Organic nano concrete impervious and sulfate corrosion resistant additive

Abstract

The invention provides an anti-permeability and anti-sulfate corrosion additive for organic nano concrete, and belongs to the technical field of concrete. The additive disclosed by the invention contains ethylenediamine methylene sodium phosphate, sodium polyacrylate, sodium thiocyanate, polylactic acid-glycolic acid copolymer (PLGA), hydroxypropyl ethanolamine, a modified nano graphite material, chitosan quaternary ammonium salt, a silane coupling agent, nano volcanic ash powder and other components in a specific proportion. Wherein the modified nano-graphite material is prepared by modifying nano-graphite powder with polyether amine and a silane coupling agent; all the components are matched and the additive is prepared by adopting a special preparation method, and the additive has good impermeability and sulfate corrosion resistance when being used in concrete, and is stable and reliable.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete, and particularly relates to an organic nano-concrete impermeability and sulfate corrosion resistance additive. Background Art

[0002] As one of the most widely used building materials in modern construction projects, concrete plays a crucial role in various infrastructure construction. However, in complex usage environments, concrete faces many durability challenges, among which impermeability and sulfate corrosion resistance are important factors affecting its long-term performance and service life.

[0003] With the booming development of the construction industry, concrete structures are widely used in underground projects, hydraulic structures, marine engineering and other fields. In these environments, concrete inevitably comes into contact with water and various corrosive media. Groundwater, seawater and moisture in the soil may all penetrate into the interior of the concrete. The infiltration of water not only increases the humidity inside the concrete, leading to the corrosion of steel bars, but also provides a channel for the intrusion of other harmful media, seriously affecting the safety and stability of the concrete structure. For example, in underground projects such as underground parking lots and subway tunnels, the concrete structure is in a humid environment for a long time, and leakage problems often occur, which not only increases the maintenance cost, but may also cause irreversible damage to the structure.

[0004] At the same time, sulfate attack is another severe problem faced by the durability of concrete. In some soils and groundwaters, there are large amounts of sulfates, such as sodium sulfate and magnesium sulfate. When these sulfates react chemically with the cement hydration products in the concrete, expansive products such as ettringite and gypsum will be generated. These expansive products generate huge expansive stresses inside the concrete, resulting in the cracking, spalling of the concrete structure and a significant decrease in strength. In projects such as road bridges in coastal areas and saline soil areas, the concrete structure is particularly severely affected by sulfate attack, greatly shortening the service life of the project and causing huge economic losses.

[0005] Traditional concrete has certain limitations in terms of impermeability and sulfate corrosion resistance. Although conventional means such as increasing the cement dosage and reducing the water-cement ratio can improve the performance of concrete to a certain extent, the effect is limited and the production cost will be increased. In addition, simply increasing the cement dosage will cause the hydration heat of the concrete to rise, resulting in temperature cracks and further reducing the durability of the concrete.

[0006] Therefore, it is necessary to develop concrete impermeability and sulfate corrosion resistance additives, which can improve the impermeability and sulfate corrosion resistance of concrete through various action mechanisms, better ensure the long-term safe and stable operation of various construction projects, reduce the maintenance cost and extend the service life. Summary of the Invention

[0007] In view of the fact that existing concrete is prone to water seepage and sulfate corrosion and needs to be treated for water resistance and sulfate corrosion resistance, the present invention provides an organic nano-concrete water resistance and sulfate corrosion resistance additive, which contains components such as sodium ethylene diamine methylene phosphonate, sodium polyacrylate, sodium thiocyanate, poly(lactic-co-glycolic acid) (PLGA), hydroxypropyl ethanolamine, modified nano-graphite material, chitosan quaternary ammonium salt, silane coupling agent and nano-volcanic ash powder in specific proportions. The additive is prepared by a special preparation method and has excellent water resistance and sulfate corrosion resistance performance when used in concrete, which is stable and reliable. The specific technical solution is as follows:

[0008] An organic nano-concrete water resistance and sulfate corrosion resistance additive, characterized in that the additive comprises the following raw materials in parts by mass: 8 to 12 parts of sodium ethylene diamine methylene phosphonate, 15 to 18 parts of sodium polyacrylate, 3 to 5 parts of sodium thiocyanate, 10 to 15 parts of poly(lactic-co-glycolic acid) (PLGA), 5 to 8 parts of hydroxypropyl ethanolamine, 0.5 to 1.2 parts of modified nano-graphite material, 6 to 9 parts of chitosan quaternary ammonium salt, 1 to 2 parts of silane coupling agent and 3 to 6 parts of nano-volcanic ash powder.

[0009] Among the above raw materials, the particle size range of the nano-volcanic ash powder is below 600 nm.

[0010] Among the above raw materials, the silane coupling agent is silane coupling agent KH-792.

[0011] Among the above raw materials, the preparation method of the modified nano-graphite material comprises the following steps: according to the mass ratio, nano-graphite powder: polyetheramine (PEI): silane coupling agent: ethanol = (1 - 2): (0.3 - 0.5): (1 - 1.5): (90 - 100). First, add nano-graphite powder and polyetheramine (PEI) into ethanol, perform ultrasonic treatment at 60°C - 65°C for 30 min - 60 min at 40 kHz - 50 kHz, then add the silane coupling agent, and perform reflux reaction at 70°C - 75°C for 4 h - 5 h, and then perform spray drying to obtain the modified nano-graphite material.

[0012] In the above preparation method of the modified nano-graphite material, the silane coupling agent is silane coupling agent KH-792.

[0013] In the above preparation method of the modified nano-graphite material, the particle size range of the nano-graphite powder is below 600 nm.

[0014] In the above preparation method of the modified nano-graphite material, the nano-graphite powder is prepared by sintering and graphitizing calcined petroleum coke powder at 2500°C - 2800°C and then pulverizing.

[0015] The preparation method of the above-mentioned organic nano-concrete impermeability and sulfate corrosion-resistant additive comprises the following steps:

[0016] S1: Add hydroxypropyl ethanolamine and chitosan quaternary ammonium salt into acetic acid aqueous solution to prepare acetic acid solution;

[0017] Under the protection of nitrogen, dissolve sodium ethylene diamine methylene phosphonate and sodium thiocyanate in deionized water, then add sodium polyacrylate and poly(lactic-co-glycolic acid) (PLGA) in sequence, control the shear rate at 1500 rpm - 2000 rpm, disperse for 30 min - 50 min, then add acetic acid solution, and shear at 1000 rpm - 1200 rpm for 20 min - 30 min to obtain liquid phase material A;

[0018] S2: Mix the modified nano-graphite material and nano-volcanic ash powder evenly by air flow to obtain solid phase material B; Under the condition of ultrasonic treatment with a power of 700 W - 800 W, add solid phase material B into liquid phase material A in three portions. Divide solid phase material B into three equal portions, and perform ultrasonic treatment for 10 min - 20 min each time after adding one portion, then add the next portion until all of solid phase material B is added, and perform ultrasonic treatment for 20 min - 30 min to obtain material C;

[0019] S3: Under the stirring state, add silane coupling agent to material C and stir for 10 min - 20 min; Then process it through a microfluidic homogenizer for 3 - 4 cycles; Spray dry to obtain a powdery additive.

[0020] In S1 of the above preparation method, the dosage of the acetic acid aqueous solution is 3 - 4 times the total mass of hydroxypropyl ethanolamine and chitosan quaternary ammonium salt; The pH value of the acetic acid aqueous solution is 5.0 - 5.5.

[0021] In S1 of the above preparation method, the dosage of the deionized water is 4 - 5 times the total mass of sodium ethylene diamine methylene phosphonate and sodium thiocyanate.

[0022] In S3 of the above preparation method, the rotation speed of the stirring is 500 r / min - 600 r / min.

[0023] In S3 of the above preparation method, the pressure of the microfluidic homogenizer is 180 MPa - 200 MPa.

[0024] In S3 of the above preparation method, the inlet air temperature of the spray drying is 160 °C - 180 °C, and the outlet air temperature of the spray drying is 80 °C - 85 °C.

[0025] The beneficial effects of the organic nano-concrete impermeability and sulfate corrosion-resistant additive of the present invention are as follows:

[0026] 1. Ethylenediamine methylene phosphonic acid sodium can undergo complexation reactions with metal ions such as calcium ions generated during the hydration process of cement. A network-like complex structure is formed inside the concrete. This structure can fill the capillary pores inside the concrete, reduce the pore size and connectivity, thereby effectively preventing the penetration of water and improving the impermeability of the concrete. When encountering sulfate erosion, it can preferentially combine with sulfate ions to form a stable complex, reducing the probability of sulfate ions reacting with calcium hydroxide, calcium aluminate hydrate, etc. in the cement stone, thus alleviating the damage of the concrete structure caused by the formation of expansive products such as ettringite and enhancing the sulfate corrosion resistance. The role of filling pores reduces the transmission channels of chloride ions, hinders the diffusion of chloride ions in the concrete, and reduces the chloride ion diffusion coefficient. Its complexation effect changes the charge distribution on the surface of cement particles to a certain extent and affects the rheological properties of the cement paste to a certain extent. However, since its main function is not to adjust workability, its impact on the slump is relatively small.

[0027] 2. As an efficient thickening agent and water retention agent, sodium polyacrylate can significantly improve the water retention of concrete mixtures. It can adsorb on the surface of cement particles to form a water film with a certain thickness and viscosity, preventing the rapid loss of water, enabling more sufficient hydration of cement during the hardening process of the concrete, and making the internal structure more dense, thereby improving the impermeability. Good water retention ensures the stability of the internal structure of the concrete, reduces the enrichment of sulfate ions inside the concrete caused by water migration, and indirectly improves the sulfate corrosion resistance. At the same time, the formed water film can also block the contact between sulfate ions and the cement stone to a certain extent. The dense structure reduces the diffusion channels of chloride ions, reduces the chloride ion diffusion coefficient, and effectively prevents chloride ions from invading the concrete interior. The thickening effect increases the cohesiveness of the concrete mixture. When initially mixing, appropriately increasing the amount of sodium polyacrylate can reduce the segregation and bleeding phenomena of the concrete, improve the slump retention performance, and reduce the slump loss within 2 hours.

[0028] III. Sodium Thiocyanate Sodium thiocyanate can accelerate the hydration reaction process of cement. In the early stage, it can promote the faster dissolution and hydration of cement particles, generating more hydration products such as calcium hydroxide and calcium silicate hydrate. These hydration products can fill the pores inside the concrete, making the concrete structure more dense and improving the impermeability. The rapid hydration reaction enables the concrete to form a relatively stable structure in the early stage, enhancing the concrete's ability to resist sulfate erosion. Moreover, the relatively large amount of calcium hydroxide generated in the early stage can consume part of the sulfate ions, reducing the harm of sulfate erosion in the later stage. The dense structure is not conducive to the diffusion of chloride ions, reducing the diffusion rate of chloride ions in the concrete. Since it accelerates the cement hydration, to a certain extent, it will accelerate the slump loss of the concrete. However, if the dosage is well controlled, its property of accelerating hydration can be utilized in the early stage to rapidly increase the initial strength of the concrete, which is beneficial to construction operations.

[0029] IV. Poly(lactic-co-glycolic acid) (PLGA) Poly(lactic-co-glycolic acid) (PLGA) has good film-forming properties. During the hydration process of concrete, it can form a continuous polymer film on the surface of cement particles and the surface of pores inside the concrete. This film acts like a waterproof barrier, effectively preventing the penetration of water and greatly improving the impermeability of the concrete. This film can not only block water but also isolate sulfate ions, making it difficult for them to contact the cement stone, thereby preventing the chemical reaction between sulfate and cement stone and enhancing the sulfate corrosion resistance. The continuous film structure completely blocks the diffusion path of chloride ions, significantly reducing the chloride ion diffusion coefficient. The film-forming effect of PLGA will increase the viscosity of the concrete mixture to a certain extent and have a certain effect on reducing the slump. However, since its main function is to enhance durability, the influence on the slump can be balanced by adjusting other components.

[0030] V. Hydroxypropyl Ethanolamine Hydroxypropyl ethanolamine is an organic amine compound that can promote the hydration reaction of cement. By chemically reacting with the active sites on the surface of cement particles, it accelerates the hydration process of cement, making the cement stone structure more dense, reducing the porosity, and thus improving the impermeability of the concrete. The dense cement stone structure enhances the concrete's ability to resist sulfate erosion. At the same time, the more hydration products generated by its promotion of hydration can react with sulfate ions, consuming part of the sulfate ions and reducing the harm of sulfate erosion. It reduces the porosity inside the concrete, reduces the diffusion channels of chloride ions, and reduces the chloride ion diffusion coefficient. The effect of promoting cement hydration will accelerate the slump loss of the concrete, but proper use can increase the strength of the concrete in the early stage and adjust the workability of the concrete by cooperating with other admixtures.

[0031] VI. The modified nano-graphite material itself has an extremely small particle size, which can fill the tiny pores inside the concrete, refine the pore structure, improve the compactness of the concrete, thus effectively preventing water penetration and enhancing the impermeability. On the one hand, its good chemical stability can resist the chemical erosion of sulfates to a certain extent; on the other hand, the role of filling pores makes the concrete structure more dense, reduces the intrusion channels of sulfate ions, and improves the sulfate corrosion resistance. The refined pore structure blocks the diffusion path of chloride ions and reduces the chloride ion diffusion coefficient. Due to its nano-scale particle characteristics, when it is well dispersed, it has little effect on the slump of the concrete.

[0032] The modified nano-graphite material has better dispersibility than the unmodified material: The modification treatment with polyetheramine (PEI) and silane coupling agent KH-792 changes the surface properties of nano-graphite powder. Active groups such as amino groups in polyetheramine can adsorb on the surface of nano-graphite powder. Through electrostatic repulsion and steric hindrance effects, the aggregation between nano-graphite powder particles is prevented. The silane coupling agent further forms an organic film on the surface of nano-graphite powder, enhancing its dispersion stability in the organic and inorganic hybrid system (such as the concrete system). Compared with the unmodified nano-graphite powder, the modified nano-graphite material can be more evenly dispersed in the concrete matrix, giving full play to the filling and strengthening effects of its nano-particles. The active groups introduced during the modification process significantly enhance the interfacial bonding force between the nano-graphite material and other components in the concrete (such as cement, aggregate, etc.). One end of the silane coupling agent reacts with the hydroxyl groups on the surface of nano-graphite powder to form chemical bonds, and the organic groups at the other end can undergo physical or chemical reactions with cement hydration products or other organic components, thus establishing a firm connection between the nano-graphite material and the concrete matrix. This enhanced interfacial bonding force can effectively transfer stress, improve the overall mechanical properties and durability of the concrete, and perform more excellently in terms of impermeability and corrosion resistance.

[0033] VII. Chitosan quaternary ammonium salt has cationic characteristics and can undergo electrostatic interactions with negative ion groups in the concrete, such as binding to some negatively charged colloidal particles in cement hydration products. This binding effect can promote the formation of the cement stone structure, fill pores, improve the compactness of the concrete, and enhance the impermeability. The dense structure reduces the intrusion of sulfate ions, and at the same time its antibacterial property can inhibit the growth of some microorganisms that produce acidic substances on or inside the concrete surface, accelerating the corrosion of the concrete, thus indirectly improving the sulfate corrosion resistance. The effect of improving the compactness reduces the diffusion channels of chloride ions and lowers the chloride ion diffusion coefficient. The interaction with other components will affect the rheological properties of the concrete mixture to a certain extent. When used in an appropriate amount, it can improve the cohesiveness of the concrete and has a certain regulating effect on the slump.

[0034] VIII. The silane coupling agent molecule contains two different types of groups. One end can chemically react with the hydroxyl groups on the surface of inorganic materials (such as cement, nano-volcanic ash powder, etc.) to form chemical bonds. The other end can physically or chemically react with organic materials (such as PLGA, sodium polyacrylate, etc.). Through this bridging effect, the interfacial bonding force between the organic phase and the inorganic phase is enhanced, making the internal structure of the concrete more compact, improving the impermeability. The enhanced interfacial bonding force makes the overall structure of the concrete more stable and enhances the ability to resist sulfate erosion. At the same time, it can improve the synergistic effect between the components and enhance the anti-sulfate corrosion performance. The compact structure and good synergistic effect reduce the diffusion channels of chloride ions and lower the chloride ion diffusion coefficient.

[0035] IX. Nano-volcanic ash powder has a very high pozzolanic activity and can undergo a secondary reaction with the calcium hydroxide generated by cement hydration to form more gel substances such as hydrated calcium silicate. These gel substances can fill the pores inside the concrete, refine the pore structure, significantly improve the compactness of the concrete, and thus enhance the impermeability. The large amount of gel substances generated makes the concrete structure more dense and reduces the intrusion channels of sulfate ions. Moreover, the secondary reaction consumes part of the calcium hydroxide, reducing the risk of expansion damage caused by the reaction of sulfate with calcium hydroxide to form gypsum, and improving the anti-sulfate corrosion ability. The refined pores and filling effect block the diffusion path of chloride ions and greatly reduce the chloride ion diffusion coefficient. Due to its fine particles and large specific surface area, to a certain extent, it will increase the water demand of the concrete mixture, resulting in a decrease in slump. However, through reasonable mix design and admixture adjustment, its impact on slump can be improved.

[0036] X. Both the modified nano-graphite material and the nano-pozzolan powder have nano-scale particle sizes, but there are differences in their particle size distributions and particle morphologies. The lamellar structure and smaller particle size of the modified nano-graphite material can fill the microscopic pores inside the concrete, while the spherical or irregular particles of the nano-pozzolan powder can fill slightly larger pores and play a role in filling and supporting between the lamellae of the modified nano-graphite material. The combined action of the two forms a multi-level pore filling system from the microscopic to the mesoscopic scale, greatly improving the compactness of the concrete and significantly enhancing its impermeability. The modified nano-graphite material has good chemical stability and certain electrical conductivity, and can form a relatively stable microenvironment inside the concrete to inhibit some electrochemical corrosion reactions. The nano-pozzolan powder has pozzolanic activity and can undergo a secondary reaction with the cement hydration products, consuming calcium hydroxide and generating more gel substances. In terms of resistance to sulfate corrosion and chloride ion diffusion, the stabilizing effect of the modified nano-graphite material and the chemical activity of the nano-pozzolan powder cooperate with each other. The gel substances generated by the nano-pozzolan powder further refine the pore structure and reduce the diffusion channels of erosive ions, while the modified nano-graphite material can, to a certain extent, prevent the electrochemical corrosion reactions caused by ion diffusion, jointly improving the corrosion resistance of the concrete.

[0037] XI. According to the characteristics of each raw material, the present invention designs a specific preparation method, which can well realize the preparation of the product, with uniform quality, ensuring a good effect of improving the performance of concrete. Specific Embodiments

[0038] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to these embodiments.

[0039] Example 1

[0040] An organic nano-concrete impermeability and sulfate corrosion resistance additive, characterized in that the additive comprises the following raw materials in parts by mass: 10 parts of ethylenediamine methylene phosphonate, 16.5 parts of sodium polyacrylate, 4 parts of sodium thiocyanate, 13 parts of poly(lactic-co-glycolic acid) (PLGA), 7 parts of hydroxypropyl ethanolamine, 0.8 part of modified nano-graphite material, 7 parts of chitosan quaternary ammonium salt, 1.5 parts of silane coupling agent and 5 parts of nano-pozzolan powder. Among them, the particle size range of the nano-pozzolan powder is below 600 nm; the silane coupling agent is silane coupling agent KH-792.

[0041] Among them, the preparation method of the modified nano-graphite material includes the following steps: by mass ratio, nano-graphite powder: polyetheramine (PEI): silane coupling agent KH-792: ethanol = 1.5: 0.4: 1.2: 95. First, add the nano-graphite powder and polyetheramine (PEI) into ethanol, and perform ultrasonic treatment at 62°C for 45 min at 45 kHz. Then add the silane coupling agent KH-792, and carry out reflux reaction at 72°C for 4.5 h. Then perform spray drying to obtain the modified nano-graphite material. Among them, the particle size range of the nano-graphite powder is below 600 nm; the nano-graphite powder is prepared by calcined petroleum coke powder through graphitization by sintering at 2600°C and then pulverization.

[0042] The preparation method of the above-mentioned organic nano-concrete impermeability and sulfate corrosion resistance additive includes the following steps:

[0043] S1: Add hydroxypropyl ethanolamine and chitosan quaternary ammonium salt into acetic acid aqueous solution to prepare acetic acid solution; among them, the dosage of acetic acid aqueous solution is 3.5 times the total mass of hydroxypropyl ethanolamine and chitosan quaternary ammonium salt; the pH value of acetic acid aqueous solution is 5.2;

[0044] Under nitrogen protection, dissolve ethylenediamine methylene phosphonic acid sodium and sodium thiocyanate in deionized water, and the dosage of deionized water is 4.5 times the total mass of ethylenediamine methylene phosphonic acid sodium and sodium thiocyanate; then add sodium polyacrylate and poly(lactic acid-glycolic acid) copolymer (PLGA) in sequence, control the shear rate at 1800 rpm and disperse for 40 min, then add the acetic acid solution and shear at 1100 rpm for 25 min to obtain the liquid-phase material A;

[0045] S2: Uniformly mix the modified nano-graphite material and nano-volcanic ash powder by air flow to obtain the solid-phase material B; under the condition of ultrasonic treatment with a power of 750 W, add the solid-phase material B into the liquid-phase material A in three portions. The solid-phase material B is divided into three equal portions, and each time one portion is added, ultrasonic treatment is carried out for 15 min, and then the next portion is added until the solid-phase material B is completely added, and ultrasonic treatment is carried out for 25 min to obtain the material C;

[0046] S3: Under the stirring state of 550 r / min, add the silane coupling agent to the material C, and continuously stir at 550 r / min for 15 min; then perform 3 cycles of treatment by a microfluidic homogenizer with a pressure of 190 MPa; perform spray drying, with the inlet air temperature of 170°C and the outlet air temperature of 82°C; obtain the powdery additive.

[0047] Example 2

[0048] An anti-seepage and anti-sulfate corrosion additive for organic nano-concrete, characterized in that the additive comprises raw materials in the following parts by mass: 8 parts of ethylenediamine methylene phosphonate, 15 parts of sodium polyacrylate, 3 parts of sodium thiocyanate, 10 parts of poly(lactic-co-glycolic acid) (PLGA), 5 parts of hydroxypropyl ethanolamine, 0.5 part of modified nano-graphite material, 6 parts of chitosan quaternary ammonium salt, 1 part of silane coupling agent and 3 parts of nano-volcanic ash powder. Among them, the particle size range of the nano-volcanic ash powder is below 600 nm; the silane coupling agent is silane coupling agent KH-792.

[0049] Among them, the preparation method of the modified nano-graphite material comprises the following steps: according to the mass ratio, nano-graphite powder: polyetheramine (PEI): silane coupling agent KH-792: ethanol = 1: 0.3: 1: 90. First, add nano-graphite powder and polyetheramine (PEI) to ethanol, and perform ultrasonic treatment at 60 °C for 30 min at 40 kHz. Then add silane coupling agent KH-792, and perform reflux reaction at 70 °C for 4 h. Then perform spray drying to obtain the modified nano-graphite material. Among them, the particle size range of the nano-graphite powder is below 600 nm; the nano-graphite powder is prepared by calcined petroleum coke powder sintered and graphitized at 2500 °C and then pulverized.

[0050] The preparation method of the above-mentioned anti-seepage and anti-sulfate corrosion additive for organic nano-concrete comprises the following steps:

[0051] S1: Add hydroxypropyl ethanolamine and chitosan quaternary ammonium salt to the acetic acid aqueous solution to prepare an acetic acid solution; among them, the dosage of the acetic acid aqueous solution is 3 times the total mass of hydroxypropyl ethanolamine and chitosan quaternary ammonium salt; the pH value of the acetic acid aqueous solution is 5.0;

[0052] Under the protection of nitrogen, dissolve ethylenediamine methylene phosphonate and sodium thiocyanate in deionized water, and the dosage of deionized water is 4 times the total mass of ethylenediamine methylene phosphonate and sodium thiocyanate; then add sodium polyacrylate and poly(lactic-co-glycolic acid) (PLGA) in sequence, control the shear rate at 1500 rpm, disperse for 30 min, and then add the acetic acid solution, shear at 1000 rpm for 20 min to obtain the liquid-phase material A;

[0053] S2: Mix the modified nano-graphite material and nano-volcanic ash powder evenly by air flow to obtain the solid-phase material B; under the condition of ultrasonic treatment with a power of 700 W, add the solid-phase material B to the liquid-phase material A in three portions. The solid-phase material B is divided into three equal portions, and each time one equal portion is added, ultrasonic treatment is performed for 10 min, and then the next equal portion is added until the solid-phase material B is completely added, and ultrasonic treatment is performed for 20 min to obtain the material C;

[0054] S3: Under the stirring state of 500 r / min, add silane coupling agent to Material C, and continuously stir at 500 r / min for 10 min; then process it through a microfluidic homogenizer for 3 cycles, with a pressure of 180 MPa; spray drying, with an inlet air temperature of 160 °C and an outlet air temperature of 80 °C; obtain a powdery additive.

[0055] Example 3

[0056] An organic nano-concrete impermeability and sulfate corrosion resistance additive, characterized in that the additive comprises the following raw materials in parts by mass: 8 parts of ethylenediamine methylene phosphonic acid sodium, 18 parts of sodium polyacrylate, 3 parts of sodium thiocyanate, 15 parts of poly (lactic-co-glycolic acid) (PLGA), 5 parts of hydroxypropyl ethanolamine, 1.2 parts of modified nano-graphite material, 6 parts of chitosan quaternary ammonium salt, 2 parts of silane coupling agent, and 3 parts of nano-volcanic ash powder. Among them, the particle size range of the nano-volcanic ash powder is below 600 nm; the silane coupling agent is silane coupling agent KH-792.

[0057] Among them, the preparation method of the modified nano-graphite material comprises the following steps: According to the mass ratio, nano-graphite powder: polyetheramine (PEI): silane coupling agent KH-792: ethanol = 2: 0.3: 1.5: 90. First, add nano-graphite powder and polyetheramine (PEI) to ethanol, and perform ultrasonic treatment at 65 °C for 60 min at 40 kHz. Then add silane coupling agent KH-792 and reflux at 70 °C for 5 h. Then spray dry to obtain the modified nano-graphite material. Among them, the particle size range of the nano-graphite powder is below 600 nm; the nano-graphite powder is prepared by calcined petroleum coke powder sintered and graphitized at 2500 °C and then pulverized.

[0058] The preparation method of the above-mentioned organic nano-concrete impermeability and sulfate corrosion resistance additive comprises the following steps:

[0059] S1: Add hydroxypropyl ethanolamine and chitosan quaternary ammonium salt to the acetic acid aqueous solution to prepare an acetic acid solution; among them, the dosage of the acetic acid aqueous solution is 4 times the total mass of hydroxypropyl ethanolamine and chitosan quaternary ammonium salt; the pH value of the acetic acid aqueous solution is 5.0;

[0060] Under nitrogen protection, dissolve ethylenediamine methylene phosphonic acid sodium and sodium thiocyanate in deionized water, and the dosage of deionized water is 5 times the total mass of ethylenediamine methylene phosphonic acid sodium and sodium thiocyanate; then add sodium polyacrylate and poly (lactic-co-glycolic acid) (PLGA) in sequence, control the shear rate at 1500 rpm and disperse for 50 min, then add the acetic acid solution and shear at 1000 rpm for 30 min to obtain the liquid-phase material A;

[0061] S2: Uniformly mix the modified nano-graphite material and nano-volcanic ash powder by air flow to obtain solid-phase material B; under the ultrasonic treatment condition of 700 W power, add solid-phase material B to liquid-phase material A in three portions. Solid-phase material B is divided into three equal parts. Each time, add one part and then perform ultrasonic treatment for 20 min, and then add the next part until all of solid-phase material B is added, and then perform ultrasonic treatment for 20 min to obtain material C;

[0062] S3: Under the stirring state of 600 r / min, add silane coupling agent to material C, and continuously stir at 600 r / min for 10 min; then process through a microfluidic homogenizer for 4 cycles, with a pressure of 180 MPa; perform spray drying, with an inlet air temperature of 180 °C and an outlet air temperature of 80 °C; obtain the powdery additive.

[0063] Example 4

[0064] An organic nano-concrete anti-seepage and anti-sulfate corrosion additive, characterized in that the additive comprises the following raw materials in parts by mass: 12 parts of ethylenediamine methylene phosphonate, 18 parts of sodium polyacrylate, 5 parts of sodium thiocyanate, 15 parts of poly(lactic-co-glycolic acid) (PLGA), 8 parts of hydroxypropyl ethanolamine, 1.2 parts of modified nano-graphite material, 9 parts of chitosan quaternary ammonium salt, 2 parts of silane coupling agent, and 6 parts of nano-volcanic ash powder. Among them, the particle size range of the nano-volcanic ash powder is below 600 nm; the silane coupling agent is silane coupling agent KH-792.

[0065] Among them, the preparation method of the modified nano-graphite material comprises the following steps: according to the mass ratio, nano-graphite powder: polyetheramine (PEI): silane coupling agent KH-792: ethanol = 2: 0.5: 1.5: 100. First, add nano-graphite powder and polyetheramine (PEI) to ethanol, and perform ultrasonic treatment at 65 °C for 60 min at 50 kHz. Then add silane coupling agent KH-792, and perform reflux reaction at 75 °C for 5 h. Then perform spray drying to obtain the modified nano-graphite material. Among them, the particle size range of the nano-graphite powder is below 600 nm; the nano-graphite powder is prepared by sintering and graphitizing calcined petroleum coke powder at 2800 °C and then pulverizing.

[0066] The preparation method of the above-mentioned organic nano-concrete anti-seepage and anti-sulfate corrosion additive comprises the following steps:

[0067] S1: Add hydroxypropyl ethanolamine and chitosan quaternary ammonium salt to acetic acid aqueous solution to prepare acetic acid solution; among them, the dosage of acetic acid aqueous solution is 4 times the total mass of hydroxypropyl ethanolamine and chitosan quaternary ammonium salt; the pH value of acetic acid aqueous solution is 5.5;

[0068] Under nitrogen protection, sodium ethylene diamine methylene phosphonate and sodium thiocyanate are dissolved in deionized water, and the amount of deionized water used is 5 times the total mass of sodium ethylene diamine methylene phosphonate and sodium thiocyanate; then sodium polyacrylate and poly(lactic-co-glycolic acid) (PLGA) are added in sequence, the shear rate is controlled at 2000 rpm, and dispersed for 50 min, then acetic acid solution is added, and sheared at 1200 rpm for 30 min to obtain liquid material A;

[0069] S2: The modified nano-graphite material and nano-volcanic ash powder are mixed evenly by air flow to obtain solid material B; under the condition of ultrasonic treatment with a power of 800 W, solid material B is added to liquid material A in three equal portions, ultrasonic treatment is carried out for 20 min each time after adding one equal portion, and then the next equal portion is added until solid material B is completely added, and ultrasonic treatment is carried out for 30 min to obtain material C;

[0070] S3: Under the stirring state of 600 r / min, silane coupling agent is added to material C, and continuously stirred at 600 r / min for 20 min; then processed through a microfluidic homogenizer for 4 cycles, and the pressure is 200 MPa; spray drying is carried out, the inlet air temperature is 180 °C, and the outlet air temperature is 85 °C; a powdery additive is obtained.

[0071] Example 5

[0072] An organic nano-concrete impermeability and sulfate corrosion resistance additive, characterized in that the additive comprises the following raw materials in parts by mass: 12 parts of sodium ethylene diamine methylene phosphonate, 15 parts of sodium polyacrylate, 5 parts of sodium thiocyanate, 10 parts of poly(lactic-co-glycolic acid) (PLGA), 8 parts of hydroxypropyl ethanolamine, 0.5 part of modified nano-graphite material, 9 parts of chitosan quaternary ammonium salt, 1 part of silane coupling agent and 6 parts of nano-volcanic ash powder. Among them, the particle size range of the nano-volcanic ash powder is below 600 nm; the silane coupling agent is silane coupling agent KH-792.

[0073] Among them, the preparation method of the modified nano-graphite material comprises the following steps: according to the mass ratio, nano-graphite powder: polyetheramine (PEI): silane coupling agent KH-792: ethanol = 1: 0.5: 1: 100, first add nano-graphite powder and polyetheramine (PEI) to ethanol, carry out ultrasonic treatment at 60 °C for 30 min at 50 kHz, then add silane coupling agent KH-792, carry out reflux reaction at 75 °C for 4 h, and then spray dry to obtain the modified nano-graphite material. Among them, the particle size range of the nano-graphite powder is below 600 nm; the nano-graphite powder is prepared by sintering and graphitizing calcined petroleum coke powder at 2800 °C and then pulverizing.

[0074] The preparation method of the above-mentioned organic nano-concrete impermeability and sulfate corrosion resistance additive comprises the following steps:

[0075] S1: Add hydroxypropyl ethanolamine and quaternary ammonium chitosan into acetic acid aqueous solution to prepare an acetic acid solution; wherein, the dosage of the acetic acid aqueous solution is 3 times the total mass of hydroxypropyl ethanolamine and quaternary ammonium chitosan; the pH value of the acetic acid aqueous solution is 5.5;

[0076] Under nitrogen protection, dissolve sodium ethylene diamine methylene phosphonate and sodium thiocyanate in deionized water, and the dosage of deionized water is 4 times the total mass of sodium ethylene diamine methylene phosphonate and sodium thiocyanate; then add sodium polyacrylate and poly (lactic acid - glycolic acid) copolymer (PLGA) in sequence, control the shear rate at 2000 rpm, disperse for 30 min, and then add the acetic acid solution, shear at 1200 rpm for 20 min to obtain liquid phase material A;

[0077] S2: Mix the modified nano - graphite material and nano - volcanic ash powder evenly by air flow to obtain solid phase material B; under the condition of ultrasonic treatment with a power of 800 W, add solid phase material B into liquid phase material A in three portions. Solid phase material B is divided into three equal parts. Each time, add one part and then carry out ultrasonic treatment for 10 min, and then add the next part until solid phase material B is completely added, and carry out ultrasonic treatment for 30 min to obtain material C;

[0078] S3: Add silane coupling agent to material C under the stirring state of 500 r / min, and continuously stir at 500 r / min for 20 min; then process it through a micro - jet homogenizer for 3 cycles with a pressure of 200 MPa; carry out spray drying with an inlet air temperature of 160 °C and an outlet air temperature of 85 °C; obtain the powdery additive.

[0079] The raw material sources of the above - mentioned examples: Sodium ethylene diamine methylene phosphonate is from Wuhan Xinzhongke Chemical Technology Co., Ltd.; Sodium polyacrylate is from Wuhan Jiyesheng Chemical Co., Ltd.; Sodium thiocyanate is from Shandong Xuchen Chemical Technology Co., Ltd.; Poly (lactic acid - glycolic acid) copolymer (PLGA) is from Henan Wokasi Biotechnology Co., Ltd.; Hydroxypropyl ethanolamine is from BASF in Germany; Quaternary ammonium chitosan is from Hebei Hongtao Bio - engineering Co., Ltd.; Silane coupling agent KH - 792 is from Dongguan Kangjin New Material Technology Co., Ltd.; Polyetheramine (PEI) is from Shandong Kelsmile New Material Co., Ltd., model T403.

[0080] Comparative Example 1

[0081] In the additive, poly (lactic acid - glycolic acid) copolymer (PLGA) is not added; other parameters and methods are the same as those in Example 1.

[0082] Comparative Example 2

[0083] In the additive, hydroxypropyl ethanolamine is not added; other parameters and methods are the same as those in Example 1.

[0084] Comparative Example 3

[0085] Among the additives, the modified nano-graphite material is replaced with nano-graphite powder without modification; other parameters and methods are the same as those in Example 1.

[0086] Comparative Example 4

[0087] Among the additives, chitosan quaternary ammonium salt is not added; other parameters and methods are the same as those in Example 1.

[0088] Comparative Example 5

[0089] Among the additives, nano-volcanic ash powder is not added; other parameters and methods are the same as those in Example 1.

[0090] Comparative Example 6

[0091] Among the additives, both the modified nano-graphite material and nano-volcanic ash powder are not added; other parameters and methods are the same as those in Example 1.

[0092] The additives prepared in each of the above examples and comparative examples were tested.

[0093] I. Raw materials and proportions of concrete specimens:

[0094] Cement: Ordinary Portland cement (P.O 42.5). Aggregates: Include river sand fine aggregates and crushed stone coarse aggregates, with good gradation, and indicators such as mud content meeting relevant standards. Coarse aggregates: Continuously graded crushed stone with a particle size of 5 mm - 25 mm, needle-like and flaky particle content of 10%, and mud content of 0.6%. Fine aggregates: Fineness modulus of 2.5 and mud content of 1.8%. Polycarboxylate water reducer (Kunming Qiang'an Concrete Admixture Co., Ltd., model QA-1). Additives: Additives prepared in each example and comparative example. Water: Clean drinking water. The designed mass ratio of the concrete specimen mixture is cement:sand:stone:polycarboxylate water reducer:additive:water = 400:700:1100:6:35:180, and concrete specimens were prepared (cured under standard conditions for 28 days).

[0095] II. Test items:

[0096] 1. Impermeability grade: The test was carried out according to the step-by-step pressure method in GB / T 50082 "Standard Test Method for Long-Term Performance and Durability of Ordinary Concrete". First, a frustum-shaped concrete specimen with an upper diameter of 175 mm, a lower diameter of 185 mm, and a height of 150 mm was placed in an impermeability tester, and 6 specimens were prepared for each group. The initial pressure was set at 0.1 MPa, and then every 8 hours, the water pressure was gradually increased by 0.1 MPa. During the test, the surface condition of the specimens was continuously and closely observed. Once water seepage occurred on the surfaces of 3 out of 6 specimens, the pressure application was immediately stopped, and the water pressure value at this time was recorded. The impermeability grade was accurately determined based on this value. The test results are shown in Table 1 below.

[0097] Classification of impermeability grade:

[0098] P4: It means that the concrete can resist a water pressure of 0.4 MPa without water seepage, that is, the maximum water pressure when 4 out of 6 specimens in a group do not show water seepage during the concrete impermeability test is 0.4 MPa. P5: It means that the concrete can resist a water pressure of 0.5 MPa without water seepage, that is, the maximum water pressure when 4 out of 6 specimens in a group do not show water seepage during the concrete impermeability test is 0.5 MPa. And so on, P6 (0.6 MPa), P7 (0.7 MPa), P8 (0.8 MPa), P9 (0.9 MPa), P10 (1.0 MPa)......P20 (2.0 MPa), etc.

[0099] 2. Sulfate corrosion resistance coefficient: It is carried out in accordance with the standard of GB / T 50082. Cubic concrete specimens with side lengths of 100 mm×100 mm×100 mm, 3 parallel samples, are placed in a sodium sulfate solution with a mass content of 5% for soaking. The whole test process includes 150 wet-dry cycles. The specific process of each cycle is as follows: soak for 16 hours to make the specimens fully contact with the sodium sulfate solution and simulate the erosion state in the actual use environment; then carry out a 4-hour air-drying treatment to allow the surface moisture of the specimens to evaporate naturally; finally, carry out a 4-hour drying treatment to further remove the internal moisture of the specimens and strengthen the effect of the wet-dry cycle. After 150 wet-dry cycles are completed, a pressure testing machine is used to measure the compressive strength of the specimens. The sulfate corrosion resistance coefficient is calculated by the formula Kf = Pn / P0, where Kf represents the sulfate corrosion resistance coefficient, Pn represents the compressive strength after n (here n = 150) wet-dry cycles, and P0 is the initial compressive strength of the specimens. The test results are shown in Table 1 below.

[0100] 3. Chloride ion diffusion coefficient: The RCM method (rapid chloride migration coefficient method) is adopted, and the test is carried out in accordance with the standard of GB / T 50082. First, cylindrical concrete specimens with a diameter of 100 mm and a height of 50 mm are pre-treated with saturated water, 3 parallel samples, to make them reach a fully saturated state. Then, the saturated specimens are installed in the test device, and a stable DC voltage is applied on both sides of the specimens, and the voltage is set to 60 V, and the test duration is 24 hours. During the test, through the voltage and current monitoring equipment, the stability of the test conditions is ensured. After the test is completed, the specimens are split, and immediately a silver nitrate solution with a concentration of 0.1 mol / L is evenly sprayed on the split surface for color development treatment. After sufficient color development, a vernier caliper with a precision of 0.1 mm is used to measure the chloride ion penetration depth, and the chloride ion diffusion coefficient is calculated by the RCM method. The test results are shown in Table 1 below.

[0101] 4.2h Slump Loss: Detection is carried out in accordance with GB / T 50080 "Standard Test Method for Properties of Ordinary Concrete Mixtures". First, use a standard slump cone to measure the slump of the freshly mixed concrete and record it as T0. When measuring, place the slump cone on a horizontal and wet iron plate, fill it with freshly mixed concrete in three layers, and insert the tamper evenly 25 times for each layer. Finally, level the mouth of the cone, lift the slump cone vertically upward, and measure the height difference between the height of the cone and the highest point of the concrete specimen after slumping, which is the slump T0. Then, quickly load the concrete into a sealed container and place it in an environment with a temperature of 20°C and a relative humidity of 50% for 2 hours. After 2 hours, measure the slump of the concrete again according to the above method for measuring slump and record it as T2. Finally, through the formula, slump loss = T0 - T2, calculate the 2h slump loss value. The test results are shown in Table 1 below.

[0102] Table 1 Test Results

[0103]

[0104] From the above results, it can be seen that due to different raw material ratios, there are differences in the performance of Examples 1 to 5. In Examples 3 and 4, the content of poly(lactic-co-glycolic acid) (PLGA) is relatively high. PLGA has good film-forming properties and adhesiveness, and can form a denser microstructure inside the concrete, effectively preventing the intrusion of moisture and harmful ions, thereby improving the impermeability grade and sulfate corrosion resistance coefficient and reducing the chloride ion diffusion coefficient. At the same time, with the increase in the content of the modified nano-graphite material, its excellent electrical conductivity and mechanical properties contribute to enhancing the structural stability inside the concrete and further improving various performances. In Example 2, the content of some key raw materials such as PLGA and the modified nano-graphite material is relatively low, resulting in insufficient optimization of the internal structure of the concrete and slightly weaker impermeability and corrosion resistance performances.

[0105] From the results of Comparative Example 1, it can be seen that without adding PLGA, an effective dense structure cannot be formed inside the concrete, the porosity is relatively large, and moisture and sulfate ions are more likely to invade the inside of the concrete, resulting in a decrease in the impermeability grade, a reduction in the sulfate corrosion resistance coefficient, and an increase in the chloride ion diffusion coefficient. At the same time, due to the lack of the water retention and thickening effect of PLGA on the concrete, the workability of the concrete decreases and the 2h slump loss increases.

[0106] From the results of Comparative Example 2, it can be seen that the lack of hydroxypropyl ethanolamine affects the interaction between the additive and the cement particles, and the hydration reaction of the cement cannot proceed fully, resulting in slow early strength development of the concrete and an insufficiently dense internal structure, thereby reducing the impermeability and corrosion resistance performances of the concrete, and at the same time increasing the 2h slump loss.

[0107] It can be seen from the results of Comparative Example 3 that the dispersibility of unmodified nano-graphite powder is poor, and it is difficult to be evenly distributed in concrete. It cannot form a good synergistic effect with other materials, and cannot effectively fill the pores and defects inside the concrete, resulting in a decrease in the compactness of the concrete, and all performance indicators are inferior to those of Example 1.

[0108] It can be seen from the results of Comparative Example 4 that without adding chitosan quaternary ammonium salt, the optimization effect of the additive on the microstructure of concrete is weakened. Chitosan quaternary ammonium salt has certain cationic characteristics, can interact with the negative ion groups in concrete, improve the interface structure of concrete, and enhance the impermeability and corrosion resistance of concrete. After lacking chitosan quaternary ammonium salt, these properties decrease accordingly, and the slump loss at 2h also increases.

[0109] It can be seen from the results of Comparative Example 5 that without nano-pozzolan powder, the filling effect and pozzolanic reaction of concrete are insufficient. Nano-pozzolan powder can fill the tiny pores inside the concrete, refine the pore size distribution, and at the same time undergo a secondary reaction with the hydration products of cement to generate more gel substances, enhancing the compactness and strength of the concrete. After lacking nano-pozzolan powder, the compactness and strength of the concrete decrease, resulting in a reduction in all performance.

[0110] It can be seen from the results of Comparative Example 6 that the simultaneous lack of modified nano-graphite material and nano-pozzolan powder has a more significant impact on the performance of concrete. The pores inside the concrete cannot be effectively filled and optimized, and the structural stability drops significantly, resulting in a large decrease in performance indicators such as the impermeability grade and the sulfate corrosion resistance coefficient, and a significant increase in the slump loss at 2h.

Claims

1. An anti-seepage and anti-sulfate corrosion additive for organic nano-concrete, characterized in that, The additive comprises raw materials in the following parts by mass: 8 to 12 parts of sodium ethylene diamine methylene phosphonate, 15 to 18 parts of sodium polyacrylate, 3 to 5 parts of sodium thiocyanate, 10 to 15 parts of poly (lactic-co-glycolic acid), 5 to 8 parts of hydroxypropyl ethanolamine, 0.5 to 1.2 parts of modified nano-graphite material, 6 to 9 parts of chitosan quaternary ammonium salt, 1 to 2 parts of silane coupling agent, and 3 to 6 parts of nano-volcanic ash powder.

2. An impermeability and sulfate corrosion resistant additive for organic nano-concrete according to claim 1, characterized in that, The particle size range of the nano-volcanic ash powder is below 600 nm.

3. An anti-seepage and anti-sulfate corrosion additive for organic nano-concrete according to claim 1, characterized in that, The silane coupling agent is silane coupling agent KH-792.

4. An anti-seepage and anti-sulfate corrosion additive for organic nano-concrete according to claim 1, characterized in that, The preparation method of the modified nano-graphite material comprises the following steps: According to the mass ratio, nano-graphite powder: polyetheramine: silane coupling agent: ethanol = (1 - 2): (0.3 - 0.5): (1 - 1.5): (90 - 100), first add nano-graphite powder and polyetheramine into ethanol, perform ultrasonic treatment at 60 °C - 65 °C for 30 min - 60 min at 40 kHz - 50 kHz, then add the silane coupling agent, perform reflux reaction at 70 °C - 75 °C for 4 h - 5 h, and then perform spray drying to obtain the modified nano-graphite material.

5. An organic nano-concrete impermeability and sulfate corrosion resistance additive according to claim 4, characterized in that, The silane coupling agent is silane coupling agent KH-792; the particle size range of the nano-graphite powder is below 600 nm; the nano-graphite powder is prepared by sintering and graphitizing calcined petroleum coke powder at 2500 °C - 2800 °C and then pulverizing.

6. An anti-permeability and anti-sulfate corrosion additive for organic nano-concrete according to claim 1, characterized in that, The preparation method of the additive comprises the following steps: S1: Add hydroxypropyl ethanolamine and chitosan quaternary ammonium salt into acetic acid aqueous solution to prepare an acetic acid solution; under nitrogen protection, dissolve sodium ethylene diamine methylene phosphonate and sodium thiocyanate in deionized water, then sequentially add sodium polyacrylate and poly (lactic-co-glycolic acid) (PLGA), control the shear rate at 1500 rpm - 2000 rpm, disperse for 30 min - 50 min, then add the acetic acid solution, and shear at 1000 rpm - 1200 rpm for 20 min - 30 min to obtain liquid phase material A; S2: Perform pneumatic mixing on the modified nano-graphite material and nano-volcanic ash powder to make them uniformly mixed to obtain solid phase material B; under the condition of ultrasonic treatment with a power of 700 W - 800 W, add solid phase material B into liquid phase material A in three portions. Solid phase material B is divided into three equal portions. Each time, add one portion and perform ultrasonic treatment for 10 min - 20 min, then add the next portion until solid phase material B is completely added, and perform ultrasonic treatment for 20 min - 30 min to obtain material C; S3: Under the stirring state, add the silane coupling agent to material C and stir for 10 min - 20 min; Then perform 3 to 4 cycles of treatment through a microfluidic homogenizer; perform spray drying to obtain the powdery additive.

7. An anti-seepage and anti-sulfate corrosion additive for organic nano-concrete according to claim 6, characterized in that, In S1, the dosage of the acetic acid aqueous solution is 3 to 4 times the total mass of hydroxypropyl ethanolamine and chitosan quaternary ammonium salt; the pH value of the acetic acid aqueous solution is 5.0 - 5.

5.

8. An anti-seepage and anti-sulfate corrosion additive for organic nano-concrete according to claim 6, characterized in that, In S1, the dosage of the deionized water is 4 to 5 times the total mass of sodium ethylene diamine methylene phosphonate and sodium thiocyanate.

9. An anti-seepage and anti-sulfate corrosion additive for organic nano-concrete according to claim 6, characterized in that, In S3, the rotational speed of the stirring is 500 r / min to 600 r / min; the pressure of the microfluidic homogenizer is 180 MPa to 200 MPa.

10. An anti-permeation and anti-sulfate corrosion additive for organic nano-concrete according to claim 6, characterized in that, In S3, the inlet air temperature of the spray drying is 160 °C to 180 °C, and the outlet air temperature of the spray drying is 80 °C to 85 °C.

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