High-strength self-repairing concrete and preparation method thereof

Abstract

The invention relates to the field of self-repairing concrete, in particular to high-strength self-repairing concrete and a preparation method thereof. The high-strength self-repairing concrete comprises the following substances in parts by weight: 45-60 parts of cement; 100 to 120 parts of recycled coarse aggregate; 65 to 80 parts of fine aggregate; 10 to 20 parts of water; 0.1 to 0.3 part of a water reducing agent; the recycled coarse aggregate is the recycled coarse aggregate immobilized with self-repairing microorganisms, and the self-repairing microorganisms comprise at least one of bacillus subtilis, bacillus megatherium and bacillus pasteurii. The concrete crack self-repairing capability is endowed through the immobilized self-repairing microorganisms. The microorganisms form resting spores in the concrete, when cracks are generated and water permeates into the cracks, the microorganisms are activated and metabolize a calcium source and urea in the surrounding environment, calcium carbonate crystals are generated through the mechanism that the microorganisms induce carbonate precipitation, the cracks are filled, and the structural integrity is recovered. The process does not need external intervention, and the mechanical structure and mechanical properties of the concrete structure can be remarkably improved.

Description

Technical Field

[0001] The present application relates to the field of self - repairing concrete, and particularly to a high - strength self - repairing concrete and a preparation method thereof. Background Art

[0002] Using recycled concrete in construction projects can solve a series of resource and environmental problems caused by construction waste, thus promoting the green and sustainable development of construction projects. However, after being crushed, the recycled aggregate has an additional layer of mortar attached to the surface of the original aggregate, so the structure of the recycled aggregate is complex, resulting in low density, high water absorption, high crushing index, and poor soundness. In actual projects, due to the material composition and processing technology of the concrete structure itself, as well as external loads and environmental factors, a certain amount of pores and cracks will be generated in the components. At the same time, under the combined action of various loads and environmental factors, the actual engineering structure often causes different degrees of damage or cracks in the concrete, and these damages or cracks will penetrate each other, thus accelerating the transmission of media inside the concrete, and having a significant impact on the durability of the concrete structure.

[0003] In view of the above - mentioned prior art, the inventor found that the existing recycled concrete is obtained by processing construction solid waste through processes such as crushing, cleaning, and screening to obtain aggregates with a particle size > 5 mm. The recycled coarse aggregate has the characteristics of more prominent edges and corners and a rough surface compared with natural coarse aggregate, and there is hardened cement mortar attached to the surface. A large number of micro - cracks are formed inside due to the crushing process. Therefore, the porosity and water absorption of the recycled coarse aggregate are higher than those of natural coarse aggregate. Compared with natural coarse aggregate, the recycled coarse aggregate has the characteristics of small bulk density and high crushing index due to the hardened cement mortar attached to the surface. As a result, the mechanical properties and mechanical performance of the prepared concrete materials are greatly reduced, limiting its scope of application. Summary of the Invention

[0004] In order to improve the above - mentioned technical problems, the present application provides a high - strength self - repairing concrete and a preparation method thereof.

[0005] In the first aspect, the present application provides a high - strength self - repairing concrete, adopting the following technical solution:

[0006] A high - strength self - repairing concrete, comprising the following substances in parts by weight:

[0007]

[0008] The recycled coarse aggregate is a recycled coarse aggregate loaded with self - repairing microorganisms, and the self - repairing microorganisms include at least one of Bacillus subtilis, Bacillus megaterium, and Bacillus pasteurii.

[0009] Through the above technical solution, the present application endows the concrete cracks with self-healing ability by immobilizing self-healing microorganisms (such as Bacillus subtilis, Bacillus megaterium or Bacillus pasteurii). These microorganisms form dormant spores inside the concrete. When cracks occur and water infiltrates, the microorganisms are activated and metabolize calcium sources (such as calcium chloride or calcium sulfate) and urea in the surrounding environment, and generate calcium carbonate crystals through the mechanism of microbial-induced carbonate precipitation (MICP) to fill the cracks and restore the structural integrity. This process requires no external intervention and can significantly extend the mechanical structure and mechanical properties of the concrete structure.

[0010] Furthermore, the recycled coarse aggregate is a surface-treated recycled coarse aggregate, and the surface treatment adopts the following technical solution:

[0011] Take the recycled coarse aggregate and soak it in hydrochloric acid and perform ultrasonic-assisted cleaning treatment. After the cleaning is completed, wash and dry it, and collect the pretreated recycled coarse aggregate;

[0012] Take nano-magnesium sulfate fiber and stir and mix it with silica sol, ultrasonically disperse it and collect the dispersion;

[0013] Take the dispersion and mix it with the pretreated recycled coarse aggregate and place it in a reaction kettle, heat it up and introduce carbon dioxide to the supercritical state, stir and mix it, and then depressurize it step by step for in-situ curing treatment, and collect the surface-treated recycled coarse aggregate.

[0014] Through the above technical solution, the present application first effectively removes the old cement paste, organic matter and metal impurities on the surface of the aggregate by hydrochloric acid soaking and ultrasonic-assisted cleaning, exposes the original pore structure of the aggregate, and provides a clean interface for subsequent coating.

[0015] Subsequently, the mixed dispersion of nano-magnesium sulfate fiber and silica sol reacts with the aggregate under the condition of supercritical carbon dioxide to form a nano-micron composite coating. Supercritical carbon dioxide has high diffusivity and low surface tension, can penetrate into the pores of the aggregate, carry the nano-fiber and silica sol to deposit uniformly, and form a carrier structure with both toughness and porosity.

[0016] The high specific surface area of nano-magnesium sulfate fiber and the inorganic bonding effect of silica sol significantly enhance the interfacial bonding force between the aggregate and the cement matrix, reduce the weak points in the interfacial transition zone, and inhibit crack propagation. The innovation of this process lies in the physical-chemical synergistic modification, which not only retains the environmental protection advantages of recycled aggregate, but also solves the defects of its high water absorption rate and low strength, and at the same time creates a stable porous microenvironment for microbial loading to ensure the long-term survival of the repair agent.

[0017] Furthermore, the step-by-step depressurization includes the following steps:

[0018] First, depressurize at a rate of 5 MPa / s until it reaches 15 MPa, and then hold the pressure for 5 minutes. After the pressure holding is completed, depressurize instantaneously to atmospheric pressure at a rate of 10 MPa / s.

[0019] Through the above technical solution, this application optimizes the internal structure of the aggregate by depressurizing in stages. First, depressurize at a rate of 5 MPa / s to 15 MPa and hold the pressure for 5 minutes. Utilize the slow release of supercritical carbon dioxide to balance the internal stress of the aggregate and avoid pore collapse or microcrack propagation caused by sudden pressure drop. During the pressure holding stage, the nanofibers and silica sol are further cross-linked to form an interlocking network structure. Subsequently, quickly release the pressure to atmospheric pressure at a rate of 10 MPa / s. Utilize the pressure difference to drive the rapid escape of supercritical carbon dioxide from the inside of the aggregate to form through pores, which not only provides a living space for microorganisms but also ensures the smoothness of the subsequent coating liquid penetration channel.

[0020] The physical principle of this process lies in the "directional design" of the pore structure of the aggregate through the kinetic control of pressure changes: the slow depressurization stage ensures structural stability, and the fast depressurization stage creates a high porosity. Compared with traditional hot pressing or chemical foaming methods, gradient depressurization avoids damage to the aggregate caused by high temperature or corrosive reagents, and at the same time significantly improves the specific surface area and mechanical strength of the aggregate, laying a foundation for the efficient loading and long-term survival of microorganisms.

[0021] Furthermore, the diameter of the nano-magnesium sulfate fiber is 20 - 50 nm, and the aspect ratio is 55 - 90.

[0022] Through the above technical solution, this application selects nano-magnesium sulfate fibers with a diameter of 20 - 50 nm and an aspect ratio of 55 - 90, makes them uniformly disperse in silica sol and anchor on the surface of the aggregate to form a structure similar to a "nano-brush", enhancing the mechanical interlocking between the aggregate and the cement matrix. The nano-magnesium sulfate fibers are arranged directionally during the supercritical carbon dioxide penetration process, forming a three-dimensional network by bridging the pores of the aggregate, which not only improves the compressive strength of the aggregate but also retains sufficient connected pores for microorganisms to reside.

[0023] Furthermore, the regenerated coarse aggregate loaded with self-healing microorganisms is made by the following technical solution:

[0024] Take the microbial freeze-dried powder and stir it with calcium chloride solution, collect the mixed solution and drop it into the sodium alginate solution, filter and vacuum dry, crush and screen, and collect the microbial microcapsule particles;

[0025] Take the microbial microcapsule particles, tetraethyl orthosilicate and dopamine and stir them to mix, and collect the mixed coating solution;

[0026] Immerse the surface-treated recycled coarse aggregate in the mixed coating solution. After immersion, introduce ozone and conduct in-situ polymerization. Collect the recycled coarse aggregate after coating is completed and heat it up for densification treatment, then the recycled coarse aggregate loaded with self-healing microorganisms can be prepared.

[0027] Through the above technical solution, the present application adopts a microorganism immobilization process to achieve efficient protection and controlled release of microorganisms through microencapsulation and double coating technologies. First, the freeze-dried microorganisms are mixed with a calcium chloride solution and then dropped into a sodium alginate solution, and hydrogel microcapsules are formed through ionic cross-linking to encapsulate the microorganisms in the inner core. The size design of the microcapsules ensures that they are not damaged during the concrete mixing process, and at the same time allows the capsules to dissolve and release microorganisms when cracks seep water.

[0028] Subsequently, tetraethyl orthosilicate hydrolyzes under alkaline conditions to generate a silica gel layer, which together with the polydopamine film formed by oxidative polymerization of dopamine constitutes a double coating barrier: the silica layer provides rigid protection against the high-alkali environment inside the concrete; the polydopamine film layer has adhesiveness and antioxidant properties to prevent reactive oxygen species from damaging the microbial DNA. The introduction of ozone can accelerate the polymerization of dopamine to form a denser coating layer.

[0029] Furthermore, the addition amount of the freeze-dried microorganisms in the calcium chloride solution is not less than 109 CFU / g.

[0030] Furthermore, the temperature of the heating densification treatment is 85 - 120 °C.

[0031] Through the above technical solution, the present application adopts heating densification treatment to strengthen the coating layer structure. Within this temperature range, the silanol groups (Si-OH) generated by the hydrolysis of TEOS condense to form a Si-O-Si network, and at the same time, the catechol groups of polydopamine are oxidatively cross-linked. The two work together to form a dense inorganic-organic hybrid layer, thus achieving a good coating effect on the recycled aggregate.

[0032] In the second aspect, the present application provides a preparation method for high-strength self-healing concrete, adopting the following technical solution:

[0033] A preparation method for high-strength self-healing concrete includes the following preparation steps:

[0034] Take cement, recycled coarse aggregate and fine aggregate, mix them and place them in a stirring device, stir and mix to collect the mixture;

[0035] Inject a water reducer and water into the mixture in three portions, stir and mix to collect the slurry;

[0036] Take the slurry, pour it, and conduct bionic gradient curing treatment, then high-strength self-healing concrete can be prepared.

[0037] Further, the bionic gradient curing treatment includes the following steps:

[0038] After sealing and curing treatment for 3 days in an environment with a humidity of 90 - 95% and a temperature of 15 - 20°C, then inject urea and calcium sulfate solution, and activate the curing treatment for 4 - 7 days; after the activation curing is completed, adopt wet-dry cycling curing for 8 - 28 days, and the preparation method of the high-strength self-healing concrete can be completed.

[0039] Further, the wet-dry cycling curing is that each water immersion treatment is for 12h, and then the drying treatment is for 12h.

[0040] Through the above technical solution, the present application optimizes the concrete performance through a staged process and a bionic curing strategy. Injecting the water reducing agent and water in three times can avoid the segregation of the slurry caused by one-time addition, ensure the uniform dispersion of the aggregate and the full hydration of the cement. The bionic gradient curing simulates the self-healing process of organisms: the initial sealing curing (humidity 90 - 95%, 15 - 20°C, 3 days) promotes the formation of C-S-H gel by cement, forms the initial strength, and at the same time the low temperature inhibits the premature activation of microorganisms; after injecting urea and calcium sulfate solution, urea hydrolyzes to generate CO 3 2- and NH 4 + in an alkaline environment, combines with Ca 2+ to form calcium carbonate, activates the microbial mineralization activity; the wet-dry cycling curing (immersion for 12h / drying for 12h, 8 - 28 days) simulates the natural environment through periodic humidity changes, induces the cycle of microcrack generation - repair, and strengthens the concrete density. The innovation of this curing strategy lies in the time sequence coupling of material hydration and biological repair: in the early stage, the cement strength is the dominant factor, and in the later stage, it relies on microbial repair of micro-damage, and finally realizes the synergistic improvement of strength and durability.

[0041] In summary, the present application has the following beneficial effects:

[0042] First, the present application endows the concrete with crack self-healing ability by immobilizing self-healing microorganisms (such as Bacillus subtilis, Bacillus megaterium or Bacillus pasteurii). These microorganisms form dormant spores inside the concrete. When cracks occur and water seeps in, the microorganisms are activated and metabolize calcium sources (such as calcium chloride or calcium sulfate) and urea in the surrounding environment, and generate calcium carbonate crystals through the microbial-induced carbonate precipitation (MICP) mechanism, filling the cracks and restoring the structural integrity. This process does not require external intervention and can significantly extend the mechanical structure and mechanical properties of the concrete structure.

[0043] Second, the present application first effectively removes the old cement paste, organic matter and metal impurities on the surface of the aggregate through hydrochloric acid immersion and ultrasonic-assisted cleaning, exposes the original pore structure of the aggregate, and provides a clean interface for subsequent coating.

[0044] Subsequently, the mixed dispersion of nano magnesium sulfate fiber and silica sol reacts with the aggregate under supercritical carbon dioxide conditions to form a nano-micro composite coating. Supercritical carbon dioxide has high diffusivity and low surface tension, which can penetrate into the pores of the aggregate, carry the nano fibers and silica sol to deposit uniformly, and form a carrier structure with both toughness and porosity.

[0045] The high specific surface area of nano magnesium sulfate fiber and the inorganic bonding effect of silica sol significantly enhance the interfacial bonding force between the aggregate and the cement matrix, reduce the weak points in the interfacial transition zone, and inhibit crack propagation. The innovation of this process lies in the physical-chemical synergistic modification, which not only retains the environmental protection advantages of recycled aggregates, but also solves the defects of high water absorption and low strength, and at the same time creates a stable porous microenvironment for microbial loading to ensure the long-term survival of the repair agent.

[0046] Thirdly, the present application adopts a microbial immobilization process to achieve the efficient protection and controlled release of microorganisms through microencapsulation and double coating technologies. First, the freeze-dried microorganisms are mixed with calcium chloride solution and then dropped into sodium alginate solution to form hydrogel microcapsules through ionic cross-linking, encapsulating the microorganisms in the core. The size design of the microcapsules ensures that they are not damaged during the concrete mixing process, while allowing the capsules to dissolve and release the microorganisms when crack seepage occurs.

[0047] Subsequently, tetraethyl orthosilicate hydrolyzes under alkaline conditions to generate a silica gel layer, which together with the polydopamine film formed by the oxidative polymerization of dopamine constitutes a double coating barrier: the silica layer provides rigid protection against the high-alkali environment inside the concrete; the polydopamine film layer has adhesiveness and antioxidant properties to prevent reactive oxygen species from damaging the microbial DNA. The introduction of ozone can accelerate the polymerization of dopamine to form a denser coating layer. Detailed implementation mode

[0048] The present application will be further described in detail below in conjunction with embodiments.

[0049] Preparation example 1

[0050] Recycled coarse aggregate 1 after surface treatment

[0051] Take the recycled coarse aggregate and soak it in 0.5 mol / L hydrochloric acid and perform ultrasonic-assisted cleaning treatment at 200 W for 10 min. After the cleaning is completed, rinse it with deionized water until neutral, and then dry it at 50 °C for 12 h to collect the pretreated recycled coarse aggregate;

[0052] Take 20 g of nano magnesium sulfate fibers with a diameter of 20 nm and a length-to-diameter ratio of 55 and stir and mix them with 1000 g of silica sol with a solid content of 10%, and perform ultrasonic dispersion at 200 W and collect the dispersion;

[0053] Take the dispersion liquid and mix it with the pretreated recycled coarse aggregate in a mass ratio of 2:1, place them in a reaction kettle, heat up and introduce carbon dioxide to the supercritical state of 25 MPa, after stirring and mixing, first depressurize to 15 MPa at a rate of 5 MPa / s, and keep the pressure for 5 min; after the pressure holding is completed, then depressurize instantaneously to atmospheric pressure at a rate of 10 MPa / s, and perform in-situ curing treatment in a hot air circulation at 80 °C for 30 min, and collect the surface-treated recycled coarse aggregate 1.

[0054] Preparation Example 2

[0055] Surface-treated recycled coarse aggregate 2

[0056] Take the recycled coarse aggregate and soak it in 0.5 mol / L hydrochloric acid, and perform ultrasonic-assisted cleaning treatment at 200 W for 10 min. After the cleaning is completed, rinse it with deionized water until neutral, and then dry it at 50 °C for 12 h to collect the pretreated recycled coarse aggregate;

[0057] Take 35 g of magnesium sulfate fibers with a diameter of 35 nm and an aspect ratio of 70, and stir and mix them with 1250 g of silica sol with a solid content of 10%, disperse them ultrasonically at 200 W and collect the dispersion liquid;

[0058] Take the dispersion liquid and mix it with the pretreated recycled coarse aggregate in a mass ratio of 2:1, place them in a reaction kettle, heat up and introduce carbon dioxide to the supercritical state of 25 MPa, after stirring and mixing, first depressurize to 15 MPa at a rate of 5 MPa / s, and keep the pressure for 5 min; after the pressure holding is completed, then depressurize instantaneously to atmospheric pressure at a rate of 10 MPa / s, and perform in-situ curing treatment in a hot air circulation at 80 °C for 30 min, and collect the surface-treated recycled coarse aggregate 2.

[0059] Preparation Example 3

[0060] Surface-treated recycled coarse aggregate 3

[0061] Take the recycled coarse aggregate and soak it in 0.5 mol / L hydrochloric acid, and perform ultrasonic-assisted cleaning treatment at 200 W for 10 min. After the cleaning is completed, rinse it with deionized water until neutral, and then dry it at 50 °C for 12 h to collect the pretreated recycled coarse aggregate;

[0062] Take 50 g of magnesium sulfate fibers with a diameter of 50 nm and an aspect ratio of 90, and stir and mix them with 1500 g of silica sol with a solid content of 10%, disperse them ultrasonically at 200 W and collect the dispersion liquid;

[0063] Take the dispersion liquid and mix it with the pretreated recycled coarse aggregate in a mass ratio of 2:1, place them in a reaction kettle, heat up and introduce carbon dioxide to the supercritical state of 25 MPa, after stirring and mixing, first depressurize to 15 MPa at a rate of 5 MPa / s, and keep the pressure for 5 minutes; after the pressure holding is completed, then depressurize instantaneously to atmospheric pressure at a rate of 10 MPa / s, and perform in-situ curing treatment in a hot air circulation at 80 °C for 30 minutes, and collect the surface-treated recycled coarse aggregate 3.

[0064] Preparation Example 4

[0065] Recycled coarse aggregate 1 with self-healing microorganisms immobilized

[0066] According to the addition amount of Bacillus subtilis being 2.5×10 9 CFU / g, take the freeze-dried powder of Bacillus subtilis and stir and mix it with 0.1 mol / L calcium chloride solution, collect the mixed solution and drop it into a 3% sodium alginate solution by mass fraction, filter and place it in a vacuum dryer at 50 °C, pulverize and sieve, and collect the microbial microcapsule particles;

[0067] Take 200 g of microbial microcapsule particles, 200 mL of tetraethyl orthosilicate and 400 mg of dopamine and stir and mix them, and collect the mixed coating solution;

[0068] Immerse the surface-treated recycled coarse aggregate 1 in the mixed coating solution, after the immersion is completed, introduce 5 ppm of ozone and perform in-situ polymerization, collect the recycled coarse aggregate after the coating is completed and heat it up to 85 °C for densification treatment, and then the recycled coarse aggregate 1 with self-healing microorganisms immobilized can be prepared.

[0069] Preparation Example 5

[0070] Recycled coarse aggregate 2 with self-healing microorganisms immobilized

[0071] According to the addition amount of Bacillus megaterium being 3×10 9 CFU / g, take the freeze-dried powder of Bacillus megaterium and stir and mix it with 0.1 mol / L calcium chloride solution, collect the mixed solution and drop it into a 3% sodium alginate solution by mass fraction, filter and place it in a vacuum dryer at 50 °C, pulverize and sieve, and collect the microbial microcapsule particles;

[0072] Take 200 g of microbial microcapsule particles, 200 mL of tetraethyl orthosilicate and 400 mg of dopamine and stir and mix them, and collect the mixed coating solution;

[0073] Immerse the surface-treated recycled coarse aggregate 2 in the mixed coating solution, after the immersion is completed, introduce 5 ppm of ozone and perform in-situ polymerization, collect the recycled coarse aggregate after the coating is completed and heat it up to 100 °C for densification treatment, and then the recycled coarse aggregate 2 with self-healing microorganisms immobilized can be prepared.

[0074] Preparation Example 6

[0075] Recycled coarse aggregate 3 immobilized with self - repairing microorganisms

[0076] With the addition amount of Bacillus pasteurii being 5×10 9 CFU / g, take the freeze - dried powder of Bacillus pasteurii and stir - mix it with 0.1 mol / L calcium chloride solution. Collect the mixed solution and drop - add it into a 3% sodium alginate solution by mass fraction. Filter and place it in a vacuum dryer at 50 °C, pulverize and sieve it, and collect the microbial microcapsule particles;

[0077] Take 200 g of microbial microcapsule particles, 200 mL of tetraethyl orthosilicate, and 400 mg of dopamine, stir - mix them, and collect the mixed coating solution;

[0078] Immerse the surface - treated recycled coarse aggregate 3 in the mixed coating solution. After the immersion is completed, introduce 5 ppm ozone and carry out in - situ polymerization. Collect the recycled coarse aggregate after coating is completed and heat it up to 120 °C for densification treatment, then the recycled coarse aggregate 3 immobilized with self - repairing microorganisms can be prepared.

[0079] Preparation Example 7

[0080] Recycled coarse aggregate 4 immobilized with self - repairing microorganisms

[0081] With the addition amount of Bacillus subtilis being 2.5×109 CFU / g, take the freeze - dried powder of Bacillus subtilis and stir - mix it with 0.1 mol / L calcium chloride solution. Collect the mixed solution and drop - add it into a 3% sodium alginate solution by mass fraction. Filter and place it in a vacuum dryer at 50 °C, pulverize and sieve it, and collect the microbial microcapsule particles;

[0082] Take 200 g of microbial microcapsule particles, 200 mL of tetraethyl orthosilicate, and 400 mg of dopamine, stir - mix them, and collect the mixed coating solution;

[0083] Immerse the untreated recycled coarse aggregate in the mixed coating solution. After the immersion is completed, introduce 5 ppm ozone and carry out in - situ polymerization. Collect the recycled coarse aggregate after coating is completed and heat it up to 100 °C for densification treatment, then the recycled coarse aggregate 4 immobilized with self - repairing microorganisms can be prepared.

[0084] Example

[0085] Example 1

[0086] A high - strength self - repairing concrete comprises the following substances by weight: 45 kg of cement, 100 kg of recycled coarse aggregate 4 immobilized with self - repairing microorganisms, 65 kg of fine aggregate, 10 kg of water, and 0.1 kg of water - reducing agent.

[0087] A preparation method of a high - strength self - repairing concrete, comprising the following steps:

[0088] Take cement, recycled coarse aggregate and fine aggregate, mix them and place them in a mixing device, mix and collect to obtain a mixture;

[0089] Add water reducing agent and water to the mixture in three portions, mix and collect to obtain a slurry;

[0090] Take the slurry and pour it. After sealing and curing in an environment with a humidity of 90% and a temperature of 15°C for 3 days, then inject urea and calcium sulfate solution and carry out activation curing for 7 days; after the activation curing is completed, carry out wet-dry cycling curing for 28 days. The wet-dry cycling curing is 12 hours of water immersion treatment followed by 12 hours of drying treatment each time. After the wet-dry cycling curing is completed, high-strength self-healing concrete can be prepared.

[0091] Example 2

[0092] A high-strength self-healing concrete comprises the following substances by weight: 52 kg of cement, 100 - 120 kg of recycled coarse aggregate 4 loaded with self-healing microorganisms, 70 kg of fine aggregate, 15 kg of water and 0.2 kg of water reducing agent.

[0093] A preparation method of a high-strength self-healing concrete comprises the following steps:

[0094] Take cement, recycled coarse aggregate and fine aggregate, mix them and place them in a mixing device, mix and collect to obtain a mixture;

[0095] Add water reducing agent and water to the mixture in three portions, mix and collect to obtain a slurry;

[0096] Take the slurry and pour it. After sealing and curing in an environment with a humidity of 92% and a temperature of 17°C for 3 days, then inject urea and calcium sulfate solution and carry out activation curing for 7 days; after the activation curing is completed, carry out wet-dry cycling curing for 28 days. The wet-dry cycling curing is 12 hours of water immersion treatment followed by 12 hours of drying treatment each time. After the wet-dry cycling curing is completed, high-strength self-healing concrete can be prepared.

[0097] Example 3

[0098] A high-strength self-healing concrete comprises the following substances by weight: 60 kg of cement, 120 kg of recycled coarse aggregate 4 loaded with self-healing microorganisms, 80 kg of fine aggregate, 20 kg of water and 0.3 kg of water reducing agent.

[0099] A preparation method of a high-strength self-healing concrete comprises the following steps:

[0100] Take cement, recycled coarse aggregate and fine aggregate, mix them and place them in a mixing device, mix and collect to obtain a mixture;

[0101] Add water reducing agent and water to the mixture in three portions, stir and mix, and collect to obtain a slurry.

[0102] After taking the slurry and pouring it, conduct sealed curing treatment in an environment with a humidity of 95% and a temperature of 20°C for 3 days, then inject urea and calcium sulfate solution, and conduct activation curing treatment for 7 days. After the activation curing is completed, conduct wet-dry cycling curing for 28 days. The wet-dry cycling curing is to soak for 12 hours each time and then dry for 12 hours. After the wet-dry cycling curing is completed, high-strength self-healing concrete can be prepared.

[0103] Example 4

[0104] A high-strength self-healing concrete comprises the following substances by weight: 60 kg of cement, 120 kg of recycled coarse aggregate 1 loaded with self-healing microorganisms, 80 kg of fine aggregate, 20 kg of water, and 0.3 kg of water reducing agent.

[0105] A preparation method of a high-strength self-healing concrete comprises the following steps:

[0106] Take cement, recycled coarse aggregate and fine aggregate, mix them and place them in a stirring device, stir and mix, and collect to obtain a mixture.

[0107] Add water reducing agent and water to the mixture in three portions, stir and mix, and collect to obtain a slurry.

[0108] After taking the slurry and pouring it, conduct sealed curing treatment in an environment with a humidity of 95% and a temperature of 20°C for 3 days, then inject urea and calcium sulfate solution, and conduct activation curing treatment for 7 days. After the activation curing is completed, conduct wet-dry cycling curing for 28 days. The wet-dry cycling curing is to soak for 12 hours each time and then dry for 12 hours. After the wet-dry cycling curing is completed, high-strength self-healing concrete can be prepared.

[0109] Example 5

[0110] A high-strength self-healing concrete comprises the following substances by weight: 60 kg of cement, 120 kg of recycled coarse aggregate 2 loaded with self-healing microorganisms, 80 kg of fine aggregate, 20 kg of water, and 0.3 kg of water reducing agent.

[0111] A preparation method of a high-strength self-healing concrete comprises the following steps:

[0112] Take cement, recycled coarse aggregate and fine aggregate, mix them and place them in a stirring device, stir and mix, and collect to obtain a mixture.

[0113] Add water reducing agent and water to the mixture in three portions, stir and mix, and collect to obtain a slurry.

[0114] After taking the slurry and pouring it, it is sealed and cured for 3 days in an environment with a humidity of 95% and a temperature of 20°C, and then a urea and calcium sulfate solution is injected for 7 days of activation curing; after the activation curing is completed, wet-dry cycling curing is carried out for 28 days. The wet-dry cycling curing is 12 hours of water immersion treatment followed by 12 hours of drying treatment each time. After the wet-dry cycling curing is completed, high-strength self-healing concrete can be prepared.

[0115] Example 6

[0116] A high-strength self-healing concrete comprises the following substances by weight: 60 kg of cement, 120 kg of recycled coarse aggregate loaded with self-healing microorganisms 3, 80 kg of fine aggregate, 20 kg of water, and 0.3 kg of water reducing agent.

[0117] A preparation method of high-strength self-healing concrete comprises the following steps:

[0118] Take cement, recycled coarse aggregate and fine aggregate, mix them and place them in a stirring device, stir and mix to collect the mixture;

[0119] Inject the water reducing agent and water into the mixture in three times, stir and mix to collect the slurry;

[0120] After taking the slurry and pouring it, it is sealed and cured for 3 days in an environment with a humidity of 95% and a temperature of 20°C, and then a urea and calcium sulfate solution is injected for 7 days of activation curing; after the activation curing is completed, wet-dry cycling curing is carried out for 28 days. The wet-dry cycling curing is 12 hours of water immersion treatment followed by 12 hours of drying treatment each time. After the wet-dry cycling curing is completed, high-strength self-healing concrete can be prepared.

[0121] Comparative Example 1

[0122] A high-strength self-healing concrete, compared with Example 1, the recycled coarse aggregate is not loaded with self-healing microorganisms, and the other components and steps are the same as those in Example 1.

[0123] Comparative Example 2

[0124] A high-strength self-healing concrete, compared with Example 1, does not adopt the bionic gradient curing treatment step, and the other components and steps are the same as those in Example 1.

[0125] Performance testing

[0126] The compressive strength is carried out according to the relevant specified method in the "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete" (GB / T 50082-2009).

[0127] The initial crack widths of the concrete materials prepared by the technical solutions of Examples 1-6 and Comparative Examples 1-2 were measured by the surface observation method, and the initial crack depths of the self-healing recycled concrete with dimensions of 100 mm×100 mm×400 mm after prefabricated cracks were measured by an ultrasonic detector. The test results are shown in Tables 1 and 2 below:

[0128] Table 1 Performance Test Table

[0129]

[0130]

[0131] Table 2 Mechanical Property Test Table

[0132]

[0133] It can be found by comparing Examples 1-3 with Comparative Example 1 that the technical solution of the present application endows the concrete cracks with self-healing ability by immobilizing self-healing microorganisms (such as Bacillus subtilis, Bacillus megaterium or Sporosarcina pasteurii). These microorganisms form dormant spores inside the concrete. When cracks occur and water seeps in, the microorganisms are activated and metabolize calcium sources (such as calcium chloride or calcium sulfate) and urea in the surrounding environment, and generate calcium carbonate crystals through the microbial-induced carbonate precipitation (MICP) mechanism to fill the cracks and restore the structural integrity. This process does not require external intervention and can significantly extend the mechanical structure and mechanical properties of the concrete structure.

[0134] By further comparing Examples 1-3 with Examples 4-6, it is illustrated that the technical solution of the present application adopts a microorganism immobilization process to achieve the efficient protection and controlled release of microorganisms through microencapsulation and double coating technologies. First, the freeze-dried microorganisms are mixed with a calcium chloride solution and then dropped into a sodium alginate solution to form hydrogel microcapsules through ionic cross-linking, encapsulating the microorganisms in the inner core. The size design of the microcapsules ensures that they are not damaged during the concrete mixing process, while allowing the capsules to dissolve and release the microorganisms when cracks seep water. Subsequently, tetraethyl orthosilicate hydrolyzes under alkaline conditions to form a silica gel layer, which together with the polydopamine film formed by the oxidative polymerization of dopamine constitutes a double coating barrier: the silica layer provides rigid protection against the high-alkali environment inside the concrete; the polydopamine film layer has adhesiveness and antioxidant properties to prevent reactive oxygen species from damaging the microbial DNA. The introduction of ozone can accelerate the polymerization of dopamine to form a denser coating layer.

[0135] Finally, by comparing Example 1 and Comparative Example 2, it is illustrated that the technical solution of this application simulates the self-healing process of organisms through bionic gradient curing: initial sealed curing (humidity 90 - 95%, 15 - 20 °C, 3 days) promotes the formation of C-S-H gel in cement to form initial strength, while low temperature inhibits premature activation of microorganisms; after injecting urea and calcium sulfate solution, urea hydrolyzes to generate CO 3 2- and NH 4 + , which combines with Ca 2+ to form calcium carbonate and activate the microbial mineralization activity; wet-dry cycling curing (immersion for 12 h / drying for 12 h, 8 - 28 days) simulates the natural environment through periodic humidity changes, induces the cycle of microcrack generation - repair, and strengthens the concrete density.

[0136] This specific embodiment is only an interpretation of this application, and it does not limit this application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of this application, it is protected by the patent law.

Claims

1. A high-strength self-repairing concrete, characterized in that: The composition includes the following materials in parts by weight: 45-60 parts of cement; 100-120 parts of recycled coarse aggregate; 65-80 parts of fine aggregate; 10-20 parts water; Water reducing agent 0.1-0.3 parts; The regenerated coarse aggregate is a regenerated coarse aggregate immobilized with self-repairing microorganisms, and the self-repairing microorganisms include at least one of Bacillus subtilis, Bacillus megaterium, and Bacillus pasteurianus.

2. The high-strength self-repairing concrete according to claim 1, characterized in that: The recycled coarse aggregate is recycled coarse aggregate that has been surface treated, and the surface treatment adopts the following technical scheme: Taking the recycled coarse aggregate and soaking it in hydrochloric acid and performing ultrasonic-assisted cleaning, after the cleaning is completed, washing and drying, and collecting the pre-treated recycled coarse aggregate; Take nano magnesium sulfate fiber and mix it with silica sol, disperse it by ultrasonic and collect the dispersion; The dispersion is taken and mixed with the pretreated recycled coarse aggregate and placed in a reactor, heated and carbon dioxide is introduced to a supercritical state, stirred and mixed, and then gradually depressurized, solidified in situ, and the surface-treated recycled coarse aggregate is collected.

3. The high-strength self-repairing concrete according to claim 2, characterized in that: The gradient pressure relief comprises the following steps: First, reduce the pressure to 15MPa at 5MPa / s, and then maintain the pressure for 5 minutes. After the pressure maintenance is completed, reduce the pressure again at 10MPa / s and release it to normal pressure instantly.

4. The high-strength self-repairing concrete according to claim 2, characterized in that: The diameter of the nano magnesium sulfate fiber is 20-50 nm, and the aspect ratio is 55-90.

5. The high-strength self-repairing concrete according to claim 2, characterized in that: The regenerated coarse aggregate immobilized with self-repairing microorganisms is prepared by the following technical solution: The microbial freeze-dried powder is mixed with the calcium chloride solution, the mixed solution is collected and added dropwise to the sodium alginate solution, filtered and vacuum dried, crushed and sieved, and the microbial microcapsule particles are collected; Take microbial microcapsule particles, ethyl orthosilicate and dopamine, stir and mix, and collect the mixed coating liquid; The surface treated recycled coarse aggregate is immersed in the mixed coating liquid. After the immersion is completed, ozone is introduced and in-situ polymerization is performed. The coated recycled coarse aggregate is collected and heated to densify, so as to prepare the recycled coarse aggregate immobilized with self-repairing microorganisms.

6. The high-strength self-repairing concrete according to claim 5, characterized in that: The amount of the microbial freeze-dried powder added to the calcium chloride solution is not less than 10 9 CFU / g.

7. The high-strength self-repairing concrete according to claim 5, characterized in that: The temperature of the heating and densification treatment is 85-120°C.

8. A method for preparing high-strength self-repairing concrete according to any one of claims 1 to 7, characterized in that: The method comprises the following preparation steps: Cement, recycled coarse aggregate and fine aggregate are mixed and placed in a mixing device, and mixed and collected to obtain a mixture; Inject water reducing agent and water into the mixture three times, stir and mix, and collect the slurry; After the slurry is taken and poured, high-strength self-repairing concrete can be prepared by bionic gradient curing treatment.

9. The method for preparing high-strength self-repairing concrete according to claim 8, characterized in that: The bionic gradient curing process comprises the following steps: After sealed curing for 3 days in an environment of 90-95% humidity and 15-20°C, urea and calcium sulfate solution are injected for activation curing for 4-7 days. After the activation curing is completed, dry-wet cycle curing is adopted for 8-28 days to complete the preparation method of the high-strength self-repairing concrete.

10. The method for preparing high-strength self-repairing concrete according to claim 9, characterized in that: The dry-wet cycle curing is to soak in water for 12 hours each time and then dry for 12 hours.

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