High-crack-resistance long-service-life concrete product and preparation method thereof

Abstract

The invention discloses a high-crack-resistance long-life concrete product and a preparation method thereof, and belongs to the technical field of marine concrete products. The concrete product is prepared from the following components in parts by weight: 70 to 90 parts of aluminoferrite cement, 15 to 30 parts of fly ash, 10 to 25 parts of slag, 0.05 to 0.2 part of modified boron nitride nanosheets, 3 to 8 parts of a hybrid binder, 0.2 to 0.8 part of double-anti-release diatom balls, 2 to 5 parts of a composite anti-cracking agent, 0.5 to 1.5 parts of a nano-clay fiber compound and 1.5 to 3 parts of a mycocolloid compound agent. Through gradient layered design and compounding of the hybrid binder and the nanofibers, the compression resistance and fracture resistance of the maritime work cement concrete material are remarkably improved, and the crack resistance is superior to that of the prior art. The Poisson's ratio is lower, which shows that the transverse deformation is smaller under stress, the structural stability is higher, and the microcrack propagation can be effectively inhibited. The anti-freezing durability index and the sulfate-resistant grade are remarkably improved, and benefit from pore filling of the double-anti-release diatom balls and the dynamic repairing effect of the bacterial gum rejuvenating agent.

Description

Technical Field

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

[0002] In the technical field of marine concrete products, precast components, as key basic materials for ocean engineering, are widely used in scenarios such as marine construction, port terminals, and ocean platforms. They must possess characteristics such as resistance to seawater erosion, resistance to chloride ion penetration, and durability to ensure the long-term stability and safety of marine structures. The losses caused by marine corrosion each year account for about 1 / 3 of the total corrosion losses, and the annual economic loss has exceeded 1.5 trillion yuan. Therefore, the problem of concrete seawater corrosion has become a worldwide problem. Traditional portland cement concrete products often face many technical bottlenecks, seriously restricting their durability and engineering applicability. Ferroaluminate cement is the third series of cement independently developed in China. Its main minerals are anhydrous calcium sulfoaluminate, dicalcium silicate, and calcium ferroaluminate. Because the amount of calcium hydroxide generated by its hydration products is small, the ettringite formed is beneficial to strength development, and iron glue can prevent chloride ions. The unique mineral composition and hydration products of ferroaluminate cement endow it with natural and decisive anti-corrosion performance advantages, which are effective technical means expected to solve marine corrosion.

[0003] In the prior art, although there are already some technical means to enhance the compressive and flexural strengths of concrete, there is still room for improvement in actual applications. For example, the internal stress distribution of the materials has not been fully optimized, resulting in the inability to achieve the best state of crack resistance and structural stability under complex stress conditions. In terms of durability, although there are various modification technologies, there is still room for improvement in the freeze-thaw durability index and sulfate resistance grade of concrete. Especially in the harsh marine environment, suffering from long-term seawater erosion and sulfate corrosion, the concrete products under the existing technology may experience durability degradation. Summary of the Invention

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

[0005] A high crack-resistant and long-life concrete product, by weight, comprises the following components: 70 - 90 parts of ferroaluminate cement, 15 - 30 parts of fly ash, 10 - 25 parts of slag, 0.05 - 0.2 part of modified boron nitride nanosheets, 3 - 8 parts of hybrid binder, 0.2 - 0.8 part of double anti-release diatom balls, 2 - 5 parts of composite crack inhibitor, 0.5 - 1.5 parts of nano-clay fiber complex, 1.5 - 3 parts of bacterial glue complexing agent, 120 - 160 parts of sand, 150 - 200 parts of gravel, 1 - 2.2 parts of admixture;

[0006] The admixture is selected as polycarboxylate water reducer;

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

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

[0009] The dual-release diatomaceous earth spheres are calcium alginate microspheres loaded with nano-silica;

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

[0011] The bacterial glue rejuvenator contains epoxy resin microcapsules and a microbial remediation agent.

[0012] A method for preparing the high crack-resistant and long-life concrete product described above includes the following steps:

[0013] S1: Mix the sodium alginate solution with the nano-silica suspension to form a mixed sol, and drop the mixed sol into the calcium chloride solution through ion cross-linking to form porous microspheres. After the porous microspheres are vacuum freeze-dried, they are calcined to obtain dual-release diatomaceous earth spheres;

[0014] S2: Grind limestone, bauxite, steel slag, and gypsum together to prepare raw materials, and obtain clinker through high-temperature calcination. Then grind the clinker together with gypsum and alunite to obtain a composite crack-resistant agent;

[0015] S3: Disperse nano-clay in an aqueous solution of polyvinyl alcohol to form a suspension, immerse basalt fiber and polyvinyl alcohol fiber in the suspension, and form a nano-clay fiber composite after hot air drying;

[0016] S4: Mix epoxy resin with the latent curing agent dicyandiamide to form a core material, use polyurea formaldehyde resin as the wall material, and form a shell layer on the surface of the core material through interfacial polymerization. After washing with ethanol and drying, epoxy resin microcapsules are obtained;

[0017] S5: Adsorb Bacillus spores and a porous zeolite carrier in a phosphate buffer solution. After the porous zeolite carrier loaded with Bacillus spores is freeze-dried, a microbial remediation agent is formed. Mix the epoxy resin microcapsules prepared in step S4 with the microbial remediation agent to obtain a bacterial glue rejuvenator;

[0018] S6: Mix nano-silica sol with an epoxy group-containing silane coupling agent, and perform ultrasonic treatment to graft epoxy groups on the surface of the silica sol. Centrifuge to remove the unreacted coupling agent to obtain modified silica sol. After washing with ethanol and drying, it is reserved for use;

[0019] Heat bisphenol A epoxy resin to reduce its viscosity, and add a diluent;

[0020] Add the modified silica sol into the epoxy resin, stir mechanically, and perform ultrasonic treatment to obtain an epoxy / silica sol system;

[0021] After drying to remove moisture, add zinc borate and perform ball milling; add a low-temperature active curing agent; cure to obtain a hybrid binder;

[0022] S7: Add the ferrite cement, fly ash, slag and the hybrid binder in batches in pairs, and mix evenly to obtain a substrate;

[0023] S8: Disperse the boron nitride nanosheets in an amino silane ethanol solution, perform ultrasonic treatment, and dry to obtain modified boron nitride nanosheets. Divide the modified boron nitride nanosheets into three layers according to a concentration gradient and pour them on the surface of the substrate to obtain a substrate with a gradient distribution;

[0024] During the pouring of the core layer, a composite crack resistance agent is synchronously incorporated; during the pouring of the middle layer, a compound of double anti-release diatom balls and nano-clay fibers is synchronously incorporated; during the pouring of the surface layer, a bacterium glue reactivation agent is synchronously incorporated;

[0025] S9: Perform steam curing on the substrate with a gradient distribution to obtain a high crack resistance and long-life concrete product.

[0026] Furthermore, S1 is specifically: Mix the sodium alginate solution and the nano-silica suspension according to a mass ratio of 1 - 1.5:0.3 - 0.6 to form a mixed sol. Drop the mixed sol into a 0.5 - 1.5 mol / L calcium chloride solution by an ion cross-linking method to form porous microspheres with a pore size of 50 - 150 μm. After vacuum freeze-drying the porous microspheres at -60 to -50 °C, calcine them at 200 - 300 °C for 1 - 2 h to obtain double anti-release diatom balls.

[0027] Furthermore, S2 is specifically: Co-grind limestone, bauxite, steel slag and gypsum with a mass ratio of 30 - 45:10 - 15:15 - 25:20 - 35 to a specific surface area of 200 - 300 m 2 / kg to obtain raw meal. Calcinate the raw meal in a rotary kiln at 1300 °C - 1400 °C for 60 - 120 min to obtain a clinker with , and CaO as the main mineral phases. Co-grind the clinker, gypsum and alunite with a mass ratio of 50 - 70:10 - 15:20 - 35 to a specific surface area of to obtain a composite crack resistance agent.

[0028] Further, S3 specifically includes: dispersing nano-clay in an aqueous solution of polyvinyl alcohol to form a suspension with a mass concentration of 5-10%, impregnating basalt fibers with fiber lengths of 8-15 mm and polyvinyl alcohol fibers with lengths of 5-10 mm in the suspension for 10-30 min, and drying with hot air at 100-120 °C to form a nano-clay fiber composite with a thickness of 50-200 nm.

[0029] Further, S4 specifically includes: mixing epoxy resin and latent curing agent dicyandiamide at a mass ratio of 10:1-3 to form a core material, using polyurea formaldehyde resin as a wall material, and forming a shell layer on the surface of the core material by interfacial polymerization at a core-wall ratio of 1:1.5-2, with a reaction temperature of 50-70 °C and a reaction time of 2-4 h. After washing with ethanol and drying, epoxy resin microcapsules with a particle size of 50-100 μm are obtained.

[0030] Further, S5 specifically includes: mixing Bacillus spores and porous zeolite carriers at a mass ratio of 2-3:5-10, adsorbing them in a phosphate buffer solution with a pH of 7-8 for 24-48 h, and subjecting the porous zeolite carriers loaded with Bacillus spores to freeze-drying treatment at -35 to -30 °C to form a microbial repair agent with an active spore loading rate of 80-95%. Seal and store it below 4 °C. Mix the epoxy resin microcapsules prepared in step S4 and the microbial repair agent at a mass ratio of 1.2-1.8:1.5-2.1 to obtain a bacterium-glue compound agent.

[0031] Further, S6 specifically includes: mixing nano-silica sol and epoxy group silane coupling agent at a mass ratio of 1:0.05-0.1, performing ultrasonic treatment at 40-60 °C for 30 min to graft epoxy groups on the surface of the silica sol, centrifuging to remove unreacted coupling agent to obtain modified silica sol, washing with ethanol and drying for standby;

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

[0033] Add the modified silica sol to the epoxy resin at a mass ratio of 1:0.8-1.5, mechanically stir at 500-800 rpm, and perform ultrasonic treatment at 40 kHz for 30 min to obtain an epoxy / silica sol system;

[0034] After drying to remove moisture, add zinc borate at 0.1-0.5% of the mass of the epoxy / silica sol system, add polyethylene glycol at 0.05% of the mass of the epoxy / silica sol system as a dispersion aid, perform ball milling for 2 h, and adjust the pH to 6.5-7.0;

[0035] Add a low-temperature active curing agent at 8-12% of the mass of the epoxy / silica sol system; cure to obtain a hybrid binder.

[0036] Further, S8 specifically includes: dispersing boron nitride nanosheets in an amino-silane ethanol solution, ultrasonically treating for 30 - 60 min, drying at 80 °C to obtain modified boron nitride nanosheets, and casting the modified boron nitride nanosheets in three layers according to a concentration gradient on the surface of a substrate to obtain a substrate with a gradient distribution;

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

[0038] During the casting of the core layer, a composite crack resistance agent is synchronously incorporated;

[0039] During the casting of the middle layer, a compound of dual anti-release diatomaceous earth balls and nano-clay fibers is synchronously incorporated;

[0040] During the casting of the surface layer, a bacterial glue reactivation agent is synchronously incorporated;

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

[0042] Further, S9 specifically includes: subjecting the cooled substrate with a gradient distribution to two-stage steam curing. The first stage is constant temperature curing at 50 - 55 °C for 3 - 5 h with a relative humidity ≥ 95%, and the second stage is constant temperature curing at 60 - 70 °C for 2 - 3 h with a relative humidity ≥ 90% to obtain a high crack resistance and long-life concrete product.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] 1. Through gradient hierarchical design, hybrid binder and nanofiber compounding, the present invention significantly improves the compressive and flexural properties of marine cement concrete materials, and the crack resistance is better than that of the prior art. Its Poisson's ratio is lower, indicating less lateral deformation during stress and higher structural stability, which can effectively inhibit the propagation of microcracks. The freeze-thaw durability index and sulfate resistance grade are significantly improved, thanks to the pore filling of dual anti-release diatomaceous earth balls and the dynamic repair effect of the bacterial glue reactivation agent.

[0045] 2. Most of the gas permeability grades of the present invention are "low permeability", indicating better compactness and effectively blocking the diffusion of chloride ions and gases. Through the compound of nano-clay fibers and gradient boron nitride nanosheets, the cracking area per unit area is significantly reduced, and plastic shrinkage is inhibited. The hybrid binder optimizes the interfacial bonding between the cement matrix and fibers / nano-materials, achieving a synergistic improvement in mechanical properties and durability.

[0046] 3. The gradient hierarchical design of the present invention endows the material with different functional characteristics at different levels, optimizes the internal stress distribution, reduces stress concentration points, and thus improves the compressive and flexural properties. The hybrid binder improves the interfacial bonding between the cement matrix, fibers, and nanomaterials through chemical modification, effectively transfers stress, and reduces interfacial defects. The addition of nanofibers forms a network structure inside the material, inhibits the propagation of microcracks, disperses stress, reduces the cracking area per unit area, fills microscopic pores at the same time, improves the compactness, and blocks the diffusion of chloride ions and gases.

[0047] 4. The double anti-release diatom balls of the present invention have a good pore filling effect, further improving the compactness. The bacterial glue rejuvenator continuously repairs microcracks and defects during the use of the material, maintaining a high-performance state. The gradient boron nitride nanosheets form a distribution structure with an increasing concentration gradient from the core to the surface, optimize the heat conduction path, reduce the accumulation of local thermal stress, inhibit the propagation of microcracks, and enhance the overall strength and toughness of the material at the same time.

[0048] 5. The addition of the composite crack inhibitor in the present invention significantly improves the strain distribution inside the concrete. It is detected by digital image correlation technology that the strain distribution inside the concrete without the addition of the composite crack inhibitor is uneven, with local high-strain and low-strain regions. After adding the composite crack inhibitor, the distribution of the second principal strain of the concrete is more uniform, the high-strain regions are significantly reduced, and the low-strain regions increase. This indicates that the composite crack inhibitor effectively reduces the shrinkage strain of the concrete and improves its crack resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

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

[0051] Figure 2 It is the X-ray diffraction pattern of the composite crack inhibitor clinker of the present invention;

[0052] Figure 3 It is the electron micrograph of the composite crack inhibitor clinker of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0054] Example 1: This example provides a high crack-resistant and long-life concrete product, which includes the following components by weight: 90 parts of ferroaluminate cement, 30 parts of fly ash, 25 parts of slag (S105 grade), 0.2 part of modified boron nitride nanosheets, 8 parts of hybrid binder, 0.8 part of double-release diatomaceous earth balls, 5 parts of composite crack-resistant agent, 1.5 parts of nano-clay fiber compound, 3 parts of biofilm complexing 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 surface grafted amino silane and an increasing concentration gradient from the core to the surface; the hybrid binder is an epoxy resin and modified silica sol composite binder; the double-release diatomaceous earth balls are calcium alginate microspheres loaded with nano-silica; the nano-clay fiber compound is a compound of basalt fiber coated with nano-clay and polyvinyl alcohol fiber; the biofilm complexing agent includes epoxy resin microcapsules and microbial remediation agents.

[0056] The preparation method of the high crack-resistant and long-life concrete product includes the following steps:

[0057] S1: Mix the sodium alginate solution and the nano-silica suspension in a mass ratio of 1.5:0.6 to form a mixed sol. Drop the mixed sol into a 1.5 mol / L calcium chloride solution by the ion cross-linking method to form porous microspheres with a pore size of 150 μm. After vacuum freeze-drying the porous microspheres at -60°C, calcine them at 300°C for 2 h to obtain double-release diatomaceous earth balls;

[0058] S2: Co-grind limestone, bauxite, steel slag, and gypsum with a mass ratio of 45:15:25:35 to a specific surface area of 300 m 2 / kg to obtain raw meal. Calcinate the raw meal in a rotary kiln at 1400°C for 120 min to obtain clinker with , and CaO as the main mineral phases. Co-grind the clinker, gypsum, and alunite with a mass ratio of 70:15:35 to a specific surface area of to obtain a composite crack-resistant agent (the prepared composite crack-resistant agent clinker is detected by electron microscopy and X-ray diffraction, and the results are as shown in Figure 2 and 3 );

[0059] S3: Disperse nano-clay in an aqueous solution of polyvinyl alcohol 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 fiber length of 10 mm (the mass ratio of basalt fibers to polyvinyl alcohol fibers is 1:1) are impregnated in the suspension for 30 min, and then dried with hot air at 120 °C to form a nano-clay fiber composite with a thickness of 200 nm;

[0060] S4: Mix epoxy resin and latent curing agent dicyandiamide in a mass ratio of 10:3 to form a core material. Using polyurea formaldehyde resin as the wall material, and according to a core-wall ratio of 1:2, form a shell layer on the surface of the core material through interfacial polymerization. The reaction temperature is 70 °C and the reaction time is 4 h. After washing with ethanol and drying, epoxy resin microcapsules with a particle size of 100 μm are obtained;

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

[0062] S6: Mix nano-silica sol (particle size 50 nm) and epoxy-based silane coupling agent (KH560) in a mass ratio of 1:0.1, and perform ultrasonic treatment at 60 °C for 30 min to graft epoxy groups on the surface of the silica sol. Centrifuge to remove the unreacted coupling agent to obtain modified silica sol, wash it with ethanol and dry it for standby;

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

[0064] Add the modified silica sol to the epoxy resin according to a mass ratio of 1:1.5, stir mechanically at 800 rpm, and perform ultrasonic treatment at 40 kHz for 30 min to obtain an epoxy / silica sol system;

[0065] After drying to remove moisture, add zinc borate at 0.5% of the mass of the epoxy / silica sol system, add polyethylene glycol (PEG-400) at 0.05% of the mass of the epoxy / silica sol system as a dispersion aid, perform ball milling for 2 h, and adjust the pH to 7.0 to inhibit the self-condensation of the silica sol;

[0066] Add a 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 °C for 1 h to initially form a cross-linked network;

[0068] Primary curing: Keep at 80 °C for 2 h to promote the formation of interfacial chemical bonds;

[0069] Post-curing: Treat at 120 °C for 1 h to eliminate internal stress and obtain a hybrid binder;

[0070] S7: Add the ferroaluminate cement, fly ash, slag and hybrid binder in batches by pairwise combination (mix the ferroaluminate cement with 1 / 3 of the hybrid binder, then add fly ash, add the remaining 2 / 3 of the hybrid binder, and finally add slag), and mix evenly to obtain the substrate;

[0071] S8: Disperse boron nitride nanosheets in an amino-silane ethanol solution, ultrasonically treat for 60 min, dry at 80 °C, and obtain modified boron nitride nanosheets after drying. Pour the modified boron nitride nanosheets onto the surface of the substrate in three layers according to a concentration gradient to obtain a substrate with gradient distribution;

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

[0073] Add a composite anti-cracking agent synchronously during the pouring of the core layer;

[0074] Add a compound of double anti-release diatomaceous earth balls and nano-clay fibers synchronously during the pouring of the middle layer;

[0075] Add a bacterial glue reactivation agent synchronously during the pouring of the surface layer;

[0076] S9: Carry out two-stage steam curing on the substrate with gradient distribution. The first stage is constant temperature curing at 55 °C for 5 h, and the relative humidity ≥ 95%. The second stage is constant temperature curing at 70 °C for 3 h, and the relative humidity ≥ 90%. Obtain a high anti-cracking and long-life concrete product.

[0077] Example 2: This example provides a high anti-cracking and long-life concrete product, which includes the following components by weight: 70 parts of ferroaluminate cement, 15 parts of fly ash, 10 parts of slag (S105 grade), 0.05 part of modified boron nitride nanosheets, 3 parts of hybrid binder, 0.2 part of double anti-release diatomaceous earth balls, 2 parts of composite anti-cracking agent, 0.5 part of compound of nano-clay fibers, 1.5 parts of bacterial glue reactivation agent, 120 parts of sand, 150 parts of stone, 1 part of polycarboxylate water reducer;

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

[0079] The preparation method of the high crack-resistant and long-life concrete product includes the following steps:

[0080] S1: Mix the sodium alginate solution and the nano-silica suspension in a mass ratio of 1:0.3 to form a mixed sol. Drop the mixed sol into a 0.5 mol / L calcium chloride solution by the ion cross-linking method to form porous microspheres with a pore size of 50 μm. After vacuum freeze-drying the porous microspheres at -50 °C, calcine them at 200 °C for 1 h to obtain double-release diatom balls;

[0081] S2: Grind limestone, bauxite, steel slag, and gypsum with a mass ratio of 30:10:15:20 together to a specific surface area of 200 m 2 / kg to obtain raw meal. Calcinate the raw meal in a rotary kiln at 1300 °C for 60 min to obtain clinker with , and CaO as the main mineral phases. Grind the clinker, gypsum, and alunite with a mass ratio of 50:10:20 together to a specific surface area of to obtain a composite crack-resistant agent;

[0082] S3: Disperse nano-clay in an aqueous solution of polyvinyl alcohol to form a suspension with a mass concentration of 5%. Immerse basalt fibers with a fiber length of 8 mm and polyvinyl alcohol fibers with a length of 5 mm (the mass ratio of basalt fibers to polyvinyl alcohol fibers is 1:1) in the suspension for 10 min, and then dry them at 100 °C with hot air to form a nano-clay fiber composite with a thickness of 50 nm;

[0083] S4: Mix epoxy resin and the latent curing agent dicyandiamide in a mass ratio of 10:1 to form a core material. Using polyurea formaldehyde resin as the wall material, form a shell layer on the surface of the core material according to a core-wall ratio of 1:1.5 by the interfacial polymerization method. The reaction temperature is 50 °C, and the reaction time is 2 h. After washing with ethanol and drying, obtain epoxy resin microcapsules with a particle size of 50 μm;

[0084] S5: Mix bacillus spores and porous zeolite carriers in a mass ratio of 2:5, adsorb them in a phosphate buffer solution with a pH of 7 - 8 for 24 h. After freeze-drying the porous zeolite carriers loaded with bacillus spores at -35 °C, form a microbial repair agent with an active spore loading rate of 80%, and store it sealed at a temperature below 4 °C. Mix the epoxy resin microcapsules prepared in step S4 and the microbial repair agent according to a mass ratio of 1.2:1.5 to obtain a bacteria-glue compound agent;

[0085] S6: Mix nano-silica sol (particle size 10 nm) and epoxy-based silane coupling agent (KH560) in a mass ratio of 1:0.05, and ultrasonically treat them at 40 °C for 30 min to graft epoxy groups on the surface of the silica sol. Centrifuge to remove the unreacted coupling agent to obtain modified silica sol, wash it with ethanol and dry it for standby;

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

[0087] Add the modified silica sol to the epoxy resin according to a mass ratio of 1:0.8, stir mechanically at 500 rpm, and perform ultrasonic treatment at 40 kHz for 30 min to obtain an epoxy / silica sol system;

[0088] After drying to remove moisture, add zinc borate at 0.1% of the mass of the epoxy / silica sol system, add polyethylene glycol (PEG-400) at 0.05% of the mass of the epoxy / silica sol system as a dispersion aid, perform ball milling for 2 h, and adjust the pH to 6.5 to inhibit the self-condensation of the silica sol;

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

[0090] Pre-cure: Let it stand at 40 °C for 1 h to initially form a crosslinked network;

[0091] Main cure: Keep it at 80 °C for 2 h to promote the formation of interfacial chemical bonds;

[0092] Post-cure: Treat it at 120 °C for 1 h to eliminate internal stress and obtain a hybrid binder;

[0093] S7: Add the ferroaluminate cement, fly ash, slag and the hybrid binder in batches by pairwise combination (mix the ferroaluminate cement with 1 / 3 of the hybrid binder, then add fly ash, add the remaining 2 / 3 of the hybrid binder, and finally add slag), and mix evenly to obtain a substrate;

[0094] S8: Disperse the boron nitride nanosheets in an amino-silane ethanol solution, perform ultrasonic treatment for 30 min, dry at 80 °C, and obtain modified boron nitride nanosheets after drying. Pour the modified boron nitride nanosheets onto the surface of the substrate in three layers according to a concentration gradient to obtain a substrate with a gradient distribution;

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

[0096] Add a composite crack resistance agent synchronously during the pouring of the core layer;

[0097] Add a compound of double-release diatomaceous earth balls and nano-clay fibers synchronously during the pouring of the middle layer;

[0098] Add a bacterial glue reactivation agent synchronously during the pouring of the surface layer;

[0099] S9: Subject the gradient distribution base material to two-stage steam curing. The first stage is constant-temperature curing at 50°C for 3 h with a relative humidity ≥ 95%, and the second stage is constant-temperature curing at 60°C for 2 h with a relative humidity ≥ 90% to obtain a high crack-resistant and long-life concrete product.

[0100] Example 3: This example provides a high crack-resistant and long-life concrete product, which includes the following components by weight: 80 parts of ferric aluminate cement, 21 parts of fly ash, 18 parts of slag (S105 grade), 0.1 part of modified boron nitride nanosheets, 5 parts of hybrid binder, 0.4 part of dual-release diatomaceous earth spheres, 3 parts of composite crack-resistant agent, 1.1 parts of nano-clay fiber complex, 2.8 parts of microbial glue complexing agent, 150 parts of sand, 180 parts of gravel, and 1.5 parts of polycarboxylate water reducer;

[0101] The modified boron nitride nanosheets are boron nitride nanosheets with an amino-silane grafted on the surface and an increasing concentration gradient from the core to the surface; the hybrid binder is an epoxy resin and modified silica sol composite binder; the dual-release diatomaceous earth spheres are calcium alginate microspheres loaded with nano-silica; the nano-clay fiber complex is a composite of basalt fibers coated with nano-clay and polyvinyl alcohol fibers; the microbial glue complexing agent contains epoxy resin microcapsules and microbial remediation agents.

[0102] The preparation method of the high crack-resistant and long-life concrete product includes the following steps:

[0103] S1: Mix the sodium alginate solution and the nano-silica suspension at a mass ratio of 1.2:0.5 to form a mixed sol. Drop the mixed sol into a 0.8 mol / L calcium chloride solution by the ion cross-linking method to form porous microspheres with a pore size of 100 μm. After vacuum freeze-drying the porous microspheres at -55°C, calcine them at 260°C for 2 h to obtain dual-release diatomaceous earth spheres;

[0104] S2: Co-grind limestone, bauxite, steel slag, and gypsum with a mass ratio of 38:12:21:32 to a specific surface area of 230 m 2 / kg to obtain raw meal. Calcinate the raw meal in a rotary kiln at 1350°C for 90 min to obtain clinker with , and CaO as the main mineral phases. Co-grind the clinker, gypsum, and alunite with a mass ratio of 60:12:28 to a specific surface area of to obtain a composite crack-resistant agent;

[0105] S3: Disperse the nano-clay in an aqueous solution of polyvinyl alcohol 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 fiber length of 7 mm (the mass ratio of basalt fibers to polyvinyl alcohol fibers is 1:1) are impregnated in the suspension for 20 min, and then dried with hot air at 105 °C to form a nano-clay fiber composite with a thickness of 100 nm;

[0106] S4: Mix epoxy resin and the latent curing agent dicyandiamide in a mass ratio of 10:2 to form a core material. Using polyurea formaldehyde resin as the wall material, and according to a core-wall ratio of 1:1.8, form a shell layer on the surface of the core material through interfacial polymerization. The reaction temperature is 64 °C and the reaction time is 3 h. After washing with ethanol and drying, an epoxy resin microcapsule with a particle size of 80 μm is obtained;

[0107] S5: Mix Bacillus spores and a porous zeolite carrier in a mass ratio of 2:7, adsorb them in a phosphate buffer solution with a pH of 7 - 8 for 48 h. The porous zeolite carrier loaded with Bacillus spores is freeze-dried at -33 °C to form a microbial repair agent with an active spore loading rate of 90%. It is sealed and stored below 4 °C. Mix the epoxy resin microcapsule prepared in step S4 and the microbial repair agent according to a mass ratio of 1.6:2.1 to obtain a bacterial glue compound agent;

[0108] S6: Mix nano-silica sol (particle size 40 nm) and epoxy-based silane coupling agent (KH560) in a mass ratio of 1:0.08, and perform ultrasonic treatment at 50 °C for 30 min to graft epoxy groups on the surface of the silica sol. Centrifuge to remove the unreacted coupling agent to obtain modified silica sol. After washing with ethanol and drying, it is reserved for use;

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

[0110] Add the modified silica sol to the epoxy resin according to a mass ratio of 1:1.3, and perform mechanical stirring at 600 rpm and ultrasonic treatment at 40 kHz for 30 min to obtain an epoxy / silica sol system;

[0111] After drying to remove moisture, add zinc borate at 0.4% of the mass of the epoxy / silica sol system, add polyethylene glycol (PEG-400) at 0.05% of the mass of the epoxy / silica sol system as a dispersion aid, perform ball milling for 2 h, and adjust the pH to 6.8 to inhibit the self-condensation of the silica sol;

[0112] Add a 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 °C for 1 h to initially form a crosslinked network;

[0114] Primary curing: Keep at 80 °C for 2 h to promote the formation of interfacial chemical bonds;

[0115] Post-curing: Treat at 120 °C for 1 h to eliminate internal stress and obtain a hybrid binder;

[0116] S7: Add the ferrite cement, fly ash, slag and hybrid binder in batches in pairs (mix the ferrite cement with 1 / 3 of the hybrid binder, then add fly ash, add the remaining 2 / 3 of the hybrid binder, and finally add slag), and mix evenly to obtain a substrate;

[0117] S8: Disperse boron nitride nanosheets in an amino silane ethanol solution, ultrasonically treat for 50 min, dry at 80 °C, and obtain modified boron nitride nanosheets after drying. Pour the modified boron nitride nanosheets onto the surface of the substrate in three layers according to a concentration gradient to obtain a substrate with a gradient distribution;

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

[0119] Add a composite crack resistance agent synchronously during the pouring of the core layer;

[0120] Add a compound of double anti-release diatomaceous earth balls and nano-clay fibers synchronously during the pouring of the middle layer;

[0121] Add a bacterial glue reactivation agent synchronously during the pouring of the surface layer;

[0122] S9: Carry out two-stage steam curing on the substrate with a gradient distribution. The first stage is to keep at a constant temperature of 52 °C for 4 h with a relative humidity ≥ 95%, and the second stage is to keep at a constant temperature of 63 °C for 2 h with a relative humidity ≥ 90% to obtain a high crack-resistant and long-life concrete product.

[0123] Comparative Example 1: The difference between this comparative example and Example 3 is that the bacterial glue reactivation agent is not added.

[0124] Comparative Example 2: The difference between this comparative example and Example 3 is that the double anti-release diatomaceous earth balls are not added.

[0125] Comparative Example 3: The difference between this comparative example and Example 3 is that in step S8, the composite crack resistance agent, double anti-release diatomaceous earth balls, nano-clay fiber compound, bacterial glue reactivation agent and boron nitride nanosheets are directly mixed into the substrate through the hybrid binder without layered pouring.

[0126] Comparative Example 4: The difference between this comparative example and Example 3 is that the bacterial glue reactivation agent and double anti-release diatomaceous earth balls are not added. At the same time, in step S8, the composite crack resistance agent, nano-clay fiber compound and boron nitride nanosheets are directly mixed into the substrate through the hybrid binder without layered pouring.

[0127] Comparative Example 5: The difference between this comparative example and Example 3 is that no compound crack inhibitor is added.

[0128] Control Example: The high crack-resistant and high-corrosion-resistant marine concrete prepared according to Chinese Patent CN116354680B comprises the following raw materials: 140 parts of ordinary Portland cement, 100 parts of sulfoaluminate cement, 110 parts of fly ash, 70 parts of slag 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, add appropriate amount of water for pre-wetting, mix it with polyurethane binder at high speed for 15 min, then slowly add graphene nanosheets in several times within 2 min, and continue to mix at high speed for 10 min to obtain the modified internal curing material;

[0131] S2: Put the composite cement, coarse aggregate, and fine aggregate into a mixer according to the mass parts and stir evenly, then add fly ash, slag powder, and the modified internal curing material prepared in the above step, and continue to stir;

[0132] S3: Take the water reducer and retarder according to the mass parts, mix them with water to form a uniform slurry, and slowly add the slurry in step S2 during the stirring process, and mix evenly to obtain the high crack-resistant and high-corrosion-resistant marine concrete.

[0133] Experimental Example 1: Mechanical property test (detected according to GB / T 50081-2019);

[0134] 1.1 Compressive strength test;

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

[0136] Size measurement, use a vernier caliper to measure the side length, and the tolerance ≤1 mm; the flatness tolerance of the bearing surface ≤0.0005d.

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

[0138] Result calculation, compressive strength , take the average value of 3 specimens, and eliminate the abnormal value when the range exceeds 15%.

[0139] 1.2 Flexural strength test;

[0140] Steps: Specimen preparation, prismatic specimens of 150×150×550mm, cured in the same way as the compressive strength test.

[0141] Loading settings, span of 450mm, loading rate divided according to strength grade (0.02 - 0.05MPa / s for below C30, 0.05 - 0.08MPa / s for C30 - C60).

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

[0143] Calculation, flexural strength , and the range treatment rule is the same as the compressive strength test.

[0144] 1.3 Poisson's ratio test;

[0145] Too high Poisson's ratio (such as μ > 0.25) indicates significant lateral expansion when the material is longitudinally compressed, which is likely to cause the expansion of internal microcracks and reduce the crack resistance of the structure.

[0146] Steps: Specimen preparation, prismatic specimens of 150×150×300mm, shared with the static compressive elastic modulus test.

[0147] Strain measurement, synchronously collect lateral and axial strains, and load to 30% of the ultimate load.

[0148] Calculation: Poisson's ratio μ = εlateral / εaxial.

[0149] Experimental example 2: Durability test (tested according to GB / T 50082 - 2024);

[0150] 2.1 Freeze - thaw resistance test (rapid freeze - thaw method);

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

[0152] Freeze - thaw cycle, freezing stage, the central temperature of the specimen drops to -18±2℃ and is maintained for 4 hours.

[0153] Melting stage, immersed in water at 5℃ until the central temperature rises to 5±2℃ and is maintained for 2 hours.

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

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

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

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

[0158] Device setting: Inject 0.3 mol / L NaOH solution at the positive electrode and 3% NaCl solution at the negative electrode.

[0159] Adjust the copper mesh aperture of the copper backing plate to 850 μm.

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

[0161] Calculation: Total electric flux .

[0162] Judgment and classification: Low permeability (Q < 1000 C), medium permeability (1000 C ≤ Q ≤ 2000 C), high permeability (Q > 2000 C).

[0163] 2.3 Gas permeability resistance test;

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

[0165] Equipment setting: Adjust the nitrogen pressure to 0.15 - 0.40 MPa and test the gas flow rate under gradient pressure.

[0166] Measure the permeation flow rate using a soap film flowmeter with an accuracy of ±0.5%.

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

[0168] 2.4 Sulfate attack resistance test;

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

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

[0171] Judgment: The sulfate attack resistance grade is divided according to the maximum cycle number.

[0172] 2.5 Crack resistance test;

[0173] Steps: Specimen preparation. A flat specimen with dimensions of 800×600×100 mm, and the surface wind speed is controlled at 5 ± 0.5 m / s (at a distance of 100 mm from the surface).

[0174] Crack observation: Record the crack width 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 following table. Among them, compressive strength (MPa), flexural strength (MPa), durability index K n , total electric flux Q (C), gas permeability kp , compressive strength loss rate of sulfate resistance test (%), total cracking area per unit area , A1 is the penetration grade of total electric flux, and A2 is the penetration grade of gas.

[0177]

[0178] It can be seen from the above data that through gradient layer design, hybrid binder and nanofiber compounding, the present invention significantly improves the compressive and flexural properties of the material, and the crack resistance is better than the prior art. Due to component lack or process simplification in Comparative Examples 1-4, the internal structure is loose and the mechanical properties are significantly reduced.

[0179] The Poisson's ratio of the present invention is lower, indicating that the material has less lateral deformation and higher structural stability when stressed, effectively inhibiting the propagation of microcracks; in Comparative Examples 1, 3 and 4, due to non-layered pouring, the strain distribution is uneven and the lateral deformation is significant.

[0180] The frost resistance durability index and sulfate resistance grade of the present invention are significantly better than those of the comparative examples, due to the pore filling of double anti-release diatomaceous earth balls and the dynamic repair effect of biofilm complexing agent. In Comparative Examples 2-4, due to the lack of functional components, the durability decay is accelerated.

[0181] The gas penetration grade of the present invention is mostly "low penetration", indicating that its compactness is better and the diffusion of chloride ions and gas is effectively blocked; in Comparative Examples 1 and 4, due to uneven material distribution or component lack, the penetration performance deteriorates.

[0182] The present invention significantly reduces the cracking area per unit area and inhibits plastic shrinkage through the compound of nano-clay fiber and gradient boron nitride nanosheets; in Comparative Examples 3 and 4, due to non-layered pouring, local stress concentration leads to an increased cracking risk. The hybrid binder of the present invention optimizes the interfacial bonding between the cement matrix and the fiber / nano material, and synergistically improves the mechanical properties and durability; in Comparative Examples 1, 3 and 4, due to the lack of functional components or direct mixing process, the interfacial defects increase and the performance deteriorates.

[0183] Experimental Example 3: Strain test (in accordance with GB / T50082-2024);

[0184] 3.1 Specimen preparation and pretreatment: Use flat specimens with dimensions of 600 mm × 600 mm × 100 mm (standard restrained shrinkage specimens);

[0185] Cure the specimens until the age of 28 days;

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

[0187] Calibration plate placement: Fix a calibration plate (known size grid) beside the specimen for image space calibration.

[0188] 3.3 DIC system setup and image acquisition;

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

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

[0191] 3.4 Loading conditions;

[0192] Conduct a restrained shrinkage test. Embed a steel bar skeleton (Φ8 mm, spacing 100 mm) on the four sides of the specimen to simulate the restraint of the actual structure;

[0193] Environmental control: Temperature 20 ± 2°C, relative humidity 60 ± 5%, continuously monitor until the cracks are stable.

[0194] 3.5 Image acquisition;

[0195] Continuously take images of the specimen surface during the loading process, with a time interval of 1 frame / minute;

[0196] Total acquisition duration: 24 hours;

[0197] For the strain test results of Comparative Example 5 and Example 3, refer to Figure 1 As shown, it can be seen from the figure that on the left is the second principal strain distribution diagram of Comparative Example 5, and on the right is the second principal strain distribution diagram after adding the composite crack - resistant agent (i.e., Example 3);

[0198] In the second principal strain distribution diagram of Comparative Example 5, the color distribution is relatively chaotic, with various 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, indicating that the second principal strain distribution inside the concrete is indeed uneven;

[0199] In the second principal strain distribution diagram after adding the composite crack inhibitor, the color distribution is relatively more uniform, the red area is significantly reduced, and the blue area increases. This indicates that the addition of the composite crack inhibitor makes the strain distribution inside the concrete more uniform and the shrinkage strain decreases;

[0200] Therefore, the addition of the composite crack inhibitor does improve the non-uniform strain and stress distribution inside the concrete, making the strain distribution more uniform and the shrinkage strain decrease.

[0201] In summary, through the synergistic effect of various technical means, the present invention comprehensively optimizes the material structure and properties from micro to macro, significantly improves the mechanical properties and durability of marine cement concrete, and makes 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 and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and 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 double-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 recovery agent, 120-160 parts of sand, 150-200 parts of stone, 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 spheres are calcium alginate microspheres loaded with nano-silicon dioxide; The nano-clay fiber composite is a composite of basalt fiber and polyvinyl alcohol fiber coated with nano-clay on the surface; The bacterial glue restoration agent comprises epoxy resin microcapsules and microbial repair agents.

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-silicon dioxide suspension are mixed to form a mixed sol, and the mixed sol is dropped into a calcium chloride solution by an ion crosslinking method to form porous microspheres, and the porous microspheres are freeze-dried in vacuum and then calcined to obtain dual-antibody-releasing diatom spheres; S2: Grinding limestone, bauxite, steel slag and gypsum together to obtain 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, immersing basalt fibers and polyvinyl alcohol fibers in the suspension, and forming a nanoclay fiber composite after hot air drying; S4: mixing epoxy resin with 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: adsorbing the Bacillus spores and the porous zeolite carrier in a phosphate buffer, subjecting the porous zeolite carrier loaded with the Bacillus spores to freeze-drying treatment to form a microbial repair agent, and mixing the epoxy resin microcapsules prepared in step S4 with the microbial repair agent to obtain a bacterial gel restoration agent; S6: nano silica sol is mixed with epoxy silane coupling agent, and subjected to ultrasonic treatment to graft epoxy groups on the surface of silica sol, and 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 into the epoxy resin, mechanically stirred, and ultrasonically treated to obtain the 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 a hybrid adhesive is obtained by curing; S7: adding ferroaluminate cement, fly ash, slag and hybrid binder in batches in combination of two by two, 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 on a substrate surface in three layers according to a concentration gradient 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 highly crack-resistant and long-life concrete product according to claim 2, characterized in that: S1 is specifically as follows: sodium alginate solution and nano-silicon dioxide 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, and the porous microspheres are vacuum freeze-dried at -60 to -50°C, and then calcined at 200-300°C for 1-2h to obtain dual-antibody-releasing diatom balls.

4. The method for preparing a highly crack-resistant and long-life concrete product according to claim 2, characterized in that: 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, the raw material is obtained, and the raw material is calcined in a rotary kiln at 1300℃-1400℃ for 60-120min to obtain , The clinker with CaO as the main mineral phase is ground into powder with the mass ratio of 50-70:10-15:20-35, gypsum and alum stone to a specific surface area of A composite anti-cracking agent is obtained.

5. The method for preparing a highly crack-resistant 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 fiber length of 5-10 mm are immersed in the suspension for 10-30 minutes, and after hot air drying at 100-120°C, a nanoclay fiber composite with a thickness of 50-200 nm is formed.

6. The method for preparing a highly crack-resistant 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.

7. The method for preparing a highly crack-resistant and long-life concrete product according to claim 2, characterized in that: 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 of pH 7-8 for 24-48 hours, 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%, and 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.

8. The method for preparing a highly crack-resistant and long-life concrete product according to claim 2, characterized in that: 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 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; Heat the bisphenol A epoxy resin to reduce viscosity, and add a diluent to adjust the solid content to 50%-60%; The modified silica sol is 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.

9. The method for preparing a highly crack-resistant and long-life concrete product according to claim 2, characterized in that: S8 is specifically: 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 on the surface of a substrate in three layers according to a concentration gradient 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, 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, the bacterial glue restoring agent is added simultaneously.

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

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