Prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on dispersion process and preparation method thereof

Abstract

The invention relates to the technical field of building materials, and discloses a prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on a dispersion process and a preparation method thereof, the prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material comprises the following components: water, cement, fine aggregate, a composite solution, fly ash, silica fume, graphene and an additive, the prestressed steel fiber accounts for 0.5-1.5% of the total volume of the components, and the modified PVA fiber accounts for 0.1-0.3% of the total volume of the components. Through the synergistic enhancement effect of the prestressed steel fibers and the modified PVA fibers and in combination with a two-dimensional conductive network constructed by prestressed steel fiber-graphene, the grouting material has a damage self-sensing function while maintaining excellent mechanical properties, can realize real-time monitoring and damage early warning of structural health, and has a wide engineering application prospect.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on a dispersion process and its preparation method. Background Technology

[0002] Prefabricated structures significantly improve overall quality, construction efficiency, and safety through factory prefabrication, while also greatly saving resources and reducing pollution. They are an important path to achieving modernization and green, low-carbon transformation of the construction industry. To ensure the quality of prefabricated structures, the connection of engineering components is crucial. Among them, grouting connection with steel sleeves has become the most commonly used connection method due to its advantages of being less prone to breakage and easy to construct. The quality of the grouting material affects the connection quality of the components, and thus the quality of the prefabricated structure. Therefore, improving the quality of the grouting material is crucial to solving the quality problems of prefabricated structures.

[0003] Currently used grouting materials generally suffer from low tensile strength and insufficient deformation capacity. When subjected to external loads, they are prone to developing microcracks that gradually propagate and eventually lead to brittle failure, affecting the reliability of their connections and the safety of the structure. Therefore, it is necessary to improve the comprehensive mechanical properties of grouting materials, especially their tensile strength and deformation toughness, to meet the high-performance requirements of prefabricated structures under complex stress conditions.

[0004] Fibers exhibit excellent reinforcing effects in enhancing the mechanical and deformation properties of cement-based composites. Compared to traditional single-fiber reinforcement systems, their limitations lie in their ability to function only within a limited strain and cracking range, and they struggle to overcome inherent drawbacks, such as the susceptibility of steel fibers to corrosion and the difficulty of effectively suppressing microcracks in the early stages with certain polymer fibers. By combining two fibers with different properties to form a hybrid fiber system, the synergistic effects of the size and performance of each fiber can be fully utilized, thereby significantly improving the mechanical strength and deformation resistance of the material. This type of hybrid fiber reinforcement strategy has significant application value in cement-based grouting materials, effectively improving their brittle characteristics, inhibiting crack propagation, and enhancing the ductility and durability of the structure under load. Summary of the Invention

[0005] The purpose of this invention is to provide a prestressed steel fiber and modified PVA fiber hybrid fiber cementitious grout with excellent mechanical properties and deformation resistance. By incorporating prestressed steel fibers and modified PVA fibers into the grout, the overall strength of the grout is improved, ensuring the safety of the structure and extending its service life. At the same time, combined with the two-dimensional conductive network constructed by prestressed steel fiber-graphene, the grout has a damage self-sensing function while maintaining excellent mechanical properties.

[0006] To achieve the above objectives, this invention provides a prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on a dispersion process, comprising the following components: water, cement, fine aggregate, composite solution, fly ash, silica fume, graphene, and admixtures, and further comprising 0.5-1.5% prestressed steel fiber and 0.1-0.3% modified PVA fiber, wherein the PVA fiber is obtained by modifying PVA fiber with a silane coupling agent modification solution, and the prestressed steel fiber is obtained by axial pretensioning, surface sandblasting, and copper plating of steel fiber.

[0007] Preferably, the mass ratio of water, cement, fine aggregate, composite solution, fly ash, silica fume, graphene, and admixture is 230:900:1000:30:60:40:0.5:10.5.

[0008] Preferably, the steel fiber is a straight copper-plated steel fiber with a length of 13 mm, a diameter of 200 μm, and a density of 7.85 g / cm³. 3 The tensile strength is 2850 MPa, and the elastic modulus is 210 GPa; the PVA fiber is Kuraray K-II fiber from Japan, with a length of 12 mm, a diameter of 40 μm, and a density of 1.3 g / cm³. 3 Its tensile strength is 1400-1600MPa and its elastic modulus is 35-39GPa.

[0009] Preferably, the cement is PO 525 silicate cement with an apparent density of 3.15 g / cm³. 3 The standard consistency is 28%, and the specific surface area is 380 m². 2 / kg.

[0010] Preferably, the fine aggregate is well-graded quartz sand with a particle size distribution of 0.08-2.0 mm.

[0011] Preferably, the composite solution is obtained by mixing an aqueous epoxy resin solution and a lithium silicate solution at a mass ratio of 3:1, wherein the aqueous epoxy resin solution has a solid content of 48-52% and an epoxy equivalent of 450-550 g / mol; and the lithium silicate solution has a modulus of 4.8-5.5.

[0012] Preferably, the fly ash is Grade I fly ash with a density of 2.1 g / cm³. 3 The bulk density is 1.10 g / cm³. 3 The silica fume is S96 silica fume, with a SiO2 content of 96% and a specific surface area of ​​19m². 2 / g; the graphene is xGnP-M25 type multilayer graphene nanosheets with a particle size of 25μm, a thickness of 6-8nm, and a density of 2.2g / cm³. 3 .

[0013] Preferably, the additive is obtained by mixing a water-reducing agent, a defoamer, and an expanding agent in a mass ratio of 8:2:0.5, wherein the water-reducing agent is a polycarboxylate water-reducing agent, the defoamer is a polyoxyethylene oxypropylene ether defoamer, and the expanding agent is a plastic expanding agent.

[0014] This invention also discloses a method for preparing a prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on a dispersion process, comprising the following steps: Step (1): The steel fiber is subjected to axial pretensioning treatment so that its tensile stress is 70% of the yield strength. The axially pretensioned steel fiber is placed in a micro-nano sandblasting equipment and sandblasted for 3 minutes at a pressure of 0.3 MPa using alumina micro-nano particles as the sandblasting medium. Then, copper plating treatment is performed to form a copper plating layer. Finally, it is dried at 40°C for 2 hours for later use to obtain prestressed steel fiber. The alumina micro-nano particles are obtained by mixing alumina particles with a particle size of 50 μm and alumina particles with a particle size of 200 nm in a mass ratio of 1:1. The thickness of the copper plating layer is 5 μm. Step (2): Immerse the PVA fiber in the silane coupling agent modification solution, stir in a constant temperature water bath at 30-40℃ for 30 min, take out the PVA fiber, rinse it with ethanol 1-2 times, and dry it at 80℃ for 2-3 h to obtain the modified PVA fiber; wherein, the mass ratio of PVA fiber to silane coupling agent modification solution is 1:20. Step (3): Mix cement, fly ash, silica fume and 70wt% modified PVA fiber evenly to obtain dry mix; Step (4): Mix the prepared composite solution, water-reducing agent, defoamer and expansion agent with water to obtain an admixture solution; mix the admixture solution with the dry mix in two batches, with a mass ratio of 7:3 for the two additions, and a mixing time of 2 minutes for each addition to obtain cement paste. Step (5): Pour well-graded quartz sand and ultrasonically dispersed graphene into cement paste, stir at low speed for 2 minutes and at high speed for 1 minute to obtain cement mortar mixture. Step (6): Add prestressed steel fibers to the cement mortar mixture, stir for 2-3 minutes, add the remaining 30wt% modified PVA fibers, and continue stirring until uniform to obtain a prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on dispersion process.

[0015] Further, the preparation method of the silane coupling agent modified solution is as follows: silane coupling agent KH-550, ethanol and deionized water are mixed in a volume ratio of 1:30:5, the pH is adjusted to 4.0-5.0 with acetic acid, and the mixture is magnetically stirred for 10-15 minutes.

[0016] The application of prestressed steel based on dispersion process and modified PVA fiber reinforced intelligent sensing grout in prefabricated structure engineering construction.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention incorporates different amounts of prestressed steel-modified PVA (polyvinyl alcohol) hybrid fibers into the prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on dispersion process. The prestressed steel fibers and modified PVA fibers have a synergistic effect, filling part of the pores in the internal structure of the grouting material, enhancing the bonding force between aggregates, promoting the dissipation of excess water in the grouting material, preventing or reducing the formation of pores, playing an effective role in crack prevention, improving the mechanical properties of the grouting material, and extending the service life of the grouting material. 2. By performing axial pretensioning, surface sandblasting, and copper plating on the steel fibers, this invention improves the mechanical properties of the steel fibers during use, enhances the interfacial bonding between the steel fibers and the grouting material, and strengthens the corrosion resistance of the steel fibers, thus solving the problem of easy corrosion of steel fibers during grouting. In addition, the conductivity of the prestressed steel fibers is significantly improved. By constructing a two-dimensional conductive network of prestressed steel fibers and graphene in the grouting material system, the grouting material can maintain excellent mechanical properties while possessing damage self-sensing function, enabling real-time monitoring of structural health and damage early warning, and has broad engineering application prospects. 3. This invention modifies PVA fibers with silane coupling agents and adds them to the grouting material in batches, so that the modified PVA fibers are evenly dispersed in the grouting material. In addition, this invention mixes the raw materials of the grouting material in batches and uses different dispersion processes to achieve uniform dispersion of each component in the grouting material, thereby improving the working performance of the grouting material. Attached Figure Description

[0018] Figure 1 This is a flowchart of the preparation method of the intelligent sensing grouting material reinforced with prestressed steel and modified PVA fiber based on the dispersion process of the present invention. Figure 2 This is a physical image of the steel fiber used in this invention; Figure 3 This is a physical image of the PVA fiber used in this invention. Detailed Implementation

[0019] 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. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] In Embodiments 1-9 and Comparative Examples 1-7 of the present invention: The cement is PO 525 Portland cement with an apparent density of 3.15 g / cm³. 3 The standard consistency is 28%, and the specific surface area is 380 m². 2 / kg; the fine aggregate is well-graded quartz sand with a particle size distribution of 0.08-2.0mm; the composite solution is a 3:1 mixture of aqueous epoxy resin solution and lithium silicate solution, wherein the aqueous epoxy resin solution has a solid content of 48-52% and an epoxy equivalent of 450-550g / mol, and the lithium silicate solution has a modulus (SiO2 / Li2O molar ratio) of 4.8-5.5; the fly ash is Grade I fly ash with a density of 2.1g / cm³. 3 The bulk density is 1.10 g / cm³. 3 The silica fume is S96 silica fume, with a SiO2 content of 96% and a specific surface area of ​​19m². 2 / g; the graphene is xGnP-M25 type multilayer graphene nanosheets with a particle size of 25μm, a thickness of 6-8nm, and a density of 2.2g / cm³. 3 The water-reducing agent is a polycarboxylate superplasticizer; the defoamer is a polyoxyethylene propylene ether defoamer; the expanding agent is a plastic expanding agent; the steel fiber is a straight copper-plated steel fiber with a length of 13mm, a diameter of 200μm, and a density of 7.85g / cm³. 3 The tensile strength is 2850 MPa, and the elastic modulus is 210 GPa; the PVA fiber is Kuraray K-II fiber from Japan, with a length of 12 mm, a diameter of 40 μm, and a density of 1.3 g / cm³. 3 Its tensile strength is 1400-1600MPa and its elastic modulus is 35-39GPa.

[0021] After extensive preliminary testing, the optimal mix proportions for achieving the best flowability were determined: 230 parts water, 900 parts PO 525 cement, 1000 parts fine aggregate, 30 parts composite solution (waterborne epoxy resin emulsion: lithium silicate solution = 3:1), 60 parts fly ash, 40 parts silica fume, 8 parts water-reducing agent, 2 parts defoamer, 0.5 parts expanding agent, and 0.5 parts graphene. Other unspecified components will be clearly described in the examples. Table 1 shows the detailed mix proportions of each component in the basic formulations of the prestressed steel and modified PVA fiber reinforced intelligent sensing grouting materials prepared in Examples 1-9 (based on dispersion process), the cement-based grouting material prepared in Comparative Example 1, the prestressed steel fiber reinforced cement-based grouting materials prepared in Comparative Examples 2-4, and the modified PVA fiber reinforced cement-based grouting materials prepared in Comparative Examples 5-7 ( / m). 3 ); Table 1 .

[0022] Table 2 shows the proportions of steel fibers and modified PVA fibers in the prestressed steel and modified PVA fiber reinforced intelligent sensing grouting materials prepared by dispersion process in Examples 1-9, the cement-based grouting material prepared in Comparative Example 1, the prestressed steel fiber reinforced cement-based grouting materials prepared in Comparative Examples 2-4, and the modified PVA fiber reinforced cement-based grouting materials prepared in Comparative Examples 5-7. Except for the materials mentioned in Table 2, the proportions of other materials are as described in Table 1. Table 2 .

[0023] Example 1 This embodiment discloses a method for preparing a prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on a dispersion process, including the following steps: Step (1): The steel fiber is subjected to axial pretensioning treatment so that its tensile stress is 70% of the yield strength. The axially pretensioned steel fiber is placed in a micro-nano sandblasting equipment and alumina micro-nano particles are used as the sandblasting medium. The surface is sandblasted for 3 minutes under a pressure of 0.3MPa to form micron protrusions and nano rough surfaces. Then, copper plating treatment is performed to form a copper plating layer with a thickness of 5μm to ensure the conductivity and corrosion resistance of the fiber. Finally, it is dried at 40℃ for 2 hours for later use to obtain prestressed steel fiber. The alumina micro-nano particles are obtained by mixing alumina particles with a particle size of 50μm and alumina particles with a particle size of 200nm in a mass ratio of 1:1. Step (2): Immerse the PVA fiber in the silane hydrolysis modification solution. The mass ratio of PVA fiber to silane coupling agent modification solution is 1:20. Stir in a constant temperature water bath at 30℃ for 30 minutes. Take out the fiber and rinse it quickly with anhydrous ethanol 1-2 times. Then place it in an 80℃ forced air drying oven to dry for 3 hours. After it is completely dried, the modified PVA fiber is obtained for use. The method for preparing the modified silane coupling agent solution is as follows: silane coupling agent KH-550, ethanol and deionized water are mixed in a volume ratio of 1:30:5, the pH is adjusted to 4.5 with acetic acid, and the mixture is magnetically stirred for 12 minutes. Step (3): Dry mix cement, fly ash, silica fume and 70% modified PVA fiber in a mixer to obtain a dry mix. Step (4): Mix the prepared composite solution, water-reducing agent, defoamer and expansion agent with water to obtain an admixture solution; mix the admixture solution with the dry mix in two batches, with a mass ratio of 7:3 for the two additions, and a mixing time of 2 minutes for each addition to obtain cement paste. Step (5): Pour well-graded quartz sand and ultrasonically dispersed graphene into cement paste at a uniform speed, stir at low speed for 2 minutes, and stir at high speed for 1 minute to obtain cement mortar mixture. Step (6): Add steel fibers to the cement mortar mixture, stir for 2 minutes, then add the remaining 30% of modified PVA fibers and continue stirring until uniform, to obtain a prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on dispersion process.

[0024] Examples 2-9 The specific steps of the preparation method of the prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on dispersion process in Examples 2-9 are the same as those in Example 1. The proportions of each group are shown in Table 1 and Table 2.

[0025] Comparative Example 1 This comparative example provides a method for preparing a cement-based grouting material, comprising the following steps: Step (1): Dry mix cement, fly ash, and silica fume in a mixer to obtain a dry mix. Step (2): Mix the prepared composite solution, water-reducing agent, defoamer, and expanding agent with water to obtain an admixture solution; mix the admixture solution with the dry mix in two batches, with a mass ratio of 7:3 for the two additions, and a mixing time of 2 minutes for each addition to obtain cement paste. Step (3): Pour well-graded quartz sand and ultrasonically dispersed graphene into cement paste at a uniform speed, stir at low speed for 2 minutes, and stir at high speed for 1 minute to obtain cement-based grout.

[0026] Comparative Example 2 This comparative example provides a method for preparing a prestressed steel fiber reinforced cementitious grout, comprising the following steps: Step (1): The steel fiber is subjected to axial pretensioning treatment so that its tensile stress is 70% of the yield strength. The axially pretensioned steel fiber is placed in a micro-nano sandblasting equipment and alumina micro-nano particles are used as the sandblasting medium. The surface is sandblasted for 3 minutes under a pressure of 0.3MPa to form micron protrusions and nano rough surfaces. Then, copper plating treatment is performed to form a copper plating layer with a thickness of 5μm to ensure the conductivity and corrosion resistance of the fiber. Finally, it is dried at 40℃ for 2 hours for later use to obtain prestressed steel fiber. The alumina micro-nano particles are obtained by mixing alumina particles with a particle size of 50μm and alumina particles with a particle size of 200nm in a mass ratio of 1:1. Step (2): Dry mix cement, fly ash, and silica fume in a mixer to obtain a dry mix. Step (3): Mix the prepared composite solution, water-reducing agent, defoamer, and expanding agent with water to obtain an admixture solution; mix the admixture solution with the dry mix in two batches, with a mass ratio of 7:3 for the two additions, and a mixing time of 2 minutes for each addition to obtain cement paste. Step (4): Pour well-graded quartz sand and ultrasonically dispersed graphene into cement paste at a uniform speed, stir at low speed for 2 minutes, and stir at high speed for 1 minute to obtain cement mortar mixture. Step (5): Add prestressed steel fibers to the cement mortar mixture and continue to stir evenly to obtain prestressed steel fiber reinforced cement-based grouting material.

[0027] Comparative Examples 3-4 The specific steps for preparing the prestressed steel fiber reinforced cement-based grouting materials of Comparative Examples 3-4 are the same as those of Comparative Example 2, and the proportions of each group are shown in Table 1 and Table 2.

[0028] Comparative Example 5 This comparative example discloses a method for preparing a modified PVA fiber-reinforced cementitious grout, comprising the following steps: Step (1): Immerse PVA fibers in silane hydrolysis modification solution. The mass ratio of PVA fibers to silane coupling agent modification solution is 1:20. Stir in a 30℃ constant temperature water bath for 30 minutes. Take out the fibers and rinse them quickly with anhydrous ethanol 1-2 times. Then place them in an 80℃ forced air drying oven to dry for 3 hours. After complete drying, the modified PVA fibers are obtained for use. The method for preparing the modified silane coupling agent solution is as follows: silane coupling agent KH-550, ethanol and deionized water are mixed in a volume ratio of 1:30:5, the pH is adjusted to 4.5 with acetic acid, and the mixture is magnetically stirred for 12 minutes. Step (2): Dry mix cement, fly ash, silica fume and 70% modified PVA fiber in a mixer to obtain a dry mix. Step (3): Mix the prepared composite solution, water-reducing agent, defoamer and expansion agent with water to obtain an admixture solution; mix the admixture solution with the dry mix in two batches, with a mass ratio of 7:3 for the two additions, and a mixing time of 2 minutes for each addition to obtain cement paste. Step (4): Pour well-graded quartz sand and ultrasonically dispersed graphene into cement paste at a uniform speed, stir at low speed for 2 minutes, and stir at high speed for 1 minute to obtain cement mortar mixture. Step (5): Add the remaining 30% of the modified PVA fiber to the cement mortar mixture and continue to stir evenly to obtain the modified PVA fiber reinforced cement-based grouting material.

[0029] Comparative Examples 6-7 The preparation methods of the modified PVA fiber reinforced cementitious grouting materials of Comparative Examples 6-7 are the same as those of Comparative Example 5, and the proportions of each group are shown in Table 1 and Table 2.

[0030] Experimental Example According to the standard "Grouting Material for Reinforcing Steel Connection Sleeves" (JG / T—2019), performance tests were conducted on the prestressed steel and modified PVA fiber reinforced intelligent sensing grouting materials prepared by dispersion process in Examples 1-9, the cement-based grouting material prepared in Comparative Example 1, the prestressed steel fiber reinforced cement-based grouting materials prepared in Comparative Examples 2-4, and the modified PVA fiber reinforced cement-based grouting materials prepared in Comparative Examples 5-7. The test items included flowability test, mechanical property test (test block size 40*40*160mm), and vertical expansion rate. The relevant performance test results are shown in Table 3. Table 3 As shown in Table 3, the mechanical strength of the prestressed steel and modified PVA fiber reinforced intelligent sensing grouting materials based on the dispersion process in Examples 1-9 was significantly improved due to the addition of prestressed steel fibers and modified PVA fibers. This indicates that prestressed steel fibers and modified PVA fibers can play a good reinforcing role in the grouting matrix. Compared with Examples 1-9, the best mechanical properties were observed in Example 5. In addition, due to the continuous increase in the total amount of fibers, the fluidity value of the cement-based grouting material decreased, and the fluidity deteriorated. The higher the fiber content in the grouting material, the lower the initial fluidity and the 30-minute fluidity. The difference between Comparative Examples 2-7 and Examples 1-9 is that Comparative Examples 2-7 are reinforced with a single type of fiber. As can be seen from the data in Table 3, although the effect of a single type of fiber on the fluidity is small, its enhancement effect on the mechanical properties of the grout is to some extent smaller than that of mixed fibers. In particular, the compressive and flexural strengths of Example 5 have reached the best effect, effectively solving the problems in engineering applications. Furthermore, no bleeding of the grout was observed during the testing of the examples and comparative examples.

[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on a dispersion process, characterized in that, It includes the following components: water, cement, fine aggregate, composite solution, fly ash, silica fume, graphene, and admixtures. It also includes 0.5-1.5% of prestressed steel fiber and 0.1-0.3% of modified PVA fiber, which are accounted for by the total volume of the above components. The PVA fiber is obtained by modifying PVA fiber with a silane coupling agent modification solution. The prestressed steel fiber is obtained by axial pretensioning, surface sandblasting, and copper plating of steel fiber.

2. The prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on dispersion process according to claim 1, characterized in that, The mass ratio of water, cement, fine aggregate, composite solution, fly ash, silica fume, graphene, and admixture is 230:900:1000:30:60:40:0.5:10.

5.

3. The prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on dispersion process according to claim 1, characterized in that, The steel fiber is a straight, copper-plated steel fiber, 13 mm in length, 200 μm in diameter, and 7.85 g / cm³. 3 The tensile strength is 2850 MPa, and the elastic modulus is 210 GPa; the PVA fiber is Kuraray K-II fiber from Japan, with a length of 12 mm, a diameter of 40 μm, and a density of 1.3 g / cm³. 3 Its tensile strength is 1400-1600MPa and its elastic modulus is 35-39GPa.

4. The prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on dispersion process according to claim 1, characterized in that, The cement is PO 525 silicate cement with an apparent density of 3.15 g / cm³. 3 The standard consistency is 28%, and the specific surface area is 380 m². 2 / kg; the fine aggregate is well-graded quartz sand with a particle size distribution of 0.08-2.0mm.

5. The prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on dispersion process according to claim 1, characterized in that, The composite solution is obtained by mixing an aqueous epoxy resin solution and a lithium silicate solution at a mass ratio of 3:

1. The aqueous epoxy resin solution has a solid content of 48-52% and an epoxy equivalent of 450-550 g / mol. The lithium silicate solution has a modulus of 4.8-5.

5.

6. The prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on dispersion process according to claim 1, characterized in that, The fly ash is Class I fly ash with a density of 2.1 g / cm³. 3 The bulk density is 1.10 g / cm³. 3 The silica fume is S96 silica fume, with a SiO2 content of 96% and a specific surface area of ​​19m². 2 / g; the graphene is xGnP-M25 type multilayer graphene nanosheets with a particle size of 25μm, a thickness of 6-8nm, and a density of 2.2g / cm³. 3 .

7. The intelligent sensing grouting material based on dispersion process and reinforced with prestressed steel and modified PVA fiber according to claim 1, characterized in that, The additive is obtained by mixing water-reducing agent, defoamer and expanding agent in a mass ratio of 8:2:0.5, wherein the water-reducing agent is a polycarboxylate water-reducing agent, the defoamer is a polyoxyethylene oxypropylene ether defoamer and the expanding agent is a plastic expanding agent.

8. A method for preparing a prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on a dispersion process as described in any one of claims 1-7, characterized in that, Includes the following steps: Step (1): The steel fiber is subjected to axial pretensioning treatment so that its tensile stress is 70% of the yield strength. The axially pretensioned steel fiber is placed in a micro-nano sandblasting equipment and alumina micro-nano particles are used as the sandblasting medium. The surface is sandblasted for 3 minutes under a pressure of 0.3 MPa. Then, copper plating treatment is performed to form a copper plating layer. Finally, it is dried at 40°C for 2 hours for later use to obtain prestressed steel fiber. The alumina micro-nano particles are obtained by mixing alumina particles with a particle size of 50 μm and alumina particles with a particle size of 200 nm in a mass ratio of 1:

1. The thickness of the copper plating layer is 5 μm. Step (2): Immerse the PVA fiber in the silane coupling agent modification solution, stir in a constant temperature water bath at 30-40℃ for 30 min, take out the PVA fiber, rinse it with ethanol 1-2 times, and dry it at 80℃ for 2-3 h to obtain the modified PVA fiber; wherein, the mass ratio of PVA fiber to silane coupling agent modification solution is 1:

20. Step (3): Mix cement, fly ash, silica fume and 70wt% modified PVA fiber evenly to obtain dry mix; Step (4): Mix the prepared composite solution, water-reducing agent, defoamer and expansion agent with water to obtain an admixture solution; mix the admixture solution with the dry mix in two batches, with a mass ratio of 7:3 for the two additions, and a mixing time of 2 minutes for each addition to obtain cement paste. Step (5): Pour well-graded quartz sand and ultrasonically dispersed graphene into cement paste, stir at low speed for 2 minutes and at high speed for 1 minute to obtain cement mortar mixture. Step (6): Add prestressed steel fibers to the cement mortar mixture, stir for 2-3 minutes, add the remaining 30wt% modified PVA fibers, and continue stirring until uniform to obtain a prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on dispersion process.

9. The prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on dispersion process according to claim 8, characterized in that, The method for preparing the modified silane coupling agent solution is as follows: silane coupling agent KH-550, ethanol and deionized water are mixed in a volume ratio of 1:30:5, the pH is adjusted to 4.0-5.0 with acetic acid, and the mixture is magnetically stirred for 10-15 minutes.

10. The application of prestressed steel and modified PVA fiber reinforced intelligent sensing grouting material based on dispersion process according to any one of claims 1-7 in the construction of prefabricated structure engineering.

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