High-strength sprayed concrete suitable for chlorine salt erosion environment

Abstract

The invention discloses high-strength sprayed concrete suitable for a chlorine salt erosion environment in the field of civil engineering materials. The concrete is prepared from cement, silica fume, fly ash, mineral powder, coarse and fine aggregates, polypropylene fibers, steel fibers, basalt fibers, a polycarboxylate water reducer, an air entraining agent, an aluminum sulfate-based alkali-free accelerator, a graphene-based imidazolium salt functionalized metal-organic framework and a silicon dioxide nanocapsule loaded corrosion inhibitor. The calcium phosphate-polymer hybrid pore regulating agent and the water are mixed according to a specific ratio. Wherein the graphene-based material is prepared through step-by-step reaction, so that the compactness of the concrete can be effectively improved; the silicon dioxide nanocapsule is subjected to surface coating and hydrophobic modification, so that the stability in an alkaline environment is enhanced, and intelligent release of the corrosion inhibitor is realized. The concrete provided by the invention has excellent chloride ion penetration resistance, high strength and durability, and is especially suitable for tunnel support and slope protection engineering in chlorine salt erosion environments such as temporary expressways and the like.

Description

Technical Field

[0001] This invention relates to the field of civil engineering materials technology, specifically to a high-strength shotcrete suitable for chloride-eroded environments. Background Technology

[0002] Shotcrete, a special type of concrete formed through spraying construction, is widely used in tunnel lining and slope protection projects in large-scale infrastructure projects such as the Linyi-Tengzhou Expressway. Compared with traditional concrete, shotcrete is required to have characteristics such as rapid setting, early strength, and strong adhesion to the substrate. However, existing shotcrete still has many limitations in practical applications: First, conventional shotcrete often uses a large amount of accelerator to meet the requirements of rapid setting and early strength, resulting in serious strength loss in the later stages, making it difficult to simultaneously meet the dual requirements of high strength and high durability; second, traditional shotcrete has insufficient durability in chloride erosion environments, and chloride ion penetration can lead to steel corrosion, which in turn causes the concrete cover to peel off, seriously affecting the service life of structures in major projects like the Linyi-Tengzhou Expressway; third, ordinary shotcrete has poor crack resistance and is prone to cracking under drying shrinkage, temperature changes, and load, providing a rapid intrusion channel for corrosive media.

[0003] To improve the durability of concrete in chloride environments, existing technologies typically employ the incorporation of mineral admixtures or fibers. Mineral admixtures such as silica fume and fly ash can improve the microstructure of concrete and reduce porosity through the pozzolanic effect; while the addition of fibers can effectively inhibit the generation and development of plastic shrinkage cracks in concrete. However, single technical approaches are often insufficient to comprehensively address the complexity of chloride erosion: mineral admixtures have a detrimental effect on early strength development and poor synergistic effect with accelerators; traditional fiber reinforcement can only improve the macroscopic properties of concrete and has limited impact on the transport process of chloride ions in concrete; common anti-corrosion measures such as the incorporation of rust inhibitors suffer from problems such as easy loss and short effective period. Especially under the special construction process of shotcrete, these problems are more prominent, and the addition of accelerators often interferes with the effects of other functional components, making it difficult to guarantee the long-term durability of concrete.

[0004] In recent years, the development of nanomaterials and smart materials technologies has provided new ideas for improving the durability of concrete. Researchers have attempted to introduce nanomaterials into concrete, utilizing their size and surface effects to optimize the concrete's microstructure; other studies have explored encapsulating corrosion inhibitors in microcapsules to achieve intelligent release under corrosive conditions. However, the application of these new materials in shotcrete still faces many challenges: nanomaterials have poor dispersibility in concrete, easily agglomerating and losing their modifying effect; conventional microcapsules lack stability in the high-alkali environment of concrete, easily releasing prematurely; and the synergistic mechanism of multiple functional materials is unclear, even showing mutual interference. Therefore, developing a high-strength shotcrete that can balance the requirements of the shotcreting process with long-term durability, especially resistance to chloride erosion, has become a pressing technical challenge in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a high-strength shotcrete suitable for chloride-corrosion environments, which solves the technical problems of short service life caused by poor impermeability, easy corrosion of steel bars and insufficient durability of existing shotcrete in chloride-corrosion environments.

[0006] The present invention achieves the above objectives through the following technical solutions:

[0007] A high-strength shotcrete comprises the following raw materials in parts by weight:

[0008] Cement: 380-420 parts by weight;

[0009] Silica fume: 25-45 parts by weight;

[0010] Fly ash: 50-70 parts by weight;

[0011] Mineral powder: 40-60 parts by weight;

[0012] Fine aggregate: 650-750 parts by weight;

[0013] Coarse aggregate: 850-950 parts by weight;

[0014] Polypropylene fiber: 1.0-2.0 parts by weight;

[0015] Steel fiber: 30-50 parts by weight;

[0016] Basalt fiber: 1.5-2.5 parts by weight;

[0017] Polycarboxylate water-reducing agent: 5-8 parts by weight;

[0018] Air-entraining agent: 0.1-0.3 parts by weight;

[0019] Aluminum sulfate-based alkali-free quick-setting agent: 25-35 parts by weight;

[0020] Graphene-based imidazolium salt functionalized metal-organic framework: 2.0-4.0 parts by weight;

[0021] Silica nanocapsules loaded with corrosion inhibitor: 1.5-3.5 parts by weight;

[0022] Calcium phosphate-polymer hybrid pore regulator: 3.0-5.0 parts by weight;

[0023] Water: 150-170 parts by weight;

[0024] The preparation method of the graphene-based imidazolium salt functionalized metal-organic framework includes: A1, dispersing graphene oxide in N,N-dimethylformamide and sonicating it; adding 2-methylimidazolium and zinc nitrate, and stirring the reaction at 78-82℃; A2, after the reaction is completed, centrifuging and washing with ethanol; reacting the washed product with 1-(3-chloropropyl)imidazolium at 68-72℃; washing with deionized water and vacuum drying at 78-82℃.

[0025] According to a preferred embodiment of the present invention, the mass ratio of graphene oxide: 2-methylimidazole: zinc nitrate: 1-(3-chloropropyl)imidazole is in the range of 1: (1.5-1.6): (1.88-2.0): (0.75-0.8).

[0026] In this invention, the preparation of graphene-based imidazolium salt functionalized metal-organic frameworks is a process of constructing multifunctional composite nanomaterials. The process begins with the dispersion and activation of graphene oxide in a solvent, where the oxygen-containing functional groups on its surface provide anchoring sites for subsequent reactions. Then, under heating conditions, zinc ions and dimethylimidazole undergo coordination self-assembly on the surface and between layers of graphene oxide, forming a metal-organic framework structure. This framework not only inherits the excellent mechanical properties and large specific surface area of ​​graphene but also possesses the high porosity and functionalizability of metal-organic framework materials. A key step involves further reacting the washed product with chloropropylimidazole to covalently graft imidazolium salt groups onto the composite framework. The resulting material exhibits that its imidazolium salt cations can efficiently adsorb and fix chloride ions infiltrating concrete through electrostatic interactions, while the nanonetwork composed of the metal-organic framework and graphene can also act as a micro-filler and reinforcement in the cement matrix, improving the density and mechanical strength of the concrete.

[0027] In this invention, during the preparation of high-strength shotcrete, three functional materials and a multi-component matrix work synergistically to form a multi-layered protective system. Cement, silica fume, fly ash, and mineral powder constitute a composite cementitious system, ensuring the foundation of the concrete's strength and durability. Polypropylene fibers, steel fibers, and basalt fibers form a multi-scale fiber reinforcement network, effectively improving the concrete's toughness and crack resistance. Polycarboxylate-based water-reducing agents and aluminum sulfate-based alkali-free quick-setting agents jointly ensure that the concrete meets the workability and rapid-setting early-strength requirements for shotcrete construction. Based on this, the three functional materials each perform their specific functions while also working synergistically: the pore regulator refines pores at the physical level, hindering the transport of corrosive media; the graphene-based framework material fixes infiltrated chloride ions through chemical adsorption; and silica nanocapsules act as intelligent reserves, releasing corrosion inhibitors to protect the reinforcing steel when needed. This multi-layered protective mechanism, combining macroscopic to microscopic, passive protection with active intervention, enables the shotcrete to maintain excellent structural performance and a long service life even in harsh chloride-salt corrosion environments.

[0028] According to a preferred embodiment of the present invention, in step A1, the stirring reaction time at 78-82°C is 12-14 hours.

[0029] According to a preferred embodiment of the present invention, in step A2, the reaction is carried out at 68-72°C for 8-10 hours.

[0030] According to a preferred embodiment of the present invention, the preparation method of the silica nanocapsule-loaded corrosion inhibitor includes: B1, dispersing mesoporous silica nanoparticles in ethanol and sonicating them; adding benzotriazole-5-carboxylic acid and 2-mercaptobenzothiazole and stirring and impregnating at 58-62°C; B2, adding tetraethyl orthosilicate and ammonia water for surface coating; then adding 3-aminopropyltriethoxysilane and ethyl acetate sequentially for reaction; after the reaction is completed, centrifuging, washing with ethanol, and vacuum drying at 68-72°C.

[0031] According to a preferred embodiment of the present invention, the mass ratio of silica nanoparticles: benzotriazole-5-carboxylic acid: 2-mercaptobenzothiazole: tetraethyl orthosilicate: 3-aminopropyltriethoxysilane: ethyl acetate is in the range of 1: (0.3-0.35): (0.2-0.3): (0.5-0.53): 0.2: (5.4-7.2).

[0032] In this invention, the core of preparing corrosion inhibitor-loaded silica nanocapsules lies in constructing a smart, responsive corrosion inhibitor delivery system. First, utilizing the large specific surface area and abundant pore structure of mesoporous silica nanoparticles, corrosion inhibitor molecules such as benzotriazole carboxylic acid and mercaptobenzothiazole are loaded into their pores through physical adsorption and capillary action. Subsequently, through the hydrolytic condensation of tetraethyl orthosilicate, a dense silica coating layer is formed on the outside of the corrosion inhibitor-loaded silica particles, encapsulating the corrosion inhibitor within and forming a core-shell structured nanocapsule. To enhance the stability of the capsules in the highly alkaline environment of concrete and achieve smart release, surface hydrophobic modification is performed using aminopropyltriethoxysilane and ethyl acetate. This constructs a hydrophobic barrier on the capsule surface, effectively resisting early erosion by moisture and ions; furthermore, this functional modification may enable the capsules to respond to local pH changes during chloride erosion of concrete. When corrosion occurs, local pH changes can damage this protective layer, triggering the directional release of corrosion inhibitors, which then migrate to the surface of the reinforcing steel to form a protective film, thereby achieving active corrosion protection for the reinforcing steel.

[0033] According to a preferred embodiment of the present invention, in step B1, the stirring and impregnation time at 58-62°C is 6-8 hours.

[0034] According to a preferred embodiment of the present invention, in step B2, the vacuum drying time at 68-72°C is 12-14 hours.

[0035] According to a preferred embodiment of the present invention, the preparation method of the calcium phosphate-polymer hybrid pore regulator includes: C1, dispersing calcium hydrogen phosphate in deionized water and stirring to form a suspension; adding isobutylene alcohol polyoxyethylene ether-methacrylic acid copolymer and polyvinyl alcohol, and reacting at 48-52°C; C2, subsequently adding calcium nitrate and urea, and hydrothermally reacting in a closed reactor at 88-92°C; after the reaction is completed, centrifuging, washing with water, and redispersing in deionized water to form a suspension.

[0036] According to a preferred embodiment of the present invention, the mass ratio of dicalcium phosphate: isobutylene alcohol polyoxyethylene ether-methacrylic acid copolymer: polyvinyl alcohol: calcium nitrate: urea is in the range of 1: (0.27-0.32): 0.2: 0.6: 0.4.

[0037] According to a preferred embodiment of the present invention, the preparation steps of the isobutylene polyoxyethylene ether-methacrylic acid copolymer include: adding 600g of isobutylene polyoxyethylene ether macromonomer and 400mL of deionized water to a 2000mL four-necked flask equipped with a mechanical stirrer, thermometer, condenser, and constant-pressure dropping funnel, and stirring and heating to 50°C to dissolve the monomer. Dissolving 4.0g of ammonium persulfate in 100mL of deionized water and placing it in the dropping funnel, and separately mixing 240g of methacrylic acid with 160mL of deionized water. After the temperature stabilizes at 50±0.5°C, simultaneously adding the initiator solution and the methacrylic acid solution, controlling the adding time to 120min and 90min respectively. After the addition is complete, continuing the reaction at 50±0.5°C for 60min, the conversion rate is measured to be approximately 12%. The reaction solution is cooled to 25°C, and the pH is adjusted to 7.0-7.5 with 20% sodium hydroxide solution. The product solution was concentrated by rotary evaporation at 60℃ and -0.095MPa to a solid content of about 40%, and finally dried under vacuum at 80℃ for 24h to obtain a white flaky solid.

[0038] In this invention, the preparation of a calcium phosphate-polymer hybrid pore regulator aims to optimize the microporous structure of concrete in situ. The process begins by dispersing dicalcium phosphate in a solution containing a specific polymer. The polymer molecules adsorb onto the surface of the calcium phosphate particles through their active groups, forming an organic-inorganic hybrid precursor. The hydrothermal reaction in a closed reactor is crucial. Urea decomposition provides the necessary alkaline and carbonate environment for the reaction, promoting the dissolution and recrystallization of calcium nitrate and dicalcium phosphate precursors under hydrothermal conditions, and their interaction with polymer molecules. The final product is a hybrid nanomaterial composed of intertwined calcium phosphate crystals and polymers. When added to concrete in suspension, these hybrid particles not only act as nano-nucleation sites to promote the deposition of hydration products, but their long polymer chains also bridge these products, filling the micropores of the cement paste. This filling effect effectively transforms larger harmful pores into smaller, harmless or less harmful pores, optimizing pore distribution and reducing pore connectivity. This significantly hinders the transport channels of chloride ions and water in concrete, improving its impermeability.

[0039] According to a preferred embodiment of the present invention, in step C1, the reaction time is 4-6 hours at 48-52°C.

[0040] According to a preferred embodiment of the present invention, in step C2, the hydrothermal reaction time at 88-92°C is 6-8 hours.

[0041] The present invention also provides an application of the high-strength shotcrete described above in a chloride-corrosion environment.

[0042] The beneficial effects of this invention are as follows:

[0043] The high-strength shotcrete provided by this invention, through innovative material ratios and structural design, exhibits superior comprehensive technical performance in chloride-alkali corrosion environments. It is particularly suitable for tunnel lining and slope protection in major projects such as the Linyi-Tengzhou Expressway, effectively solving the technical challenge of balancing durability, mechanical properties, and workability in traditional shotcrete. Firstly, in terms of mechanical properties and durability, this invention achieves a balance between high strength and high durability. By optimizing the cementitious material system and using a composite ratio of cement, silica fume, fly ash, and mineral powder, and with the aid of an aluminum sulfate-based alkali-free accelerator, it ensures the early strength required for shotcrete while continuously improving later-stage strength through the secondary hydration reaction of active admixtures. The synergistic effect of the three fibers significantly enhances the toughness and crack resistance of the concrete: polypropylene fibers effectively inhibit plastic shrinkage cracks, steel fibers provide excellent flexural tensile strength, and basalt fibers enhance impact resistance. Of particular note is the significant improvement in the durability of concrete in chloride environments achieved through the introduction of three functional materials: graphene-based imidazolium salt functionalized metal-organic frameworks, with their unique pore structure and surface properties, can efficiently adsorb and fix chloride ions, effectively slowing down the migration rate of chloride ions into the concrete interior; silica nanocapsules loaded with corrosion inhibitors remain stable in alkaline concrete environments, intelligently releasing corrosion-inhibiting components only when local pH changes, providing long-term protection for the reinforcing steel; and calcium phosphate-polymer hybrid pore regulators optimize the pore structure distribution of concrete by regulating the morphology of hydration products, significantly reducing the proportion of harmful pores and forming a dense microstructure.

[0044] Secondly, regarding the protective mechanism and long-term performance, this invention constructs a multi-level protection system. Graphene-based materials not only act as physical barriers, but their surface functional groups can also chemically interact with chloride ions, achieving active chloride ion capture. The hydrophobic treatment of the nanocapsules ensures their long-term stability in the highly alkaline environment of concrete, avoiding the easy loss of traditional rust inhibitors and achieving intelligent protection through "on-demand release." The pore regulator, through interaction with hydration products, promotes the transformation of low-density ettringite into high-density hydration products, effectively reducing defects in the interfacial transition zone and improving the overall density of the concrete. This multi-mechanism synergistic protection system enables concrete to maintain excellent performance under long-term chloride salt corrosion, significantly extending the service life of the structure.

[0045] Finally, regarding workability and engineering applicability, this invention fully considers the special process requirements of shotcrete. By precisely controlling the proportions and compatibility of each component, it ensures that the concrete has good cohesion and atomization during spraying, effectively reducing the rebound rate. The functional additives and accelerators are optimized to meet the construction requirements of rapid setting while ensuring the long-term effectiveness of various functional materials.

[0046] In summary, the product of this invention, through the synergistic effect of multiple functional components, possesses excellent resistance to chloride ion penetration, intelligent damage response characteristics, reliable mechanical properties, and good construction adaptability. It can provide long-term durability protection for major infrastructure projects in harsh chloride-salt environments such as the Lin-Teng Expressway, demonstrating significant technological advancement and engineering application value. Detailed Implementation

[0047] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0048] The following is information on domestic suppliers of key related equipment and materials:

[0049] The cement was purchased from Anhui Conch Cement Co., Ltd., specifically the PO42.5 grade.

[0050] The fine aggregate is river sand, which was purchased from Jiangxi Southern Cement Co., Ltd.

[0051] The coarse aggregate is basalt crushed stone, which was purchased from Hubei Changjiang New Building Materials Co., Ltd.

[0052] The polycarboxylate superplasticizer is a high-performance polycarboxylate superplasticizer, specifically the PC-1006 powdered polycarboxylate superplasticizer purchased from Wuhan Huaxuan High-Tech Co., Ltd.

[0053] The air-entraining agent is a synthetic saponin-based air-entraining agent, specifically the tea saponin liquid triterpenoid saponin air-entraining agent model purchased from Guangzhou Zhangdao Chemical Co., Ltd.

[0054] The aluminum sulfate-based alkali-free quick-setting agent was purchased from Shandong Yonglida New Material Technology Co., Ltd.

[0055] The silica fume was purchased from Shanghai Elken Silica Fume Materials Co., Ltd.

[0056] The fly ash was purchased from Shanxi Jintou Basalt Development Co., Ltd.

[0057] The mineral powder was purchased from Tangshan Arctic Bear Special Cement Co., Ltd.

[0058] The polypropylene fiber was purchased from Jiangsu Qingyun New Material Technology Co., Ltd.

[0059] The steel fibers were purchased from Shanghai Harrex Steel Fiber Technology Co., Ltd.

[0060] The basalt fiber was purchased from Sichuan Aerospace Tuoxin Basalt Industry Co., Ltd.

[0061] The graphene oxide was purchased from Changzhou Sixth Element Materials Technology Co., Ltd.

[0062] The 2-methylimidazole was purchased from Aladdin Reagent (Shanghai) Co., Ltd.

[0063] The zinc nitrate was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0064] The 1-(3-chloropropyl)imidazol was purchased from Jinan Henghua Technology Co., Ltd.

[0065] The mesoporous silica nanoparticles were purchased from Guangzhou Jibisheng Technology Industry Co., Ltd.

[0066] The benzotriazole-5-carboxylic acid was purchased from Jiangsu Kangpeng New Material Technology Co., Ltd.

[0067] The 2-mercaptobenzothiazole was purchased from Shandong Qilu Keli Chemical Research Institute Co., Ltd.

[0068] The tetraethyl orthosilicate was purchased from Hubei Xinlantian New Materials Co., Ltd.

[0069] The 3-aminopropyltriethoxysilane was purchased from Nanjing Chenggong Organosilicon Materials Co., Ltd.

[0070] The ethyl acetate was purchased from Jiangsu Hualun Chemical Co., Ltd.

[0071] The dicalcium phosphate was purchased from Yunnan Phosphate Group Co., Ltd.

[0072] The polyvinyl alcohol was purchased from Sichuan Vinylon Plant of China Petrochemical Corporation.

[0073] Example 1

[0074] The raw material ratio for high-strength shotcrete is as follows: cement 400g, silica fume 35g, fly ash 60g, mineral powder 50g, fine aggregate 700g, coarse aggregate 900g, polypropylene fiber 1.5g, steel fiber 40g, basalt fiber 2.0g, polycarboxylate water-reducing agent 6.5g, air-entraining agent 0.2g, aluminum sulfate-based alkali-free quick-setting agent 30g, graphene-based imidazolium salt functionalized metal-organic framework 3.0g, silica nanocapsule-loaded corrosion inhibitor 2.5g, calcium phosphate-polymer hybrid pore regulator 4.0g, and water 160g. The preparation process of graphene-based imidazolium salt functionalized metal-organic frameworks is as follows: First, 0.8 g of graphene oxide was added to 200 mL of N,N-dimethylformamide and ultrasonically treated at 600 W for 30 minutes to ensure thorough dispersion. Then, 1.2 g of 2-methylimidazole and 1.5 g of zinc nitrate were added. The mixture was transferred to an 80 °C oil bath and stirred at 400 rpm for 13 hours. After the reaction, the mixture was centrifuged at 8000 rpm for 5 minutes and washed three times with 100 mL of ethanol. The washed product was then reacted with 0.6 g of 1,3-chloropropylimidazole at 70 °C at 300 rpm for 9 hours. Finally, the product was washed three times with deionized water and dried in a vacuum drying oven at 80 °C for 12 hours to obtain the final product. The preparation process of silica nanocapsules loaded with corrosion inhibitors is as follows: 1.5g of mesoporous silica nanoparticles are dispersed in 150mL of ethanol and ultrasonically treated for 20 minutes. 0.5g of benzotriazole-5-carboxylic acid and 0.4g of 2-mercaptobenzothiazole are added, and the mixture is stirred and impregnated in a 60℃ water bath at 350rpm for 7 hours. Then, 0.8g of tetraethyl orthosilicate and 5mL of 25% ammonia solution are slowly added, and the reaction is continued for 2 hours to complete the surface coating. Subsequently, 0.3g of 3-aminopropyltriethoxysilane and 10mL of ethyl acetate are added sequentially, and the mixture is reacted at 60℃ for 1 hour to complete the hydrophobic modification. Finally, the mixture is centrifuged at 8000rpm, washed three times with ethanol, and vacuum dried at 70℃ for 13 hours to obtain the finished product. The preparation process of the calcium phosphate-polymer hybrid pore regulator is as follows: 2.0 g of dicalcium phosphate is dispersed in 100 mL of deionized water and stirred at 500 rpm to form a uniform suspension. 0.6 g of isobutylene alcohol polyoxyethylene ether-methacrylic acid copolymer and 0.4 g of polyvinyl alcohol are added and reacted in a 50 °C water bath for 5 hours. Then, 1.2 g of calcium nitrate and 0.8 g of urea are added. The mixture is transferred to a 100 mL stainless steel reactor lined with polytetrafluoroethylene and hydrothermally reacted in a 90 °C oven for 7 hours. After the reaction is completed, the mixture is centrifuged at 8000 rpm, washed three times with deionized water, and finally redispersed in 50 mL of deionized water to form a stable suspension.The concrete preparation process is as follows: First, cement, silica fume, fly ash, mineral powder, fine aggregate, and coarse aggregate are poured into a forced mixer and dry-mixed for 2 minutes. Then, polypropylene fiber, steel fiber, and basalt fiber are added and mixed for another minute. Polycarboxylate superplasticizer, air-entraining agent, graphene-based imidazolium salt functionalized metal-organic framework, silica nanocapsule-loaded corrosion inhibitor, and calcium phosphate-polymer hybrid pore regulator are pre-dissolved in 160g of water to form a homogeneous solution. This solution is poured into the mixer and stirred for 3 minutes to form fluid concrete. Finally, aluminum sulfate-based alkali-free quick-setting agent is added and quickly stirred for 1 minute. Spraying is then carried out immediately.

[0075] Example 2

[0076] The specific implementation method is the same as in Example 1, except that the raw material ratio of the high-strength shotcrete is as follows: cement 380g, silica fume 25g, fly ash 50g, mineral powder 40g, fine aggregate 650g, coarse aggregate 850g, polypropylene fiber 1.0g, steel fiber 30g, basalt fiber 1.5g, polycarboxylate water-reducing agent 5.0g, air-entraining agent 0.1g, aluminum sulfate-based alkali-free quick-setting agent 25g, graphene-based imidazolium salt functionalized metal-organic framework 2.0g, silica nanocapsule-loaded corrosion inhibitor 1.5g, calcium phosphate-polymer hybrid pore regulator 3.0g, and water 150g. The preparation process of graphene-based imidazole onium salt functionalized metal-organic frameworks is as follows: First, 0.5 g of graphene oxide was added to 150 mL of N,N-dimethylformamide and ultrasonically treated at 550 W for 25 minutes to ensure complete dispersion. Then, 0.8 g of 2-methylimidazole and 1.0 g of zinc nitrate were added. The mixture was transferred to an oil bath at 78 °C and stirred at 350 rpm for 12 hours. After the reaction, the mixture was centrifuged at 7500 rpm for 5 minutes and washed three times with 80 mL of ethanol. The washed product was then reacted with 0.4 g of 1,3-chloropropylimidazole at 68 °C at 280 rpm for 8 hours. Finally, the product was washed three times with deionized water and dried in a vacuum drying oven at 78 °C for 12 hours to obtain the final product. The preparation process of silica nanocapsules loaded with corrosion inhibitor is as follows: 1.0 g of mesoporous silica nanoparticles are dispersed in 100 mL of ethanol and ultrasonically treated for 15 minutes. 0.3 g of benzotriazole-5-carboxylic acid and 0.2 g of 2-mercaptobenzothiazole are added, and the mixture is stirred and impregnated in a water bath at 300 rpm at 58 °C for 6 hours. Then, 0.5 g of tetraethyl orthosilicate and 3 mL of 25% ammonia solution are slowly added, and the reaction is continued for 2 hours to complete the surface coating. Subsequently, 0.2 g of 3-aminopropyltriethoxysilane and 8 mL of ethyl acetate are added sequentially, and the mixture is reacted at 58 °C for 1 hour to complete the hydrophobic modification. Finally, the mixture is centrifuged at 7500 rpm, washed three times with ethanol, and vacuum dried at 68 °C for 12 hours to obtain the finished product. The preparation process of the calcium phosphate-polymer hybrid pore regulator is as follows: 1.5g of dicalcium phosphate is dispersed in 80mL of deionized water and stirred at 450rpm to form a uniform suspension. 0.4g of isobutylene alcohol polyoxyethylene ether-methacrylic acid copolymer and 0.3g of polyvinyl alcohol are added and reacted in a water bath at 48℃ for 4 hours. Then, 0.9g of calcium nitrate and 0.6g of urea are added. The mixture is transferred to an 80mL stainless steel reactor lined with polytetrafluoroethylene and hydrothermally reacted in an oven at 88℃ for 6 hours. After the reaction is completed, the mixture is centrifuged at 7500rpm, washed three times with deionized water, and finally redispersed in 40mL of deionized water to form a stable suspension.The concrete preparation process is as follows: First, cement, silica fume, fly ash, mineral powder, fine aggregate, and coarse aggregate are poured into a forced mixer and dry-mixed for 2 minutes. Then, polypropylene fiber, steel fiber, and basalt fiber are added and mixed for another minute. Polycarboxylate superplasticizer, air-entraining agent, graphene-based imidazolium salt functionalized metal-organic framework, silica nanocapsule-loaded corrosion inhibitor, and calcium phosphate-polymer hybrid pore regulator are pre-dissolved in 150g of water to form a uniform solution. This solution is poured into the mixer and stirred for 3 minutes to form fluid concrete. Finally, aluminum sulfate-based alkali-free quick-setting agent is added and quickly stirred for 1 minute. Spraying is then carried out immediately.

[0077] Example 3

[0078] The specific implementation method is the same as in Example 1, except that the raw material ratio of the high-strength shotcrete is as follows: cement 420g, silica fume 45g, fly ash 70g, mineral powder 60g, fine aggregate 750g, coarse aggregate 950g, polypropylene fiber 2.0g, steel fiber 50g, basalt fiber 2.5g, polycarboxylate water-reducing agent 8.0g, air-entraining agent 0.3g, aluminum sulfate-based alkali-free quick-setting agent 35g, graphene-based imidazolium salt functionalized metal-organic framework 4.0g, silica nanocapsule-loaded corrosion inhibitor 3.5g, calcium phosphate-polymer hybrid pore regulator 5.0g, and water 170g. The preparation process of graphene-based imidazole onium salt functionalized metal-organic frameworks is as follows: First, 1.0 g of graphene oxide was added to 250 mL of N,N-dimethylformamide and ultrasonically treated at 650 W for 35 minutes to ensure complete dispersion. Then, 1.5 g of 2-methylimidazole and 2.0 g of zinc nitrate were added. The mixture was transferred to an oil bath at 82 °C and stirred at 450 rpm for 14 hours. After the reaction, the mixture was centrifuged at 8500 rpm for 6 minutes and washed three times with 120 mL of ethanol. The washed product was then reacted with 0.8 g of 1,3-chloropropylimidazole at 72 °C at 320 rpm for 10 hours. Finally, the product was washed three times with deionized water and dried in a vacuum drying oven at 82 °C for 13 hours to obtain the final product. The preparation process of silica nanocapsules loaded with corrosion inhibitors is as follows: 2.0 g of mesoporous silica nanoparticles are dispersed in 200 mL of ethanol and ultrasonically treated for 25 minutes. 0.7 g of benzotriazole-5-carboxylic acid and 0.6 g of 2-mercaptobenzothiazole are added, and the mixture is stirred and impregnated in a 62 °C water bath at 400 rpm for 8 hours. Then, 1.0 g of tetraethyl orthosilicate and 7 mL of 25% ammonia solution are slowly added, and the reaction is continued for 2 hours to complete the surface coating. Subsequently, 0.4 g of 3-aminopropyltriethoxysilane and 12 mL of ethyl acetate are added sequentially, and the mixture is reacted at 62 °C for 1 hour to complete the hydrophobic modification. Finally, the mixture is centrifuged at 8500 rpm, washed three times with ethanol, and vacuum dried at 72 °C for 14 hours to obtain the final product. The preparation process of the calcium phosphate-polymer hybrid pore regulator is as follows: 2.5g of dicalcium phosphate is dispersed in 120mL of deionized water and stirred at 550rpm to form a uniform suspension. 0.8g of isobutylene alcohol polyoxyethylene ether-methacrylic acid copolymer and 0.5g of polyvinyl alcohol are added and reacted in a water bath at 52℃ for 6 hours. Then, 1.5g of calcium nitrate and 1.0g of urea are added. The mixture is transferred to a 120mL stainless steel reactor lined with polytetrafluoroethylene and hydrothermally reacted in an oven at 92℃ for 8 hours. After the reaction, the mixture is centrifuged at 8500rpm, washed three times with deionized water, and finally redispersed in 60mL of deionized water to form a stable suspension.The concrete preparation process is as follows: First, cement, silica fume, fly ash, mineral powder, fine aggregate, and coarse aggregate are poured into a forced mixer and dry-mixed for 2 minutes. Then, polypropylene fiber, steel fiber, and basalt fiber are added and mixed for another minute. Polycarboxylate superplasticizer, air-entraining agent, graphene-based imidazolium salt functionalized metal-organic framework, silica nanocapsule-loaded corrosion inhibitor, and calcium phosphate-polymer hybrid pore regulator are pre-dissolved in 170g of water to form a homogeneous solution. This solution is poured into the mixer and stirred for 3 minutes to form fluid concrete. Finally, aluminum sulfate-based alkali-free quick-setting agent is added and quickly stirred for 1 minute before spraying.

[0079] Comparative Example 1

[0080] The specific implementation method is the same as in Example 1, except that the graphene-based imidazolium salt functionalized metal-organic framework is omitted, and the corresponding mass is replaced with water.

[0081] Comparative Example 2

[0082] The specific implementation method is the same as in Example 1, except that the silica nanocapsule-loaded corrosion inhibitor is omitted and the corresponding mass is replaced with water.

[0083] Comparative Example 3

[0084] The specific implementation method is the same as in Example 1, except that the calcium phosphate-polymer hybrid pore regulator is omitted and the corresponding mass of water is used instead.

[0085] Comparative Example 4

[0086] The specific implementation method is the same as in Example 1, except that the graphene-based imidazolium salt functionalized metal-organic framework, silica nanocapsule-loaded corrosion inhibitor, and calcium phosphate-polymer hybrid pore regulator are omitted, and water is used to replace them in the corresponding mass.

[0087] Performance testing

[0088] The high-strength shotcrete suitable for chloride-erosion environments prepared in Examples 1-3 and Comparative Examples 1-4 were tested according to the following performance testing methods: Specimen preparation: Three types of specimens were prepared according to the proportions of each example and comparative example, including 150 mm cube specimens, 100 mm × 100 mm × 400 mm prism specimens, and 100 mm diameter, 50 mm height cylindrical specimens. After molding, all specimens were placed in a standard curing room at a temperature of 20±2℃ and a relative humidity of over 95% for 28 days. Mechanical property testing: A 2000 kN compression testing machine was used. The cube specimen was placed in the center of the lower pressure plate and uniformly loaded at a loading rate of 0.5 MPa / s until failure. The maximum load was recorded, and the 28-day compressive strength was calculated. The average value of 6 specimens in each group was taken. In the durability performance test, the chloride ion permeation performance was tested using the rapid migration coefficient method. A cylindrical specimen was vacuum-saturated with water and installed in the testing apparatus. 0.3 mol / L NaOH solution and 3.0% NaCl solution were injected into both sides of the specimen, respectively. A 30 V DC voltage was applied for 24 h. After the test, the specimen was split, and the permeation depth was measured using a 0.1 mol / L AgNO3 solution for colorimetric analysis. The chloride ion diffusion coefficient was calculated using a theoretical formula. For the electrical flux test, a cylindrical specimen of the same size was tested at 60 V DC voltage for 6 h to measure the total amount of electricity passing through. For the rebar corrosion test, a prism specimen with an internal diameter of 12 mm and a length of 50 mm carbon steel rebar was prepared and immersed in a 3.5% NaCl solution for 90 wet-dry cycles. Each cycle included drying at 60℃ for 12 h and immersion in the solution for 12 h. After the test, the rebar was removed, corrosion products were cleaned, and the mass loss was measured to calculate the corrosion weight loss rate. The rebound rate test determined the percentage of rebound material mass through actual spraying. The early strength test used a 100 mm side cube specimen to determine the 1-day compressive strength under standard curing conditions.

[0089] Performance test results:

[0090] Table 1: Performance test results of each embodiment and comparative example

[0091] Test Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 28-day compressive strength / MPa 78.5 75.8 80.2 72.3 73.6 71.8 65.2 <![CDATA[Chloride ion diffusion coefficient / (×10 -12 m² / s)]]> 0.85 0.92 0.78 1.35 1.28 1.41 2.15 Electric flux / C 1250 1380 1150 2150 1950 2280 3250 Steel reinforcement corrosion weight loss rate / % 0.12 0.15 0.10 0.31 0.42 0.38 0.65 Rebound rate / % 8.5 9.2 7.8 13.5 12.8 14.2 18.6 1-day intensity / MPa 15.2 14.6 16.1 14.8 14.9 14.5 13.2

[0092] As shown in Table 1, the test data fully demonstrates that Examples 1-3 systematically solved the technical challenges under chloride erosion environments through the synergistic effect of the three functional materials. Regarding impermeability, the chloride ion diffusion coefficients of Examples 1-3 remained stable at 0.78-0.92 × 10⁻⁶. -12 Within the range of m² / s, compared to 2.15 × 10⁻⁶ in Comparative Example 4. -12The m² / s was reduced by approximately 63%, and the electrical flux index also showed an improvement of approximately 65% ​​compared to Comparative Example 4. This is mainly attributed to the dual barrier formed by the chloride ion adsorption function of the graphene-based material and the pore size optimization effect of the pore regulator. Regarding rebar protection, the rebar corrosion weight loss rate of the embodiment was only 0.10%-0.15%, while Comparative Examples 2 and 4 reached 0.42% and 0.65%, respectively, demonstrating that the intelligent slow-release mechanism of the silica nanocapsules can effectively inhibit rebar corrosion. In terms of mechanical properties and construction adaptability, the 28-day compressive strength of the embodiment was increased by approximately 20% compared to Comparative Example 4, and the rebound rate was reduced to 7.8%-9.2%, far lower than the 18.6% of Comparative Example 4, showing that the functional material significantly improves sprayability while maintaining strength. It is particularly noteworthy that when each of the Comparative Examples 1-3 lacked a single functional material, all performance characteristics deteriorated significantly. However, Examples 1-3 constructed a multi-layered protection system through the synergistic complementarity of three materials: graphene-based materials provide physicochemical adsorption sites, nanocapsules establish an intelligent slow-release defense line, and pore regulators optimize the microstructure. Ultimately, this enabled the concrete to maintain excellent durability under harsh chloride salt environments, effectively extending the service life of the structure.

[0093] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A high-strength shotcrete, characterized in that, Including the following parts by weight of raw materials: Cement: 380-420 parts by weight; Silica fume: 25-45 parts by weight; Fly ash: 50-70 parts by weight; Mineral powder: 40-60 parts by weight; Fine aggregate: 650-750 parts by weight; Coarse aggregate: 850-950 parts by weight; Polypropylene fiber: 1.0-2.0 parts by weight; Steel fiber: 30-50 parts by weight; Basalt fiber: 1.5-2.5 parts by weight; Polycarboxylate water-reducing agent: 5-8 parts by weight; Air-entraining agent: 0.1-0.3 parts by weight; Aluminum sulfate-based alkali-free quick-setting agent: 25-35 parts by weight; Graphene-based imidazolium salt functionalized metal-organic framework: 2.0-4.0 parts by weight; Silica nanocapsules loaded with corrosion inhibitor: 1.5-3.5 parts by weight; Calcium phosphate-polymer hybrid pore regulator: 3.0-5.0 parts by weight; Water: 150-170 parts by weight; The preparation method of the graphene-based imidazolium salt functionalized metal-organic framework includes: A1, dispersing graphene oxide in N,N-dimethylformamide and sonicating it; adding 2-methylimidazolium and zinc nitrate, and stirring the reaction at 78-82℃; A2, after the reaction is completed, centrifuging and washing with ethanol; reacting the washed product with 1-(3-chloropropyl)imidazolium at 68-72℃; washing with deionized water and vacuum drying at 78-82℃.

2. The high-strength shotcrete according to claim 1, characterized in that, In step A1, the stirring reaction is carried out at 78-82℃ for 12-14 hours.

3. The high-strength shotcrete according to claim 1, characterized in that, In step A2, the reaction is carried out at 68-72℃ for 8-10 hours.

4. The high-strength shotcrete according to claim 1, characterized in that, The preparation method of the silica nanocapsule-loaded corrosion inhibitor includes: B1, dispersing mesoporous silica nanoparticles in ethanol and sonicating them; adding benzotriazole-5-carboxylic acid and 2-mercaptobenzothiazole and stirring and impregnating at 58-62℃; B2, adding tetraethyl orthosilicate and ammonia water for surface coating; then adding 3-aminopropyltriethoxysilane and ethyl acetate sequentially for reaction; after the reaction is completed, centrifuging, washing with ethanol, and vacuum drying at 68-72℃.

5. The high-strength shotcrete according to claim 4, characterized in that, In step B1, the stirring and soaking time is 6-8 hours at 58-62℃.

6. The high-strength shotcrete according to claim 4, characterized in that, In step B2, the vacuum drying time at 68-72℃ is 12-14 hours.

7. The high-strength shotcrete according to claim 1, characterized in that, The preparation method of the calcium phosphate-polymer hybrid pore regulator includes: C1, dispersing calcium hydrogen phosphate in deionized water and stirring to form a suspension; adding isobutylene alcohol polyoxyethylene ether-methacrylic acid copolymer and polyvinyl alcohol, and reacting at 48-52℃; C2, subsequently adding calcium nitrate and urea, and hydrothermally reacting in a closed reactor at 88-92℃; after the reaction is completed, centrifuging, washing with water, and redispersing in deionized water to form a suspension.

8. The high-strength shotcrete according to claim 7, characterized in that, In step C1, the reaction time is 4-6 hours at 48-52℃.

9. The high-strength shotcrete according to claim 7, characterized in that, In step C2, the hydrothermal reaction time at 88-92℃ is 6-8 hours.

10. An application of high-strength shotcrete according to any one of claims 1-9, characterized in that, The application of high-strength shotcrete in chloride-corrosion environments.