phosphate, with a mass ratio of 3.44:1. In Comparative Example 4, the ratio of recalcined MgO to potassium dihydrogen phosphate was 1.66:1 (50 parts recalcined MgO and 30 parts potassium dihydrogen phosphate). The bonding strength after 7 days was 3.34 MPa, which was 17.7% lower than that in Example 4. After immersion in seawater for 28 days, the bonding strength was 2.78 MPa, which was 20.1% lower than that in Example 4. The corrosion current density was also higher than that in Example 4, indicating that the corrosion resistance was correspondingly reduced.

[0100] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A concrete coating prepared from waste magnesium phosphate material, characterized in that, It is composed of the following raw materials in parts by weight: 70-85 parts gelling agent, 1-3 parts retarder, 10-15 parts waste treated phosphorus and magnesium materials, 3-5 parts composite modifier, and 22-25 parts mixing water.

2. The concrete coating prepared from waste magnesium phosphate material as described in claim 1, characterized in that, The gelling agent includes potassium dihydrogen phosphate and calcined magnesium oxide, wherein the mass ratio of calcined magnesium oxide to potassium dihydrogen phosphate is 2~3.5:

1.

3. The concrete coating prepared from waste magnesium phosphate material as described in claim 2, characterized in that, The composite modifier includes polyacrylic acid and citric acid, wherein the mass ratio of polyacrylic acid to citric acid is 0.25~2.5:

1.

4. The concrete coating prepared from waste magnesium phosphate material as described in claim 3, characterized in that, When the mass ratio of Mg to P in the waste magnesium phosphate material is 7 to 20, the mass ratio of polyacrylic acid to citric acid is 2 to 2.5:1, and the mass ratio of calcined magnesium oxide to potassium dihydrogen phosphate is 2 to 2.5:

1.

5. The concrete coating prepared from waste magnesium phosphate material as described in claim 3, characterized in that, When the mass ratio of Mg to P in the waste magnesium phosphate material is 1 to 6, the mass ratio of polyacrylic acid to citric acid is 0.25 to 1:1, and the mass ratio of calcined magnesium oxide to potassium dihydrogen phosphate is 3 to 3.5:

1.

6. The concrete coating prepared from waste magnesium phosphate material as described in claim 1, characterized in that, The waste magnesium phosphate material is one or more of magnesium phosphate slurry and anti-corrosion coating. The mass ratio of magnesium phosphate material in the waste magnesium phosphate material is not less than 80%, and the storage time does not exceed 2 years.

7. The concrete coating prepared from waste magnesium phosphate material as described in claim 1, characterized in that, The retarder is one of borax, boric acid, and sodium citrate.

8. A method for preparing a concrete coating made from waste magnesium phosphate material as described in any one of claims 1-7, characterized in that, Includes the following steps: Waste magnesium phosphate materials are processed by washing, drying, crushing, and grinding to a particle size of 400-500 mesh. The mass ratio of Mg to P in the treated waste magnesium phosphate material was measured. Based on the mass ratio of Mg to P, the mass ratio of polyacrylic acid to citric acid in the composite modifier is determined, and the mass ratio of calcined magnesium oxide to potassium dihydrogen phosphate in the gelling agent is determined. Citric acid is added to the mixing water and stirred to form a citric acid solution. The treated waste phosphorus and magnesium materials are then added and stirred to form a suspension. Polyacrylic acid is then added and stirred to form a composite modified suspension. Potassium dihydrogen phosphate, calcined magnesium oxide and retarder are mixed and stirred to obtain dry gelling agent powder; The dry powder of the gelling agent is added to the composite modified suspension and stirred to obtain the concrete coating.

9. The preparation method according to claim 8, characterized in that, After adding the treated waste magnesium phosphate material, stir at a speed of 200~300 r / min; after adding polyacrylic acid, stir at a speed of 200~300 r / min; after adding the dry gelling agent powder to the composite modified suspension, stir at a speed of 100~200 r / min.

10. An application of a concrete coating prepared from waste magnesium phosphate material, characterized in that, The concrete coating prepared from waste magnesium phosphate material as described in any one of claims 1-7 is brushed onto the concrete surface to form an anti-corrosion coating.

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