An anti-corrosion concrete additive and its preparation method

Abstract

The present 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. The concrete additive, by weight, 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, 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. In the anticorrosive concrete additive provided by the present invention, 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, and the multi-component composite enables the additive to comprehensively improve the comprehensive performance of concrete, especially the anticorrosion ability and service life in harsh environments.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical additives for building materials, and particularly to an anti-corrosion 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, and has the advantages of rich raw materials, low price, high strength, etc. However, the durability problem of concrete structures, especially the corrosion of steel bars in reinforced concrete, seriously affects the service safety and service life of the structures. In special environments such as the ocean and salt lakes, the erosion of chloride ions and sulfates is the main factor leading to the damage of concrete structures. Chloride ions penetrate into the surface of steel bars through the pores of concrete, and when the concentration reaches about 0.4%, the passivation film can be damaged, accelerating the corrosion of steel bars; while sulfate erosion will cause the concrete to expand, crack, and spall, losing its strength and viscosity. Research shows that hydrostatic pressure and seawater impact will accelerate the penetration of harmful ions into the interior of concrete, and the corrosion degrees of concrete in different marine zones (tidal zone, underwater zone, atmospheric zone) are also different. At present, the methods to improve the corrosion resistance of concrete mainly include reducing the water-cement ratio, using cement with better erosion resistance, adding mineral admixtures, using surface coatings, and adding anti-corrosion additives, etc.

[0003] Chinese Patent CN202011138536.1 discloses an anti-corrosion concrete and a preparation method thereof. The anti-corrosion concrete includes 6-10 parts of methylbenzotriazole; 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; 200-250 parts of water. The preparation method is as follows: Step 1), mix cement, fly ash, sand, and silane impregnating agent together and stir evenly to obtain anti-corrosion concrete powder; Step 2), mix methylbenzotriazole and dibutyltin dilaurate evenly, then add them to the anti-corrosion concrete powder, stir evenly, and then add water and mix and stir evenly to obtain anti-corrosion concrete slurry; Step 3), pour the anti-corrosion concrete slurry into a mold and fix it into shape. In this patent, through the cooperation of barium stearate and silane impregnating agent, the anti-corrosion effect of the silane impregnating agent on concrete is improved, thereby extending the service life of the concrete structure. However, the above technical solution mainly realizes anti-corrosion through chemical additives, and the anti-corrosion effect is limited. And the chemical additives may gradually fail in a harsh environment and cannot effectively cope with long-term cyclic corrosion; at the same time, the existence of pores in the concrete will increase the risk of penetration of harmful substances, thereby affecting the long-term anti-corrosion effect. Summary of the Invention

[0004] In view of this, the present invention provides an anti-corrosion concrete additive and its preparation method to solve the problems of poor anti-corrosion effect and durability of concrete in the prior art, and the inability to effectively cope with long-term cyclic corrosion.

[0005] The technical solution of the present invention is realized as follows: The present invention provides an anti-corrosion concrete additive, which includes 40 - 80 parts by weight 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. The modified plant fiber is obtained by grafting modification of semi-carbonized plant fiber with fluorosilane; the water reducer is an amphoteric polycarboxylate water reducer.

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

[0007] Furthermore, fly ash refines the pore structure through the pozzolanic reaction, while the modified plant fiber forms a three-dimensional network to fill the micro-pores. Through the synergistic effect of fly ash and the modified plant fiber, the permeability of the concrete can be significantly reduced, effectively preventing the intrusion of corrosive substances; the inorganic salt forms a protective film on the surface of the steel bars, and groups such as amino and carboxyl 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 fiber can also prevent the penetration of water and harmful ions, jointly enhancing the anti-corrosion ability and durability of the concrete.

[0008] Based on the above technical solutions, preferably, the preparation method of the modified plant fiber includes:

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

[0010] S2. Mix the semi-carbonized plant fiber with a fluorosilane solution and perform microwave oscillation 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] Based on the above technical solutions, preferably, in step S2, the mass ratio of the semi-carbonized plant fiber to 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] Based on the above technical solutions, preferably, the plant fiber includes one or more of corn stalk fiber, sorghum stalk fiber, and bamboo fiber, and the fluorosilane includes 3,3,3-trifluoropropyltrimethoxysilane or 3,3,3-trifluoropropyltriethoxysilane.

[0013] Specifically, in step S1, by performing semi-carbonization treatment on 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 have hydrophobic properties, and the hydrophobic surface can effectively prevent the penetration of moisture and harmful ions, enhancing the anti-corrosion performance of the concrete.

[0014] Based on the above technical solutions, preferably, the preparation method of the water reducer includes:

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

[0016] A2. Mix histidine p-toluenesulfonate, isopentenyl alcohol polyoxyethylene ether, and water, add a catalyst, and perform an esterification reaction at 110 - 130 °C for 2.5 - 3.5 h to obtain a macromonomer mixture;

[0017] A3. Prepare a first solution and a second solution. The first solution is acrylic acid, acrylic acid-α-hydroxyethyl ester, dimethyldiallylammonium chloride, and water, and the second solution is ammonium persulfate, mercaptopropionic acid, and water; mix the macromonomer mixture evenly with water, heat while stirring, adjust the peristaltic pump to control the addition of the first solution and the second solution into the macromonomer mixture solution. The dropping time of the first solution is 2 - 4 h, and the dropping time of the second solution is 2 - 4 h. After dropping, keep the reaction at a constant temperature for 1.5 - 2 h, and adjust the pH value to neutral to obtain the water reducer.

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

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

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

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

[0022] Based on the above technical solutions, preferably, the inorganic salt is calcium nitrite and / or sodium hexametaphosphate.

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

[0024] The anti-corrosion concrete additive and its preparation method 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 fibers, amphoteric polycarboxylate water reducer, and inorganic salts. Fly ash fills the pores of concrete and improves the microstructure; modified plant fibers enhance the mechanical properties and crack resistance of concrete; the amphoteric polycarboxylate water reducer not only improves the workability of concrete but also forms a protective film on the surface of steel bars; inorganic salts further enhance 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 polycarboxylate water reducer contains an imidazole ring derived from histidine, an amino group, and the benzene ring and sulfonic acid group of p-toluenesulfonic acid, 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 molecule can form coordination bonds with metallic iron to enhance the adsorption force; the large-sized aromatic ring and polyether chain segments form steric hindrance to block corrosive ions; the sulfonic acid group further enhances adsorption through electrostatic action, jointly improving the anti-corrosion performance of steel bars and at the same time improving the fluidity and compactness of concrete;

[0027] (3) The plant fibers modified by semi-carbonization and fluoro-silane grafting have excellent hydrophobicity and alkali resistance. Semi-carbonization treatment increases the surface area and adsorption capacity of the fibers, while fluoro-silane grafting endows the fibers with hydrophobic properties. This modification not only improves the interfacial bonding strength between the fibers and the cement matrix but also effectively reduces the degradation of the fibers in an alkaline environment. At the same time, the network structure of the modified fibers helps to prevent crack propagation, enhancing the crack resistance and toughness of concrete, thereby indirectly improving the anti-corrosion performance of concrete;

[0028] (4) Inorganic salts can react chemically with the hydration products of cement to form insoluble compounds, filling the pores of concrete and improving the compactness of concrete; at the same time, inorganic salts may also produce a synergistic effect 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 anti-corrosion performance and durability of concrete. Specific Embodiments

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] Example 1

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

[0032] (1) Prepare modified plant fibers:

[0033] S1. Dry and crush corn stalk fibers and sorghum stalk fibers to a particle size of 100 - 200 μm. After screening, place them in a closed environment with an oxygen content of 2 - 2.5%, heat to 320 - 340 °C at a rate of 8 °C / min, keep the temperature constant for 15 min, and then cool to room temperature to obtain semi-carbonized plant fibers.

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

[0035] (2) Prepare a 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 then cool to room temperature to obtain histidine p-toluenesulfonate.

[0037] A2. Mix 38 g of histidine p-toluenesulfonate, 10 g of isopentenyl alcohol polyoxyethylene ether, and 65 g of water, add 1.2 g of p-toluenesulfonic acid, and perform an esterification reaction at 120 °C for 3 h, then cool to room temperature to obtain a macromonomer mixture.

[0038] A3. Mix 39 g of acrylic acid, 20 g of α-hydroxyethyl acrylate, 2.5 g of dimethyldiallylammonium chloride, and 100 g of water to obtain a first solution; mix 0.35 g of ammonium persulfate, 0.45 g of mercaptopropionic acid, and 40 g of water to obtain a second solution; mix 10 g of the macromonomer mixture with 45 g of water evenly, heat to 75 °C while stirring, adjust the peristaltic pump to control the simultaneous dropping of the first solution and the second solution into the macromonomer mixture solution, with a dropping time of 3 h. After dropping, continue to keep the temperature for reaction for 1.5 h. After the reaction is completed, cool to room temperature, adjust the pH value to 6.5 - 7.5 with 30% sodium hydroxide solution, purify the solution through an ultrafiltration membrane (cut-off molecular weight is 1000 Da) to remove unreacted monomers and small molecule by-products, and concentrate to a solid content of 35% to obtain the water reducing agent.

[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 fibers and 6.5 g of the water reducing agent, 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. The specific preparation method includes the following steps:

[0042] (1) Prepare modified plant fibers:

[0043] S1. Dry and crush corn stalk fibers and sorghum stalk fibers to a particle size of 100 - 200 μm. After screening, place them in a closed environment with an oxygen content of 2 - 2.5%, heat to 320 °C at a rate of 5 °C / min, keep the temperature constant for 15 min, and then cool to room temperature to obtain semi-carbonized plant fibers;

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

[0045] (2) Prepare a 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 then cool to room temperature to obtain histidine p-toluenesulfonate;

[0047] A2. Mix 35 g of histidine p-toluenesulfonate, 10 g of isopentenyl alcohol polyoxyethylene ether, and 50 g of water, add 0.7 g of p-toluenesulfonic acid, perform an esterification reaction at 110 °C for 3.5 h, and then cool to room temperature to obtain a macromonomer mixture;

[0048] A3. Mix 38 g of acrylic acid, 18 g of acrylic acid-α-hydroxyethyl ester, 2 g of dimethyldiallylammonium chloride, and 80 g of water to obtain a first solution; mix 0.3 g of ammonium persulfate, 0.4 g of mercaptopropionic acid, and 30 g of water to obtain a second solution; mix 10 g of the macromonomer mixture with 40 g of water evenly, heat to 75 °C while stirring, adjust the peristaltic pump to control the simultaneous dropping of the first solution and the second solution into the macromonomer mixture solution, the dropping time is 4 h, after dropping, continue to keep the temperature for reaction for 2 h, after the reaction ends, cool to room temperature, adjust the pH value to 6.5 - 7.5 with 30% sodium hydroxide solution, purify the solution through an ultrafiltration membrane (cut-off molecular weight is 1000 Da) to remove unreacted monomers and small molecule by-products, and concentrate to a solid content of 30% to obtain the water reducing agent.

[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 fibers and 5 g of the water reducing agent, and stir at a speed of 500 r / min for 30 min to obtain the anti-corrosion concrete additive.

[0050] Example 3

[0051] This example provides an anti-corrosion concrete additive and its preparation method. The specific preparation method includes the following steps:

[0052] (1) Prepare modified plant fibers:

[0053] S1. Dry and crush corn stalk fibers and sorghum stalk fibers to a particle size of 100 - 200 μm. After screening, place them in a closed environment with an oxygen content of 2 - 2.5%, heat to 340 °C at a rate of 10 °C / min, keep the temperature constant for 15 min, and then cool to room temperature to obtain semi-carbonized plant fibers;

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

[0055] (2) Prepare a water reducer:

[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 then cool to room temperature to obtain histidine p-toluenesulfonate;

[0057] A2. Mix 40 g of histidine p-toluenesulfonate, 10 g of isopentenyl alcohol polyoxyethylene ether, and 80 g of water, add 2 g of p-toluenesulfonic acid, perform an esterification reaction at 130 °C for 2.5 h, and then cool to room temperature to obtain a macromonomer mixture;

[0058] A3. Mix 40 g of acrylic acid, 22 g of acrylic acid-α-hydroxyethyl ester, 3 g of dimethyldiallylammonium chloride, and 120 g of water to obtain a first solution; mix 0.4 g of ammonium persulfate, 0.5 g of mercaptopropionic acid, and 50 g of water to obtain a second solution; mix 10 g of the macromonomer mixture evenly with 50 g of water, heat to 80 °C while stirring, adjust the peristaltic pump to control the simultaneous dropping of the first solution and the second solution into the macromonomer mixture solution. The dropping time is 2 h. After dropping, continue to keep the temperature for reaction for 1.5 h. After the reaction is completed, cool to room temperature, adjust the pH value to 6.5 - 7.5 with 30% sodium hydroxide solution, purify the solution through an ultrafiltration membrane (cut-off molecular weight is 1000 Da) to remove unreacted monomers and small molecular by-products, and concentrate to a solid content of 40% to obtain 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 fibers 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 example provides an anti-corrosion concrete additive and a preparation method thereof. The specific preparation method includes the following steps:

[0062] (1) Prepare modified plant fibers:

[0063] S1. Dry and crush corn stalk fibers and sorghum stalk fibers to a particle size of 100 - 200 μm. After screening, place them in a closed environment with an oxygen content of 2 - 2.5%, heat to 340 °C at a rate of 8.5 °C / min, keep the temperature constant for 18 min, and then cool to room temperature to obtain semi-carbonized plant fibers;

[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 fibers with 11 g of the fluorosilane solution, perform microwave oscillation at a power of 500 W for 18 min, filter, and dry at 60 °C for 2 h to obtain silane-modified plant fibers.

[0065] (2) Prepare a 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 then cool to room temperature to obtain histidine p-toluenesulfonate;

[0067] A2. Mix 36 g of histidine p-toluenesulfonate, 10 g of isopentenyl alcohol polyoxyethylene ether, and 75 g of water, add 1.0 g of p-toluenesulfonic acid, perform esterification reaction at 120 °C for 2.5 h, and then cool to room temperature to obtain a macromonomer mixture;

[0068] A3. Mix 38 g of acrylic acid, 19 g of α-hydroxyethyl acrylate, 2.8 g of dimethyldiallylammonium chloride, and 110 g of water to obtain a first solution; mix 0.35 g of ammonium persulfate, 0.4 g of mercaptopropionic acid, and 45 g of water to obtain a second solution; mix 10 g of the macromonomer mixture with 45 g of water evenly, heat to 80 °C while stirring, adjust the peristaltic pump to control the simultaneous dropping of the first solution and the second solution into the macromonomer mixture solution, the dropping time is 2.5 h, after dropping, continue to keep the temperature for reaction for 1.8 h. After the reaction is completed, cool to room temperature, adjust the pH value to 6.5 - 7.5 with 30% sodium hydroxide solution, purify the solution through an ultrafiltration membrane (cut-off molecular weight is 1000 Da) to remove unreacted monomers and small molecule by-products, and concentrate to a solid content of 35% to obtain the water reducing agent.

[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 example provides an anti-corrosion concrete additive and its preparation method. The specific preparation method includes the following steps:

[0072] (1) Prepare modified plant fiber:

[0073] S1. Dry and crush corn stalk fiber and sorghum stalk fiber to a particle size of 100 - 200 μm. After screening, place them in a closed environment with an oxygen content of 2 - 2.5%, heat to 320 - 340 °C at a rate of 8 °C / min, keep the temperature constant for 15 min, and then cool to room temperature to obtain semi-carbonized plant fiber.

[0074] S2. Weigh 10 g of 3-trifluoropropyltriethoxysilane, 25 g of ethanol and 65 g of water, mix them evenly to obtain a fluorosilane solution; mix 6.5 g of semi-carbonized plant fiber with 11 g of fluorosilane solution, perform microwave oscillation 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) Prepare water reducer:

[0076] Mix 39 g of acrylic acid, 20 g of acrylic acid-α-hydroxyethyl ester, 2.5 g of dimethyldiallylammonium chloride and 100 g of water to obtain a first solution; mix 0.35 g of ammonium persulfate, 0.45 g of mercaptopropionic acid and 40 g of water to obtain a second solution; mix 10 g of isopentenyl alcohol polyoxyethylene ether with 45 g of water evenly, heat to 75 °C while stirring, adjust the peristaltic pump to control the simultaneous dropping of the first solution and the second solution into the macromonomer mixture solution. The dropping time is 3 h. After dropping, continue to keep the temperature for reaction for 1.5 h. After the reaction ends, cool to room temperature, adjust the pH value to 6.5 - 7.5 with 30% sodium hydroxide solution, purify the solution through an ultrafiltration membrane (cut-off molecular weight is 1000 Da) to remove unreacted monomers and small molecule by-products, and concentrate to a solid content of 35% to obtain 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. The specific preparation method includes the following steps:

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

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

[0082] (2) Prepare a 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 then cool to room temperature to obtain histidine p-toluenesulfonate.

[0084] A2. Mix 38 g of histidine p-toluenesulfonate, 10 g of isopentenyl alcohol polyoxyethylene ether, and 65 g of water, add 1.2 g of p-toluenesulfonic acid, and carry out an esterification reaction at 120 °C for 3 h. After cooling to room temperature, obtain a macromonomer mixture.

[0085] A3. Mix 39 g of acrylic acid, 20 g of acrylic acid-α-hydroxyethyl ester, 2.5 g of dimethyldiallylammonium chloride, and 100 g of water to obtain a first solution; mix 0.35 g of ammonium persulfate, 0.45 g of mercaptopropionic acid, and 40 g of water to obtain a second solution; mix 10 g of the macromonomer mixture evenly with 45 g of water, heat to 75 °C while stirring, adjust the peristaltic pump to control the simultaneous dropping of the first solution and the second solution into the macromonomer mixture solution. The dropping time is 3 h. After dropping, continue to keep the temperature for reaction for 1.5 h. After the reaction is completed, cool to room temperature, adjust the pH value to 6.5 - 7.5 with 30% sodium hydroxide solution, purify the solution through an ultrafiltration membrane (cut-off molecular weight of 1000 Da) to remove unreacted monomers and small molecule by-products, and concentrate to a solid content of 35% to obtain the water-reducing agent.

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

[0087] Performance testing

[0088] The anti-corrosion concrete additives prepared in Examples 1-4 and Comparative Examples 1-2 were used to prepare concrete. Concrete with a strength grade of C30 was prepared, and the addition amount of the anti-corrosion concrete additive was 10%. Performance tests were carried out. Specimens were made in accordance with the Standard Test Method for Long-Term and Durability Performance of Ordinary Concrete (GB / T 50082-2009) to test the anti-sulfate erosion grade and the loss rate of steel bar corrosion weight at the test time; specimens were made in accordance with the Standard Test Method for Mechanical Properties of Ordinary Concrete (GB / T 50081-2019) to test the compressive strength of the specimens. The specific test results are shown in Table 1.

[0089] Table 1 Performance Tests

[0090]

[0091] It can be seen from the data in Table 1 that the anti-corrosion concrete additive prepared by the present invention can improve the anti-corrosion performance of concrete when applied to concrete, with a low loss rate of steel bar corrosion weight, an extended anti-corrosion effect, and good compressive strength.

[0092] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An anticorrosive concrete additive, characterized in that: The invention comprises, by weight, 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, wherein the modified plant fiber is obtained by grafting and modifying the semi-carbonized plant fiber with fluorosilane; The water reducer is an amphoteric polycarboxylic acid water reducer; 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; 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.

2. The anticorrosive concrete additive according to claim 1, 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.

3. The anticorrosive concrete additive according to claim 2, 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.

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

5.

5. The anticorrosive concrete additive according to claim 1, 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.

6. The anticorrosive concrete additive according to claim 1, 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.

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

8. A method for preparing an anticorrosive concrete additive according to any one of claims 1 to 7, 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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