Preparation method of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor and its product application

Abstract

The present invention discloses a preparation method of a modified natural biomass starch sodium phosphate organic permeable steel bar rust inhibitor and its product application. Starch is subjected to high-temperature gelatinization, acidification, and cross-linking reaction to obtain epichlorohydrin starch oligomers; phosphoric acid reacts with liquid ammonia to obtain ammonium phosphate, and ammonium phosphate and allyl alcohol undergo a hydrogen-borrowing reaction to obtain an N(-propylene)aminophosphoric acid intermediate; epichlorohydrin starch oligomers and the N(-propylene)aminophosphoric acid intermediate are grafted to obtain a modified natural biomass starch sodium phosphate organic permeable steel bar rust inhibitor. The present invention broadens the application field of starch, reduces the cost of rust inhibitor raw materials, reduces the use of toxic chemicals, simplifies the process and production time. By adjusting the molecular structure of the steel bar rust inhibitor, the rust prevention needs of different reinforced concrete can be met. Adding this organic permeable steel bar rust inhibitor improves the performance of concrete and increases the resistance of steel bars in concrete to chloride ion corrosion, which can produce good economic, social and environmental benefits and has broad application prospects.

Description

Technical Field

[0001] The invention belongs to the field of biomass material utilization and steel bar rust inhibitor preparation, and particularly relates to a preparation method of a modified natural biomass starch sodium phosphate organic permeable steel bar rust inhibitor and product application thereof. Background Art

[0002] Steel bars and concrete materials have similar linear expansion coefficients, good adhesion, and low contact stress. The combination of steel bars and concrete can give full play to the advantages of steel bars that do not break directly after exceeding the yield limit, have high tensile strength, and absorb stress well within the strain range, and can make up for the weaknesses of concrete itself, such as high brittleness and poor flexural strength, bending and shear strength, and fatigue resistance. Reinforced concrete has the characteristics of abundant raw material sources, low price, simple production process, and strong and durable structure. The emergence of reinforced concrete composite materials has broadened the application fields of traditional steel bars and concrete materials. Today, reinforced concrete is widely used in civil engineering fields such as civil buildings, roads, bridges, tunnels, and seaport projects, and plays an increasingly important role in the development of the national economy. Generally speaking, in reinforced concrete materials, due to the cement hydration reaction, a large amount of calcium hydroxide and potassium and sodium ions exist in the pore solution, and the pore solution is in a highly alkaline state (pH value is 12-13). At this time, the steel bars in the concrete undergo a passivation reaction, and a dense metal oxide passivation film is formed on the surface of the steel bars. This passivation film is adsorbed on the surface of the steel bars to separate the steel bars from the concrete, slowing down the dissolution of Fe inside the steel bars into Fe 2+ The passivation film reduces the speed of oxygen and water entering the solution, and at the same time reduces the diffusion rate of oxygen and water in the environment into the interior of the steel bars. This passivation film can effectively protect the steel bars in the concrete in a low-corrosion state or even a corrosion-free state for a long time. However, for reinforced concrete structures serving in complex environments, the acidic CO2 gas in the air enters the concrete through the capillaries and microcracks in the concrete, and reacts with the alkaline hydration products in the concrete, causing the alkalinity of the concrete pore solution to continue to decrease. When the pH value of the pore solution in the concrete drops to 9-10, the passivation film on the steel bars in the concrete is destroyed, and the steel bars cannot be protected, and the steel bars begin to gradually rust. For offshore and marine engineering reinforced concrete structures, chloride ions invade the concrete, penetrate into the passivation film through adsorption, and acidify the pore solution near the anode. When the pH in the pore solution drops to less than 11.5, the passivation film partially dissolves. As the chloride ions on the steel bar interface in the concrete are enriched, the adsorbed chloride ions react with the iron element in the steel bar to produce soluble FeCl2. FeCl2 reacts with OH in the pore solution to produce soluble FeCl2. - Combined, consumes the anode product Fe 2+, releasing chloride ions, which further promote the anodic reaction and accelerate the corrosion of the steel bars. The intrusion of external carbon dioxide and chloride ions triggers the corrosion of steel bars in concrete, resulting in a reduction in the cross-sectional area of ​​the steel bars, a decrease in the bearing capacity of the reinforced concrete, a decrease in the ultimate elongation, and an increase in stress corrosion cracking. The tensile stress generated by the volume expansion of the steel corrosion products reduces the stiffness of the reinforced concrete and the bond between the steel and concrete, causing the concrete cover to crack and spall along the reinforcement, affecting the normal use and service life of the structure.

[0003] At present, the commonly used methods for controlling steel corrosion in concrete at home and abroad include corrosion-resistant steel bars, steel bar surface coating protective layer, electrochemical cathodic protection method, electrochemical desalination method, re-alkalization method, and steel bar rust inhibitor method. Among them, the simplest and most economical method is to add steel bar rust inhibitor to inhibit steel bar corrosion in concrete. When steel bar rust inhibitor is added to reinforced concrete, the steel bar rust inhibitor adsorbs harmful ions to form a film or forms a passivation film on the steel bar surface, which can inhibit the occurrence of electrochemical corrosion reactions in the pore solution at the interface between concrete and steel bar, thereby delaying the corrosion time of steel bars in concrete, reducing the corrosion rate of steel bars, and protecting steel bars. Existing steel bar rust inhibitors can be divided into three types according to their chemical composition: inorganic rust inhibitors, organic rust inhibitors, and organic penetrating rust inhibitors. Inorganic rust inhibitors react with metal ions in the anode area of ​​the steel bar surface to form an oxide or hydroxide passivation film covering the anode to inhibit the anode electrochemical reaction, prevent metal dissolution and slow down steel bar corrosion. Commonly used inorganic rust inhibitors include nitrites, nitrates, chromates, molybdates, phosphates, silicates and arsenic compounds. Inorganic rust inhibitors exhibit a high ability to prevent steel corrosion at pH values ​​above 6.0. However, as chloride ions erode and corrosion reactions consume concrete, the pH of the pore solution decreases, mitigating the protective effect of the inorganic rust inhibitor on the steel in the concrete. In marine environments or those with high chloride concentrations, sufficient amounts of inorganic rust inhibitors are required to provide long-term protection for the steel. Otherwise, localized pore corrosion is likely to occur within the steel. Inorganic rust inhibitors are expensive and require high dosage, resulting in unsatisfactory economic benefits. Adding inorganic rust inhibitors to reinforced concrete negatively impacts the setting time and strength of the concrete and can even trigger an alkali-aggregate reaction. In recent decades, due to environmental concerns, countries such as the United States, Germany, and Switzerland have banned the use of inorganic rust inhibitors, limiting their use. Organic rust inhibitors are primarily composed of organic substances such as amines, aldehydes, acetylenic alcohols, organosulfur compounds, carboxylates, sulfonates, and heterocyclic compounds. These organic molecules adsorb onto the surface of rebar and, through polar groups on the organic molecules, bind to hydrocarbon chains to form a stable, tight five-membered ring chelate membrane, effectively protecting the rebar. Hydrophobic groups on the organic molecules are distributed on the outer surface of the protective membrane, blocking and repelling harmful chloride ions and oxygen in the concrete pore solution. Compared to inorganic rust inhibitors, organic rust inhibitors are non-toxic, environmentally safe, and highly compatible with high-efficiency water reducers. They inhibit both the cathodic and anodic electrochemical processes of rebar corrosion, providing effective protection for rebar in concrete containing varying chloride ion concentrations. They have minimal impact on the setting time, slump and slump loss of fresh concrete, air content, strength development of hardened concrete, and the bond between rebar and concrete. However, an inappropriate ratio of organic rust inhibitor to chloride ion content can accelerate rebar corrosion. At the same time, organic rust inhibitors also have problems such as relatively high cost, long synthesis cycle, and difficulty in biodegradation.Organic penetrating rust inhibitors are a new type of organic rust inhibitor, including alcohol amine compounds, organophosphorus compounds, imidazoline derivative salts, and organic ester compounds. Organic penetrating rust inhibitors are added to concrete in a liquid phase. A portion of the surface active groups on the organic penetrating rust inhibitors are adsorbed by cement hydration products and react with the concrete hydration products to form precipitates, clogging capillaries and preventing harmful media such as carbon dioxide and chloride ions from entering the concrete, thereby improving the concrete's density, water absorption, freeze-thaw resistance, and shrinkage properties. The remaining organic penetrating rust inhibitor reaches the surface of the steel bars through a period of gas phase penetration or liquid phase diffusion. The polar nitrogen in the amino groups of the rust inhibitors is adsorbed on the surface of the steel bars through physical and chemical reactions, eliminating water molecules and chloride ions, and forming a dense monomolecular organic compound protective film that covers the anode or cathode areas of the electrochemical reaction on the surface of the steel bars, inhibiting the electrochemical reaction process of steel bar corrosion and protecting the steel bars. Organic permeable rust inhibitor has the advantages of being easy to use, long-term effective, simple to construct and not changing the performance of concrete itself, and has been considered by the European Committee for Standardization as a measure that can effectively protect the steel bars in concrete. Research on alcoholamine organic permeable rust inhibitors has found that alcoholamine organic permeable rust inhibitor molecules contain hard base groups (-NH2) and soft base groups (-OH), and alcoholamine rust inhibitor molecules can be firmly adsorbed on the passivation film on the surface of steel bars to form a protective film, and can be adsorbed on the body metal surface after the passivation film is destroyed, playing the role of repairing the passivation film, limiting the movement of harmful ions in the cathode region, reaching the purpose of isolating harmful ions from contacting steel bars and preventing steel bar corrosion in concrete. However, when organic permeable rust inhibitors are used, it is necessary to ensure that there are enough organic permeable rust inhibitors to continuously accumulate on the surface of steel bars and reach a certain concentration to form a passivation film on the surface of steel bars. The penetration speed of alcoholamine organic matter is slow, the electromigration ability is weak, and it is difficult to dissociate enough rust-inhibiting groups under high alkaline conditions, which causes the insufficient concentration of the inhibitor arriving at the surface of steel bars, and is not enough to the steel bar protective power. Adding alcoholamine-based organic penetrating rust inhibitors to reinforced concrete can also cause shrinkage cracking, and the steel bars in the concrete may corrode due to direct contact with harmful substances. In recent years, domestic and foreign scholars have developed an imidazoline-based organic penetrating rust inhibitor suitable for alkaline environments and saline solutions. Adding imidazoline compounds to reinforced concrete allows the inhibitor to diffuse through the concrete, reach the surface of the steel bars, establish a passivation film, and cause a positive shift in the potential of the steel bars, thereby preventing chloride ion corrosion of the steel bars. Imidazoline-based rust inhibitors have good chemical structure stability and are unaffected by acidic and alkaline environments. They can be used in conjunction with inorganic and organic rust inhibitors, but they have poor solubility during use. Optimizing the molecular structure of imidazoline-based organic penetrating rust inhibitors can produce imidazoline derivatives with good water solubility. Modified imidazoline-based organic rust inhibitors can quickly diffuse to the surface of the steel bars, then lose or gain electrons and adsorb on the steel surface.Currently, there are reports on the use of such organic penetrating rust inhibitors in reinforced concrete structures. However, the limited raw material sources, high cost, harsh synthesis conditions, complex processes, and large yield variations in the preparation of alcohol amines and imidazoline organic penetrating rust inhibitors, as well as the generation of highly toxic waste gases that are harmful to the surrounding environment and human health during the production process, have hindered the application of organic penetrating rust inhibitors in reinforced concrete materials. Developing an organic penetrating rust inhibitor with a wide range of raw material sources, low cost, simple process, good water solubility, good compatibility with the alkaline environment in concrete, environmental friendliness, and high efficiency has become a hot topic in this field of research and has important practical significance for improving the durability of reinforced concrete structures.

[0004] Researchers are currently exploring the extraction of active ingredients from natural plants (kelp, ginger, banana peels, cucumber seeds, kun hemp, green bamboo leaves, and tamarisk bamboo) to create natural organic penetrating steel bar rust inhibitors to replace traditional organic penetrating inhibitors. The chemical composition of natural plant extracts contains N, O, S, and P multiple bonds and heteroatom groups. These groups form a film on the surface of steel bars through physical and chemical adsorption, inhibiting steel corrosion in concrete. Cathodic inhibition is predominant in the early stages, while anodic inhibition is predominant in the later stages. The plant polyphenols in these plant extracts possess multiple ortho-phenolic hydroxyl groups. Under alkaline conditions, the polyphenols complex and coordinate with rust ions on the steel bars to form a precipitate, transforming the rust into a protective layer that prevents contact between the metal and the corrosive medium. Saltwater immersion tests and corrosion tests of steel bars in concrete with the kelp extract organic penetrating inhibitor showed that the kelp extract, at a dosage of 4% by weight of cement, achieved an 85.5% corrosion inhibition rate against steel bars in concrete. Ginger extract can effectively inhibit steel corrosion in concrete and improve the corrosion resistance of the steel bars. In acidic media, banana peel and cucumber seed extracts were used as rust inhibitors for carbon steel rebar, achieving an inhibition efficiency exceeding 92%. Protonation of Kunma extract resulted in a positive charge, which can bind chloride ions in concrete through electrostatic adsorption. The potassium ions in green bamboo leaf extract mitigate the problem of cation depletion caused by Friedels salts entering the rebar, reducing the corrosion potential of the rebar in reinforced concrete and effectively protecting the rebar. Foreign researchers conducted comparative tests on the rust inhibition effects of a Bamboo extract and calcium nitrite inhibitor, finding that the Bamboo extract exhibited superior steel bar rust inhibition compared to calcium nitrite. Researchers also extracted components from natural plant sources such as mangrove bark tannins, date palm seeds, indole alkaloids, rice husk ash, Chlorophytum comosum roots, Safflower, and propolis, exploring their rust-inhibiting effects on metals in acidic, neutral, and alkaline environments. Related reports also found that adding DNA-based organic penetrating inhibitors can reduce the number of harmful pores in mortar and increase the proportion of micropores and gel pores. Its rust inhibition mechanism is completely different from that of natural plant extracts containing nitrogen functional groups. The phosphate group in the DNA-based organic penetrating inhibitor molecules is the main rust-inhibiting functional group. Researchers have also demonstrated that glycoside organic penetrating inhibitors can effectively prevent steel corrosion and promote the formation of a protective film on the steel surface. The higher the concentration of glycoside compounds, the more stable the protective film on the steel surface, and the stronger the steel's corrosion resistance.

[0005] Currently, there are reports on the use of plant extracts to prepare organic penetrating steel bar rust inhibitors. This method offers the advantages of abundant raw material reserves, low cost, biodegradability, green and non-toxic properties, and the ability to be compounded with other types of steel bar rust inhibitors. However, there are still some problems with the use of plant extracts of natural organic penetrating steel bar rust inhibitors. First, although plant extracts of organic penetrating steel bar rust inhibitors are inherently green and environmentally friendly, the extraction process is relatively complex. The extraction of active ingredients from plants requires the use of chemical solvents such as strong acids and strong bases, which can cause environmental pollution. Second, the composition of plant extract green rust inhibitors is relatively complex, making it difficult to determine the molecular structure and rust inhibition mechanism of plant extracts of green rust inhibitors. In addition, research on the inhibition of steel bar corrosion by plant extracts of organic penetrating steel bar rust inhibitors has mainly focused on inhibiting metal corrosion in acidic environments, and there is limited research on the rust inhibition effect of steel bars in concrete under alkaline conditions. Furthermore, research on the effects of plant extracts of organic penetrating steel bar rust inhibitors on the mechanical properties and durability of concrete is still relatively limited. The development of a biomass organic penetrating steel bar rust inhibitor with low cost, simple process, small product quality fluctuation and broad industrialization prospects, and the application research of its rust inhibition effect on reinforced concrete performance and steel bars in concrete has become a hot topic in the field of civil engineering research and has attracted the attention of relevant technical personnel.

[0006] Starch is a natural polymer produced through photosynthesis and is the second largest renewable carbohydrate in nature. It is commonly found in plant tubers (potatoes) and roots (cassava, sweet potatoes), the seed endosperm cells of cereals (barley, wheat, oats, corn, and rice), the fruits of plants (bananas, plantains, sago), and the leaves of crops (broad beans, mung beans, red beans, and peas). It has a wide range of sources, abundant reserves, a short regeneration cycle, low prices, and is biodegradable. my country is the second largest starch producer after the United States. In 2000, my country's starch production reached 5.02 million tons. In 2005, the total starch production reached 11.06 million tons. In 2012, my country's total starch production exceeded 22.53 million tons. In 2018, starch production exceeded 30 million tons. Since then, my country's annual starch production has continued to increase at a rate of 5-12%. Starch is a polysaccharide polymer compound composed of dehydrated glucose units linked by glycosidic bonds. Its general structural formula is (C6H 10 Natural starch consists of amylose and amylopectin. Amylose accounts for approximately 15-20% of the total starch content, while amylopectin accounts for 70-80%. Amylose molecules are composed of D-glucose units linked by α-1,4-glycosidic bonds. They contain 600-3000 D-glucose units. The long chain of amylose molecules forms a regular helical structure, with hydrogen atoms on the inside and hydroxyl groups on the outside. Its relative molecular mass is 3.2×10 4-1.6×10 5 Amylopectin molecules are chain compounds composed mainly of α-1,4-glycosidic bonds and supplemented by α-1,6-glycosidic bonds. Each amylopectin molecule contains 6,000-60,000 D-glucose units. On average, there is one α-1,4-glycosidic bond in every 20 D-glucose units. The average molecular weight of amylopectin is 1×10 6 The number of D-glucose units between different branches on amylopectin varies, and amylopectin presents an irregular cross-linked network structure similar to a tree. Each basic D-glucose structural unit in the starch molecule contains two C2 and C3 secondary alcohol hydroxyl groups and one C6 primary alcohol hydroxyl group, and these hydroxyl groups have strong reactivity. However, the hydroxyl groups within the starch molecule and the hydroxyl groups between the molecules are bonded by hydrogen bonds. Starch is insoluble in cold water and can only be dissolved in strong polar organic solvents such as dimethyl sulfoxide and dimethylformamide. Natural starch polymers have large molecular weight and steric hindrance, and are unstable under acid, heat, and shear. Natural biological starch materials cannot meet the use requirements of industrial products, and starch needs to be physically and chemically modified before it can be effectively utilized. Physical modification is the treatment of starch by mechanical, thermal, and enzymatic methods. Mechanical activation can destroy the crystalline structure of starch and change the molecular structure, making it easier for reaction reagents to enter the interior of the starch, thereby enhancing the reactivity of starch. When a starch solution is heated to a certain temperature, water enters the starch crystallites, disrupting intra- and intermolecular hydrogen bonds and eliminating the crystalline structure, thereby improving the thermal stability, stirring stability, acid resistance, and aging resistance of the starch solution. Enzymatic modification of starch can effectively enhance its biological activity. Oxidation and acid hydrolysis of starch can destroy the amorphous regions of starch granules while preserving their crystalline structure, improving its water solubility and its ability to adsorb, complex, or exchange metal ions. Chemical modification utilizes the active hydroxyl groups of secondary and primary alcohols at the C2, C3, and C6 positions of the starch D-glucose structural unit to undergo grafting, etherification, and esterification reactions, introducing new groups such as acetal, olefin, ether, amine, and ester bonds into the starch molecular chain. Physical and chemical modification of natural biomass starch polymers overcomes many of the drawbacks associated with traditional starch applications, enabling the preparation of high-performance, low-cost, biodegradable, and environmentally friendly modified biomass starch functional materials. This further expands the application areas of biomass starch polymers and holds broad prospects for application in modern civil engineering. Summary of the Invention

[0007] Purpose of the invention: The technical problem to be solved by the present invention is to provide a high-performance, low-cost, biodegradable, green preparation method of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor.

[0008] The present invention also aims to solve the technical problem of obtaining a modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor through the preparation method.

[0009] The final technical problem to be solved by the present invention is to provide an application of a modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor in reinforced concrete materials.

[0010] Technical solution: In order to solve the above technical problems, the present invention provides a preparation method of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor, comprising the following steps:

[0011] (1) Natural starch polymer is mixed with water to form a suspension and subjected to high-temperature gelatinization and acidification treatment. The glycosidic bonds in the starch polymer molecular chain are broken to obtain starch polyol oligomers. The C6 primary alcohol hydroxyl group on the starch polyol oligomer undergoes a cross-linking reaction with epichlorohydrin to obtain epichlorohydrin starch oligomers.

[0012] (2) Under acidic conditions, phosphoric acid reacts with liquid ammonia to produce ammonium phosphate. Under the action of phosphine nitrogen ligand iridium catalyst, ammonium phosphate and allyl alcohol undergo hydrogen-borrowing reaction to produce N(-allyl)aminophosphoric acid intermediate;

[0013] (3) Under the action of ammonium cerium nitrate initiator, epichlorohydrin starch oligomer and N (-propylene) aminophosphoric acid intermediate undergo grafting reaction to prepare modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor containing -OH, -NH, and -PO3 groups;

[0014] The high-temperature gelatinization step in step (1) is as follows: weighing natural starch polymer and water into a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser, rapidly stirring for 20-30 minutes, dispersing the natural starch polymer into the water to form a uniform suspension solution, raising the temperature to 70-75°C, accelerating the stirring of the starch suspension solution, and performing gelatinization reaction at this temperature for 50-60 minutes to obtain a starch gelatinization solution, wherein the mass ratio of the natural starch polymer to water is 1:4.5-5.0, and the viscosity of the starch gelatinization solution is constant at 2219-2365 Pa.

[0015] The acidification step in step (1) is as follows: after the viscosity of the starch gelatinization solution becomes constant, a dilute sulfuric acid solution is added to the starch gelatinization solution, the temperature of the suspension solution is raised to 80-85°C, and the suspension solution is acidified for 2-3 hours at this temperature. The starch polymer gelatinization solution is acidified and degraded into a starch polyol oligomer solution, wherein the dilute sulfuric acid solution is 2.5-3.0 wt % of the natural starch amount, and the weight-average molecular weight of the starch polyol oligomer is 1053-1107.

[0016] Wherein, the preparation steps of the epichlorohydrin starch oligomer described in step (1) are as follows: starch polyol oligomer solution and sodium chloride solution are placed in a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser, the stirrer is started and stirred for 30-40 minutes, the starch polyol oligomer solution and the sodium chloride solution are fully mixed into a uniform, clear solution, sodium hydroxide solution is added at a temperature of 45-50°C, the pH value is adjusted to 9-10, alkalization treatment is performed for 1-2 hours, epichlorohydrin liquid is slowly added dropwise over 30-40 minutes, the addition is completed and stirring is continued, the above mixed solution is placed in a microwave radiation organic synthesis reactor for cross-linking reaction with epichlorohydrin to obtain a white epichlorohydrin starch oligomer solution, the ratio of the starch polyol oligomer solution to the sodium chloride solution is 0.35-0.45 kg / L, and the mass ratio of the starch polyol oligomer solution to the epichlorohydrin solution is 6.5-7.0:1, The microwave radiation reaction power is 100-130W, the reaction time is 10-15 minutes, and the maximum reaction temperature is 80-85°C.

[0017] The specific steps of step (2) are as follows: phosphoric acid is placed in a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser, dilute hydrochloric acid is used to adjust the pH value of the solution to 3-5, the system temperature is maintained at 30-40°C, liquid ammonia solution is slowly added dropwise within 30-50 minutes, and the system temperature is maintained at no more than 60-65°C. After the addition of the liquid ammonia solution, the system temperature is increased to 90-95°C with continuous stirring, and the reaction is carried out for 5-6 hours to obtain an ammonium phosphate solution, and the temperature of the ammonium phosphate solution is reduced to 50-60°C, and allyl alcohol is added to the ammonium phosphate solution, and the system temperature is maintained constant. A phosphine nitrogen ligand iridium catalyst is added and the addition is completed within 20-30 minutes, and the solution temperature is increased to 70-80°C. At this temperature, hydrogen is reacted for 48-50 hours to obtain a clear solution of N(-propylene)aminophosphoric acid intermediate. The mass ratio of the phosphoric acid to liquid ammonia is 0.50-0.55:1, the mass ratio of the ammonium phosphate solution to allyl alcohol is 4.5-5.0:1, and the phosphine nitrogen ligand iridium catalyst is 1.0-1.05% by weight of the ammonium phosphate solution.

[0018] The specific steps of step (3) are as follows: adding the epichlorohydrin starch oligomer solution and water to a reaction vessel, starting the stirrer to completely mix the epichlorohydrin starch oligomer and water into a uniform solution, using 20% ​​sodium hydroxide to adjust the pH value of the system to 11-12, constantly stirring the mixture solution, maintaining the temperature at 80-85°C, slowly adding the N (-propylene) aminophosphoric acid intermediate solution to the epichlorohydrin starch oligomer solution, adding it for about 60-90 minutes, adding ammonium cerium nitrate initiator, grafting reaction at 90-95°C for 3-4 hours, stopping the reaction and naturally cooling to ambient temperature, aging in the reaction vessel for 2-3 hours, adding sodium hydroxide solution to adjust the pH value to 10-11, and obtaining a light yellow modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor solution with a solid content of 17-20%. The mass ratio of the epichlorohydrin starch oligomer solution to water is 0.039-0.040:1, the mass ratio of the epichlorohydrin starch oligomer solution to N(-propylene)aminophosphoric acid intermediate is 0.15-0.20:1, and the cerium nitrate initiator accounts for 2.0-2.1% by weight of the epichlorohydrin starch oligomer solution.

[0019] The present invention also includes the modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor obtained by the preparation method.

[0020] The present invention also includes the use of the modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor in the preparation of concrete.

[0021] The present invention measured the properties of hardened concrete and the rust-inhibiting effect of steel bars in hardened concrete after adding a modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor at different dosages. The modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor was added in an amount of 0.2-0.5wt%.

[0022] The mechanism of the present invention includes the following: Based on the gelatinization, acid degradation, and cross-linking reaction of natural starch polymer materials, the glycosidic bonds in the starch polymer molecular chains are broken, resulting in a decrease in the starch polymerization degree, thereby producing epichlorohydrin starch oligomers. Epichlorohydrin starch oligomers have a regular chemical structure and higher hydroxyl reactivity. Under the action of an initiator, the hydroxyl groups on the epichlorohydrin starch oligomers undergo a ring-opening grafting reaction with the propenyl groups on the N(-propenyl)aminophosphoric acid intermediate to produce a modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor.

[0023] Beneficial effects: The use of biomass starch phosphate modification to prepare organic penetrating steel bar rust inhibitors has broadened the application field of natural starch polymer materials and reduced the cost of raw materials in the preparation process of organic penetrating steel bar rust inhibitors. Conventional industrial products replace fine chemicals to prepare organic penetrating steel bar rust inhibitors, overcoming the problems of complex preparation process and long production time of organic penetrating steel bar rust inhibitors. This method of preparing organic penetrating steel bar rust inhibitors also reduces the use of strong acids, strong bases, and toxic formaldehyde chemicals, avoiding the negative impact of the steel bar rust inhibitor production process on the environment. The molecular structure and molecular weight of the modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor are adjustable, and organic penetrating steel bar rust inhibitors that meet the rust prevention needs of different reinforced concrete can be prepared, avoiding the molecular composition, complex molecular structure, and large product volatility of plant extract organic penetrating steel bar rust inhibitors. Compared with the prior art, the modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor prepared by the present invention also has the following significant advantages, specifically including the following points:

[0024] (1) The present invention uses starch polymer modification to prepare an organic penetrating steel bar rust inhibitor, which consumes a large amount of natural biomass starch materials, broadens the application field of natural starch polymer materials, and reduces the amount of alcohol amines, imidazolines, pyridine five-membered or six-membered heterocyclic fine chemicals used in the preparation of the organic penetrating steel bar rust inhibitor. According to the method of Specific Example 1, the production of one ton of this modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor can save 659 yuan in raw material costs.

[0025] (2) This method is used to prepare a modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor, avoiding the complex extraction process of plant extract organic penetrating steel bar rust inhibitors, simplifying the production process of natural organic penetrating steel bar rust inhibitors, and shortening the production time by 1-2 hours. According to the method of specific embodiment 1, each ton of this product produced can save 265,000 yuan in production equipment investment, and the reduction in production time and labor costs can bring an economic benefit of 76.8 yuan. This method of preparing an organic penetrating steel bar rust inhibitor also avoids the use of strong acids, strong bases, and toxic formaldehyde chemicals in the production process, reducing the negative impact of the production process on the environment.

[0026] (3) This preparation method can prepare natural biomass starch modified sodium phosphate organic penetrating steel bar rust inhibitors with different molecular structures and molecular weights according to actual engineering needs, meeting the needs of steel bar rust prevention in different reinforced concretes, and avoiding the problems of plant extract organic penetrating rust inhibitors with complex molecular composition and molecular structure, large product volatility, and difficulty in meeting actual engineering needs.

[0027] (4) Adding modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor to reinforced concrete can improve the performance of hardened concrete and the long-term resistance of the steel bars in the concrete to chloride ion corrosion. Compared with traditional organic penetrating steel bar rust inhibitors, this modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor has a good protective effect on the steel bars in reinforced concrete even at a very low dosage. According to the method of specific example 1, the cost of using organic penetrating steel bar rust inhibitor can be saved by 1.14 yuan per cubic meter of reinforced concrete, and the economic benefit of 2.76 yuan can be generated by extending the service life of each cubic meter of reinforced concrete and saving maintenance costs.

[0028] In summary, based on the annual production of 6,000 tons of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor, excluding the environmental benefits generated by reducing the emission of highly toxic substances, the present invention can save 4.4148 million yuan in raw materials, production time, and labor costs, and save 265,000 yuan in production equipment investment. 6 The cost of organic penetrating steel bar rust inhibitor and maintenance cost per cubic meter of reinforced concrete can be saved by RMB 11.622 million. Annual production of 6,000 tons of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor can generate economic benefits of RMB 16.3018 million. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The invention relates to the preparation process of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor;

[0030] Figure 2 The initial slump flowability of fresh concrete added with modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor;

[0031] Figure 3 The setting time of fresh concrete added with modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor;

[0032] Figure 4 The compressive strength of hardened concrete mixed with modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor;

[0033] Figure 5 This is the time-varying curve of the anodic polarization potential of steel bars in hardened concrete added with modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor;

[0034] Figure 6 This is the curve of the steel bar surface corrosion area rate changing with time in hardened concrete added with modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor;

[0035] Figure 7 This is the curve showing the weight loss rate of steel bars in hardened concrete added with modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor over time. DETAILED DESCRIPTION

[0036] One ton of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor (MIC) was produced according to the preparation method described in the embodiment of the present invention. The performance of hardened concrete added with this organic penetrating steel bar rust inhibitor and the rust inhibition effect on steel bars in hardened concrete were studied.

[0037] The natural starch polymer of the present invention is corn starch (pharmaceutical grade, amylose and amylopectin account for 25% and 75% respectively, and the weight average molecular weight is 2.7416 million) purchased from Shanghai Aladdin Reagent Co., Ltd.; dilute sulfuric acid (industrial grade, concentration 30%) is produced by Yangzhou Huafu Chemical Co., Ltd.; sodium chloride (chemically pure, purity 99.5%) is produced by Tianjin Jinyaoxiangcheng Technology Co., Ltd.; sodium hydroxide (industrial grade, purity 98.2%) is produced by Hebei Cangzhou Xincheng Chemical Products Co., Ltd.; epichlorohydrin (industrial grade) is produced by Shandong Chuangying Chemical Co., Ltd.; dilute hydrochloric acid (industrial grade, concentration 31-36%) is produced by Taizhou Fengcheng Chemical Co., Ltd.; phosphoric acid (industrial grade, concentration 85%) is produced by Nantong Donglin Chemical Co., Ltd.; liquid ammonia (industrial grade, ammonia content of 25-30%) is produced by Nantong Donglin Chemical Co., Ltd. %) is produced by Taixing Yimin Chemical Co., Ltd.; allyl alcohol (industrial grade) is produced by Jiangsu Zhongyu Trading Co., Ltd.; phosphine nitrogen ligand iridium catalyst (industrial grade) is produced by Shaanxi Xinyan Bomei Biotechnology Co., Ltd.; ammonium cerium nitrate (industrial grade) is produced by Henan Yutai Qixin Chemical Co., Ltd.

[0038] Example 1 Preparation of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor

[0039] 1. Preparation of starch polyol oligomers

[0040] 7 kg of corn starch and 33 kg of water were weighed and placed in a reactor equipped with a stirrer, thermometer, dropping funnel, and reflux condenser. Rapid stirring was performed for 25 minutes to uniformly disperse the starch polymer in the water to form a suspension. The temperature was then raised to 75°C, and the starch suspension was gelatinized for 50 minutes at this temperature. After the viscosity of the starch suspension reached a constant value of 2326 mPa·s, 0.21 kg of dilute sulfuric acid solution was added to the suspension. The temperature was then raised to 80°C and acidified for 2 hours at this temperature. This yielded 3734 kg of a clear starch polyol oligomer solution with a weight-average molecular weight of 1096.

[0041] 2. Preparation of epichlorohydrin starch oligomers

[0042] 32 kg of starch polyol oligomer solution and 80 L of sodium chloride solution (1% by weight) were placed in a reactor equipped with an agitator, thermometer, dropping funnel, and reflux condenser. The agitator was started and stirred for 40 minutes to thoroughly mix the starch polyol oligomer solution and the sodium chloride solution into a homogeneous, clear solution. Sodium hydroxide solution was added to adjust the pH to 9.76 at 45°C, and the mixture was alkalized at this temperature for 2 hours. Then, 4.6 kg of epichlorohydrin liquid was slowly added dropwise over 40 minutes with continuous stirring. The above solution was placed in a microwave-irradiated organic synthesis reactor and refluxed for 10 minutes under microwave irradiation conditions set at 120 W microwave radiation power and a maximum reaction temperature of 80°C using the system control software. The starch polyol oligomer and epichlorohydrin underwent a cross-linking reaction, yielding 35.32 kg of a white epichlorohydrin starch oligomer solution.

[0043] 3. Preparation of N(-allyl)aminophosphoric acid intermediate

[0044] 60 kg of phosphoric acid was placed in a reactor equipped with an agitator, thermometer, dropping funnel, and reflux condensing tube. Using dilute hydrochloric acid to adjust the solution pH to 4.71, the system temperature was maintained at 40 ° C. Within 45 minutes, 113.4 kg of liquid ammonia solution was slowly added dropwise, with the system temperature not exceeding 65 ° C. After adding the liquid ammonia solution, the solution temperature was raised to 95 ° C and stirred continuously, and the reaction was performed for 6 hours to obtain 169.57 kg of ammonium phosphate solution. After lowering the temperature of the ammonium phosphate solution to 60 ° C, 34.33 kg of propenol was added to the ammonium phosphate solution, the system temperature was maintained at 60 ° C, and 1.70 kg of phosphine nitrogen ligand iridium catalyst was added and added within 30 minutes. The solution temperature was raised to 80 ° C, and at this temperature, the reaction was performed for 50 hours to obtain 198.21 kg of N (-propenyl) aminophosphoric acid intermediate clear solution.

[0045] 4. Preparation of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor

[0046] 31.85 kg of epichlorohydrin starch oligomer solution and 800 kg of water were added to a reactor equipped with a stirrer, thermometer, and reflux condenser. The stirrer was started, and the epichlorohydrin starch oligomer and water were thoroughly mixed to form a homogeneous solution. The pH of the system was adjusted to 10.41 using 20% ​​sodium hydroxide (weight percent), and the mixture was continuously stirred. 168.15 kg of N(-propylene)aminophosphoric acid intermediate solution was slowly added dropwise to the epichlorohydrin starch oligomer solution over approximately 60 minutes. 0.65 kg of cerium ammonium nitrate initiator was added, and the grafting reaction was carried out at 95°C for 4 hours. The reaction was terminated, the mixture was cooled to ambient temperature, and matured in the reaction vessel for 3 hours. Sodium hydroxide solution was added to adjust the pH to 10.29, yielding 994.32 kg of a light yellow, organically permeable steel bar rust inhibitor solution containing 18.47% solids.

[0047] Example 2: Concrete performance and corrosion resistance of steel bars in hardened concrete by adding modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor

[0048] 1. Preparation of concrete

[0049] 1.1 Concrete mix ratio

[0050] The concrete strength grade used in the present invention is C60, and the cement is P.II52.5 ordinary Portland cement produced by Hubei Wuhan Huaxin Cement Co., Ltd. The fly ash is the first-grade fly ash from Sichuan Suining Thermal Power Plant, with a loss on ignition of 1.56. The coarse aggregate is crushed stone from Hubei Yangxin, which is a secondary mix, with 5-20 mm crushed stone accounting for 38.5% and 20-40 mm crushed stone accounting for 61.5%. The fine aggregate is the river sand from Nanjing Outer Qinhuai River, with a fineness modulus of 2.76. The high-efficiency water reducer is a naphthalene-based high-efficiency water reducer (powder) produced by Jiangsu Bot New Materials Co., Ltd. The mixing water is drinking water. The cementitious material (cement + fly ash) in the test concrete mix ratio is: coarse aggregate: fine aggregate: water = 1:2.78:1.46:0.3 (weight percentage). The total amount of cementitious material (cement + fly ash) in one cubic meter of concrete is 450 kg / m 3 The fly ash accounted for 22% of the total cementitious material, the naphthalene-based high-efficiency water reducer was used at a rate of 0.6% by weight of the cementitious material, and the test concrete mix ratio is shown in Table 1. The properties of blank concrete and concrete mixed with 0.2%, 0.3%, 0.4%, and 0.5% of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor (MIC) based on the weight of the cementitious material were determined. The amount of organic penetrating steel bar rust inhibitor was expressed as a percentage of the weight of the cementitious material.

[0051] Table 1. Concrete mix ratio for experiment

[0052]

[0053] 1.2. Preparation and curing of concrete

[0054] 350 kg of cement and 100 kg of fly ash were placed in a blender and mixed at 30 rev / min for 3 minutes. Then, 770 kg of 5-20 mm coarse aggregate, 482 kg of 20-40 mm coarse aggregate, and 658 kg of fine aggregate were added and mixed at 40 rev / min for 3 minutes. Then, 2.70 kg of naphthalene-based high-efficiency water reducer and 0-2.25 kg of modified natural biomass starch sodium phosphate organic permeable steel bar rust inhibitor (MIC) (based on solids) (0%, 0.2%, 0.3%, 0.4%, 0.5%) were dissolved in 135 kg of mixing water and added to the solid mixture. Stirring was continued at 60 rev / min for 3 minutes. Finally, the fresh concrete slurry was accelerated and mixed at 80 rev / min for 2 minutes. After testing a small amount of fresh MIC concrete for initial fluidity and setting time, 12 specimens were prepared by pouring the fresh MIC concrete into 100 mm × 100 mm × 100 mm molds. The molds containing the MIC concrete were covered with wet burlap sacks and placed indoors (temperature 25°C, humidity 55-65%). After 24 hours, the MIC concrete specimens were removed from the molds and placed in a standard environment (temperature 20°C, humidity 90 ± 5%) for curing to the specified ages of 3, 7, 28, and 90 days. The concrete compressive strength was then tested.

[0055] 2. Preparation of reinforced concrete

[0056] 2.1. Preparation of steel bar samples

[0057] Q235 round steel bars with a diameter of 9 mm and a length of 200 mm were processed into segments with a diameter of 9 mm and a length of approximately 140 mm. The segments were pickled in a 12% (by weight) hydrochloric acid solution for 10 minutes and rinsed with water. The segments were then polished with 100-1000 mesh SiC wet sandpaper and then 200 mesh metallographic sandpaper to a maximum allowable surface roughness of 11.6 μm. The polished steel bars were then wiped with alcohol and acetone to degrease and dry, then placed in a desiccator for later use. The mass of the dried segments was then measured.

[0058] 2.2 Preparation of hardened reinforced concrete electrode specimens

[0059] Surface-treated rebar was placed in a 300 mm × 300 mm × 210 mm test mold, with one end of the rebar exposed and the other end capped against a baffle. Five sets of concrete were prepared according to the concrete mix ratio in Table 1 and poured into 85 test molds, ensuring a concrete cover thickness of approximately 35 mm for each set. The 85 test molds with reinforced concrete were placed on a vibrating table and vibrated to compact the concrete. The vibrated molds were then placed in an environment (temperature 25°C, humidity 55-65%) for 24 hours and removed after one day. Next, one specimen in each reinforced concrete set was wire brushed to remove rust and cement slurry from the exposed rebar surfaces at both ends. A high-temperature copper conductor was welded to one end of the rebar. The welded end of the rebar was cleaned with alcohol and acetone, and the exposed rebar and end were sealed with epoxy resin to prevent rust. The other reinforced concrete specimens did not require high-temperature copper conductor welding. All reinforced concrete specimens were placed in a standard environment (temperature of 20 °C and humidity of 90 ± 5%) and cured for the specified age of 28 days. Then, the reinforced concrete specimens were immersed in a 3.5% NaCl simulated seawater solution for 30 days.

[0060] 3. Test of concrete properties and corrosion resistance of steel bars in hardened concrete

[0061] 3.1. Initial slump fluidity of fresh concrete

[0062] A conical slump test cylinder was wiped clean with a damp cloth and placed on a horizontal steel plate. Fresh blank concrete and fresh concrete mixed with 0.2%, 0.3%, 0.4%, and 0.5% modified natural biomass starch sodium phosphate organic penetrating steel rust inhibitor (MIC) were loaded into the slump test cylinder in three layers. After each layer, a vibrator was used to evenly tamp the concrete from the edge to the center 25 times. After the concrete was fully filled and compacted, the concrete surface was smoothed and the slump cylinder was gently lifted vertically. After the fresh concrete stopped flowing, the average value of the fresh concrete mixture in two mutually perpendicular directions was measured as the initial slump flow of the fresh concrete.

[0063] Figure 2 The figure shows the initial slump flow of fresh concrete added with modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor. Figure 2 It can be seen that the concrete added with modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor has a higher initial slump flowability than the blank concrete. As the amount of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor increases, the initial slump flowability of fresh concrete increases.

[0064] 3.2 Setting time of fresh concrete

[0065] Mix concrete according to the mix proportions in Table 1. After recording the water addition time during the fresh concrete preparation process, sieve out the mortar from the fresh concrete sample using a 5 mm sieve. Place the fresh mortar into a 150 mm × 150 mm × 150 mm test mold. Use a vibrator to tamp the mortar in the mold 35 times. Place the mortar sample on the penetration resistance tester. Determine the setting time of fresh concrete using the penetration resistance method. During the test, insert the probe on the penetration resistance tester into the mortar to a depth of 25 mm. Measure the mortar penetration resistance at regular intervals until the penetration resistance exceeds 28 MPa. Note the time the probe is inserted into the mortar and the penetration resistance. A penetration resistance-time curve is then plotted. The times corresponding to penetration resistances of 3.5 MPa and 28 MPa are the initial and final setting times of the concrete.

[0066] Figure 3 The figure shows the setting time of fresh concrete added with modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor. Figure 3 It can be seen that the concrete mixed with modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor has a longer setting time than the blank concrete. With the increase of the amount of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor, the initial setting time and final setting time of the fresh concrete increase.

[0067] 3.3 Compressive strength of hardened concrete

[0068] The compressive strength of hardened concrete was tested according to the national standard "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T50081-2002). After 3, 7, 28, and 90 days of standard curing, the 100 mm × 100 mm × 100 mm concrete specimens were loaded using a YAW-3000 electro-hydraulic servo loading system at a loading rate of 1.3 MPa / s until the concrete specimens failed. The compressive strength of the hardened concrete was then measured.

[0069] Figure 4 The figure shows the compressive strength of hardened concrete mixed with modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor. Figure 4 It can be seen that with the increase of curing age, the compressive strength of all hardened concretes continues to increase. At the same curing age, with the increase of the content of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor, the compressive strength of hardened concrete increases.

[0070] 3.4. Anodic Polarization Potential Test of Steel Bars in Hardened Concrete

[0071] Electrochemical testing was conducted using the anodic polarization potential method described in ASTM C 876 to evaluate the corrosion inhibition effect of a modified natural biomass starch sodium phosphate organic penetrating steel bar inhibitor on rebar embedded in hardened concrete. Reinforced concrete specimens were removed from a simulated seawater solution at different immersion times and the liquid on the specimen surface was wiped clean. The rebar in the concrete, due to its relatively negative corrosion potential, acts as the anode. The auxiliary platinum electrode, which does not corrode, forms a relatively positive cathode, forming a corrosion circuit between the two regions, resulting in a potential difference between the anodic and cathodic regions. After temperature correction of the electrode potential at the measuring point, an applied current was applied to determine the starting time of the half-cell potential test. Polarization was performed at a polarization current of 50 μA / cm for 30 minutes. When the anodic polarization potential of the internal rebar reached equilibrium, the anodic polarization potential was recorded. The anodic polarization potential of the rebar in the hardened concrete specimens was retested every two days to determine the change in anodic polarization potential over time.

[0072] Figure 5 The figure shows the time-varying curve of the anodic polarization potential of steel bars in hardened concrete added with modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor. Figure 5 As can be seen from the figure, with the increase of immersion time, the absolute value of the anodic polarization potential of the steel bars in all hardened concrete increases. At the same immersion time, with the increase of the content of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor, the absolute value of the anodic polarization potential of the steel bars in hardened concrete decreases.

[0073] 3.5. Determination of the surface corrosion area of ​​steel bars in hardened concrete

[0074] The steel bar surface corrosion area ratio is the most direct method for evaluating the rust inhibition effect of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor. Before the test, the initial surface area of ​​the steel bars was measured. Every two days of immersion, the concrete specimens were split to remove the internal steel bars. The exposed steel bars at both ends of the concrete were cut off. The steel bar surface was covered with transparent sulfuric acid paper, and the rusted areas were depicted and blackened. The obtained data was reverse-modeled, and the steel bar surface corrosion area was calculated using relevant analysis software. The steel bar surface corrosion area ratio in concrete added with modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor at the specified immersion age was calculated using formula (1).

[0075] (1)

[0076] Where: P-corrosion area ratio of steel bar surface in concrete (%); S0-original surface area of ​​steel bar sample (mm 2 ); S-surface area of ​​corroded steel bar specimen (mm 2 ).

[0077] Figure 6The curve showing the change of steel bar surface corrosion area over time in hardened concrete added with modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor. Figure 6 As can be seen from the figure, with the increase of immersion time, the surface corrosion area of ​​steel bars in all hardened concretes increased. At the same immersion time, with the increase of the content of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor, the surface corrosion area of ​​steel bars in hardened concrete decreased significantly.

[0078] 3.6 Determination of weight loss rate of steel bars in hardened concrete

[0079] The weight loss rate of steel bars in concrete can be used to evaluate the ability of modified natural biomass starch sodium phosphate organic permeable steel bar rust inhibitor to slow the corrosion rate of steel bars in concrete. The original mass of the steel bars was weighed, and the reinforced concrete specimens were immersed in simulated seawater. Every two days, the reinforced concrete specimens were broken open to remove the steel bars. The concrete sample and rust remaining on the steel bar surface were removed with a scraper. The steel bars were pickled with a 12% hydrochloric acid solution and then brushed with a brush. The pickled steel bars were rinsed with deionized water and dried in an oven for four hours. The corroded steel bars were weighed. The weight loss rate of the steel bars in the concrete during the specified soaking time was calculated according to formula (2).

[0080] (2)

[0081] Where: Q is the weight loss rate of steel bars in concrete (%); W0 is the weight of the steel bar sample before corrosion (kg); W is the mass of the steel bar sample after immersion for different times (kg).

[0082] Figure 7 The figure shows the weight loss rate of steel bars in hardened concrete added with modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor over time. Figure 7 As can be seen from the figure, with the increase of immersion time, the weight loss rate of steel bars in all hardened concretes increases. At the same immersion time, with the increase of the content of modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor, the weight loss rate of steel bars in hardened concrete decreases significantly.

Claims

1. A method for preparing a modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor, characterized in that: The following steps are involved: (1) Natural starch polymer and water are mixed into a suspension and subjected to high-temperature gelatinization and acidification treatment to break the glycosidic bonds in the starch polymer molecular chain to obtain starch polyol oligomers, and the C6 primary alcohol hydroxyl group on the starch polyol oligomer undergoes a cross-linking reaction with epichlorohydrin to obtain epichlorohydrin starch oligomers; (2) Under acidic conditions, phosphoric acid reacts with liquid ammonia to produce ammonium phosphate. Under the action of phosphine nitrogen ligand iridium catalyst, ammonium phosphate and allyl alcohol undergo hydrogen-borrowing reaction to produce N(-allyl)aminophosphoric acid intermediate; (3) Under the action of ammonium cerium nitrate initiator, epichlorohydrin starch oligomer and N (-propylene) aminophosphoric acid intermediate undergo grafting reaction to prepare modified natural biomass starch sodium phosphate containing -OH, -NH, and -PO3 groups as an organic penetrating steel bar rust inhibitor.

2. The preparation method of the modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor according to claim 1, characterized in that: The high-temperature gelatinization step in step (1) is as follows: weighing natural starch polymer and water into a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser, rapidly stirring for 20-30 minutes, dispersing the natural starch polymer into the water to form a uniform suspension solution, raising the temperature to 70-75°C, accelerating the stirring of the starch suspension solution, and performing gelatinization reaction at this temperature for 50-60 minutes to obtain a starch gelatinization solution, wherein the mass ratio of the natural starch polymer to water is 1:4.5-5.0, and the viscosity of the starch gelatinization solution is constant at 2219-2365 Pa·s.

3. The preparation method of the modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor according to claim 2, characterized in that: The acidification step in step (1) is as follows: after the viscosity of the starch gelatinization solution becomes constant, a dilute sulfuric acid solution is added to the starch gelatinization solution, the temperature of the suspension solution is raised to 80-85°C, and the acidification treatment is performed at this temperature for 2-3 hours. The starch polymer gelatinization solution is acidified and degraded into a starch polyol oligomer solution, wherein the dilute sulfuric acid solution is 2.5-3.0 wt% of the amount of the natural starch polymer, and the weight-average molecular weight of the starch polyol oligomer is 1053-1107.

4. The preparation method of the modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor according to claim 1, characterized in that: The preparation steps of the epichlorohydrin starch oligomer described in step (1) are as follows: placing a starch polyol oligomer solution and a sodium chloride solution in a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser, starting the stirrer and stirring for 30-40 minutes, and fully mixing the starch polyol oligomer solution and the sodium chloride solution into a uniform, clear solution; adding sodium hydroxide solution at a temperature of 45-50°C, adjusting the pH value to 9-10, and alkalizing for 1-2 hours; slowly adding epichlorohydrin liquid dropwise over 30-40 minutes, adding and continuously stirring; placing the mixed solution in a microwave radiation organic synthesis reactor for cross-linking reaction with epichlorohydrin to obtain a white epichlorohydrin starch oligomer solution, wherein the mass volume ratio of the starch polyol oligomer solution to the sodium chloride solution is 0.35- 0.45kg / L, the mass ratio of the starch polyol oligomer solution to epichlorohydrin is 6.5-7.0:1, the microwave radiation reaction power is 100-130W, the reaction time is 10-15 minutes, and the maximum reaction temperature is 80-85°C.

5. The preparation method of the modified natural biomass starch sodium phosphate organic permeable steel bar rust inhibitor according to claim 1, characterized in that: The specific steps of step (2) are as follows: put phosphoric acid into a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser, use dilute hydrochloric acid to adjust the pH value of the solution to 3-5, maintain the system temperature at 30-40°C, slowly add liquid ammonia solution dropwise within 30-50 minutes, maintain the system temperature not exceeding 60-65°C, after adding the liquid ammonia solution, increase the system temperature to 90-95°C and stir continuously, react for 5-6 hours to obtain ammonium phosphate solution, and then reduce the temperature of the ammonium phosphate solution to 50-60°C. , add allyl alcohol to the ammonium phosphate solution, keep the system temperature unchanged, add the phosphine nitrogen ligand iridium catalyst, add it within 20-30 minutes, raise the solution temperature to 70-80 ° C, and react with hydrogen at this temperature for 48-50 hours to obtain a clear solution of N (-propylene) aminophosphoric acid intermediate, the mass ratio of the phosphoric acid to liquid ammonia is 0.50-0.55:1, the weight ratio of the ammonium phosphate solution to allyl alcohol is 4.5-5.0:1, and the phosphine nitrogen ligand iridium catalyst is 1.0-1.05% by weight of the ammonium phosphate solution.

6. The preparation method of the modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor according to claim 1, characterized in that: The specific steps of step (3) are as follows: add the epichlorohydrin starch oligomer solution and water to the reaction vessel, start the stirrer to completely mix the epichlorohydrin starch oligomer and water into a uniform solution, use 20% sodium hydroxide to adjust the pH value of the system to 11-12, continuously stir the mixture solution, maintain the temperature at 80-85°C, slowly add the N (-propylene) aminophosphoric acid intermediate solution to the epichlorohydrin starch oligomer solution, add it within 60-90 minutes, add cerium ammonium nitrate initiator, carry out grafting reaction at 90-95°C for 3-4 hours, stop the reaction and cool it naturally to ambient temperature, mature it in the reaction vessel for 2-3 hours, add sodium hydroxide solution to adjust the pH value to 10-11, and obtain a light yellow solution with a solid content of 17-20 % modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor solution, the mass ratio of the epichlorohydrin starch oligomer solution to water is 0.039-0.040:1, the mass ratio of the epichlorohydrin starch oligomer solution to N (-propylene) aminophosphoric acid intermediate solution is 0.15-0.20:1, and the cerium nitrate initiator is 2.0-2.1% by weight of the epichlorohydrin starch oligomer solution.

7. The modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor obtained by the preparation method according to any one of claims 1 to 6.

8. Use of the modified natural biomass starch sodium phosphate organic penetrating steel bar rust inhibitor according to claim 7 in the preparation of concrete.

9. The use according to claim 8, characterized in that The added amount of the modified natural biomass starch sodium phosphate organic permeable steel bar rust inhibitor is 0.2-0.5wt%.

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