A high-crack-resistance and long-life concrete product and its preparation method

Abstract

The present invention discloses a high crack resistance and long life concrete product and its preparation method, which belongs to the technical field of marine concrete products. The concrete product includes the following components: 70-90 parts of ferroaluminate cement, 15-30 parts of fly ash, 10-25 parts of slag, 0.05-0.2 parts of modified boron nitride nanosheets, 3-8 parts of hybrid binders, 0.2-0.8 parts of double-anti-release diatom balls, 2-5 parts of composite anti-cracking agents, 0.5-1.5 parts of nano-clay fiber compounds, and 1.5-3 parts of bacterial glue recovery agents. The present invention significantly improves the compressive and flexural properties of marine cement concrete materials through gradient layering design, hybrid binders and nanofiber compounding, and crack resistance is better than the prior art. Its Poisson's ratio is lower, indicating that the lateral deformation is smaller when stressed, the structural stability is higher, and the propagation of microcracks can be effectively suppressed. The antifreeze durability index and sulfate resistance grade are significantly improved, thanks to the pore filling of the double-anti-release diatom balls and the dynamic repair effect of the bacterial glue recovery agent.

Description

Technical Field

[0001] The present invention relates to the technical field of marine engineering concrete products, and in particular to a high-crack-resistance and long-life concrete product and a preparation method thereof. Background Art

[0002] In the field of marine concrete product technology, precast components, as key foundational materials for marine engineering, are widely used in offshore structures, ports, docks, and offshore platforms. They must possess properties such as resistance to seawater erosion, resistance to chloride ion penetration, and durability to ensure the long-term stability and safety of marine structures. Annual losses due to marine corrosion account for approximately one-third of total corrosion losses, resulting in economic losses exceeding 1.5 trillion yuan. Therefore, seawater corrosion of concrete has become a global challenge. Traditional Portland cement concrete products often face numerous technical bottlenecks, severely restricting their durability and engineering applicability. Ferroaluminate cement, a third-generation cement independently developed in my country, primarily consists of anhydrous calcium sulfoaluminate, dicalcium silicate, and calcium aluminoferrite. Its hydration product, calcium hydroxide, produces low levels of calcium hydroxide, which contributes to its strength development, and its ferric gel can block chloride ions. Ferroaluminate cement's unique mineral composition and hydration products give it a natural and decisive advantage in corrosion resistance, making it a promising and effective technical solution to marine corrosion.

[0003] Although some existing technologies have been used to enhance the compressive and flexural strength of concrete, there is still room for improvement in practical applications. For example, the internal stress distribution of the material has not been fully optimized, resulting in the material's crack resistance and structural stability not being able to reach the optimal state under complex stress conditions. In terms of durability, despite various modification technologies, there is still room for improvement in the frost resistance durability index and sulfate resistance level of concrete. Especially in harsh marine environments, long-term exposure to seawater erosion and sulfate corrosion may cause concrete products using existing technologies to experience durability degradation. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the present invention provides a high-crack-resistance and long-life concrete product and a preparation method thereof.

[0005] A highly crack-resistant and long-life concrete product, comprising the following components, by weight: 70-90 parts of ferroaluminate cement, 15-30 parts of fly ash, 10-25 parts of slag, 0.05-0.2 parts of modified boron nitride nanosheets, 3-8 parts of a hybrid binder, 0.2-0.8 parts of dual-anti-release diatom balls, 2-5 parts of a composite anti-cracking agent, 0.5-1.5 parts of a nanoclay fiber compound, 1.5-3 parts of a bacterial glue restoring agent, 120-160 parts of sand, 150-200 parts of gravel, and 1-2.2 parts of an admixture;

[0006] The admixture is a polycarboxylate water reducer;

[0007] The modified boron nitride nanosheets are boron nitride nanosheets with aminosilane grafted on the surface and with a concentration gradient increasing from the core to the surface;

[0008] The hybrid binder is a composite binder of epoxy resin and modified silica sol;

[0009] The dual-antibiotic-releasing diatom balls are calcium alginate microspheres loaded with nano-silica;

[0010] The nanoclay fiber composite is a composite of basalt fiber and polyvinyl alcohol fiber coated with nanoclay on the surface;

[0011] The bacterial glue restoration agent comprises epoxy resin microcapsules and microbial repair agents.

[0012] A method for preparing the highly crack-resistant and long-life concrete product comprises the following steps:

[0013] S1: Sodium alginate solution and nano-silica suspension are mixed to form a mixed sol, and the mixed sol is dropped into a calcium chloride solution by ion crosslinking to form porous microspheres. The porous microspheres are freeze-dried in a vacuum and then calcined to obtain dual-antibody-releasing diatom balls;

[0014] S2: Grinding limestone, bauxite, steel slag, and gypsum together to prepare raw material, calcining at high temperature to obtain clinker, and grinding the clinker with gypsum and alum stone to obtain a composite anti-cracking agent;

[0015] S3: dispersing nanoclay in a polyvinyl alcohol aqueous solution to form a suspension, impregnating basalt fiber and polyvinyl alcohol fiber in the suspension, and forming a nanoclay fiber composite after hot air drying;

[0016] S4: Mixing epoxy resin with a latent curing agent, dicyandiamide, to form a core material, using polyurea-formaldehyde resin as a wall material, forming a shell layer on the surface of the core material by interfacial polymerization, washing with ethanol, and then drying to obtain epoxy resin microcapsules;

[0017] S5: Bacillus spores are adsorbed on a porous zeolite carrier in a phosphate buffer solution, and the porous zeolite carrier loaded with Bacillus spores is freeze-dried to form a microbial remediation agent. The epoxy resin microcapsules prepared in step S4 are mixed with the microbial remediation agent to obtain a bacterial gel restoration agent;

[0018] S6: nano-silica sol is mixed with epoxy silane coupling agent, and ultrasonic treatment is performed to graft epoxy groups on the surface of the silica sol. Unreacted coupling agent is removed by centrifugation to obtain modified silica sol, which is then washed with ethanol and dried for later use;

[0019] The bisphenol A epoxy resin is heated to reduce the viscosity and a diluent is added;

[0020] The modified silica sol is added to the epoxy resin, mechanically stirred, and ultrasonically treated to obtain an epoxy / silica sol system;

[0021] After drying to remove moisture, zinc borate is added and ball milled; a low-temperature active curing agent is added; and the hybrid adhesive is cured;

[0022] S7: adding ferroaluminate cement, fly ash, slag and hybrid binder in batches in pairs and mixing them evenly to obtain a base material;

[0023] S8: dispersing boron nitride nanosheets in an aminosilane ethanol solution, ultrasonically treating, and drying to obtain modified boron nitride nanosheets, and casting the modified boron nitride nanosheets into three layers according to a concentration gradient on a substrate surface to obtain a gradient distribution substrate;

[0024] When pouring the core layer, a composite anti-cracking agent is added simultaneously; when pouring the middle layer, a compound of double-anti-release diatom balls and nano-clay fibers is added simultaneously; when pouring the surface layer, a bacterial glue restoring agent is added simultaneously;

[0025] S9: Steam-curing the gradient distribution substrate to obtain a highly crack-resistant and long-life concrete product.

[0026] Furthermore, S1 is specifically as follows: sodium alginate solution and nano-silica suspension are mixed in a mass ratio of 1-1.5:0.3-0.6 to form a mixed sol, and the mixed sol is dropped into a 0.5-1.5 mol / L calcium chloride solution by an ionic crosslinking method to form porous microspheres with a pore size of 50-150 μm. After the porous microspheres are vacuum freeze-dried at -60 to -50°C, they are calcined at 200-300°C for 1-2 hours to obtain dual-anti-release diatom balls.

[0027] Furthermore, S2 is specifically: limestone, bauxite, steel slag and gypsum with a mass ratio of 30-45:10-15:15-25:20-35 are ground together to a specific surface area of 200-300m 2 / kg, to obtain raw material, which is calcined in a rotary kiln at 1300℃-1400℃ for 60-120min to obtain 、 Clinker with CaO as the main mineral phase, clinker, gypsum and alum stone with a mass ratio of 50-70:10-15:20-35 are ground together to a specific surface area of A composite anti-cracking agent is obtained.

[0028] Furthermore, S3 is specifically as follows: nanoclay is dispersed in a polyvinyl alcohol aqueous solution to form a suspension with a mass concentration of 5-10%, basalt fibers with a fiber length of 8-15 mm and polyvinyl alcohol fibers with a length of 5-10 mm are immersed in the suspension for 10-30 minutes, and then dried with hot air at 100-120°C to form a nanoclay fiber composite with a thickness of 50-200 nm.

[0029] Furthermore, S4 is specifically as follows: epoxy resin and latent curing agent dicyandiamide are mixed in a mass ratio of 10:1-3 to form a core material, polyurea-formaldehyde resin is used as the wall material, and a shell layer is formed on the surface of the core material by interfacial polymerization according to a core-to-wall ratio of 1:1.5-2. The reaction temperature is 50-70°C, the reaction time is 2-4h, and the epoxy resin microcapsules are washed with ethanol and then dried to obtain epoxy resin microcapsules with a particle size of 50-100μm.

[0030] Furthermore, S5 is specifically as follows: Bacillus spores and a porous zeolite carrier are mixed in a mass ratio of 2-3:5-10, adsorbed in a phosphate buffer solution with a pH of 7-8 for 24-48 hours, and the porous zeolite carrier loaded with Bacillus spores is freeze-dried at -35 to -30°C to form a microbial remediation agent with an active spore loading rate of 80-95%, which is sealed and stored below 4°C. The epoxy resin microcapsules prepared in step S4 are mixed with the microbial remediation agent in a mass ratio of 1.2-1.8:1.5-2.1 to obtain a bacterial glue restoration agent.

[0031] Furthermore, S6 is specifically as follows: nano-silica sol and epoxy silane coupling agent are mixed in a mass ratio of 1:0.05-0.1, ultrasonically treated at 40-60° C. for 30 min to graft epoxy groups on the surface of the silica sol, centrifuged to remove unreacted coupling agent to obtain modified silica sol, washed with ethanol and dried for later use;

[0032] Heat bisphenol A epoxy resin to 60°C to reduce viscosity, and add diluent to adjust the solid content to 50%-60%;

[0033] The modified silica sol was added to the epoxy resin at a mass ratio of 1:0.8-1.5, mechanically stirred at 500-800 rpm, and ultrasonicated at 40 kHz for 30 min to obtain an epoxy / silica sol system;

[0034] After drying to remove moisture, zinc borate was added at a rate of 0.1-0.5% by mass of the epoxy / silica sol system, and polyethylene glycol was added at a rate of 0.05% by mass of the epoxy / silica sol system as a dispersing aid. The mixture was ball-milled for 2 h, and the pH was adjusted to 6.5-7.0.

[0035] A low-temperature active curing agent is added at 8-12% of the mass of the epoxy / silica sol system; and the hybrid adhesive is obtained by curing.

[0036] Furthermore, S8 is specifically as follows: dispersing boron nitride nanosheets in an aminosilane ethanol solution, ultrasonically treating for 30-60 minutes, drying at 80° C. to obtain modified boron nitride nanosheets, and casting the modified boron nitride nanosheets into three layers according to a concentration gradient on the surface of a substrate to obtain a gradient distribution substrate;

[0037] Among them, the concentration of the core layer is 0.03-0.08wt%, the middle layer is 0.08-0.15wt%, and the surface layer is 0.15-0.25wt%;

[0038] When pouring the core layer, add the composite anti-cracking agent simultaneously;

[0039] When pouring the middle layer, a mixture of double-anti-release diatom balls and nano-clay fibers is added simultaneously;

[0040] When pouring the surface layer, add the bacterial glue restoration agent simultaneously;

[0041] The above gradient casting is achieved by spraying.

[0042] Furthermore, S9 is specifically as follows: the cooled gradient distribution substrate is subjected to two-stage steam curing, the first stage is constant temperature curing at 50-55℃ for 3-5h, relative humidity ≥95%, and the second stage is constant temperature curing at 60-70℃ for 2-3h, relative humidity ≥90%, to obtain highly crack-resistant and long-life concrete products.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1. This invention significantly improves the compressive and flexural properties of marine cement concrete materials through a gradient layering design, hybrid binders, and nanofiber compounding, while also offering superior crack resistance compared to existing technologies. Its lower Poisson's ratio indicates less lateral deformation under stress, greater structural stability, and effective suppression of microcrack propagation. The significant improvement in frost resistance and sulfate resistance is attributed to the pore-filling properties of the dual-anti-release diatomaceous earth spheres and the dynamic repair effects of the mycocolloid restoration agent.

[0045] 2. The gas permeability rating of this invention is mostly "low permeability," indicating superior compactness and effective barrier to chloride ion and gas diffusion. The nanoclay fiber composite and gradient boron nitride nanosheets significantly reduce the cracking area per unit area and inhibit plastic shrinkage. The hybrid binder optimizes the interface between the cement matrix and the fiber / nanomaterial, achieving synergistic improvements in mechanical properties and durability.

[0046] 3. The gradient layered design of the present invention enables the material to have different functional properties at different levels, optimizes the internal stress distribution, reduces stress concentration points, and thus improves compressive and flexural properties. The hybrid binder improves the interface between the cement matrix and the fibers and nanomaterials through chemical modification, effectively transferring stress and reducing interface defects. The addition of nanofibers forms a network structure within the material, inhibiting the propagation of microcracks, dispersing stress, reducing the cracking area per unit area, and simultaneously filling microscopic pores, improving density, and blocking chloride ion and gas diffusion.

[0047] 4. The dual-anti-release diatom spheres of this invention have excellent pore-filling properties, further improving compactness, while the bacterial gel restoration agent continuously repairs microcracks and defects during use, maintaining high performance. The gradient boron nitride nanosheets form a distribution structure with a concentration gradient increasing from the core to the surface, optimizing the heat conduction path, reducing local thermal stress accumulation, inhibiting microcrack propagation, and enhancing the overall strength and toughness of the material.

[0048] 5. The present invention significantly improves the strain distribution inside concrete by adding a composite anti-cracking agent. Using digital image correlation technology, it was found that the strain distribution inside concrete without the composite anti-cracking agent was uneven, with local high-strain and low-strain areas. However, after adding the composite anti-cracking agent, the second principal strain distribution of the concrete became more uniform, with a significant decrease in high-strain areas and an increase in low-strain areas. This indicates that the composite anti-cracking agent effectively reduces the shrinkage strain of concrete and improves its crack resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0050] Figure 1 1 is a stress distribution diagram of Comparative Example 5 and Example 3 of the present invention;

[0051] Figure 2 is the X-ray diffraction pattern of the composite anti-cracking agent clinker of the present invention;

[0052] Figure 3 This is an electron microscope image of the composite anti-cracking agent clinker of the present invention. DETAILED DESCRIPTION

[0053] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0054] Example 1: This example provides a highly crack-resistant and long-life concrete product, comprising the following components, by weight: 90 parts of ferroaluminate cement, 30 parts of fly ash, 25 parts of slag (grade S105), 0.2 parts of modified boron nitride nanosheets, 8 parts of hybrid binder, 0.8 parts of dual-anti-release diatom balls, 5 parts of composite anti-cracking agent, 1.5 parts of nanoclay fiber compound, 3 parts of bacterial glue restoration agent, 160 parts of sand, 200 parts of gravel, and 2.2 parts of polycarboxylate water reducer;

[0055] The modified boron nitride nanosheets are boron nitride nanosheets with aminosilane grafted on the surface and with a concentration gradient increasing from the core to the surface; the hybrid binder is a composite binder of epoxy resin and modified silica sol; the dual-anti-release diatom balls are calcium alginate microspheres loaded with nano-silica; the nano-clay fiber compound is a compound of basalt fiber and polyvinyl alcohol fiber coated with nano-clay on the surface; and the bacterial glue restoration agent contains epoxy resin microcapsules and microbial remediation agents.

[0056] The method for preparing the highly crack-resistant and long-life concrete product comprises the following steps:

[0057] S1: Sodium alginate solution and nano-silica suspension were mixed in a mass ratio of 1.5:0.6 to form a mixed sol. The mixed sol was dropped into a 1.5 mol / L calcium chloride solution by ion crosslinking to form porous microspheres with a pore size of 150 μm. The porous microspheres were freeze-dried at -60°C in a vacuum and calcined at 300°C for 2 h to obtain dual-antibody-releasing diatom balls.

[0058] S2: Grind limestone, bauxite, steel slag and gypsum in a mass ratio of 45:15:25:35 to a specific surface area of 300m 2 / kg, the raw material was obtained, and the raw material was calcined in a rotary kiln at 1400℃ for 120min to obtain 、 Clinker with CaO as the main mineral phase, clinker, gypsum and alum stone with a mass ratio of 70:15:35 are ground together to a specific surface area of The composite anti-cracking agent was obtained (the composite anti-cracking agent clinker was tested by electron microscope and X-ray diffraction, and the results were as follows Figure 2 and 3 shown);

[0059] S3: Nanoclay was dispersed in a polyvinyl alcohol aqueous solution to form a suspension with a mass concentration of 10%. Basalt fibers with a fiber length of 15 mm and polyvinyl alcohol fibers with a mass ratio of 1:1 were immersed in the suspension for 30 min. After hot air drying at 120°C, a nanoclay fiber composite with a thickness of 200 nm was formed.

[0060] S4: Epoxy resin and latent curing agent dicyandiamide were mixed in a mass ratio of 10:3 to form a core material. Polyurea-formaldehyde resin was used as the wall material. A shell layer was formed on the surface of the core material by interfacial polymerization at a core-to-wall ratio of 1:2. The reaction temperature was 70°C and the reaction time was 4 hours. The resulting particles were washed with ethanol and dried to obtain epoxy resin microcapsules with a particle size of 100 μm.

[0061] S5: Bacillus spores and a porous zeolite carrier are mixed in a mass ratio of 3:10, and adsorbed in a phosphate buffer solution of pH 7-8 for 48 hours. The porous zeolite carrier loaded with Bacillus spores is freeze-dried at -30°C to form a microbial remediation agent with an active spore loading rate of 95%, and the microbial remediation agent is sealed and stored below 4°C. The epoxy resin microcapsules prepared in step S4 are mixed with the microbial remediation agent in a mass ratio of 1.8:2.1 to obtain a bacterial glue restoration agent;

[0062] S6: Nano-silica sol (particle size 50 nm) and epoxy silane coupling agent (KH560) were mixed in a mass ratio of 1:0.1 and ultrasonically treated at 60°C for 30 min to graft epoxy groups on the surface of the silica sol. Unreacted coupling agent was removed by centrifugation to obtain modified silica sol, which was washed with ethanol and dried for later use.

[0063] Heat bisphenol A epoxy resin (E-51) to 60°C to reduce viscosity, and add diluent (acetone) to adjust the solid content to 60%;

[0064] The modified silica sol was added to the epoxy resin at a mass ratio of 1:1.5, mechanically stirred at 800 rpm, and ultrasonicated at 40 kHz for 30 min to obtain an epoxy / silica sol system;

[0065] After drying to remove moisture, zinc borate was added at 0.5% by weight of the epoxy / silica sol system, and polyethylene glycol (PEG-400) was added at 0.05% by weight of the epoxy / silica sol system as a dispersing aid. The mixture was ball-milled for 2 h, and the pH was adjusted to 7.0 to inhibit the self-condensation of the silica sol.

[0066] Add low-temperature active curing agent (YK31 low-temperature curing agent) at 12% of the mass of the epoxy / silica sol system;

[0067] Pre-curing: let it stand at 40℃ for 1 hour to initially form a cross-linking network;

[0068] Main curing: keep at 80℃ for 2h to promote the formation of chemical bonds at the interface;

[0069] Post-curing: treating at 120℃ for 1h to eliminate internal stress and obtain hybrid adhesive;

[0070] S7: adding ferroaluminate cement, fly ash, slag and hybrid binder in batches in pairs (ferroaluminate cement is mixed with 1 / 3 of the hybrid binder, then fly ash is added, the remaining 2 / 3 of the hybrid binder is added, and finally slag is added), and mixing evenly to obtain a base material;

[0071] S8: dispersing boron nitride nanosheets in an aminosilane ethanol solution, ultrasonically treating for 60 minutes, and drying at 80° C. to obtain modified boron nitride nanosheets. The modified boron nitride nanosheets are divided into three layers according to a concentration gradient and cast on the surface of a substrate to obtain a gradient distribution substrate;

[0072] Among them, the concentration of the core layer is 0.08wt%, the middle layer is 0.15wt%, and the surface layer is 0.25wt%;

[0073] When pouring the core layer, add the composite anti-cracking agent simultaneously;

[0074] When pouring the middle layer, a mixture of double-anti-release diatom balls and nano-clay fibers is added simultaneously;

[0075] When pouring the surface layer, add the bacterial glue restoration agent simultaneously;

[0076] S9: The gradient distribution substrate is subjected to two-stage steam curing. The first stage is constant temperature curing at 55°C for 5 hours and relative humidity ≥95%. The second stage is constant temperature curing at 70°C for 3 hours and relative humidity ≥90%, thereby obtaining a highly crack-resistant and long-life concrete product.

[0077] Example 2: This example provides a highly crack-resistant and long-life concrete product, comprising the following components, by weight: 70 parts of ferroaluminate cement, 15 parts of fly ash, 10 parts of slag (grade S105), 0.05 parts of modified boron nitride nanosheets, 3 parts of a hybrid binder, 0.2 parts of dual-anti-release diatom balls, 2 parts of a composite anti-cracking agent, 0.5 parts of a nanoclay fiber compound, 1.5 parts of a bacterial glue restoration agent, 120 parts of sand, 150 parts of gravel, and 1 part of a polycarboxylate water reducer.

[0078] The modified boron nitride nanosheets are boron nitride nanosheets with aminosilane grafted on the surface and with a concentration gradient increasing from the core to the surface; the hybrid binder is a composite binder of epoxy resin and modified silica sol; the dual-anti-release diatom balls are calcium alginate microspheres loaded with nano-silica; the nano-clay fiber compound is a compound of basalt fiber and polyvinyl alcohol fiber coated with nano-clay on the surface; and the bacterial glue restoration agent contains epoxy resin microcapsules and microbial remediation agents.

[0079] The method for preparing the highly crack-resistant and long-life concrete product comprises the following steps:

[0080] S1: Sodium alginate solution and nano-silica suspension were mixed in a mass ratio of 1:0.3 to form a mixed sol. The mixed sol was dropped into a 0.5 mol / L calcium chloride solution by ion crosslinking to form porous microspheres with a pore size of 50 μm. The porous microspheres were freeze-dried at -50 °C in a vacuum and calcined at 200 °C for 1 h to obtain dual-antibody-releasing diatom balls.

[0081] S2: Grind limestone, bauxite, steel slag and gypsum in a mass ratio of 30:10:15:20 to a specific surface area of 200m 2 / kg, the raw material was obtained, and the raw material was calcined in a rotary kiln at 1300℃ for 60min to obtain 、 Clinker with CaO as the main mineral phase, clinker, gypsum and alum stone with a mass ratio of 50:10:20 are ground together to a specific surface area of Obtaining a composite anti-cracking agent;

[0082] S3: Nanoclay was dispersed in a polyvinyl alcohol aqueous solution to form a suspension with a mass concentration of 5%. Basalt fibers with a fiber length of 8 mm and polyvinyl alcohol fibers with a mass ratio of 5 mm (basalt fibers to polyvinyl alcohol fibers was 1:1) were immersed in the suspension for 10 minutes. After drying with hot air at 100°C, a nanoclay fiber composite with a thickness of 50 nm was formed.

[0083] S4: Epoxy resin and latent curing agent dicyandiamide were mixed in a mass ratio of 10:1 to form a core material. Polyurea-formaldehyde resin was used as the wall material. A shell layer was formed on the surface of the core material by interfacial polymerization at a core-to-wall ratio of 1:1.5. The reaction temperature was 50°C and the reaction time was 2 hours. The resulting particles were washed with ethanol and dried to obtain epoxy resin microcapsules with a particle size of 50 μm.

[0084] S5: Bacillus spores and a porous zeolite carrier are mixed in a mass ratio of 2:5, and adsorbed in a phosphate buffer solution of pH 7-8 for 24 hours. The porous zeolite carrier loaded with Bacillus spores is freeze-dried at -35°C to form a microbial remediation agent with an active spore loading rate of 80%, which is sealed and stored below 4°C. The epoxy resin microcapsules prepared in step S4 are mixed with the microbial remediation agent in a mass ratio of 1.2:1.5 to obtain a bacterial glue restoration agent;

[0085] S6: Nano-silica sol (particle size 10 nm) and epoxy silane coupling agent (KH560) were mixed at a mass ratio of 1:0.05 and ultrasonically treated at 40°C for 30 min to graft epoxy groups on the surface of the silica sol. Unreacted coupling agent was removed by centrifugation to obtain modified silica sol, which was washed with ethanol and dried for later use.

[0086] Heat bisphenol A epoxy resin (E-51) to 60°C to reduce viscosity, and add diluent (ethyl acetate) to adjust the solid content to 50%;

[0087] The modified silica sol was added to the epoxy resin at a mass ratio of 1:0.8, mechanically stirred at 500 rpm, and ultrasonicated at 40 kHz for 30 min to obtain an epoxy / silica sol system;

[0088] After drying to remove moisture, zinc borate was added at 0.1% by weight of the epoxy / silica sol system, and polyethylene glycol (PEG-400) was added at 0.05% by weight of the epoxy / silica sol system as a dispersing aid. The mixture was ball-milled for 2 h, and the pH was adjusted to 6.5 to inhibit the self-condensation of the silica sol.

[0089] Add low-temperature active curing agent (YK31 low-temperature curing agent) at 8% of the mass of the epoxy / silica sol system;

[0090] Pre-curing: let it stand at 40℃ for 1 hour to initially form a cross-linking network;

[0091] Main curing: keep at 80℃ for 2h to promote the formation of chemical bonds at the interface;

[0092] Post-curing: treating at 120℃ for 1h to eliminate internal stress and obtain hybrid adhesive;

[0093] S7: adding ferroaluminate cement, fly ash, slag and hybrid binder in batches in pairs (ferroaluminate cement is mixed with 1 / 3 of the hybrid binder, then fly ash is added, the remaining 2 / 3 of the hybrid binder is added, and finally slag is added), and mixing evenly to obtain a base material;

[0094] S8: dispersing boron nitride nanosheets in an aminosilane ethanol solution, ultrasonically treating for 30 minutes, and drying at 80° C. to obtain modified boron nitride nanosheets. The modified boron nitride nanosheets are divided into three layers according to a concentration gradient and cast on the surface of a substrate to obtain a gradient distribution substrate;

[0095] Among them, the concentration of the core layer is 0.03wt%, the middle layer is 0.08wt%, and the surface layer is 0.15wt%;

[0096] When pouring the core layer, add the composite anti-cracking agent simultaneously;

[0097] When pouring the middle layer, a mixture of double-anti-release diatom balls and nano-clay fibers is added simultaneously;

[0098] When pouring the surface layer, add the bacterial glue restoration agent simultaneously;

[0099] S9: The gradient distribution substrate is subjected to two-stage steam curing. The first stage is constant temperature curing at 50°C for 3 hours and relative humidity ≥95%. The second stage is constant temperature curing at 60°C for 2 hours and relative humidity ≥90%, thereby obtaining a highly crack-resistant and long-life concrete product.

[0100] Example 3: This example provides a highly crack-resistant and long-life concrete product, comprising the following components, by weight: 80 parts of ferroaluminate cement, 21 parts of fly ash, 18 parts of slag (grade S105), 0.1 parts of modified boron nitride nanosheets, 5 parts of a hybrid binder, 0.4 parts of dual-anti-release diatom balls, 3 parts of a composite anti-cracking agent, 1.1 parts of a nanoclay fiber compound, 2.8 parts of a bacterial glue restoration agent, 150 parts of sand, 180 parts of gravel, and 1.5 parts of a polycarboxylate water reducer.

[0101] The modified boron nitride nanosheets are boron nitride nanosheets with aminosilane grafted on the surface and with a concentration gradient increasing from the core to the surface; the hybrid binder is a composite binder of epoxy resin and modified silica sol; the dual-anti-release diatom balls are calcium alginate microspheres loaded with nano-silica; the nano-clay fiber compound is a compound of basalt fiber and polyvinyl alcohol fiber coated with nano-clay on the surface; and the bacterial glue restoration agent contains epoxy resin microcapsules and microbial remediation agents.

[0102] The method for preparing the highly crack-resistant and long-life concrete product comprises the following steps:

[0103] S1: Sodium alginate solution and nano-silica suspension were mixed in a mass ratio of 1.2:0.5 to form a mixed sol. The mixed sol was dropped into a 0.8 mol / L calcium chloride solution by ion crosslinking to form porous microspheres with a pore size of 100 μm. The porous microspheres were freeze-dried at -55°C in a vacuum and then calcined at 260°C for 2 h to obtain dual-antibody-releasing diatom spheres.

[0104] S2: Grind limestone, bauxite, steel slag and gypsum in a mass ratio of 38:12:21:32 to a specific surface area of 230m 2 / kg, the raw material was obtained, and the raw material was calcined in a rotary kiln at 1350 ° C for 90 minutes to obtain 、 Clinker with CaO as the main mineral phase, clinker, gypsum and alum stone with a mass ratio of 60:12:28 are ground together to a specific surface area of Obtaining a composite anti-cracking agent;

[0105] S3: Nanoclay was dispersed in a polyvinyl alcohol aqueous solution to form a suspension with a mass concentration of 8%. Basalt fibers with a fiber length of 10 mm and polyvinyl alcohol fibers with a mass ratio of 7 mm (basalt fibers to polyvinyl alcohol fibers was 1:1) were immersed in the suspension for 20 min. After hot air drying at 105°C, a nanoclay fiber composite with a thickness of 100 nm was formed.

[0106] S4: Epoxy resin and latent curing agent dicyandiamide were mixed in a mass ratio of 10:2 to form a core material. Polyurea-formaldehyde resin was used as the wall material. A shell layer was formed on the surface of the core material by interfacial polymerization at a core-to-wall ratio of 1:1.8. The reaction temperature was 64°C and the reaction time was 3 hours. The resulting particles were washed with ethanol and dried to obtain epoxy resin microcapsules with a particle size of 80 μm.

[0107] S5: Bacillus spores and a porous zeolite carrier are mixed in a mass ratio of 2:7, and adsorbed in a phosphate buffer solution of pH 7-8 for 48 hours. The porous zeolite carrier loaded with Bacillus spores is freeze-dried at -33°C to form a microbial remediation agent with an active spore loading rate of 90%, which is sealed and stored below 4°C. The epoxy resin microcapsules prepared in step S4 are mixed with the microbial remediation agent in a mass ratio of 1.6:2.1 to obtain a bacterial glue restoration agent;

[0108] S6: Nano-silica sol (particle size 40 nm) and epoxy silane coupling agent (KH560) were mixed at a mass ratio of 1:0.08 and ultrasonically treated at 50°C for 30 min to graft epoxy groups on the surface of the silica sol. Unreacted coupling agent was removed by centrifugation to obtain modified silica sol, which was washed with ethanol and dried for later use.

[0109] Heat bisphenol A epoxy resin (E-51) to 60°C to reduce viscosity, and add diluent (acetone) to adjust the solid content to 55%;

[0110] The modified silica sol was added to the epoxy resin at a mass ratio of 1:1.3, mechanically stirred at 600 rpm, and ultrasonicated at 40 kHz for 30 min to obtain an epoxy / silica sol system;

[0111] After drying to remove moisture, zinc borate was added at 0.4% by mass of the epoxy / silica sol system, and polyethylene glycol (PEG-400) was added at 0.05% by mass of the epoxy / silica sol system as a dispersing aid. The mixture was ball-milled for 2 h, and the pH was adjusted to 6.8 to inhibit the self-condensation of the silica sol.

[0112] Add low-temperature active curing agent (YK31 low-temperature curing agent) at 10% of the mass of the epoxy / silica sol system;

[0113] Pre-curing: let it stand at 40℃ for 1 hour to initially form a cross-linking network;

[0114] Main curing: keep at 80℃ for 2h to promote the formation of chemical bonds at the interface;

[0115] Post-curing: treating at 120℃ for 1h to eliminate internal stress and obtain hybrid adhesive;

[0116] S7: adding ferroaluminate cement, fly ash, slag and hybrid binder in batches in pairs (ferroaluminate cement is mixed with 1 / 3 of the hybrid binder, then fly ash is added, the remaining 2 / 3 of the hybrid binder is added, and finally slag is added), and mixing evenly to obtain a base material;

[0117] S8: dispersing boron nitride nanosheets in an aminosilane ethanol solution, ultrasonically treating for 50 minutes, and drying at 80° C. to obtain modified boron nitride nanosheets. The modified boron nitride nanosheets are divided into three layers according to a concentration gradient and cast on the surface of a substrate to obtain a gradient distribution substrate;

[0118] Among them, the concentration of the core layer is 0.05wt%, the middle layer is 0.1wt%, and the surface layer is 0.2wt%;

[0119] When pouring the core layer, add the composite anti-cracking agent simultaneously;

[0120] When pouring the middle layer, a mixture of double-anti-release diatom balls and nano-clay fibers is added simultaneously;

[0121] When pouring the surface layer, add the bacterial glue restoration agent simultaneously;

[0122] S9: The gradient distribution substrate is subjected to two-stage steam curing. The first stage is constant temperature curing at 52°C for 4 hours and relative humidity ≥95%. The second stage is constant temperature curing at 63°C for 2 hours and relative humidity ≥90%, thereby obtaining a highly crack-resistant and long-life concrete product.

[0123] Comparative Example 1: This comparative example differs from Example 3 in that no bacterial glue restoring agent is added.

[0124] Comparative Example 2: This comparative example differs from Example 3 in that no dual-antibiotic-releasing diatom balls are added.

[0125] Comparative Example 3: The difference between this comparative example and Example 3 is that in step S8, the composite anti-cracking agent, dual-anti-release diatom balls, nanoclay fiber compound, bacterial glue restoration agent and boron nitride nanosheets are directly mixed into the substrate through a hybrid binder without layered casting.

[0126] Comparative Example 4: The difference between this comparative example and Example 3 is that the bacterial glue restoration agent and the dual-anti-release diatom balls are not added. At the same time, in step S8, the composite anti-cracking agent, the nanoclay fiber compound and the boron nitride nanosheets are directly mixed into the substrate through a hybrid binder without layered casting.

[0127] Comparative Example 5: This comparative example differs from Example 3 in that no composite anti-cracking agent is added.

[0128] Comparative Example: High crack resistance and high corrosion resistance marine concrete prepared according to Chinese patent CN116354680B includes the following raw materials: 140 parts of ordinary Portland cement, 100 parts of sulfoaluminate cement, 110 parts of fly ash, 70 parts of mineral powder, 770 parts of river sand, 212 parts of small stones, 848 parts of large stones, 147 parts of water, 5 parts of modified internal curing material, 4.8 parts of water reducer, and 1.4 parts of retarder; wherein, the modified internal curing material comprises, by mass percentage, 45% of graphene nanosheets, 5% of binder, and 50% of internal curing agent;

[0129] The preparation method is as follows:

[0130] S1: Take SAP and add appropriate amount of water to pre-wet it, mix it with polyurethane binder at high speed for 15 minutes, then slowly add graphene nanosheets several times within 2 minutes, and continue to mix at high speed for 10 minutes to obtain the modified internal curing material;

[0131] S2: Add composite cement, coarse aggregate, and fine aggregate into a mixer according to their mass proportions and mix them evenly. Then add fly ash, mineral powder, and the modified internal curing material prepared in the above steps and continue mixing.

[0132] S3: Mix a water reducer, a setting retarder and water in parts by mass into a uniform slurry, slowly add the mixture to the slurry of step S2 during stirring, and mix evenly to obtain a high crack resistance and high corrosion resistance marine concrete.

[0133] Experimental Example 1: Mechanical properties test (tested in accordance with GB / T 50081-2019);

[0134] 1.1 Compressive strength test;

[0135] Steps: Specimen preparation: 150 × 150 × 150 mm cubic specimens were used and the curing conditions were temperature 20 ± 2 °C and humidity ≥ 95% for 28 days.

[0136] For size measurement, use a vernier caliper to measure the side length with a tolerance of ≤1mm; the flatness tolerance of the pressure-bearing surface is ≤0.0005d.

[0137] Loading rate: below C30 0.3-0.5MPa / s, C30-C60 0.5-0.8MPa / s, above C60 0.8-1.0MPa / s.

[0138] Calculation results, compressive strength , take the average value of 3 specimens, and remove outliers when the range exceeds 15%.

[0139] 1.2 Flexural strength test;

[0140] Steps: Specimen preparation: 150×150×550mm prism specimen, curing is the same as the compression test.

[0141] The loading setting is 450 mm in span, and the loading rate is divided according to the strength grade (0.02-0.05 MPa / s for C30 and below, 0.05-0.08 MPa / s for C30-C60).

[0142] Fracture judgment: if the fracture position is outside the load action line, the result is invalid.

[0143] Calculation, flexural strength , the extreme difference processing rules are the same as those for compression test.

[0144] 1.3 Poisson's ratio test;

[0145] A Poisson's ratio that is too high (such as μ>0.25) indicates that the material expands significantly laterally when subjected to longitudinal compression, which can easily cause internal microcracks to expand and reduce the structure's crack resistance.

[0146] Steps: Specimen preparation: 150×150×300mm prism specimen, used in conjunction with the static compressive elastic modulus test.

[0147] Strain measurement, simultaneous acquisition of transverse and axial strains, loading to 30% of the ultimate load.

[0148] Calculation: Poisson's ratio μ = ε transverse / ε axial.

[0149] Experimental Example 2: Durability test (tested in accordance with GB / T 50082-2024);

[0150] 2.1 Freezing resistance test (quick freezing method);

[0151] Steps: Specimen preparation: 100×100×400mm prism specimens were cured to the specified age, saturated with water for 48 hours, and pre-cooled to the initial temperature (-18℃ to 5℃);

[0152] During the freeze-thaw cycle, the temperature at the center of the specimen dropped to -18 ± 2 °C and was maintained for 4 h.

[0153] During the melting stage, immerse in 5°C water until the center temperature rises to 5±2°C and maintain for 2 hours.

[0154] Termination conditions: mass loss ≥ 5% or dynamic elastic modulus ≤ 60% or the designed number of freeze-thaw cycles is reached.

[0155] Result calculation, durability index , P is the relative dynamic elastic modulus retention value, and N is the number of termination cycles.

[0156] 2.2 Electric flux test (chloride ion permeability resistance);

[0157] Steps: Specimen treatment: core specimen with a diameter of 100 mm and a height of 50 mm, vacuum saturated with water (negative pressure of 1-5 kPa for 3 hours, immersed in water for 18 hours).

[0158] The device was set up so that 0.3 mol / L NaOH solution was injected into the positive electrode and 3% NaCl solution was injected into the negative electrode.

[0159] The pore size of the copper mesh of the copper backing plate is adjusted to 850μm.

[0160] Loading parameters: 60V DC for 6 hours, record the initial current I0 and the current value every 30 minutes.

[0161] Calculation, total electric flux .

[0162] Determination of classification: low permeability (Q<1000C), medium permeability (1000C≤Q≤2000C), high permeability (Q>2000C).

[0163] 2.3 Gas permeation resistance test;

[0164] Steps: Specimen preparation: cylindrical specimens with a diameter of 150 mm and a height of 50 mm, the maximum aggregate particle size is ≤ 25 mm, and pre-dried to constant weight.

[0165] Equipment settings: Nitrogen pressure was adjusted to 0.15-0.40 MPa, and gradient pressurization was used to test gas flow.

[0166] The permeate flow rate was measured using a soap film flow meter with an accuracy of ±0.5%.

[0167] Calculation, gas permeability , Q is the flow rate, L is the specimen thickness, and ΔP is the pressure difference.

[0168] 2.4 Sulfate corrosion resistance test;

[0169] Procedure: Specimen treatment, wet-dry cycle (immersion in 5% Na2SO4 solution for 15 hours, drying for 9 hours).

[0170] Termination condition: measure the compressive strength loss rate every 15 cycles. If the loss rate is ≥25% or the designed number of cycles is reached,

[0171] Determination, sulfate resistance level is divided according to the maximum number of cycles.

[0172] 2.5 Cracking resistance test;

[0173] Steps: Specimen preparation: 800×600×100mm flat specimen, surface wind speed controlled at 5±0.5m / s (100mm from the surface).

[0174] For crack observation, the crack width was recorded every 30 minutes within 24 hours (microscope accuracy 0.01 mm).

[0175] Calculation: Total cracking area per unit area , is the crack width, is the crack length.

[0176] The test data are shown in the table below, including compressive strength (MPa), flexural strength (MPa), durability index K n , total electric flux Q (C), gas permeability kp , compressive strength loss rate of sulfate corrosion resistance test (%), total cracking area per unit area , A1 is the penetration level of total electric flux, and A2 is the penetration level of gas.

[0177]

[0178] The above data show that the present invention significantly improves the material's compressive and flexural properties through a gradient layering design, hybrid binder, and nanofiber compounding, and its crack resistance is superior to that of the prior art. Comparative Examples 1-4, due to missing components or simplified processes, have loose internal structures and significantly reduced mechanical properties.

[0179] The Poisson's ratio of the present invention is lower, indicating that the material has smaller lateral deformation when subjected to stress, higher structural stability, and effectively inhibits the expansion of microcracks; Comparative Examples 1, 3 and 4 have uneven strain distribution and significant lateral deformation due to non-layered casting.

[0180] The frost resistance index and sulfate resistance rating of the present invention are significantly better than those of the comparative examples, thanks to the pore filling of the dual-anti-release diatom balls and the dynamic repair effect of the bacterial glue restoration agent. Comparative examples 2-4 lack functional components, and their durability decays faster.

[0181] The gas permeability grade of the present invention is mostly "low permeability", indicating that its density is better and the diffusion of chloride ions and gas is effectively blocked; the permeability of comparative examples 1 and 4 is deteriorated due to uneven material distribution or missing components.

[0182] The present invention significantly reduces the cracking area per unit area and inhibits plastic shrinkage by using a nanoclay fiber compound and gradient boron nitride nanosheets; Comparative Examples 3 and 4 are not cast in layers, resulting in local stress concentration and increased cracking risk. The hybrid binder of the present invention optimizes the interface bonding between the cement matrix and the fiber / nanomaterial, and the mechanical properties and durability are synergistically improved; Comparative Examples 1, 3 and 4 have increased interface defects and deteriorated performance due to the lack of functional components or direct mixing process.

[0183] Experimental Example 3: Strain test (according to GB / T50082-2024);

[0184] 3.1 Specimen preparation and pretreatment: A flat specimen with a size of 600 mm × 600 mm × 100 mm (standard restrained shrinkage specimen) was used.

[0185] The specimens were cured to 28 days of age;

[0186] 3.2 Surface treatment: spray a black and white speckle pattern (spot diameter 0.5-1mm, contrast ≥50%) on the surface of the specimen to ensure the accuracy of DIC analysis;

[0187] The calibration plate is placed and a calibration plate (grid of known size) is fixed next to the specimen for image space calibration.

[0188] 3.3 DIC system setup and image acquisition;

[0189] A dual-camera stereo DIC system (resolution ≥5MP, frame rate 10-30Hz) was used, with a baseline distance of 500mm and a 30° angle to the specimen;

[0190] Uniform cold light source (to avoid interference from reflections on the specimen surface).

[0191] 3.4 Loading conditions;

[0192] In the restrained shrinkage test, a steel bar skeleton (Φ8mm, 100mm spacing) was embedded on all four sides of the specimen to simulate the actual structural restraint;

[0193] Environmental control: temperature 20±2℃, relative humidity 60±5%, continuous monitoring until the cracks stabilize.

[0194] 3.5 Image acquisition;

[0195] During the loading process, the specimen surface images were continuously captured with an interval of 1 frame / minute;

[0196] The total collection time is 24 hours;

[0197] The strain test results of Comparative Example 5 and Example 3 are shown in Table 1. Figure 1 As shown in the figure, it can be seen that the left side is the second principal strain distribution diagram of comparative example 5, and the right side is the second principal strain distribution diagram after adding the composite anti-cracking agent (ie, embodiment 3);

[0198] In the second principal strain distribution diagram of comparative example 5, the color distribution is relatively chaotic, with multiple colors such as red, yellow, green, and blue. The red area represents a higher strain value, while the blue area represents a lower strain value, which indicates that the second principal strain distribution inside the concrete is indeed uneven;

[0199] In the second principal strain distribution diagram after adding the composite anti-cracking agent, the color distribution is relatively more uniform, the red area is significantly reduced, and the blue area is increased, which shows that the addition of the composite anti-cracking agent makes the strain distribution inside the concrete more uniform and the shrinkage strain is reduced;

[0200] Therefore, the addition of composite anti-cracking agent does improve the non-uniform strain and stress distribution inside the concrete, making the strain distribution more uniform and reducing the shrinkage strain.

[0201] In summary, the present invention optimizes the material structure and performance from the microscopic to the macroscopic level through the synergistic effect of multiple technical means, significantly improving the mechanical properties and durability of marine cement concrete, making it more suitable for harsh environments such as marine engineering.

[0202] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A high crack resistance and long life concrete product, characterized in that: The invention comprises the following components by weight: 70-90 parts of ferroaluminate cement, 15-30 parts of fly ash, 10-25 parts of slag, 0.05-0.2 parts of modified boron nitride nanosheets, 3-8 parts of hybrid binder, 0.2-0.8 parts of dual-anti-release diatom balls, 2-5 parts of composite anti-cracking agent, 0.5-1.5 parts of nano-clay fiber compound, 1.5-3 parts of bacterial glue restoration agent, 120-160 parts of sand, 150-200 parts of gravel, and 1-2.2 parts of admixture; The modified boron nitride nanosheets are boron nitride nanosheets with aminosilane grafted on the surface and with a concentration gradient increasing from the core to the surface; The hybrid binder is a composite binder of epoxy resin and modified silica sol; The dual-antibiotic-releasing diatom balls are calcium alginate microspheres loaded with nano-silica; The nanoclay fiber composite is a composite of basalt fiber and polyvinyl alcohol fiber coated with nanoclay on the surface; The bacterial glue restoration agent comprises epoxy resin microcapsules and microbial repair agents; The composite anti-cracking agent is specifically: limestone, bauxite, steel slag and gypsum with a mass ratio of 30-45:10-15:15-25:20-35 are ground together to a specific surface area of , obtain raw material, and calcine the raw material in a rotary kiln at 1300℃-1400℃ for 60-120min to obtain 、 Clinker with CaO as the main mineral phase, clinker, gypsum and alum stone with a mass ratio of 50-70:10-15:20-35 are ground together to a specific surface area of A composite anti-cracking agent is obtained.

2. A method for preparing a high crack resistance and long life concrete product according to claim 1, characterized in that: The following steps are involved: S1: Sodium alginate solution and nano-silica suspension are mixed to form a mixed sol, and the mixed sol is dropped into a calcium chloride solution by ion crosslinking to form porous microspheres. The porous microspheres are freeze-dried in a vacuum and then calcined to obtain dual-antibody-releasing diatom balls; S2: Grinding limestone, bauxite, steel slag, and gypsum together to prepare raw material, calcining at high temperature to obtain clinker, and grinding the clinker with gypsum and alum stone to obtain a composite anti-cracking agent; S3: dispersing nanoclay in a polyvinyl alcohol aqueous solution to form a suspension, impregnating basalt fiber and polyvinyl alcohol fiber in the suspension, and forming a nanoclay fiber composite after hot air drying; S4: Mixing epoxy resin with a latent curing agent, dicyandiamide, to form a core material, using polyurea-formaldehyde resin as a wall material, forming a shell layer on the surface of the core material by interfacial polymerization, washing with ethanol, and then drying to obtain epoxy resin microcapsules; S5: Bacillus spores are adsorbed on a porous zeolite carrier in a phosphate buffer solution, and the porous zeolite carrier loaded with Bacillus spores is freeze-dried to form a microbial remediation agent. The epoxy resin microcapsules prepared in step S4 are mixed with the microbial remediation agent to obtain a bacterial gel restoration agent; S6: nano-silica sol is mixed with epoxy silane coupling agent, and ultrasonic treatment is performed to graft epoxy groups on the surface of the silica sol. Unreacted coupling agent is removed by centrifugation to obtain modified silica sol, which is then washed with ethanol and dried for later use; The bisphenol A epoxy resin is heated to reduce the viscosity and a diluent is added; The modified silica sol is added to the epoxy resin, mechanically stirred, and ultrasonically treated to obtain an epoxy / silica sol system; After drying to remove moisture, zinc borate is added and ball milled; a low-temperature active curing agent is added; and the hybrid adhesive is cured; S7: adding ferroaluminate cement, fly ash, slag and hybrid binder in batches in pairs and mixing them evenly to obtain a base material; S8: dispersing boron nitride nanosheets in an aminosilane ethanol solution, ultrasonically treating, and drying to obtain modified boron nitride nanosheets, and casting the modified boron nitride nanosheets into three layers according to a concentration gradient on a substrate surface to obtain a gradient distribution substrate; When pouring the core layer, a composite anti-cracking agent is added simultaneously; when pouring the middle layer, a compound of double-anti-release diatom balls and nano-clay fibers is added simultaneously; when pouring the surface layer, a bacterial glue restoring agent is added simultaneously; S9: Steam-curing the gradient distribution substrate to obtain a highly crack-resistant and long-life concrete product.

3. The method for preparing a high crack resistance and long life concrete product according to claim 2, characterized in that: S1 is specifically as follows: sodium alginate solution and nano-silica suspension are mixed in a mass ratio of 1-1.5:0.3-0.6 to form a mixed sol, and the mixed sol is dropped into a 0.5-1.5 mol / L calcium chloride solution through an ion crosslinking method to form porous microspheres with a pore size of 50-150 μm. The porous microspheres are vacuum freeze-dried at -60 to -50 ° C, and then calcined at 200-300 ° C for 1-2 hours to obtain dual-antibiotic-releasing diatom balls.

4. The method for preparing a high crack resistance and long life concrete product according to claim 2, characterized in that: S3 is specifically as follows: nanoclay is dispersed in a polyvinyl alcohol aqueous solution to form a suspension with a mass concentration of 5-10%, basalt fibers with a fiber length of 8-15 mm and polyvinyl alcohol fibers with a length of 5-10 mm are immersed in the suspension for 10-30 minutes, and then dried with hot air at 100-120°C to form a nanoclay fiber composite with a thickness of 50-200 nm.

5. The method for preparing a high crack resistance and long life concrete product according to claim 2, characterized in that: S4 is specifically as follows: epoxy resin and latent curing agent dicyandiamide are mixed in a mass ratio of 10:1-3 to form a core material, polyurea-formaldehyde resin is used as the wall material, and a shell layer is formed on the surface of the core material by interfacial polymerization according to a core-to-wall ratio of 1:1.5-2. The reaction temperature is 50-70°C, the reaction time is 2-4h, and the epoxy resin microcapsules are washed with ethanol and then dried to obtain epoxy resin microcapsules with a particle size of 50-100μm.

6. The method for preparing a high crack resistance and long life concrete product according to claim 2, characterized in that: S5 specifically comprises: mixing Bacillus spores and a porous zeolite carrier in a mass ratio of 2-3:5-10, adsorbing the mixture in a phosphate buffer solution with a pH of 7-8 for 24-48 hours, freeze-drying the porous zeolite carrier loaded with Bacillus spores at -35 to -30°C to form a microbial remediation agent with an active spore loading rate of 80-95%, and mixing the epoxy resin microcapsules prepared in step S4 with the microbial remediation agent in a mass ratio of 1.2-1.8:1.5-2.1 to obtain a bacterial glue restoration agent.

7. The method for preparing a high crack resistance and long life concrete product according to claim 2, characterized in that: S6 specifically comprises: mixing nano-silica sol and epoxy silane coupling agent in a mass ratio of 1:0.05-0.1, ultrasonically treating at 40-60° C. to graft epoxy groups onto the surface of the silica sol, removing unreacted coupling agent by centrifugation to obtain modified silica sol, washing with ethanol and drying for later use; Heat the bisphenol A epoxy resin to reduce the viscosity, and add a diluent to adjust the solid content to 50%-60%; The modified silica sol was added to the epoxy resin at a mass ratio of 1:0.8-1.5, mechanically stirred at 500-800 rpm, and ultrasonically treated to obtain an epoxy / silica sol system; After drying to remove moisture, zinc borate is added at 0.1-0.5% of the mass of the epoxy / silica sol system, polyethylene glycol is added as a dispersing aid, ball milling is performed, and the pH is adjusted to 6.5-7.0; A low-temperature active curing agent is added at 8-12% of the mass of the epoxy / silica sol system; and the hybrid adhesive is obtained by curing.

8. The method for preparing a high crack resistance and long life concrete product according to claim 2, characterized in that: S8 specifically comprises: dispersing boron nitride nanosheets in an aminosilane ethanol solution, ultrasonically treating for 30-60 minutes, drying to obtain modified boron nitride nanosheets, and casting the modified boron nitride nanosheets into three layers according to a concentration gradient on the surface of a substrate to obtain a gradient distribution substrate; Among them, the concentration of the core layer is 0.03-0.08wt%, the middle layer is 0.08-0.15wt%, and the surface layer is 0.15-0.25wt%; When pouring the core layer, add the composite anti-cracking agent simultaneously; When pouring the middle layer, a mixture of double-anti-release diatom balls and nano-clay fibers is added simultaneously; When pouring the surface layer, add the bacterial glue restoration agent simultaneously.

9. The method for preparing a high crack resistance and long life concrete product according to claim 2, characterized in that: S9 is specifically as follows: the gradient distribution substrate is subjected to two-stage steam curing, the first stage is constant temperature curing at 50-55℃ for 3-5h, relative humidity ≥95%, and the second stage is constant temperature curing at 60-70℃ for 2-3h, relative humidity ≥90%, to obtain highly crack-resistant and long-life concrete products.

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