Anticorrosive concrete additive and preparation method thereof

Abstract

The invention relates to the technical field of chemical additives of building materials, in particular to an anti-corrosion concrete additive and a preparation method thereof. The concrete additive comprises the following components in parts by weight: 40-80 parts of fly ash, 10-20 parts of modified plant fibers, 5-8 parts of a water reducing agent, 3-6 parts of inorganic salt and 10-30 parts of water, and the modified plant fibers are obtained by grafting and modifying semi-carbonized plant fibers and fluorosilane; the water reducing agent is an amphoteric polycarboxylic acid water reducing agent. In the anticorrosive concrete additive provided by the invention, concrete pores are filled with the fly ash, so that the microstructure is improved; the modified plant fiber enhances the mechanical property and crack resistance of the concrete; the amphoteric polycarboxylate superplasticizer not only improves the workability of the concrete, but also forms a protective film on the surface of the steel bar; the inorganic salt further enhances the impermeability of the concrete, and the additive can comprehensively improve the comprehensive performance of the concrete, especially the corrosion resistance and the service life of the concrete in a severe environment through multi-component compounding.

Description

Technical Field

[0001] The invention relates to the technical field of chemical additives for building materials, and in particular to an anticorrosive concrete additive and a preparation method thereof. Background Art

[0002] Concrete is one of the most widely used building materials in the world today, accounting for a large proportion in infrastructure construction. It has the advantages of abundant raw materials, low price and high strength. However, the durability of concrete structures, especially the corrosion of steel bars in reinforced concrete, seriously affects the service safety and service life of the structure. In special environments such as oceans and salt lakes, the corrosion of chloride ions and sulfates is the main factor leading to the destruction of concrete structures. Chloride ions penetrate into the surface of steel bars through the pores of concrete. When the concentration reaches about 0.4%, it can destroy the passivation film and accelerate the corrosion of steel bars; while sulfate corrosion will cause concrete to expand, crack and peel off, causing its strength and viscosity to lose. Studies have shown that hydrostatic pressure and seawater impact will accelerate the penetration of harmful ions into concrete, and the degree of corrosion of concrete in different marine zones (tidal zone, underwater zone, atmospheric zone) is also different. At present, the methods to improve the corrosion resistance of concrete mainly include reducing the water-cement ratio, using cement with better corrosion resistance, adding mineral admixtures, using surface coatings and adding anti-corrosion additives.

[0003] Chinese patent CN202011138536.1 discloses an anticorrosive concrete and a preparation method thereof, wherein the anticorrosive concrete comprises 6-10 parts of methyl benzotriazole, 5-9 parts of dibutyltin dilaurate, 300-400 parts of cement, 50-70 parts of fly ash, 600-700 parts of sand, 1-2 parts of silane impregnating agent, and 200-250 parts of water. The preparation method is as follows: Step 1), cement, fly ash, sand, and silane impregnating agent are mixed together and stirred evenly to obtain anticorrosive concrete powder; Step 2), methyl benzotriazole and dibutyltin dilaurate are mixed evenly, and then added to the anticorrosive concrete powder, stirred evenly, and then water is added, mixed and stirred evenly to obtain anticorrosive concrete slurry; Step 3), the anticorrosive concrete slurry is poured into a mold and fixed into shape. This patent uses barium stearate and silane impregnating agent to improve the anti-corrosion effect of concrete, thereby extending the service life of concrete structures. However, the above technical solution mainly uses chemical additives to achieve anti-corrosion, which has limited anti-corrosion effect. In addition, chemical additives may gradually become ineffective in harsh environments and cannot effectively cope with long-term cyclic corrosion. At the same time, the presence of pores in concrete will increase the risk of harmful substances penetrating, thereby affecting the long-term anti-corrosion effect. Summary of the invention

[0004] In view of this, the present invention proposes an anti-corrosion concrete additive and a preparation method thereof to solve the problem that the concrete anti-corrosion effect is poor and the durability is poor in the prior art and cannot effectively cope with long-term cyclic corrosion.

[0005] The technical solution of the present invention is achieved as follows: The present invention provides an anti-corrosion concrete additive, which includes 40-80 parts of fly ash, 10-20 parts of modified plant fiber, 5-8 parts of water reducer, 3-6 parts of inorganic salt and 10-30 parts of water by weight, wherein the modified plant fiber is obtained by grafting and modifying semi-carbonized plant fiber with fluorosilane; and the water reducer is an amphoteric polycarboxylic acid water reducer.

[0006] In the present invention, fly ash, as an active mineral admixture, can react with calcium hydroxide in cement hydration products to generate additional CSH gel, thereby improving the later strength and durability of concrete. The modified plant fiber is modified by semi-carbonization treatment and fluorosilane grafting, wherein the semi-carbonization treatment improves the durability and mechanical properties of the fiber, while the fluorosilane modification gives the plant fiber hydrophobicity, prompting the modified plant fiber to form a three-dimensional network structure in the concrete, significantly improving the crack resistance and toughness of the concrete, thereby enhancing the anti-corrosion performance. The amphoteric polycarboxylic acid water reducer can significantly reduce the water consumption of concrete, improve the density and strength of concrete, thereby improving its impermeability and durability; at the same time, the amphoteric structure makes the water reducer molecule have both hydrophilic and hydrophobic groups, which may have the ability to adsorb certain harmful ions, further enhancing the anti-corrosion performance of concrete. Calcium nitrite can form a protective film on the surface of steel bars to inhibit steel corrosion, especially in an environment where chloride ions exist; sodium hexametaphosphate can improve the impermeability of concrete, and may also react with cement hydration products to form more stable compounds, thereby improving the acid resistance of concrete.

[0007] Furthermore, fly ash refines the pore structure through volcanic ash reaction, while modified plant fibers form a three-dimensional network and fill the microscopic pores. The synergistic effect of fly ash and modified plant fibers can significantly reduce the permeability of concrete and effectively prevent the invasion of corrosive substances; inorganic salts form a protective film on the surface of steel bars, and the amino, carboxyl and other groups contained in the water reducer can form coordination bonds with the metal on the surface of the steel bars, forming an insoluble protective film on the surface of the steel bars through adsorption, and the hydrophobic part of the modified plant fibers can also prevent the penetration of moisture and harmful ions, thereby jointly enhancing the corrosion resistance and durability of concrete.

[0008] On the basis of the above technical solution, preferably, the preparation method of the modified plant fiber comprises:

[0009] S1. After drying, crushing and screening the plant fiber, place it in a closed environment with an oxygen content of 2-2.5%, heat it to 320-340°C at a rate of 5-10°C / min, keep the temperature constant for 15-20min, and cool it to obtain semi-carbonized plant fiber;

[0010] S2. Mix the semi-carbonized plant fiber with the fluorosilane solution, and oscillate the mixture with microwaves to obtain silane-modified plant fiber. The power of the microwave oscillation treatment is 400-800 W, and the time of the microwave oscillation is 10-20 min.

[0011] On the basis of the above technical scheme, preferably, in step S2, the mass ratio of the semi-carbonized plant fiber and the fluorosilane solution is 5-8:10-12, the fluorosilane solution is obtained by mixing fluorosilane, ethanol and water, the content of fluorosilane in the fluorosilane solution is 8-12%, the content of ethanol is 20-30%, and the balance is water.

[0012] On the basis of the above technical solution, preferably, the plant fiber includes one or more of corn stalk fiber, sorghum stalk fiber and bamboo fiber, and the fluorosilane includes trifluoropropyl trimethoxysilane or trifluoropropyl triethoxysilane.

[0013] Specifically, in step S1, by semi-carbonizing the plant fiber, the specific surface area and porosity of the fiber can be increased, and its heat resistance and chemical stability can be improved; in step S2, by introducing a fluorosilane structure into the semi-carbonized plant fiber structure, the fluorine group makes the modified plant fiber hydrophobic, and the hydrophobic surface can effectively prevent the penetration of moisture and harmful ions, thereby enhancing the anti-corrosion performance of concrete.

[0014] On the basis of the above technical solution, preferably, the preparation method of the water reducing agent comprises:

[0015] A1. Mix histidine, p-toluenesulfonic acid and water, and heat and stir at 75-85° C. to obtain histidine p-toluenesulfonate;

[0016] A2, mixing histidine p-toluenesulfonate, isopentanol polyoxyethylene ether and water, adding a catalyst, and performing an esterification reaction at 110-130° C. for 2.5-3.5 hours to obtain a macromonomer mixture;

[0017] A3. Prepare a first solution and a second solution, wherein the first solution is acrylic acid, α-hydroxyethyl acrylic acid, dimethyldiallylammonium chloride and water, and the second solution is ammonium persulfate, mercaptopropionic acid and water; mix the macromonomer mixture and water evenly, heat while stirring, adjust the peristaltic pump to control the first solution and the second solution to be added to the macromonomer mixture solution, wherein the first solution is added for 2-4 hours, and the second solution is added for 2-4 hours. After the addition is complete, keep the reaction warm for 1.5-2 hours, adjust the pH value to be neutral, and obtain the water reducer.

[0018] Based on the above technical solution, preferably, in step A1, the mass ratio of histidine to p-toluenesulfonic acid is 1:2-2.5.

[0019] Based on the above technical solution, preferably, in step A2, the mass ratio of histidine p-toluenesulfonate to isopentenol polyoxyethylene ether is 3.5-4.0:1, the catalyst is p-toluenesulfonic acid, and the added amount of the catalyst is 2-5% of the mass of histidine p-toluenesulfonate.

[0020] On the basis of the above technical scheme, preferably, in step A3, the mass ratio of the macromonomer mixture, acrylic acid, α-hydroxyethyl acrylate and dimethyldiallylammonium chloride is 1:3.8-4.0:1.8-2.2:0.2-0.3, the amount of ammonium persulfate added is 3-4% of the mass of the macromonomer mixture, and the amount of mercaptopropionic acid added is 4-5% of the mass of the macromonomer mixture.

[0021] Specifically, in step A1, p-toluenesulfonic acid groups are introduced by acid-base neutralization reaction, in step A2, the carboxyl group of histidine and the hydroxyl group of isopentanol polyoxyethylene ether undergo esterification reaction to synthesize a macromonomer, and in step A3, a free radical polymerization reaction is performed, ammonium persulfate is used as an initiator, and mercaptopropionic acid is used as a chain transfer agent to synthesize an amphoteric polycarboxylic acid water reducer. The water reducer molecule contains imidazole rings and amino groups from histidine, as well as benzene rings and sulfonic acid groups from p-toluenesulfonic acid, and these groups form a multi-point telechelic structure. At the same time, the isopentanol polyoxyethylene ether side chain introduced by the esterification reaction provides a comb-like structure. This composite structure enables the water reducer molecule to interact with the steel bar surface in a variety of ways: the amino group and carboxyl group can form a coordination bond with the metal iron to enhance the adsorption capacity; the large-sized aromatic ring and polyether segment can form a steric hindrance to prevent corrosive ions from approaching the steel bar surface; and the sulfonic acid group can further enhance the adsorption through electrostatic action. These interactions together form a dense protective film on the surface of the steel bars, effectively isolating harmful substances such as chloride ions and significantly improving the corrosion resistance of the steel bars.

[0022] On the basis of the above technical solution, preferably, the inorganic salt is calcium nitrite and / or sodium hexametaphosphate.

[0023] The invention provides a method for preparing an anticorrosive concrete additive, comprising the following steps: weighing fly ash, a water reducing agent, an inorganic salt and water in parts by weight and mixing them evenly, then adding modified plant fiber and the water reducing agent, and stirring at a rotation speed of 500-1000 r / min for 10-30 min to obtain the anticorrosive concrete additive.

[0024] The anticorrosive concrete additive and the preparation method thereof of the present invention have the following beneficial effects compared with the prior art:

[0025] (1) The anti-corrosion concrete additive provided by the present invention significantly improves the anti-corrosion performance and durability of concrete through the synergistic effect of fly ash, modified plant fiber, amphoteric polycarboxylic acid water reducer and inorganic salt. Fly ash fills the pores of concrete and improves the microstructure; the modified plant fiber enhances the mechanical properties and crack resistance of concrete; the amphoteric polycarboxylic acid water reducer not only improves the workability of concrete, but also forms a protective film on the surface of steel bars; the inorganic salt further enhances the impermeability of concrete. This multi-component composite design enables the additive to comprehensively improve the comprehensive performance of concrete, especially the anti-corrosion ability and service life in harsh environments;

[0026] (2) The amphoteric polycarboxylic acid water reducer contains histidine-derived imidazole ring, amino group, and p-toluenesulfonic acid benzene ring and sulfonic acid group, forming a multi-point telechelic structure, which not only provides excellent water-reducing performance, but also can form a dense protective film on the surface of steel bars; the polar groups in the water reducer molecules can form coordination bonds with metallic iron to enhance adsorption; the large-sized aromatic rings and polyether segments form steric hindrance to block corrosive ions; the sulfonic acid group further enhances adsorption through electrostatic action, which together improves the anti-corrosion performance of steel bars and improves the fluidity and density of concrete;

[0027] (3) Plant fibers modified by semi-carbonization and fluorosilane grafting have excellent hydrophobicity and alkali resistance. Semi-carbonization treatment increases the surface area and adsorption capacity of the fiber, while fluorosilane grafting gives the fiber hydrophobicity. This modification not only improves the interfacial bonding strength between the fiber and the cement matrix, but also effectively reduces the degradation of the fiber in an alkaline environment. At the same time, the network structure of the modified fiber helps to prevent crack propagation, enhance the crack resistance and toughness of concrete, and thus indirectly improve the anti-corrosion performance of concrete;

[0028] (4) Inorganic salts can react chemically with cement hydration products to generate insoluble compounds, which fill the pores in concrete and improve the density of concrete. At the same time, inorganic salts may also produce synergistic effects with other components, such as promoting the dispersion of modified plant fibers or enhancing the adsorption capacity of water reducers, thereby further improving the overall corrosion resistance and durability of concrete. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] This embodiment provides an anti-corrosion concrete additive and a preparation method thereof, and the specific preparation method comprises the following steps:

[0032] (1) Preparation of modified plant fibers:

[0033] S1. Drying and crushing corn stalk fiber and sorghum stalk fiber to a particle size of 100-200 μm, sieving, placing in a closed environment with an oxygen content of 2-2.5%, heating to 320-340° C. at 8° C. / min, keeping the temperature constant for 15 min, and cooling to room temperature to obtain semi-carbonized plant fiber;

[0034] S2. Weigh 10 g of trifluoropropyltriethoxysilane, 25 g of ethanol and 65 g of water and mix them evenly to obtain a fluorosilane solution; mix 6.5 g of semi-carbonized plant fiber with 11 g of the fluorosilane solution, microwave oscillate at a power of 600 W for 15 min, filter, and dry at 60° C. for 2 h to obtain silane-modified plant fiber.

[0035] (2) Preparation of water reducing agent:

[0036] A1. Mix 10 g of histidine, 22.5 g of p-toluenesulfonic acid and 125 g of water, heat and stir at 80° C. for 2-3 h, and cool to room temperature to obtain histidine p-toluenesulfonate;

[0037] A2, 38g of histidine p-toluenesulfonate, 10g of isopentanol polyoxyethylene ether and 65g of water were mixed, 1.2g of p-toluenesulfonic acid was added, and esterification reaction was carried out at 120°C for 3h, and cooled to room temperature to obtain a macromonomer mixture;

[0038] A3, 39g of acrylic acid, 20g of acrylic acid-α-hydroxyethyl ester, 2.5g of dimethyldiallylammonium chloride and 100g of water were mixed to obtain a first solution; 0.35g of ammonium persulfate, 0.45g of mercaptopropionic acid and 40g of water were mixed to obtain a second solution; 10g of the macromonomer mixture was evenly mixed with 45g of water, heated to 75°C while stirring, and the peristaltic pump was adjusted to control the first solution and the second solution to be simultaneously added dropwise to the macromonomer mixture solution for 3h. After the addition was completed, the reaction was continued to be kept warm for 1.5h. After the reaction was completed, it was cooled to room temperature, the pH value was adjusted to 6.5-7.5 with 30% sodium hydroxide solution, and the solution was purified by ultrafiltration membrane (molecular weight cutoff of 1000Da) to remove unreacted monomers and small molecule by-products, and concentrated to a solid content of 35%, thereby obtaining the water reducer.

[0039] (3) Weigh 60 g of fly ash, 4.5 g of calcium nitrite and 20 g of water, mix them evenly, then add 15 g of modified plant fiber and 6.5 g of water reducer, and stir at a speed of 800 r / min for 20 min to obtain the anti-corrosion concrete additive.

[0040] Example 2

[0041] This embodiment provides an anti-corrosion concrete additive and a preparation method thereof, and the specific preparation method comprises the following steps:

[0042] (1) Preparation of modified plant fibers:

[0043] S1. Drying and crushing corn stalk fiber and sorghum stalk fiber to a particle size of 100-200 μm, sieving, placing in a closed environment with an oxygen content of 2-2.5%, heating to 320° C. at 5° C. / min, keeping the temperature constant for 15 min, and cooling to room temperature to obtain semi-carbonized plant fiber;

[0044] S2. Weigh 8 g of trifluoropropyltriethoxysilane, 30 g of ethanol and 72 g of water and mix them evenly to obtain a fluorosilane solution; mix 5 g of semi-carbonized plant fiber with 10 g of the fluorosilane solution, microwave oscillate at 400 W for 20 min, filter, and dry at 60° C. for 2 h to obtain silane-modified plant fiber.

[0045] (2) Preparation of water reducing agent:

[0046] A1. Mix 10 g of histidine, 20 g of p-toluenesulfonic acid and 100 g of water, heat and stir at 75° C. for 3 h, and cool to room temperature to obtain histidine p-toluenesulfonate;

[0047] A2, 35g of histidine p-toluenesulfonate, 10g of isopentanol polyoxyethylene ether and 50g of water were mixed, 0.7g of p-toluenesulfonic acid was added, and esterification reaction was carried out at 110°C for 3.5h, and cooled to room temperature to obtain a macromonomer mixture;

[0048] A3, 38g of acrylic acid, 18g of acrylic acid-α-hydroxyethyl ester, 2g of dimethyldiallylammonium chloride and 80g of water were mixed to obtain a first solution; 0.3g of ammonium persulfate, 0.4g of mercaptopropionic acid and 30g of water were mixed to obtain a second solution; 10g of the macromonomer mixture was evenly mixed with 40g of water, heated to 75°C while stirring, and the peristaltic pump was adjusted to control the first solution and the second solution to be simultaneously added dropwise to the macromonomer mixture solution for 4h. After the addition was completed, the reaction was continued to be kept warm for 2h. After the reaction was completed, it was cooled to room temperature, the pH value was adjusted to 6.5-7.5 with 30% sodium hydroxide solution, and the solution was purified by ultrafiltration membrane (molecular weight cutoff of 1000Da) to remove unreacted monomers and small molecule by-products, and concentrated to a solid content of 30%, thereby obtaining the water reducer.

[0049] (3) Weigh 40 g of fly ash, 3 g of sodium hexametaphosphate and 10 g of water, mix them evenly, then add 10 g of modified plant fiber and 5 g of water reducer, and stir at a speed of 500 r / min for 30 min to obtain the anticorrosive concrete additive.

[0050] Example 3

[0051] This embodiment provides an anti-corrosion concrete additive and a preparation method thereof, and the specific preparation method comprises the following steps:

[0052] (1) Preparation of modified plant fibers:

[0053] S1. Drying and crushing corn stalk fiber and sorghum stalk fiber to a particle size of 100-200 μm, sieving, placing in a closed environment with an oxygen content of 2-2.5%, heating to 340° C. at 10° C. / min, keeping the temperature constant for 15 min, and cooling to room temperature to obtain semi-carbonized plant fiber;

[0054] S2. Weigh 12 g of trifluoropropyltriethoxysilane, 30 g of ethanol and 58 g of water and mix them evenly to obtain a fluorosilane solution; mix 8 g of semi-carbonized plant fiber with 12 g of the fluorosilane solution, microwave oscillate at 800 W for 10 min, filter, and dry at 60° C. for 2 h to obtain silane-modified plant fiber.

[0055] (2) Preparation of water reducing agent:

[0056] A1. Mix 10 g of histidine, 25 g of p-toluenesulfonic acid and 150 g of water, heat and stir at 85°C for 2 h, and cool to room temperature to obtain histidine p-toluenesulfonate;

[0057] A2, 40g of histidine p-toluenesulfonate, 10g of isopentanol polyoxyethylene ether and 80g of water were mixed, 2g of p-toluenesulfonic acid was added, and esterification reaction was carried out at 130°C for 2.5h, and cooled to room temperature to obtain a macromonomer mixture;

[0058] A3, 40g of acrylic acid, 22g of acrylic acid-α-hydroxyethyl ester, 3g of dimethyldiallylammonium chloride and 120g of water were mixed to obtain a first solution; 0.4g of ammonium persulfate, 0.5g of mercaptopropionic acid and 50g of water were mixed to obtain a second solution; 10g of the macromonomer mixture was evenly mixed with 50g of water, heated to 80°C while stirring, and the peristaltic pump was adjusted to control the first solution and the second solution to be simultaneously added dropwise to the macromonomer mixture solution for 2h. After the addition was completed, the reaction was continued to be kept warm for 1.5h. After the reaction was completed, it was cooled to room temperature, the pH value was adjusted to 6.5-7.5 with 30% sodium hydroxide solution, and the solution was purified by ultrafiltration membrane (molecular weight cutoff of 1000Da) to remove unreacted monomers and small molecule by-products, and concentrated to a solid content of 40%, thereby obtaining the water reducer.

[0059] (3) Weigh 80 g of fly ash, 6 g of calcium nitrite and 30 g of water, mix them evenly, then add 20 g of modified plant fiber and 8 g of water reducer, and stir at a speed of 1000 r / min for 30 min to obtain the anti-corrosion concrete additive.

[0060] Example 4

[0061] This embodiment provides an anti-corrosion concrete additive and a preparation method thereof, and the specific preparation method comprises the following steps:

[0062] (1) Preparation of modified plant fibers:

[0063] S1. Drying and crushing corn stalk fiber and sorghum stalk fiber to a particle size of 100-200 μm, sieving, placing in a closed environment with an oxygen content of 2-2.5%, heating to 340° C. at 8.5° C. / min, keeping the temperature constant for 18 min, and cooling to room temperature to obtain semi-carbonized plant fiber;

[0064] S2. Weigh 11 g of trifluoropropyltriethoxysilane, 24 g of ethanol and 65 g of water and mix them evenly to obtain a fluorosilane solution; mix 7 g of semi-carbonized plant fiber with 11 g of the fluorosilane solution, microwave oscillate at a power of 500 W for 18 min, filter, and dry at 60° C. for 2 h to obtain silane-modified plant fiber.

[0065] (2) Preparation of water reducing agent:

[0066] A1. Mix 10 g of histidine, 21 g of p-toluenesulfonic acid and 140 g of water, heat and stir at 80°C for 2 h, and cool to room temperature to obtain histidine p-toluenesulfonate;

[0067] A2, 36g of histidine p-toluenesulfonate, 10g of isopentanol polyoxyethylene ether and 75g of water were mixed, 1.0g of p-toluenesulfonic acid was added, and esterification reaction was carried out at 120°C for 2.5h, and cooled to room temperature to obtain a macromonomer mixture;

[0068] A3, 38g of acrylic acid, 19g of acrylic acid-α-hydroxyethyl ester, 2.8g of dimethyldiallylammonium chloride and 110g of water were mixed to obtain a first solution; 0.35g of ammonium persulfate, 0.4g of mercaptopropionic acid and 45g of water were mixed to obtain a second solution; 10g of the macromonomer mixture was evenly mixed with 45g of water, heated to 80°C while stirring, and the peristaltic pump was adjusted to control the first solution and the second solution to be simultaneously added dropwise to the macromonomer mixture solution for 2.5h. After the addition was completed, the reaction was continued to be kept warm for 1.8h. After the reaction was completed, it was cooled to room temperature, the pH value was adjusted to 6.5-7.5 with 30% sodium hydroxide solution, and the solution was purified by ultrafiltration membrane (molecular weight cutoff of 1000Da) to remove unreacted monomers and small molecule by-products, and concentrated to a solid content of 35%, thereby obtaining the water reducer.

[0069] (3) Weigh 50 g of fly ash, 2 g of calcium nitrite, 2 g of sodium hexametaphosphate and 25 g of water, mix them evenly, then add 16 g of modified plant fiber and 6 g of water reducer, and stir at a speed of 800 r / min for 25 min to obtain the anti-corrosion concrete additive.

[0070] Comparative Example 1

[0071] This embodiment provides an anti-corrosion concrete additive and a preparation method thereof, and the specific preparation method comprises the following steps:

[0072] (1) Preparation of modified plant fibers:

[0073] S1. Drying and crushing corn stalk fiber and sorghum stalk fiber to a particle size of 100-200 μm, sieving, placing in a closed environment with an oxygen content of 2-2.5%, heating to 320-340° C. at 8° C. / min, keeping the temperature constant for 15 min, and cooling to room temperature to obtain semi-carbonized plant fiber;

[0074] S2. Weigh 10 g of trifluoropropyltriethoxysilane, 25 g of ethanol and 65 g of water and mix them evenly to obtain a fluorosilane solution; mix 6.5 g of semi-carbonized plant fiber with 11 g of the fluorosilane solution, microwave oscillate at a power of 600 W for 15 min, filter, and dry at 60° C. for 2 h to obtain silane-modified plant fiber.

[0075] (2) Preparation of water reducing agent:

[0076] 39g of acrylic acid, 20g of α-hydroxyethyl acrylic acid, 2.5g of dimethyldiallylammonium chloride and 100g of water are mixed to obtain a first solution; 0.35g of ammonium persulfate, 0.45g of mercaptopropionic acid and 40g of water are mixed to obtain a second solution; 10g of isopentanol polyoxyethylene ether is evenly mixed with 45g of water, heated to 75°C while stirring, and the peristaltic pump is adjusted to control the first solution and the second solution to be simultaneously added dropwise to the macromonomer mixture solution for 3h. After the addition is completed, the reaction is continued by heat preservation for 1.5h. After the reaction is completed, the solution is cooled to room temperature, the pH value is adjusted to 6.5-7.5 with 30% sodium hydroxide solution, and the solution is purified by ultrafiltration membrane (molecular weight cutoff is 1000Da) to remove unreacted monomers and small molecule by-products, and concentrated to a solid content of 35%, thereby obtaining the water reducer.

[0077] (3) Weigh 60 g of fly ash, 4.5 g of calcium nitrite and 20 g of water, mix them evenly, then add 15 g of modified plant fiber and 6.5 g of water reducer, and stir at a speed of 800 r / min for 20 min to obtain the anti-corrosion concrete additive.

[0078] Comparative Example 2

[0079] This embodiment provides an anti-corrosion concrete additive and a preparation method thereof, and the specific preparation method comprises the following steps:

[0080] (1) Preparation of semi-carbonized plant fibers:

[0081] S1. Dry and crush corn stalk fiber and sorghum stalk fiber to a particle size of 100-200 μm, screen and place in a closed environment with an oxygen content of 2-2.5%, heat to 320-340° C. at 8° C. / min, keep the temperature constant for 15 minutes, and cool to room temperature to obtain semi-carbonized plant fiber.

[0082] (2) Preparation of water reducing agent:

[0083] A1. Mix 10 g of histidine, 22.5 g of p-toluenesulfonic acid and 125 g of water, heat and stir at 80° C. for 2-3 h, and cool to room temperature to obtain histidine p-toluenesulfonate;

[0084] A2, 38g of histidine p-toluenesulfonate, 10g of isopentanol polyoxyethylene ether and 65g of water were mixed, 1.2g of p-toluenesulfonic acid was added, and esterification reaction was carried out at 120°C for 3h, and cooled to room temperature to obtain a macromonomer mixture;

[0085] A3, 39g of acrylic acid, 20g of acrylic acid-α-hydroxyethyl ester, 2.5g of dimethyldiallylammonium chloride and 100g of water were mixed to obtain a first solution; 0.35g of ammonium persulfate, 0.45g of mercaptopropionic acid and 40g of water were mixed to obtain a second solution; 10g of the macromonomer mixture was evenly mixed with 45g of water, heated to 75°C while stirring, and the peristaltic pump was adjusted to control the first solution and the second solution to be simultaneously added dropwise to the macromonomer mixture solution for 3h. After the addition was completed, the reaction was continued to be kept warm for 1.5h. After the reaction was completed, it was cooled to room temperature, the pH value was adjusted to 6.5-7.5 with 30% sodium hydroxide solution, and the solution was purified by ultrafiltration membrane (molecular weight cutoff of 1000Da) to remove unreacted monomers and small molecule by-products, and concentrated to a solid content of 35%, thereby obtaining the water reducer.

[0086] (3) Weigh 60 g of fly ash, 4.5 g of calcium nitrite and 20 g of water, mix them evenly, then add 15 g of semi-carbonized plant fiber and 6.5 g of water reducer, and stir at a speed of 800 r / min for 20 min to obtain the anti-corrosion concrete additive.

[0087] Performance Testing

[0088] The anticorrosive concrete additives prepared in Examples 1-4 and Comparative Examples 1-2 were used to prepare concrete with a strength grade of C30, and the amount of the anticorrosive concrete additive added was 10%. Performance tests were performed, and test specimens were made according to GB / T50082-2009 "Standard for Test Methods for Long-term Performance and Durability of Ordinary Concrete", and the sulfate corrosion resistance grade and steel bar corrosion weight loss rate over time were tested; test specimens were made according to GB / T50081-2019 "Standard for Test Methods for Mechanical Properties of Ordinary Concrete", and the compressive strength of the test specimens was tested. The specific test results are shown in Table 1.

[0089] Table 1 Performance test

[0090]

[0091] It can be seen from the data in Table 1 that the anti-corrosion concrete additive prepared by the present invention can be applied to concrete to improve the corrosion resistance of concrete, reduce the weight loss rate of steel bar corrosion, prolong the anti-corrosion effect, and have good compressive strength.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An anticorrosive concrete additive, characterized in that: The invention comprises 40-80 parts of fly ash, 10-20 parts of modified plant fiber, 5-8 parts of water reducer, 3-6 parts of inorganic salt and 10-30 parts of water by weight. The modified plant fiber is obtained by grafting and modifying semi-carbonized plant fiber with fluorosilane. The water reducer is an amphoteric polycarboxylic acid water reducer.

2. The anticorrosive concrete additive according to claim 1, characterized in that: The preparation method of the modified plant fiber comprises: S1. After drying, crushing and screening the plant fiber, place it in a closed environment with an oxygen content of 2-2.5%, heat it to 320-340°C at a rate of 5-10°C / min, keep the temperature constant for 15-20min, and cool it to obtain semi-carbonized plant fiber; S2. Mixing the semi-carbonized plant fiber with the fluorosilane solution and subjecting the mixture to microwave vibration to obtain the silane-modified plant fiber.

3. The anticorrosive concrete additive according to claim 2, characterized in that: In step S2, the mass ratio of the semi-carbonized plant fiber to the fluorosilane solution is 5-8:10-12, and the fluorosilane solution is obtained by mixing fluorosilane, ethanol and water.

4. The anticorrosive concrete additive according to claim 3, characterized in that: The plant fiber includes one or more of corn stalk fiber, sorghum stalk fiber and bamboo fiber, and the fluorosilane includes trifluoropropyl trimethoxy silane or trifluoropropyl triethoxy silane.

5. The anticorrosive concrete additive according to claim 1, characterized in that: The preparation method of the water reducing agent comprises: A1. Mix histidine, p-toluenesulfonic acid and water, and heat and stir at 75-85° C. to obtain histidine p-toluenesulfonate; A2, mixing histidine p-toluenesulfonate, isopentanol polyoxyethylene ether and water, adding a catalyst, and performing an esterification reaction at 110-130° C. for 2.5-3.5 hours to obtain a macromonomer mixture; A3. Prepare a first solution and a second solution, wherein the first solution is acrylic acid, α-hydroxyethyl acrylic acid, dimethyldiallylammonium chloride and water, and the second solution is ammonium persulfate, mercaptopropionic acid and water; mix the macromonomer mixture and water evenly, heat while stirring, adjust the peristaltic pump to control the first solution and the second solution to be added to the macromonomer mixture solution, wherein the first solution is added for 2-4 hours, and the second solution is added for 2-4 hours. After the addition is complete, keep the reaction warm for 1.5-2 hours, adjust the pH value to be neutral, and obtain the water reducer.

6. The anticorrosive concrete additive according to claim 5, characterized in that: In step A1, the mass ratio of histidine to p-toluenesulfonic acid is 1:2-2.

5.

7. The anticorrosive concrete additive according to claim 5, characterized in that: In step A2, the mass ratio of histidine p-toluenesulfonate to isopentenol polyoxyethylene ether is 3.5-4.0:1, the catalyst is p-toluenesulfonic acid, and the added amount of the catalyst is 2-5% of the mass of histidine p-toluenesulfonate.

8. The anticorrosive concrete additive according to claim 5, characterized in that: In step A3, the mass ratio of the macromonomer mixture, acrylic acid, α-hydroxyethyl acrylic acid and dimethyldiallylammonium chloride is 1:3.8-4.0:1.8-2.2:0.2-0.3, the amount of ammonium persulfate added is 0.3-0.4% of the mass of the macromonomer mixture, and the amount of mercaptopropionic acid added is 0.4-0.5% of the mass of the macromonomer mixture.

9. The anticorrosive concrete additive according to claim 1, characterized in that: The inorganic salt is calcium nitrite and / or sodium hexametaphosphate.

10. The method for preparing an anticorrosive concrete additive according to any one of claims 1 to 9, characterized in that: The following steps are involved: The fly ash, inorganic salt and water are weighed in parts by weight and mixed evenly, and then the modified plant fiber and water reducing agent are added, and stirred at a rotation speed of 500-1000 r / min for 10-30 minutes to obtain the anticorrosive concrete additive.

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