Pccp pipe crack grouting repair slurry and preparation method thereof

Abstract

The application discloses a PCCP pipe crack grouting repair slurry and a preparation method thereof, and relates to the technical field of grouting materials. In the preparation of the PCCP pipe crack grouting repair slurry, an antioxidant is prepared by reacting 2,6-di-tert-butyl-4-hydroxymethylphenol with bis(2-furan) chlorophosphine, and then reacting with N-(2-hydroxyethyl) maleimide to obtain a chain extender; modified carbon fibers are prepared by reacting oxidized carbon fibers with 4-amino-2,2,6,6-tetramethylpiperidine, and then mixed with polycarboxylic acid water reducing agent and deionized water to obtain a modified carbon fiber dispersion liquid; the PCCP pipe crack grouting repair slurry is prepared by reacting polyurethane prepolymer, polymethylene polyphenyl polyisocyanate, the chain extender, cystamine and the modified carbon fiber dispersion liquid. The PCCP pipe crack grouting repair slurry prepared by the application has good flame-retardant, self-repairing, anti-aging performance and bonding strength.

Description

Technical Field

[0001] This invention relates to the field of grouting materials technology, specifically to a grouting repair material for PCCP pipe cracks and its preparation method. Background Technology

[0002] PCCP pipes are mainly composed of a concrete core, steel cylinder, prestressed steel wire, and mortar protective layer. Due to their high strength, high sealing performance, and high impermeability, they are widely used in large-scale water transmission projects between inter-regional water sources, such as the Liaoning Northwest Water Supply Project. However, due to external loads and climate influences, cracks in the concrete core are inevitable. Therefore, repairing concrete cracks has always been a key focus in engineering projects. To date, the main crack repair methods used in engineering practice include surface treatment, filling, and chemical grouting. Chemical grouting is suitable for crack repair in many special environments. For example, for crack repair under high-speed water flow conditions, surface treatment and filling methods often result in problems such as material peeling, detachment, and erosion, leading to poor repair results. In contrast, the grouting material used in chemical grouting has good wetting ability on concrete, high bonding strength with the crack surface, and does not damage the integrity of the concrete structure surface. Therefore, chemical grouting is considered an ideal crack repair method.

[0003] Polyurethane grouting material is one of the most commonly used organic polymer grouting materials. It stands out among many chemical grouting materials due to its non-toxic, harmless, safe, reliable, highly impermeable, controllable curing speed, and good chemical stability and durability. However, polyurethane grouting materials have a fast reaction rate and release a large amount of heat during curing. Due to its poor thermal conductivity, heat can easily accumulate locally, leading to spontaneous combustion and posing a safety hazard in practical engineering operations. Therefore, the development of polyurethane grouting materials with low heat storage and excellent flame retardant properties has received widespread attention. Summary of the Invention

[0004] The purpose of this invention is to provide a grout for repairing cracks in PCCP pipes and its preparation method, so as to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A PCCP pipe crack grouting and repair grout is prepared by reacting polyurethane prepolymer, polymethylene polyphenyl polyisocyanate, chain extender, cystamine, and modified carbon fiber dispersion.

[0006] As an optimization, the chain extender is prepared by reacting 2,6-di-tert-butyl-4-hydroxymethylphenol with di(2-furan)phosphine chloride to obtain an antioxidant, and then reacting it with N-(2-hydroxyethyl)maleimide.

[0007] As an optimization, the modified carbon fiber dispersion is prepared by reacting oxidized carbon fiber with 4-amino-2,2,6,6-tetramethylpiperidine to obtain modified carbon fiber, and then mixing it with polycarboxylate superplasticizer and deionized water.

[0008] As an optimization, the polycarboxylate superplasticizer is an ether-based high-efficiency polycarboxylate superplasticizer with a solid content of 40%.

[0009] A method for preparing a grout for repairing cracks in PCCP pipes includes the following preparation steps: (1) Mix 2,6-di-tert-butyl-4-hydroxymethylphenol, triethylamine and toluene evenly, add di(2-furan)phosphine chloride at 10~15℃, heat to 75~85℃, stir and react for 3~5h, cool to room temperature, filter, distill under reduced pressure and dry to obtain antioxidant; mix antioxidant, N-(2-hydroxyethyl)maleimide and N,N-dimethylformamide evenly, stir and react at 75~85℃ for 20~24h, cool to room temperature, filter, wash and dry to obtain chain extender; (2) The oxidized carbon fiber, 4-amino-2,2,6,6-tetramethylpiperidine, N,N'-dicyclohexylcarboimide and tetrahydrofuran were mixed evenly and stirred at room temperature for 4-6 h. The mixture was then filtered, washed and dried to obtain the modified carbon fiber. (3) Mix the modified carbon fiber, polycarboxylate superplasticizer and deionized water evenly, and ultrasonically disperse them to obtain the modified carbon fiber dispersion; mix the polyurethane prepolymer, polymethylene polyphenyl polyisocyanate, chain extender and cystamine evenly, stir at 40~50℃ for 5~10min, add the modified carbon fiber dispersion, stir at room temperature for 8~15min, let stand for 3~5min to obtain the PCCP pipe crack grouting repair slurry.

[0010] As an optimization, the preparation steps of the chain extender in step (1) are as follows: 2,6-di-tert-butyl-4-hydroxymethylphenol, triethylamine, and toluene are mixed evenly at a mass ratio of 1:(0.4~0.45):(6~8). At 10~15℃, 0.78~0.82 times the mass of 2,6-di-tert-butyl-4-hydroxymethylphenol di(2-furan)phosphine chloride is added. The temperature is raised to 75~85℃, and the reaction is stirred for 3~5 hours. After cooling to room temperature, the mixture is filtered. Toluene was removed by vacuum distillation, and the product was dried under vacuum at 50-60°C for 10-12 hours to obtain an antioxidant. The antioxidant, N-(2-hydroxyethyl)maleimide, and N,N-dimethylformamide were mixed in a mass ratio of 1:(0.3-0.4):(5-10), and the mixture was stirred at 75-85°C for 20-24 hours. After cooling to room temperature, the mixture was filtered and washed 3-5 times with ether. The product was then dried under vacuum at 50-60°C for 10-12 hours to obtain a chain extender.

[0011] As an optimization, the preparation steps of the modified carbon fiber in step (2) are as follows: oxidized carbon fiber, 4-amino-2,2,6,6-tetramethylpiperidine, N,N'-dicyclohexylcarboimide and tetrahydrofuran are mixed evenly in a mass ratio of 1:(0.6~0.8):(0.8~1):(10~12), stirred and reacted at room temperature for 4~6h, filtered and washed 3~5 times with anhydrous ethanol, and dried under vacuum at 50~60℃ for 10~12h to obtain the modified carbon fiber.

[0012] As an optimization, the preparation steps of the PCCP pipe crack grouting repair slurry in step (3) are as follows: Modified carbon fiber, polycarboxylate superplasticizer, and deionized water are mixed evenly at a mass ratio of 1:(2~3):(0.2~0.3), and ultrasonically dispersed for 20~40 min to obtain modified carbon fiber dispersion; polyurethane prepolymer, polymethylene polyphenyl polyisocyanate, chain extender, and cystamine are mixed evenly at a mass ratio of 1:(0.6~0.8):(0.2~0.3):(0.2~0.3), stirred at 40~50℃ for 5~10 min, and modified carbon fiber dispersion of 0.01~0.02 times the mass of polyurethane prepolymer is added at a rate of 1~2 mL / min, stirred at room temperature for 8~15 min, and allowed to stand for 3~5 min to remove air bubbles to obtain PCCP pipe crack grouting repair slurry.

[0013] As an optimization, the preparation steps of the oxidized carbon fiber are as follows: immerse the carbon fiber in ultrapure water, treat it at 65℃ for 20~24h, and dry it at 120℃ for 4h to obtain pretreated carbon fiber; immerse the pretreated carbon fiber in 30wt% nitric acid aqueous solution, modify it at 100℃ for 2h, take it out and wash it with ultrapure water until the pH is neutral, and dry it at 120℃ for 4h to obtain oxidized carbon fiber.

[0014] As an optimization, the preparation steps of the polyurethane prepolymer are as follows: under a nitrogen atmosphere, polymethylene polyphenyl polyisocyanate and polyether polyol are mixed evenly at a molar ratio of isocyanate group to hydroxyl group of 1:(0.5~0.6), and an organic bismuth compound of 0.004~0.006 times the mass of polymethylene polyphenyl polyisocyanate is added. The mixture is stirred and reacted at 80~90℃ for 6~8h to obtain the polyurethane prepolymer.

[0015] As an optimization, the carbon fibers have a diameter of 5~50nm and a length of 5~50µm, and were purchased from Hangzhou Gaoke Composite Materials Co., Ltd.

[0016] As an optimization, the polyether polyol is a mixture of polyether polyol N303 and polyether polyol N210, wherein the weight average molecular weight of polyether polyol N303 is 3000, the weight average molecular weight of polyether polyol N210 is 1000, and the mass ratio of polyether polyol N303 to polyether polyol N210 is 1:(0.4~0.5).

[0017] As an optimization, the organobismuth compound is designated as BiCAT 8118.

[0018] As an optimization, the reaction process of the antioxidant is as follows: .

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are: In preparing the PCCP pipe crack grouting repair slurry, this invention involves reacting 2,6-di-tert-butyl-4-hydroxymethylphenol with di(2-furan)phosphine chloride to obtain an antioxidant, which is then reacted with N-(2-hydroxyethyl)maleimide to obtain a chain extender. Oxidized carbon fiber is reacted with 4-amino-2,2,6,6-tetramethylpiperidine to obtain modified carbon fiber, which is then mixed with polycarboxylate superplasticizer and deionized water to obtain a modified carbon fiber dispersion. Finally, a polyurethane prepolymer, polymethylene polyphenyl polyisocyanate, chain extender, cystamine, and modified carbon fiber dispersion are reacted to obtain the PCCP pipe crack grouting repair slurry.

[0020] First, an antioxidant is prepared by reacting 2,6-di-tert-butyl-4-hydroxymethylphenol with di(2-furan)phosphine chloride. The hydroxyl groups on 2,6-di-tert-butyl-4-hydroxymethylphenol react with the P-Cl on di(2-furan)phosphine chloride to generate an antioxidant containing phosphite and hindered phenolic structures. The hindered phenolic structure plays an antioxidant role by capturing all free radicals generated during aging. The phosphite structure acts as an auxiliary antioxidant, synergistically improving the antioxidant performance of the PCCP pipe crack grouting repair slurry. At the same time, the prepared antioxidant contains phosphorus and furan groups. The addition of phosphorus improves the flame retardant performance of the PCCP pipe crack grouting repair slurry. The furan groups on the antioxidant undergo a Diels-Alder reaction with N-(2-hydroxyethyl)maleimide to generate a chain extender with dynamic reversible covalent bonds, giving the PCCP pipe crack grouting repair slurry good self-healing properties.

[0021] Secondly, carbon fiber, as a reinforcing material, possesses excellent mechanical, electrical, and flame-retardant properties. Adding carbon fiber to grouting materials allows for the assessment of grout density by testing the electrical conductivity of the crack area. Immersing carbon fiber in nitric acid aqueous solution generates oxidized carbon fiber with carboxyl and hydroxyl groups on its surface. This oxidized carbon fiber then undergoes an amidation reaction with 4-amino-2,2,6,6-tetramethylpiperidine, introducing hindered amine structures onto the carbon fiber surface. This, in synergy with hindered phenols and phosphites, improves the oxidation resistance of the PCCP pipe crack grouting repair slurry. Simultaneously, the hydroxyl and other groups on the modified carbon fiber surface can react with isocyanate groups for cross-linking and curing, thereby enhancing the mechanical properties of the PCCP pipe crack grouting repair slurry. A modified carbon fiber dispersion is prepared by mixing modified carbon fiber with polycarboxylate superplasticizer and deionized water. The polycarboxylate superplasticizer is adsorbed onto the modified carbon fiber surface, preventing agglomeration of the modified carbon fiber through electrostatic repulsion and steric hindrance.

[0022] Finally, polyurethane prepolymer, polymethylene polyphenyl polyisocyanate, chain extender, cystamine, and modified carbon fiber dispersion are reacted to generate a PCCP pipe crack grouting repair slurry with good flame retardant, self-healing, antioxidant, and mechanical properties. Among them, the disulfide bond and DA bond in the cystamine structure work together to further improve the self-healing performance of the PCCP pipe crack grouting repair slurry. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Example 1

[0024] A method for preparing a grout for repairing cracks in PCCP pipes includes the following preparation steps: (1) 2,6-di-tert-butyl-4-hydroxymethylphenol, triethylamine, and toluene were mixed evenly in a mass ratio of 1:0.4:6. At 10°C, 0.78 times the mass of 2,6-di-tert-butyl-4-hydroxymethylphenol di(2-furan)phosphine chloride was added, the temperature was raised to 75°C, and the mixture was stirred for 3 hours. After cooling to room temperature, the mixture was filtered, toluene was removed by vacuum distillation, and the mixture was dried under vacuum at 50°C for 10 hours to obtain an antioxidant. The antioxidant, N-(2-hydroxyethyl)maleimide, and N,N-dimethylformamide were mixed evenly in a mass ratio of 1:0.3:5. After stirring for 20 hours at 75°C, the mixture was cooled to room temperature, filtered, and washed three times with ether. After drying under vacuum at 50°C for 10 hours, the chain extender was obtained. (2) The carbon fiber was immersed in ultrapure water, treated at 65℃ for 20h, and dried at 120℃ for 4h to obtain pretreated carbon fiber; the pretreated carbon fiber was immersed in 30wt% nitric acid aqueous solution, modified at 100℃ for 2h, taken out and washed with ultrapure water until the pH was neutral, and dried at 120℃ for 4h to obtain oxidized carbon fiber; the oxidized carbon fiber, 4-amino-2,2,6,6-tetramethylpiperidine, N,N'-dicyclohexylcarboimide and tetrahydrofuran were mixed evenly at a mass ratio of 1:0.6:0.8:10, stirred and reacted at room temperature for 4h, filtered and washed 3 times with anhydrous ethanol, and dried under vacuum at 50℃ for 10h to obtain modified carbon fiber; (3) Under a nitrogen atmosphere, polymethylene polyphenyl polyisocyanate and polyether polyol were mixed evenly at a molar ratio of isocyanate group to hydroxyl group of 1:0.5. Organic bismuth compound of 0.004 times the mass of polymethylene polyphenyl polyisocyanate was added and stirred at 80°C for 6 hours to obtain polyurethane prepolymer. Modified carbon fiber, polycarboxylate superplasticizer and deionized water were mixed evenly at a mass ratio of 1:2:0.2 and ultrasonically dispersed for 20 minutes to obtain modified carbon fiber dispersion. Polyurethane prepolymer, polymethylene polyphenyl polyisocyanate, chain extender and cystamine were mixed evenly at a mass ratio of 1:0.6:0.2:0.2 and stirred at 40°C for 5 minutes. Modified carbon fiber dispersion of 0.01 times the mass of polyurethane prepolymer was added at a rate of 1 mL / min. The mixture was stirred at room temperature for 8 minutes and allowed to stand for 3 minutes to remove air bubbles to obtain PCCP pipe crack grouting repair slurry. Example 2

[0025] A method for preparing a grout for repairing cracks in PCCP pipes includes the following preparation steps: (1) 2,6-di-tert-butyl-4-hydroxymethylphenol, triethylamine, and toluene were mixed evenly in a mass ratio of 1:0.42:7. At 12°C, 0.8 times the mass of 2,6-di-tert-butyl-4-hydroxymethylphenol di(2-furan)phosphine chloride was added, the temperature was raised to 80°C, and the mixture was stirred for 4 hours. After cooling to room temperature, the mixture was filtered, toluene was removed by vacuum distillation, and the mixture was dried under vacuum at 55°C for 11 hours to obtain an antioxidant. The antioxidant, N-(2-hydroxyethyl)maleimide, and N,N-dimethylformamide were mixed evenly in a mass ratio of 1:0.35:8. After stirring for 22 hours at 80°C, the mixture was cooled to room temperature, filtered, and washed 4 times with ether. After drying under vacuum at 55°C for 11 hours, the chain extender was obtained. (2) The carbon fiber was immersed in ultrapure water, treated at 65℃ for 22h, and dried at 120℃ for 4h to obtain pretreated carbon fiber; the pretreated carbon fiber was immersed in 30wt% nitric acid aqueous solution, modified at 100℃ for 2h, taken out and washed with ultrapure water until the pH was neutral, and dried at 120℃ for 4h to obtain oxidized carbon fiber; the oxidized carbon fiber, 4-amino-2,2,6,6-tetramethylpiperidine, N,N'-dicyclohexylcarboimide and tetrahydrofuran were mixed evenly at a mass ratio of 1:0.7:0.9:11, stirred and reacted at room temperature for 5h, filtered and washed 4 times with anhydrous ethanol, and dried under vacuum at 55℃ for 11h to obtain modified carbon fiber; (3) Under a nitrogen atmosphere, polymethylene polyphenyl polyisocyanate and polyether polyol were mixed evenly at a molar ratio of isocyanate group to hydroxyl group of 1:0.55. Organic bismuth compound of 0.005 times the mass of polymethylene polyphenyl polyisocyanate was added and stirred at 85°C for 7 h to obtain polyurethane prepolymer. Modified carbon fiber, polycarboxylate superplasticizer and deionized water were mixed evenly at a mass ratio of 1:2.5:0.25 and ultrasonically dispersed for 30 min to obtain modified carbon fiber dispersion. Polyurethane prepolymer, polymethylene polyphenyl polyisocyanate, chain extender and cystamine were mixed evenly at a mass ratio of 1:0.7:0.25:0.25 and stirred at 45°C for 8 min. Modified carbon fiber dispersion of 0.015 times the mass of polyurethane prepolymer was added at a rate of 1.5 mL / min. The mixture was stirred at room temperature for 12 min and allowed to stand for 4 min to remove air bubbles to obtain PCCP pipe crack grouting repair slurry. Example 3

[0026] A method for preparing a grout for repairing cracks in PCCP pipes includes the following preparation steps: (1) 2,6-di-tert-butyl-4-hydroxymethylphenol, triethylamine, and toluene were mixed evenly in a mass ratio of 1:0.45:8. At 15°C, 0.82 times the mass of 2,6-di-tert-butyl-4-hydroxymethylphenol di(2-furan)phosphine chloride was added. The mixture was heated to 85°C and stirred for 5 hours. After cooling to room temperature, the mixture was filtered, toluene was removed by vacuum distillation, and the mixture was dried under vacuum at 60°C for 12 hours to obtain an antioxidant. The antioxidant, N-(2-hydroxyethyl)maleimide, and N,N-dimethylformamide were mixed evenly in a mass ratio of 1:0.4:10. After stirring for 24 hours at 85°C, the mixture was cooled to room temperature, filtered, and washed 5 times with ether. After drying under vacuum at 60°C for 12 hours, the chain extender was obtained. (2) The carbon fiber was immersed in ultrapure water, treated at 65℃ for 24h, and dried at 120℃ for 4h to obtain pretreated carbon fiber; the pretreated carbon fiber was immersed in 30wt% nitric acid aqueous solution, modified at 100℃ for 2h, taken out and washed with ultrapure water until the pH was neutral, and dried at 120℃ for 4h to obtain oxidized carbon fiber; the oxidized carbon fiber, 4-amino-2,2,6,6-tetramethylpiperidine, N,N'-dicyclohexylcarboimide and tetrahydrofuran were mixed evenly at a mass ratio of 1:0.8:1:12, stirred and reacted at room temperature for 6h, filtered and washed 5 times with anhydrous ethanol, and dried under vacuum at 60℃ for 12h to obtain modified carbon fiber; (3) Under a nitrogen atmosphere, polymethylene polyphenyl polyisocyanate and polyether polyol were mixed evenly at a molar ratio of isocyanate group to hydroxyl group of 1:0.6. Organic bismuth compound of 0.006 times the mass of polymethylene polyphenyl polyisocyanate was added and stirred at 90°C for 8 hours to obtain polyurethane prepolymer. Modified carbon fiber, polycarboxylate superplasticizer and deionized water were mixed evenly at a mass ratio of 1:3:0.3 and ultrasonically dispersed for 40 minutes to obtain modified carbon fiber dispersion. Polyurethane prepolymer, polymethylene polyphenyl polyisocyanate, chain extender and cystamine were mixed evenly at a mass ratio of 1:0.8:0.3:0.3 and stirred at 50°C for 10 minutes. Modified carbon fiber dispersion of 0.02 times the mass of polyurethane prepolymer was added at a rate of 2 mL / min. The mixture was stirred at room temperature for 15 minutes and allowed to stand for 5 minutes to remove air bubbles to obtain PCCP pipe crack grouting repair slurry.

[0027] Comparative Example 1 The difference between the preparation method of the PCCP pipe crack grouting repair slurry in Comparative Example 1 and Example 2 lies in the difference in step (3). Step (3) is modified as follows: Under a nitrogen atmosphere, polymethylene polyphenyl polyisocyanate and polyether polyol are mixed evenly according to the molar ratio of isocyanate group to hydroxyl group of 1:0.55. Organic bismuth compound with a mass of 0.005 times that of polymethylene polyphenyl polyisocyanate is added. The mixture is stirred and reacted at 85°C for 7 hours to obtain polyurethane prepolymer. Modified carbon fiber, polycarboxylate superplasticizer, and deionized water are added according to the mass ratio of polymethylene polyphenyl polyisocyanate. The modified carbon fiber dispersion was prepared by mixing the polyurethane prepolymer, polymethylene polyphenyl polyisocyanate, chain extender, and cystamine in a mass ratio of 1:0.4:0.25:0.25 and stirring at 45°C for 8 minutes. Then, 0.015 times the mass of the modified carbon fiber dispersion was added at a rate of 1.5 mL / min, stirred at room temperature for 12 minutes, and allowed to stand for 4 minutes to remove air bubbles, thus obtaining the PCCP pipe crack grouting repair slurry. The remaining steps were the same as in Example 2.

[0028] Comparative Example 2 The difference between the preparation method of the PCCP pipe crack grouting repair slurry in Comparative Example 2 and Example 2 lies in the difference in step (3). Step (3) is modified as follows: Under a nitrogen atmosphere, polymethylene polyphenyl polyisocyanate and polyether polyol are mixed evenly according to the molar ratio of isocyanate group to hydroxyl group of 1:0.55. Organic bismuth compound with a mass of 0.005 times that of polymethylene polyphenyl polyisocyanate is added. The mixture is stirred and reacted at 85°C for 7 hours to obtain polyurethane prepolymer. Modified carbon fiber, polycarboxylate superplasticizer, and deionized water are added according to the mass ratio of polymethylene polyphenyl polyisocyanate. The modified carbon fiber dispersion was prepared by mixing the polyurethane prepolymer, polymethylene polyphenyl polyisocyanate, chain extender, and cystamine in a mass ratio of 1:0.5:0.25:0.25 and stirring at 45°C for 8 minutes. Then, 0.015 times the mass of the modified carbon fiber dispersion was added at a rate of 1.5 mL / min. The mixture was stirred at room temperature for 12 minutes and allowed to stand for 4 minutes to remove air bubbles, thus obtaining the PCCP pipe crack grouting repair slurry. The remaining steps were the same as in Example 2.

[0029] Comparative Example 3 The difference between the preparation method of the PCCP pipe crack grouting repair slurry in Comparative Example 3 and Example 2 lies in the difference in step (3). Step (3) is modified as follows: Under a nitrogen atmosphere, polymethylene polyphenyl polyisocyanate and polyether polyol are mixed evenly according to the molar ratio of isocyanate group to hydroxyl group of 1:0.55. Organic bismuth compound with a mass of 0.005 times that of polymethylene polyphenyl polyisocyanate is added. The mixture is stirred and reacted at 85°C for 7 hours to obtain polyurethane prepolymer. Modified carbon fiber, polycarboxylate superplasticizer and deionized water are added according to the mass ratio of polymethylene polyphenyl polyisocyanate. The modified carbon fiber dispersion was prepared by mixing the polyurethane prepolymer, polymethylene polyphenyl isocyanate, chain extender, and cystamine in a mass ratio of 1:0.9:0.25:0.25 and stirring at 45°C for 8 minutes. Then, 0.015 times the mass of the modified carbon fiber dispersion was added at a rate of 1.5 mL / min, stirred at room temperature for 12 minutes, and allowed to stand for 4 minutes to remove air bubbles, thus obtaining the PCCP pipe crack grouting repair slurry. The remaining steps were the same as in Example 2.

[0030] Comparative Example 4 The difference between the preparation method of the PCCP pipe crack grouting repair slurry in Comparative Example 4 and Example 2 lies in the difference in step (3). Step (3) is modified as follows: Under a nitrogen atmosphere, polymethylene polyphenyl polyisocyanate and polyether polyol are mixed evenly according to the molar ratio of isocyanate group to hydroxyl group of 1:0.55. Organic bismuth compound with a mass of 0.005 times that of polymethylene polyphenyl polyisocyanate is added. The mixture is stirred and reacted at 85°C for 7 hours to obtain polyurethane prepolymer. Modified carbon fiber, polycarboxylate superplasticizer, and deionized water are added according to the mass ratio of polymethylene polyphenyl polyisocyanate. The modified carbon fiber dispersion was prepared by mixing the polyurethane prepolymer, polymethylene polyphenyl isocyanate, chain extender, and cystamine in a mass ratio of 1:1:0.25:0.25 and stirring at 45°C for 8 minutes. Then, 0.015 times the mass of the modified carbon fiber dispersion was added at a rate of 1.5 mL / min, stirred at room temperature for 12 minutes, and allowed to stand for 4 minutes to remove air bubbles, thus obtaining the PCCP pipe crack grouting repair slurry. The remaining steps were the same as in Example 2.

[0031] Comparative Example 5 The difference between the preparation method of the PCCP pipe crack grouting repair slurry in Comparative Example 5 and Example 2 lies in the different step (1). Step (1) is modified as follows: Ethoxybis(5-methylfuran-2-yl)phosphonane, N-(2-hydroxyethyl)maleimide, and N,N-dimethylformamide are mixed evenly at a mass ratio of 1:0.7:16, stirred and reacted at 80°C for 22 h, cooled to room temperature, filtered and washed 4 times with diethyl ether, and dried under vacuum at 55°C for 11 h to obtain the chain extender. The remaining steps are the same as in Example 2.

[0032] Comparative Example 6 The difference between the preparation method of the PCCP pipe crack grouting repair slurry in Comparative Example 6 and Example 2 lies in the different step (1). Step (1) is modified as follows: 2,2'-(phenylphosphine-1,2')bisfuran, N-(2-hydroxyethyl)maleimide, and N,N-dimethylformamide are mixed evenly at a mass ratio of 1:0.7:16, stirred and reacted at 80°C for 22 h, cooled to room temperature, filtered, washed 4 times with diethyl ether, and dried under vacuum at 55°C for 11 h to obtain the chain extender. The remaining steps are the same as in Example 2.

[0033] Comparative Example 7 The difference between the preparation method of the PCCP pipe crack grouting repair slurry in Comparative Example 7 and Example 2 lies in the different step (1). Step (1) is modified as follows: 2-[2-(furan-2-yl)ethyl]furan, N-(2-hydroxyethyl)maleimide, and N,N-dimethylformamide are mixed evenly in a mass ratio of 1:1:24, stirred and reacted at 80°C for 22 h, cooled to room temperature, filtered and washed 4 times with diethyl ether, and dried under vacuum at 55°C for 11 h to obtain the chain extender. The remaining steps are the same as in Example 2.

[0034] Comparative Example 8 The preparation method of the PCCP pipe crack grouting repair slurry in Comparative Example 8 differs from that in Example 2 in that step (1) is omitted, and step (3) is modified as follows: Under a nitrogen atmosphere, polymethylene polyphenyl polyisocyanate and polyether polyol are mixed evenly at a molar ratio of isocyanate group to hydroxyl group of 1:0.55, and an organic bismuth compound of 0.005 times the mass of polymethylene polyphenyl polyisocyanate is added. The mixture is stirred and reacted at 85°C for 7 hours to obtain a polyurethane prepolymer; modified carbon fiber, polycarboxylate superplasticizer, and deionized carbon fiber are added. Water was mixed evenly at a mass ratio of 1:2.5:0.25 and ultrasonically dispersed for 30 min to obtain a modified carbon fiber dispersion. Polyurethane prepolymer, polymethylene polyphenyl isocyanate, and cystamine were mixed evenly at a mass ratio of 1:0.7:0.25 and stirred at 45°C for 8 min. 0.015 times the mass of the modified carbon fiber dispersion was added at a rate of 1.5 mL / min, stirred at room temperature for 12 min, and allowed to stand for 4 min to remove air bubbles, thus obtaining a PCCP pipe crack grouting repair slurry. The remaining steps were the same as in Example 2.

[0035] Comparative Example 9 The difference between the preparation method of the PCCP pipe crack grouting repair slurry in Comparative Example 9 and Example 2 lies in step (2). Step (2) is modified as follows: carbon fiber is immersed in ultrapure water, treated at 65°C for 22 hours, and dried at 120°C for 4 hours to obtain pretreated carbon fiber; the pretreated carbon fiber is immersed in 30wt% nitric acid aqueous solution, modified at 100°C for 2 hours, taken out and washed with ultrapure water until the pH is neutral, and dried at 120°C for 4 hours to obtain modified carbon fiber. The remaining steps are the same as in Example 2.

[0036] Comparative Example 10 The preparation method of the PCCP pipe crack grouting repair slurry in Comparative Example 10 differs from that in Example 2 in that step (2) is omitted, and step (3) is modified as follows: Under a nitrogen atmosphere, polymethylene polyphenyl polyisocyanate and polyether polyol are mixed evenly at a molar ratio of isocyanate group to hydroxyl group of 1:0.55. An organic bismuth compound with a mass ratio of 0.005 times that of polymethylene polyphenyl polyisocyanate is added, and the mixture is stirred at 85°C for 7 hours to obtain a polyurethane prepolymer. The polyurethane prepolymer, polymethylene polyphenyl polyisocyanate, chain extender, and cystamine are mixed evenly at a mass ratio of 1:0.7:0.25:0.25, stirred at 45°C for 8 minutes, and allowed to stand for 4 minutes to remove air bubbles to obtain the PCCP pipe crack grouting repair slurry. The remaining steps are the same as in Example 2.

[0037] Comparative Example 11 The difference between the preparation method of the PCCP pipe crack grouting repair slurry in Comparative Example 11 and Example 2 lies in the difference in step (3). Step (3) is modified as follows: Under a nitrogen atmosphere, polymethylene polyphenyl polyisocyanate and polyether polyol are mixed evenly according to the molar ratio of isocyanate group to hydroxyl group of 1:0.55. Organic bismuth compound with a mass of 0.005 times that of polymethylene polyphenyl polyisocyanate is added. The mixture is stirred and reacted at 85°C for 7 hours to obtain polyurethane prepolymer. Modified carbon fiber, polycarboxylate superplasticizer, and deionized water are added according to the mass ratio of polymethylene polyphenyl polyisocyanate. The modified carbon fiber dispersion was prepared by mixing the polyurethane prepolymer, polymethylene polyphenyl isocyanate, chain extender, and hexamethylenediamine in a mass ratio of 1:0.7:0.25:0.25 and stirring at 45°C for 8 minutes. Then, 0.015 times the mass of the modified carbon fiber dispersion was added at a rate of 1.5 mL / min. The mixture was stirred at room temperature for 12 minutes and allowed to stand for 4 minutes to remove air bubbles, thus obtaining the PCCP pipe crack grouting repair slurry. The remaining steps were the same as in Example 2.

[0038] Test Example 1 Bond strength test: Ordinary Portland cement with a strength grade of 42.5 was used to prepare mortar according to the mass ratio of cement:medium sand:water:water-reducing agent of 1:2:0.3:0.006. The prepared mortar was poured into a metal mold, compacted, and smoothed. After 24 hours, the mold was removed, and the specimens were cured for 7 days to produce concrete specimens. The concrete specimens were broken, and the PCCP pipe crack grouting repair slurry prepared in Example 2 and Comparative Examples 1-4 was filled into the grouting equipment. Grout was injected into the crack until it overflowed, then the injection was stopped, and excess grout on the surface was wiped off. The grouting pressure was 0.2 MPa. After 48 hours of grouting, the grout initially solidified. Copper electrodes were arranged parallel to each other on both sides of the crack with a spacing of 100 mm. The measurement accuracy was... A resistance tester was used to measure the volume resistivity of the crack region. Since the continuity of the conductive network formed by the carbon nanofibers is positively correlated with the grout density, if the volume resistivity... And the uniform distribution indicates that the grouting is dense; if the local resistivity is... If a sudden change occurs, it indicates that the area is not fully filled and needs to be marked for grouting. After the grout has completely cured, clean off any remaining grout from the surface to complete the repair. Use a tensile testing machine to determine the bond strength of the specimen. Perform a tensile bond test at a loading rate of 5 mm / min and record the maximum tensile force value.

[0039] The results are shown in Table 1.

[0040] Table 1 A comparison of the experimental data from Example 2 and Comparative Examples 1-4 in Table 1 reveals that the PCCP pipe crack grouting repair slurry prepared by this invention has good bonding strength.

[0041] By comparing the bond strength data of Example 2 with Comparative Examples 1-4, it was demonstrated that increasing the isocyanate content of the system, especially with excess isocyanate, not only increases the content of polar groups in the solidified body, but more importantly, it can chemically react with the active hydroxyl groups on the concrete surface and the trace moisture adsorbed in the pores of the substrate medium. This can form chemical bonds between the solidified body and the concrete surface that are stronger than intermolecular forces, resulting in stronger adhesion between the grouting material and the concrete. However, as the isocyanate content continues to increase, excess isocyanate can also react with free water in the air, causing the solidified body to foam, transforming its morphology from resin to foam. The strength of the foamed solidified body decreases significantly, the effective force formed between it and the concrete weakens, and the bond strength of the material decreases.

[0042] Test Example 2 Flame retardant performance test: The grouting and repair slurries for PCCP pipe cracks prepared in Examples 1-3 and Comparative Examples 5-11 were tested for combustion performance using a cone calorimeter according to ISO 5660 standard.

[0043] The results are shown in Table 2.

[0044] Table 2 A comparison of the experimental data from Examples 1-3 and Comparative Examples 5-11 in Table 2 reveals that the PCCP pipe crack grouting repair slurry prepared by this invention has good flame retardant properties.

[0045] By comparing the data of Examples 1-3 with those of Comparative Examples 7-8, it can be found that the hydroxyl group on 2,6-di-tert-butyl-4-hydroxymethylphenol reacts with the P-Cl on di(2-furan)phosphine chloride to generate an antioxidant containing phosphorus. The addition of phosphorus improves the flame retardant properties of the grout for repairing cracks in PCCP pipes.

[0046] By comparing the data of Examples 1-3 with Comparative Example 10, it can be found that carbon fiber can promote the formation of a carbon layer during combustion, thereby further improving the flame retardant performance of the PCCP pipe crack grout repair slurry.

[0047] Test Example 3 Self-healing and antioxidant performance test: The specific testing method is as follows: Tensile strength test: The PCCP pipe crack repair grout obtained in Examples 1-3 and Comparative Examples 5-11 were prepared into test specimens of the same size. The specimens were tested using an electronic universal testing machine according to GB / T 2567-2021 "Test Methods for Performance of Resin Castings". The specimens were clamped so that their central axis was aligned with the center lines of the upper and lower clamps. During the test, a constant and continuous load was applied until the specimen failed. The test speed was set to 10 mm / min, and the tensile strength X was recorded.

[0048] Self-healing performance test: The PCCP pipe crack grouting repair slurry obtained in Examples 1-3 and Comparative Examples 5-11 were made into test samples of the same size. The samples were cut in the middle, and the cross-sections were quickly attached to a mold of the same size at room temperature and sealed for storage. The samples were placed at room temperature for 1 hour for repair, and the tensile strength Y was tested again. Self-healing efficiency = Y / X×100%.

[0049] Antioxidant performance test: The PCCP pipe crack grouting repair slurry obtained in Examples 1-3 and Comparative Examples 5-11 were made into test samples of the same size. They were aged in an aging chamber at a temperature of 90℃ and a relative humidity of 85% for 360 hours. The tensile strength Z was tested again, and the performance decline rate was calculated as 1-Z / X×100%.

[0050] The results are shown in Table 3.

[0051] Table 3 A comparison of the experimental data from Examples 1-3 and Comparative Examples 5-11 in Table 3 reveals that the PCCP pipe crack grouting repair slurry prepared by this invention has good self-healing and antioxidant properties.

[0052] By comparison, the self-healing efficiency of Examples 1-3 is greater than that of Comparative Example 8, indicating that the furan group on the antioxidant undergoes a Diels-Alder reaction with N-(2-hydroxyethyl)maleimide to generate a chain extender with dynamic reversible covalent bonds, which endows the PCCP pipe crack grout with good self-healing properties.

[0053] By comparison, the self-healing efficiency of Examples 1-3 is greater than that of Comparative Example 11, indicating that the disulfide bond and DA bond in the cystamine structure work together to further improve the self-healing performance of the PCCP pipe crack grout.

[0054] By comparison, the performance degradation rate of Examples 1-3 was less than that of Comparative Examples 5-8, indicating that the hydroxyl group on 2,6-di-tert-butyl-4-hydroxymethylphenol reacts with the P-Cl on di(2-furan)phosphine chloride to generate an antioxidant containing phosphite and hindered phenol structure. The hindered phenol structure plays an antioxidant role because it can capture all free radicals that appear during aging. The phosphite structure, as an auxiliary antioxidant, works synergistically with the hindered phenol to improve the antioxidant performance of the PCCP pipe crack grouting repair slurry.

[0055] By comparison, the performance degradation rate of Examples 1-3 was less than that of Comparative Example 9, indicating that the oxidized carbon fiber undergoes an amidation reaction with 4-amino-2,2,6,6-tetramethylpiperidine, introducing a hindered amine structure on the carbon fiber surface. This structure, in synergy with hindered phenols and phosphites, improves the oxidation resistance of the grout for repairing cracks in PCCP pipes.

[0056] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A grouting material for repairing cracks in PCCP pipes, characterized in that, The PCCP pipe crack grouting repair slurry is prepared by reacting polyurethane prepolymer, polymethylene polyphenyl polyisocyanate, chain extender, cystamine, and modified carbon fiber dispersion. The chain extender is prepared by reacting 2,6-di-tert-butyl-4-hydroxymethylphenol with di(2-furan)phosphine chloride to obtain an antioxidant, and then reacting it with N-(2-hydroxyethyl)maleimide. The modified carbon fiber dispersion is prepared by reacting oxidized carbon fiber with 4-amino-2,2,6,6-tetramethylpiperidine to obtain modified carbon fiber, and then mixing it with polycarboxylate superplasticizer and deionized water.

2. The PCCP pipe crack grouting repair grout according to claim 1, characterized in that, The polycarboxylate superplasticizer is an ether-based high-efficiency polycarboxylate superplasticizer with a solid content of 40%.

3. A method for preparing a grout for repairing cracks in PCCP pipes, characterized in that, The preparation steps include the following: (1) Mix 2,6-di-tert-butyl-4-hydroxymethylphenol, triethylamine and toluene evenly, add di(2-furan)phosphine chloride at 10~15℃, heat to 75~85℃, stir and react for 3~5h, cool to room temperature, filter, distill under reduced pressure and dry to obtain antioxidant; mix antioxidant, N-(2-hydroxyethyl)maleimide and N,N-dimethylformamide evenly, stir and react at 75~85℃ for 20~24h, cool to room temperature, filter, wash and dry to obtain chain extender; (2) The oxidized carbon fiber, 4-amino-2,2,6,6-tetramethylpiperidine, N,N'-dicyclohexylcarboimide and tetrahydrofuran were mixed evenly and stirred at room temperature for 4-6 h. The mixture was then filtered, washed and dried to obtain the modified carbon fiber. (3) Mix the modified carbon fiber, polycarboxylate superplasticizer and deionized water evenly, and ultrasonically disperse them to obtain the modified carbon fiber dispersion; mix the polyurethane prepolymer, polymethylene polyphenyl polyisocyanate, chain extender and cystamine evenly, stir at 40~50℃ for 5~10min, add the modified carbon fiber dispersion, stir at room temperature for 8~15min, let stand for 3~5min to obtain the PCCP pipe crack grouting repair slurry.

4. The method for preparing a PCCP pipe crack grouting repair slurry according to claim 3, characterized in that, The preparation steps of the chain extender in step (1) are as follows: 2,6-di-tert-butyl-4-hydroxymethylphenol, triethylamine, and toluene are mixed evenly at a mass ratio of 1:(0.4~0.45):(6~8). At 10~15℃, 0.78~0.82 times the mass of 2,6-di-tert-butyl-4-hydroxymethylphenol di(2-furan)phosphine chloride is added. The temperature is raised to 75~85℃, and the mixture is stirred for 3~5 hours. After cooling to room temperature, the mixture is filtered and evaporated under reduced pressure. Toluene was removed by distillation, and the product was dried under vacuum at 50-60°C for 10-12 hours to obtain an antioxidant. The antioxidant, N-(2-hydroxyethyl)maleimide, and N,N-dimethylformamide were mixed in a mass ratio of 1:(0.3-0.4):(5-10), and the mixture was stirred and reacted at 75-85°C for 20-24 hours. After cooling to room temperature, the mixture was filtered and washed 3-5 times with ether. The product was then dried under vacuum at 50-60°C for 10-12 hours to obtain a chain extender.

5. The method for preparing a PCCP pipe crack grouting repair slurry according to claim 3, characterized in that, The preparation steps of the modified carbon fiber in step (2) are as follows: oxidized carbon fiber, 4-amino-2,2,6,6-tetramethylpiperidine, N,N'-dicyclohexylcarboimide and tetrahydrofuran are mixed evenly in a mass ratio of 1:(0.6~0.8):(0.8~1):(10~12), stirred and reacted at room temperature for 4~6h, filtered and washed 3~5 times with anhydrous ethanol, and dried under vacuum at 50~60℃ for 10~12h to obtain the modified carbon fiber.

6. The method for preparing a PCCP pipe crack grouting repair slurry according to claim 3, characterized in that, The preparation steps of the PCCP pipe crack grouting repair slurry in step (3) are as follows: Modified carbon fiber, polycarboxylate superplasticizer, and deionized water are mixed evenly at a mass ratio of 1:(2~3):(0.2~0.3), and ultrasonically dispersed for 20~40 min to obtain modified carbon fiber dispersion; polyurethane prepolymer, polymethylene polyphenyl polyisocyanate, chain extender, and cystamine are mixed evenly at a mass ratio of 1:(0.6~0.8):(0.2~0.3):(0.2~0.3), stirred at 40~50℃ for 5~10 min, and 0.01~0.02 times the mass of modified carbon fiber dispersion of polyurethane prepolymer is added at a rate of 1~2 mL / min, stirred at room temperature for 8~15 min, and allowed to stand for 3~5 min to remove air bubbles to obtain PCCP pipe crack grouting repair slurry.

7. The method for preparing a PCCP pipe crack grouting repair grout according to claim 5, characterized in that, The preparation steps of the oxidized carbon fiber are as follows: immerse the carbon fiber in ultrapure water, treat it at 65℃ for 20~24h, and dry it at 120℃ for 4h to obtain pretreated carbon fiber. Pretreated carbon fibers were immersed in a 30wt% nitric acid aqueous solution and modified at 100℃ for 2 hours. After removal, they were washed with ultrapure water until the pH was neutral and dried at 120℃ for 4 hours to obtain oxidized carbon fibers.

8. The method for preparing a PCCP pipe crack grouting repair slurry according to claim 6, characterized in that, The preparation steps of the polyurethane prepolymer are as follows: Under a nitrogen atmosphere, polymethylene polyphenyl polyisocyanate and polyether polyol are mixed evenly at a molar ratio of isocyanate group to hydroxyl group of 1:(0.5~0.6), and an organic bismuth compound of 0.004~0.006 times the mass of polymethylene polyphenyl polyisocyanate is added. The mixture is stirred and reacted at 80~90℃ for 6~8h to obtain the polyurethane prepolymer.

9. The method for preparing a PCCP pipe crack grouting repair grout according to claim 7, characterized in that, The carbon fiber has a diameter of 5~50nm and a length of 5~50µm.

10. A method for preparing a PCCP pipe crack grouting repair slurry according to claim 8, characterized in that, The polyether polyol is a mixture of polyether polyol N303 and polyether polyol N210, wherein the weight average molecular weight of polyether polyol N303 is 3000, the weight average molecular weight of polyether polyol N210 is 1000, and the mass ratio of polyether polyol N303 to polyether polyol N210 is 1:(0.4~0.5).

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