CNT / PAN composite fiber reinforced cement-based grouting material and preparation method thereof

Abstract

The invention provides a CNT / PAN composite fiber reinforced cement-based grouting material and a preparation method thereof, and belongs to the field of building materials and high-performance composite materials. The method comprises the following steps: carrying out purification and surface carboxylation on CNT to prepare CNT-COOH; pAN is treated through a water phase precipitation polymerization method, and itaconic acid grafted PAN is prepared; cNT-COOH and a PAN solution are mixed, and after ultrasonic treatment and stirring dispersion, composite fibers are prepared through wet spinning; mixing the composite fiber into concrete, and performing conventional stirring, pouring and curing to obtain the composite fiber reinforced concrete. CNT is introduced through a fiber carrier, the problem of agglomeration in concrete is effectively avoided, the problem of poor interface bonding of CNT, PAN and cement is solved, the tensile strength, toughness, crack resistance and durability of the concrete are remarkably improved, the concrete is endowed with certain electric conduction and heat conduction performance, and the concrete is suitable for high-performance structural engineering and intelligent buildings and has good application prospects. The process is simple and convenient and has a good industrial prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of building materials and high-performance composite materials, and relates to a CNT / PAN composite fiber reinforced cement-based grouting material and a preparation method thereof. BACKGROUND

[0002] The information disclosed in this Background section is only for the purpose of increasing an understanding of the general background of the application and does not necessarily constitute an admission by the patent applicant or the patent owner that this information forms part of the prior art that is already known in this field.

[0003] Concrete is a widely used structural material, which has high compressive strength, but has the disadvantages of brittleness, low tensile strength and easy cracking. Traditional fiber reinforcement methods (such as steel fiber, glass fiber or polypropylene fiber) can improve the mechanical properties of concrete to some extent, but the enhancement effect is limited, and it is difficult to endow the concrete with functional properties such as electrical conductivity and thermal conductivity.

[0004] Some studies have used multi-walled carbon nanotube / polyacrylonitrile (PAN) composite fibers to enhance the mechanical properties and crack resistance of concrete, but the problem of double ITZ (interfacial transition zone) densification has not been solved, and the enhancement effect still needs to be improved.

[0005] At the same time, most of the dispersion techniques for carbon nanotubes (CNT) today use covalent modification methods. This method sacrifices the mechanical properties of CNT to obtain better dispersion effect, which cannot fully play the role of CNT as a reinforcing phase. SUMMARY

[0006] To solve the above problems, the present application provides a new type of CNT / PAN composite fiber reinforced cement-based grouting material and a preparation method thereof. The present application forms a reinforcing material by compounding CNT and PAN fiber, and introduces it into concrete. Unlike conventional CNT dispersion methods, the present application innovatively starts from the treatment of PAN, retains the excellent mechanical properties of CNT, and embeds CNT in the form of fiber as a reinforcing phase in concrete, effectively solving the problems of carbon nanotube agglomeration in concrete, CNT agglomeration in inorganic matrix, and poor CNT-polymer, composite fiber-concrete double interface effect. This method can significantly improve the tensile strength, toughness, crack resistance and durability of concrete, and endow the concrete with certain electrical conductivity and thermal conductivity. This composite fiber reinforced concrete is suitable for high-performance structural engineering and intelligent building, has a simple preparation process and good industrial application prospect.

[0007] To achieve the above purpose, the present application adopts the following technical solutions: In a first aspect of the present application, a preparation method of a CNT / PAN composite fiber reinforced cement-based grouting material is provided, comprising: In the basic condition, the itaconic acid grafted PAN is prepared by aqueous phase precipitation polymerization; The carboxyl carbon nanotubes and tannic acid are uniformly mixed in a solvent to obtain a carboxyl carbon nanotube-tannic acid dispersion; The itaconic acid grafted PAN and the carboxyl carbon nanotube-tannic acid dispersion are uniformly mixed and dispersed in a solvent to obtain a wet spinning precursor solution; The wet spinning precursor solution is subjected to wet spinning to obtain a composite fiber; The composite fiber is uniformly mixed with a concrete slurry, and is poured and cured to obtain the cement-based grouting material.

[0008] The method of the present application not only solves the problems of agglomeration of CNT in the inorganic matrix and poor interaction between CNT-polymer and composite fiber-concrete, but also significantly improves the tensile strength, toughness and durability of the concrete, and endows the concrete with certain electric conductivity and thermal conductivity, thereby providing a new idea for the research and development of high-performance and multifunctional concrete.

[0009] In a second aspect, the present application provides the CNT / PAN composite fiber reinforced cement-based grouting material prepared by the method.

[0010] In a third aspect, the present application provides the application of the CNT / PAN composite fiber reinforced cement-based grouting material in the fields of building and transportation.

[0011] Advantages of the present application (1) Compared with the traditional method, the core innovation of the present application is that: in view of the problems of easy agglomeration, difficult dispersion, limited control of macroscopic cracks, limited improvement of pore structure, poor interfacial adhesion between fiber and concrete, etc. of single-doped carbon nanotubes as reinforcing phase or single-doped PAN fibers as reinforcing phase, the present application combines the refining effect of CNT on pore structure and interface with the constraint effect of PAN fiber on macroscopic cracks, thereby improving the strength and toughness of the concrete, and synergistically improving the impermeability, erosion resistance and durability, and providing a multi-scale structural basis for the functionalization of the concrete such as electric conductivity and self-sensing.

[0012] (2) The present application effectively solves the problems of easy agglomeration, uneven dispersion and poor interface effect of CNT-polymer, composite fiber-concrete when CNT is directly doped into concrete. Since CNT is fixed and uniformly distributed in PAN fiber, and the uniaxial spinning technology adopted in the present application can make part of CNT leak out, and the surfaces of PAN and CNT both have hydrophilic groups, the composite fiber can form more reliable interface bonding with the concrete matrix, thereby significantly improving the overall reinforcing effect.

[0013] (3) The composite method of the present application significantly improves the mechanical properties of concrete. The composite fiber not only can improve the tensile strength and toughness of concrete, but also can play a bridging and crack resistance role in the process of micro-crack formation and expansion, thereby effectively improving the crack resistance and durability of concrete. Compared with the free state particle form of CNT of traditional reinforcing fiber, the CNT / PAN composite fiber prepared by the present application can achieve more excellent reinforcing effect at a lower use amount of CNT and at a lower cost.

[0014] (4) The present application endows concrete with new functional properties. Since the electrical conductivity and thermal conductivity of CNT can be effectively transmitted to the concrete matrix through the fiber, the obtained composite material not only has high strength and high toughness, but also shows certain electrical conductivity and heat conduction capacity, and can be applied to intelligent monitoring, structural health detection and functional building engineering.

[0015] (5) The process preparation steps of the present application are simple and controllable, the composite fiber can be directly added into the existing concrete production process, without the need for additional complex equipment or special conditions, and has good prospects for large-scale production and engineering application.

[0016] In summary, the present application introduces CNT into concrete efficiently and stably by the way of "fiber carrier", designs a multi-level load transfer chain from nano-reinforcement to macro-fiber, breaks through the limitations of traditional free state CNT reinforced concrete, significantly improves the comprehensive mechanical properties and functionality of concrete, and has important technical value and application potential. BRIEF DESCRIPTION OF DRAWINGS

[0017] The drawings accompanying the specification of the present application serve to provide further understanding of the present application, and the exemplary embodiments of the present application and the description thereof serve to explain the present application, and do not constitute an improper limitation on the present application.

[0018] Figure 1 is the CNT / PAN composite fiber reinforced concrete prepared in Example 4; Figure 2 is a chemical reaction mechanism diagram of the present application; Figure 3 is an OM diagram of the wet spinning precursor spinning solution in Example 2; Figure 4 is a fiber prepared in Example 2; Figure 5 is a cross section of the concrete prepared in Example 2. DETAILED DESCRIPTION

[0019] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0020] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. As used herein, except as otherwise expressly provided herein, all measurements are made at 25 °C using standard techniques, and all units are SI units unless otherwise stated. All percentages refer to weight / weight unless otherwise stated. The practice of the present application will employ, unless otherwise indicated, conventional methods of chemistry, biochemistry, and immunology, which are well known in the art and as described in various general and more specific references that are cited herein. The practice of the present application will employ, unless otherwise indicated, conventional methods of chemistry, biochemistry, and immunology, which are well known in the art and as described in various general and more specific references that are cited herein.

[0021] As described in the background, the original CNTs are prone to aggregation due to hydrophobicity. By introducing surface negative charge and polar groups through carboxylation (-COOH), and coating with tannic acid (TA), the benzene ring of TA forms a π-π bond with the π orbital of CNTs, and the rich phenolic hydroxyl groups of TA endow CNTs with hydrophilicity, making them stably dispersed in aqueous and organic solvents. The TA layer on the surface of CNTs@TA forms strong hydrogen bonds with the carboxyl groups of IA, and CNTs@TA and PAN-co-IA form multiple cross-linking through hydrogen bonds (TA-IA) and π-π bonds (TA-CNTs), which have stronger interfacial bonding force than single physical mixing or simple blending. The copolymerization of IA breaks the regularity of PAN molecular chains and introduces carboxyl groups (-COOH), greatly improving the hydrophilicity.

[0022] To this end, the present application provides a preparation method of CNT / PAN composite fiber reinforced cement-based grouting material, comprising: In an alkaline condition, itaconic acid grafted PAN is prepared by aqueous phase precipitation polymerization; Carboxyl CNTs and tannic acid are uniformly mixed in a solvent to obtain a carboxyl CNT-tannic acid dispersion; The itaconic acid grafted PAN and the carboxyl CNT-tannic acid dispersion are uniformly mixed and dispersed in a solvent to obtain a wet spinning precursor solution; The wet spinning precursor solution is subjected to wet spinning to obtain a composite fiber; Mix the composite fiber with the concrete slurry uniformly, and then pour and maintain, to obtain the product.

[0023] The pH value affects the efficiency and stability of the aqueous phase precipitation polymerization reaction, therefore, the pH value of the alkaline condition is studied in the application, in some embodiments, the alkaline condition is pH 10±0.5, to obtain a more optimal polymerization efficiency.

[0024] The specific conditions of the aqueous phase precipitation polymerization method are not specially limited in the application, and the existing synthesis method can be used, in some embodiments, the specific steps of the aqueous phase precipitation polymerization method include: uniformly mixing itaconic acid and acrylonitrile solution, then adding initiator and uniformly mixing, carrying out polymerization reaction, after the reaction is completed, pouring the polymer slurry into water, and carrying out precipitation, to obtain itaconic acid grafted PAN.

[0025] The amount of acrylonitrile and itaconic acid affects the modification effect of itaconic acid on PAN, therefore, the amount of acrylonitrile and itaconic acid is studied in the application, in some embodiments, the mass ratio of acrylonitrile and itaconic acid is 98-99:1-2, to obtain itaconic acid grafted PAN with more optimal performance.

[0026] In order to ensure that the carboxyl carbon nanotube (CNT-COOH) is fully dispersed in the itaconic acid grafted PAN, the mass ratio of the itaconic acid grafted PAN and CNT-COOH is studied in the application, in some embodiments, the mass ratio of the itaconic acid grafted PAN and CNT-COOH is 1:0.028-0.040, to obtain a more optimal dispersion effect.

[0027] The preparation method of CNT-COOH is not specially limited in the application, in some embodiments, the preparation method of CNT-COOH includes: purifying CNT, and treating CNT with a carboxylation reagent, to better modify carboxylic acid groups on the surface of CNT.

[0028] The type of CNT is not specially limited in the application, in some embodiments, the CNT is selected from at least one of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes, to meet the use requirements of different scenes.

[0029] In some embodiments, the mass ratio of the CNT-COOH to tannic acid is 1:0.5-2. The tannic acid can non-covalently modify the CNTs, without damaging the mechanical properties of the CNTs and optimizing the dispersion effect. Secondly, the benzene ring of the TA forms a π-π bond with the π orbital of the CNTs, and meanwhile the TA is rich in phenolic hydroxyl groups, which endows the CNTs@TA with hydrophilicity, so that it can be stably dispersed in aqueous phase and organic solvents. Meanwhile, the CNTs@TA and the PAN-co-IA form multiple cross-linking through hydrogen bonds (TA-IA) and π-π bonds (TA-CNTs), and have relatively strong interaction, serving as a bridge connecting the PAN and the CNTs.

[0030] The application will be further described in detail below with reference to specific examples, which are intended to explain but not limit the application.

[0031] Example 1 (1) A certain amount of CNTs were put into a crucible, and heated to 420℃ at a rate of 5℃ / min in a box furnace, and kept for 1h, and then slowly cooled to remove amorphous carbon; the heat-treated CNTs were transferred to a 50ml beaker, and an excess of 3M hydrogen chloride solution was added, and then put into an ultrasonic cleaning tank for ultrasonic treatment for 1h, and then stirred for 2h using a magnetic stirrer; after purification, the mixture was washed with deionized water, and filtered through a 2-micron polytetrafluoroethylene (PTFE) membrane until the pH value of the filtrate was about 7.

[0032] (2) The purified CNTs were mixed with a 30% (volume fraction) hydrogen peroxide and 3M dilute hydrochloric acid mixture to perform a carboxyl group reaction, and the reaction conditions were 60℃ magnetic stirring for 3h; then the mixture was filtered through a 2-micron polytetrafluoroethylene (PTFE) membrane, and the obtained solid was put into a vacuum drying oven at 60℃ for 1h under vacuum to obtain CNT-COOH.

[0033] (3) 1.68 g of acrylonitrile (AN) and 0.17 g of itaconic acid (IA) were added to a three-necked flask, 20ml of deionized water was added, 2-3 drops of ammonia water were added to make the pH value of the solution close to 10, the solution was magnetically stirred at 60℃ for 30min in a magnetic stirrer, and nitrogen was introduced into the system during the stirring to make the system in an inert atmosphere, then 0.025 g of azobisisobutyronitrile (initiator) was added to the beaker, and the mixture was polymerized at 60℃ for 6h, and then cooled to room temperature, the polymer slurry after polymerization was poured into an excess of deionized water, and after 12h of preliminary natural precipitation, the mixture was filtered through a 2-micron polytetrafluoroethylene (PTFE) membrane, and washed with deionized water to remove unreacted monomers, and then put into a vacuum drying oven at 60℃ for 6h to obtain a dry PAN-CO-IA powder.

[0034] (4) Take 50ml beaker, 0.05g CNT-COOH is added into 13g dimethyl sulfoxide (DMSO), and dispersed by ultrasonic disperser at 40% power for 10 minutes (ultrasonic 1 minute, interval 1 minute), to form a preliminary dispersion liquid, 0.1g tannic acid (TA) is added after ultrasonic dispersion at 40% power for 30 minutes (ultrasonic 1 minute, interval 1 minute), to form a CNT-TA dispersion, dry 1.7g PAN-co-IA powder is dissolved in the CNT-TA dispersion, and 60℃ magnetic stirring is carried out for 12 hours, to obtain a well-dispersed spinning solution.

[0035] (5) A syringe (selected as 50ml) is used, the injection / withdrawal speed is changed to 13ml / h, the nozzle caliber is selected as No. 18, the outer diameter is 1.27mm, and the inner diameter is 0.84mm, the spinning solution is sprayed out in the form of droplets through the spinneret, the sprayed solution enters the coagulation bath through a certain path, the first coagulation bath adopts dimethyl sulfoxide / deionized water mixed at a volume ratio of 1:2, the liquid temperature is 40℃, and the draw ratio is 1.5; then it enters the washing bath, which is 60℃ deionized water, the draw ratio is 1.5; finally it enters the hot dip bath at 70℃, the draw ratio is 3, and it is dried at room temperature for 24 hours, and the fiber is cut into small pieces with a length of about 1cm.

[0036] (6) The cement is put into the mixer, and the required water (216g cement, 86.4g water, water-cement ratio is 0.37) is added, and the preliminary stirring is started, the time is 1 minute. The composite fiber prepared in step (5) 3.24g is mixed uniformly with part of the cement (216g cement, 86.4g water), and then added to the mixer, and the stirring is continued for 2 to 3 minutes, to ensure that the composite fiber is uniformly dispersed in the concrete.

[0037] (7) The manually pouring equipment is used, the well-stirred composite fiber reinforced concrete is quickly poured into a 20x20x50 eight-union steel mold, and the vibrator is used for vibrating after each pouring, to reduce the bubbles and ensure the compactness of the concrete.

[0038] (8) After pouring, the concrete surface is covered with plastic film, wet sack or other moisture-retaining material to keep the concrete moist to prevent water evaporation, and curing is maintained for 3 days, 7 days, and 28 days as a cycle. The concrete block is cured in water, and the marked test body is immediately placed horizontally or vertically in 20°C±1°C water. When placed horizontally, the scraped surface should face upwards. The test body is placed on a non-rotting pallet (with a certain distance between each other, so that water can contact the six surfaces of the test body. The water depth between the test bodies or on the upper surface of the test body should not be less than 5mm during the curing period. Initially, the curing tank (or container) is filled with tap water, and then water is added in time to maintain the appropriate water level. During the curing period, no more than 50% of the water can be replaced. After 28 days, the composite material is demolded.

[0039] Example 2 The same as Example 1, but the CNT / PAN fiber mass is 2.16g.

[0040] Example 3 The same as Example 1, but the CNT / PAN fiber mass is 1.08g.

[0041] Example 4 The same as Example 1, but the CNT / PAN fiber mass is 0.54g.

[0042] Example 5 (1) A certain amount of CNT is placed in a crucible and heated to 420°C at a rate of 5°C / min in a box furnace, and kept at this temperature for 1h. Slow cooling is used to remove amorphous carbon. The heat-treated CNT is transferred to a 50ml beaker, an excess of 3M hydrogen chloride solution is added, and ultrasonic cleaning is performed for 1h. Then a magnetic stirrer is used for stirring for 2h. After purification, the mixture is washed with deionized water and filtered through a 2 micron polytetrafluoroethylene (PTFE) membrane until the pH of the filtrate is about 7.

[0043] (2) The purified CNT is mixed with a 30% (by volume) hydrogen peroxide and 3M dilute hydrochloric acid mixture for carboxyl group reaction, with a reaction condition of 60°C magnetic stirring for 3h. Then the mixture is filtered through a 2 micron polytetrafluoroethylene (PTFE) membrane, and the obtained solid is placed in a vacuum drying oven at 60°C for 1h to obtain CNT-COOH.

[0044] (3) In a three-necked flask, 1.68 g of acrylonitrile (AN) and 0.17 g of itaconic acid (IA) were added, 20 ml of deionized water was added, 2-3 drops of ammonia water were added to make the pH value of the solution close to 10, the solution was stirred at 60°C in a magnetic stirrer for 30 min, nitrogen was introduced into the system during the stirring to make the system in an inert atmosphere, then 0.025 g of azobisisobutyronitrile initiator was added to the beaker, and the mixture was polymerized at 60°C for 6 h, and then cooled to room temperature. The polymer slurry after polymerization was poured into excess deionized water, and preliminary natural precipitation was carried out for 12 h, then the mixture was filtered using a 2 micron polytetrafluoroethylene (PTFE) membrane, and washed with deionized water to remove unreacted monomers, and placed in a vacuum drying oven at 60°C for 6 h to obtain PAN-CO-IA dry powder.

[0045] (4) 0.41 g of CNT-COOH was taken into a 100 ml beaker and dispersed in 65 g of dimethyl sulfoxide (DMSO) using an ultrasonic disperser at a power of 40% for 10 min (ultrasonic 1 min, interval 1 min) to form a preliminary dispersion liquid, 0.25 g of tannic acid (TA) was added and dispersed using an ultrasonic disperser at a power of 40% for 30 min (ultrasonic 1 min, interval 1 min) to form a CNT-TA dispersion, and 1.7 g of dry PAN-co-IA powder was dissolved in the CNT-TA dispersion, and stirred at 60°C for 12 h to obtain a well-dispersed spinning solution.

[0046] (5) Preferably, a 0.3 mm thin film was prepared to investigate its conductivity, the mold with the thin film was immersed in a 40°C coagulation bath prepared by mixing dimethyl sulfoxide / deionized water at a volume ratio of 1:2 for 10 min, then placed in a washing bath of deionized water at a temperature of 70°C for 1 h, and finally placed in an air oven at 60°C for drying for 24 h.

[0047] (8) Preferably, a conductive copper foil tape with a thickness of 30-50 μm was pasted on both ends of the sample, the electrode width was preferably 3-5 mm, and in this embodiment, the electrode width was 5 mm; the distance D between the inner edges of the two electrodes was preferably 6 mm, and the copper foil electrodes at both ends of the sample were extended or folded a small section towards the back, a digital multimeter was selected to measure the resistance, nine measurements were taken at different positions in the length direction of three thin films with a width of 1.5 cm, and the average value was taken, the electrode distance was 0.6 cm, and the surface sheet resistance of the thin film was calculated to be about 1.5×10 4 Ω / sq according to Rs (Ω / sq) = (W / D) × R. Wherein R is the resistance measured by the multimeter (Ω), W is the width of the sample (mm), and D (mm) is the distance between the two electrodes. It is considered in the present application that the sheet resistance is less than 1×10 6 Ω / sq, and the material has conductivity.

[0048] Comparative Example 1 The difference from Example 1 is that the CNT is directly added to the PAN for physical dispersion. Specifically, it includes: 0.05 g of CNT is added to 13 ml of dimethyl sulfoxide (DMSO) and dispersed for 10 min (ultrasonic 1 min, interval 1 min) with an ultrasonic disperser at 40% power to form a CNT dispersion liquid. 1.7 g of dry PAN-co-IA powder is dissolved in the CNT dispersion liquid, and the mixture is stirred magnetically at 60°C for 12 h to obtain a spinning solution.

[0049] Comparative Example 2 The difference from Example 1 is that the CNT is acidized and then added to the PAN for dispersion. Specifically, it includes: The preparation method of CNT-COOH is the same as steps (1) and (2) in Example 1. 0.05 g of CNT-COOH is added to 13 ml of dimethyl sulfoxide (DMSO) and dispersed for 10 min (ultrasonic 1 min, interval 1 min) with an ultrasonic disperser at 40% power to form a CNT-COOH dispersion liquid. 1.7 g of dry PAN powder is dissolved in the CNT-COOH dispersion liquid, and the mixture is stirred magnetically at 60°C for 12 h to obtain a spinning solution.

[0050] Experimental Example 1 The dispersion effect of CNT in the spinning solution prepared in Example 1 and Comparative Examples 1 and 2 is tested, as shown in Table 1.

[0051] Table 1 Comparison of dispersion effect data

[0052] From the comparison of Example 1 and Comparative Examples 1 and 2, it can be seen that by wrapping CNT-COOH with tannic acid and modifying polyacrylonitrile with itaconic acid, a better interfacial bonding force is formed, and the agglomeration of CNT in the inorganic matrix is effectively improved, which lays a foundation for the subsequent improvement of CNT agglomeration in concrete and the improvement of CNT-polymer, composite fiber-concrete double interface effect.

[0053] Experimental Example 2 On the basis of Experimental Example 1, the compressive strength and flexural strength of the cement paste test blocks prepared in Examples 1-4 and the blank group (CNT / PAN fiber content is 0 wt%) at 3 days, 7 days and 28 days are tested, and the results are as follows: refer to the national standards "Hydraulic Universal Testing Machine" GB / T 3159 and "General Technical Requirements for Testing Machines" GB / T 2611. Table 1 Performance test results

[0054] As shown in Table 2, the method of the present application effectively solves the problems of CNT agglomeration in concrete, CNT agglomeration in inorganic matrix and poor interaction of CNT-polymer, composite fiber-concrete double interface, and the prepared CNT / PAN fiber can significantly improve the mechanical strength of concrete.

[0055] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can be variously changed and altered for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing a CNT / PAN composite fiber-reinforced cement-based grouting material, characterized by, The application relates to a CNT / PAN composite fiber reinforced cement-based grouting material and a preparation method thereof. The itaconic acid grafted PAN is prepared by using a water phase precipitation polymerization method under alkaline conditions; The carboxyl CNT and tannic acid are uniformly mixed in a solvent to obtain a carboxyl CNT-tannic acid dispersion; The itaconic acid grafted PAN and the CNT-COOH tannic acid dispersion are uniformly mixed and dispersed in a solvent to obtain a wet spinning precursor solution; The wet spinning precursor solution is subjected to wet spinning to obtain a composite fiber. The composite fiber is uniformly mixed with a concrete slurry, and is poured and maintained to obtain the CNT / PAN composite fiber reinforced cement-based grouting material.

2. The method for producing a CNT / PAN composite fiber-reinforced cement-based grouting material according to claim 1, wherein The alkaline condition is pH 10+ / -0.

5.

3. The method for producing a CNT / PAN composite fiber-reinforced cement-based grouting material according to claim 1, wherein The specific steps of the water phase precipitation polymerization method include the following steps: uniformly mixing itaconic acid and an acrylonitrile solution, adding an initiator and uniformly mixing, performing polymerization reaction, pouring the polymer slurry into water after the reaction is completed, and performing precipitation.

4. The method for producing a CNT / PAN composite fiber-reinforced cement-based grouting material according to claim 1, wherein The mass ratio of the acrylonitrile and the itaconic acid is 98-99:1-2.

5. The method for producing a CNT / PAN composite fiber-reinforced cement-based grouting material according to claim 1, wherein The mass ratio of the itaconic acid grafted PAN and the CNT-COOH is 1:0.028-0.

040.

6. The method for producing a CNT / PAN composite fiber-reinforced cement-based grouting material according to claim 1, wherein The preparation method of the CNT-COOH includes the following steps: purifying CNT, and treating the CNT with a carboxylation reagent.

7. The method for producing a CNT / PAN composite fiber-reinforced cement-based grouting material according to claim 5, wherein The CNT is selected from at least one of single-walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes.

8. The method for producing a CNT / PAN composite fiber-reinforced cement-based grouting material according to claim 5, wherein The mass ratio of the CNT-COOH and the tannic acid is 1:0.5-2. 9.The CNT / PAN composite fiber reinforced cement-based grouting material prepared by the method in any one of claims 1-8. 10.The application of the CNT / PAN composite fiber reinforced cement-based grouting material in claims 9 in the fields of building and transportation.

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