Microbial self-repairing shell concrete and preparation method thereof

Abstract

The invention discloses microorganism self-repairing shell concrete and a preparation method thereof, belongs to the technical field of engineering materials, and aims to solve the problems of land occupation and environmental pollution caused by stacking of a large number of waste shell resources and insufficient durability caused by easy cracking of a coastal engineering concrete structure in the prior art. The shell sand comprises the following components in parts by weight: 95-105 parts of shell sand; 7-8 parts of a microbial liquid; 85-90 parts of a microbial nutrient substance; 55 to 58 parts of cement; 28 to 30 parts of water; 0.4 to 0.6 part of a water reducing agent; 0.07 to 0.09 part of a defoaming agent; the concrete material is suitable for coastal environment protection and engineering construction, and the purposes of waste resource utilization, crack self-repairing and concrete durability improvement can be achieved.

Description

Technical Field

[0001] This invention relates to the field of engineering materials technology, and in particular to a microbial self-healing shell concrete and its preparation method. Background Technology

[0002] With the continuous development of shellfish farming and processing, a large number of waste shells have been generated. Piling up these shells occupies a significant amount of land. Furthermore, over long periods, the remaining meat attached to the shells decomposes and is broken down by microorganisms into H2S and NH3, producing toxic gases and causing air pollution. Disposing of waste shells requires substantial human and material resources. Therefore, how to transform waste shells into valuable resources has become one of the key research directions for the future.

[0003] Concrete has high strength and good stability, making it one of the most widely used building materials. However, in coastal environments with high temperature, high humidity, and high salinity, concrete structures are prone to cracking, which allows external corrosive media to enter the concrete, leading to steel corrosion and seriously affecting the durability of the engineering structure.

[0004] Therefore, designing a microbial self-healing shell concrete prepared from waste shells has significant engineering value. Summary of the Invention

[0005] The purpose of this invention is to provide a microbial self-healing shell concrete and its preparation method, so as to solve the problems of land occupation and environmental pollution caused by the large-scale accumulation of waste shell resources, as well as the problem of insufficient durability caused by easy cracking of concrete structures in coastal engineering projects.

[0006] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0007] On one hand, the present invention provides a microbial self-healing shell concrete, characterized in that, by weight, it comprises the following components:

[0008] 95-105 parts shell sand;

[0009] 7-8 portions of microbial inoculum solution;

[0010] 85-90 parts of microbial nutrients;

[0011] 55-58 parts cement;

[0012] 28-30 parts water;

[0013] Water-reducing agent: 0.4~0.6 parts;

[0014] Defoamer 0.07~0.09 parts.

[0015] The above-mentioned self-healing shell concrete fully utilizes waste shell resources, reduces the land occupation and environmental pollution caused by waste shells, and achieves green production benefits of protecting the ecological environment and utilizing waste resources. By incorporating microbial liquid and microbial nutrients into the shell aggregate, and utilizing the microbial mineralization mechanism, calcium carbonate crystals are generated when cracks occur in the structure, which self-repair the concrete cracks, improve the mechanical properties and durability of the concrete, and reduce the cost of manual repair. It has the advantages of being green, intelligent and efficient.

[0016] The organic components of seashells are mainly proteins, phospholipids, and polysaccharides, which can control the nucleation of inorganic mineral phases. This gives seashells extremely high strength, making them suitable as building materials. Simultaneously, the porous structure of seashell sand is ideal for immobilizing microorganisms. Compared to traditional manual repair, microbial self-healing is automatic and timely, which is of great significance for improving the safety and durability of concrete structures. When cracks appear in concrete, moisture and oxygen from the external environment seep into the concrete. At this time, dormant microorganisms are activated and undergo metabolic activity, ultimately generating CaCO3 crystals to repair the cracks in the concrete structure.

[0017] Furthermore, the shell sand is obtained by crushing waste shells.

[0018] In the above technical solution, shell sand has a high CaCO3 content, making it a high-quality building material, with an apparent density of approximately 2600 kg / m³. 3 The bulk density is approximately 1400 kg / m³. 3 The specific gravity is approximately 2.71, the fineness modulus is approximately 3.5, and the mud content is approximately 1.7%. Meanwhile, the shell sand has a porosity of approximately 46%, and its porous structure can be used to immobilize microorganisms; vacuum adsorption can be used for this purpose. Obtaining shell sand of the target particle size through the crushing and processing of waste shells enables the resource utilization of waste and protects the ecological environment.

[0019] Furthermore, the microorganism used is Bacillus pasteurellus.

[0020] In the above technical solution, *Bacillus pasteurellii* is suitable for the highly alkaline internal environment of concrete and the high-temperature, high-humidity, and high-salt coastal service environment. When the concrete structure does not develop cracks, the microorganisms are in a dormant state. When cracks develop in the concrete structure, moisture and oxygen from the external environment seep into the concrete, activating the microorganisms and causing metabolic activity. They produce CO2 through aerobic respiration and react with OH-. - The reaction forms HCO3 - Because of the high pH value inside the shell concrete, the alkaline environment promotes the reaction of Ca. 2+ With HCO3 -A mineralization reaction occurs, eventually generating CaCO3 crystals that fill cracks in the concrete structure;

[0021] The above technical solution uses BNCC Beina Biotechnology's Pasteurella multocida (No.: BNCC337394), whose colonies are 1-2 mm in diameter, round, with neat edges, opaque, grayish-white on the front, raised in the middle, smooth and bright on the surface, moist in texture, and belong to bacilli, with a purity of pure.

[0022] Furthermore, the microbial nutrients have the molecular formula C6H. 10 Calcium lactate of CaO·5H2O.

[0023] The above technical solution uses Ruipu brand calcium lactate, with the molecular formula C6H. 10 CaO·5H2O, with a purity of approximately 99% and a density of approximately 12.26 g / ml, is a white powder. It is easily soluble in water, has high solubility, and dissolves quickly, enabling it to rapidly undergo a mineralization reaction to fill cracks.

[0024] Furthermore, the cement is silicate cement; the water is tap water; the water-reducing agent is polycarboxylate water-reducing agent; and the defoamer is XP-2 type defoamer.

[0025] In the above technical solution, the silicate cement is silicate cement suitable for marine engineering, which has strong resistance to chloride ion penetration and strong resistance to seawater and sulfuric acid corrosion.

[0026] Optionally, the polycarboxylate superplasticizer is selected with a solid content of 39%, a water reduction rate of 28%, and an air content of 3%.

[0027] On the other hand, the present invention provides a method for preparing microbial self-healing shell concrete, comprising the following steps:

[0028] The collected waste seashells are cleaned, crushed, ground, and screened to obtain seashell sand with the target particle size.

[0029] Prepare and preserve microbial culture;

[0030] Weigh out the following ingredients according to their weight proportions: shell sand, microbial inoculum, microbial nutrients, cement, water, water-reducing agent, and defoamer.

[0031] Using shell sand as a carrier, microbial inoculum and microbial nutrients are immobilized in the shell sand;

[0032] Cement, water, water-reducing agent, defoamer, and shell sand that has been immobilized with microbial inoculum and microbial nutrients are mixed to obtain a mixture.

[0033] The mixture was cured to obtain microbial self-healing shell concrete.

[0034] The above technical solution provides a method for preparing microbial self-healing shell concrete using waste shells, which has the advantages of waste resource utilization and crack self-healing.

[0035] Furthermore, the curing of the mixture to obtain microbial self-healing shell concrete includes the following steps:

[0036] The mixture was poured into a mold, placed on a vibrating table and vibrated for 120 seconds. After curing at room temperature for 24 hours, the mold was removed. The demolded specimens were then subjected to standard curing to obtain microbial self-healing shell concrete.

[0037] Furthermore, the preparation and preservation of the microbial culture includes the following steps:

[0038] The experimental equipment and culture medium were placed in a high-pressure steam sterilizer for high-temperature sterilization at 120°C for 20 minutes.

[0039] The culture medium was prepared according to the following ratio: 5.0 g peptone, 3.0 g beef extract, 20 g urea and 1 L distilled water.

[0040] Open the ampoule and use a sterile pipette to add 0.3-0.5 mL of culture medium into the opened ampoule;

[0041] Shaking dissolves the freeze-dried bacterial powder, causing it to suspend in a state, thus obtaining a bacterial suspension.

[0042] The bacterial suspension was aspirated with a pipette and inoculated into a sterilized culture medium centrifuge tube. The tube was then incubated at a constant temperature of 30 °C for 24 h to activate the culture and obtain the original strain.

[0043] Using a sterile pipette, the original strain obtained above was inoculated into the sterilized culture medium on a clean bench and placed in a constant temperature shaker at 30 ℃ for 24 h to obtain a microbial culture solution with a concentration of 200 μL / L.

[0044] The cultured microbial solution was placed into test tubes and stored.

[0045] Furthermore, the specific steps for immobilizing the microbial inoculum and microbial nutrients in the shell sand are as follows:

[0046] Place the shell sand carrier inside a vacuum pot and seal it.

[0047] After starting the vacuum pump and reducing the pressure inside the pot to -0.06 MPa through the air intake, immerse the conduit connected to the air intake valve into the microbial liquid storage tank.

[0048] Slowly open the air inlet valve to allow the microbial liquid to be drawn into the container under negative pressure, and dynamically maintain the pressure inside the container at -0.06 MPa during this process.

[0049] After the bacterial solution is completely absorbed, close all valves and allow for static adsorption for 15 minutes.

[0050] After the adsorption of the shell sand carrier is completed, it is filtered through a sieve to remove residual microbial liquid, and then dried in a constant temperature oven at 40℃ until the quality is constant.

[0051] Further, the process of mixing cement, water, water-reducing agent, defoamer, and shell sand that has been immobilized with microbial inoculum and microbial nutrients to obtain a mixture includes the following steps:

[0052] First, pour cement, water, water-reducing agent, and defoamer into the mixer and mix at low speed for 30 seconds. In the second 30 seconds, evenly add shell sand that has been immobilized with microbial liquid and microbial nutrients. Then mix at high speed for 30 seconds, stop mixing for 90 seconds, and at the same time use a scraper to scrape the mortar from the blades, pot walls, and pot bottom into the pot. Then mix at high speed for 60 seconds to obtain the mixture.

[0053] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0054] Microbial self-healing shell concrete makes full use of waste shell resources, reducing the land occupation and environmental pollution caused by waste shells, and achieving green production benefits of protecting the ecological environment and utilizing waste resources. It incorporates microbial inoculum and microbial nutrients into shell aggregates, and utilizes microbial mineralization to generate CaCO3 crystals to self-repair concrete cracks when cracks occur in the structure. This improves the mechanical properties and durability of concrete, reduces the cost of manual repair, and has the advantages of being green, intelligent, and efficient, with the characteristics of waste resource utilization and crack self-healing. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0056] Figure 1 This is a schematic diagram illustrating the preparation process and crack repair principle of microbial self-healing shell concrete provided by the present invention;

[0057] Figure 2 This invention provides examples 3 and 3, which describe the crack repair width and repair rate of microbial self-healing shell concrete at different repair ages.

[0058] Figure 3 The compressive strength and recovery rate of microbial self-healing shell concrete under different repair ages in Examples 1-3 and Comparative Examples 1-3 provided by this invention;

[0059] Figure 4 The present invention provides examples 1-3 and comparative examples 1-3, which demonstrate the flexural strength and recovery rate of microbial self-healing shell concrete at different repair ages. Detailed Implementation

[0060] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use.

[0061] It should be understood that all experimental procedures not detailed in the experiment are routine experimental procedures well known to those skilled in the art.

[0062] Example 1

[0063] This embodiment provides a microbial self-healing shell concrete and its preparation method, and its preparation process and crack repair principle are illustrated in the following diagram. Figure 1 As shown.

[0064] The microorganism used in this embodiment is Bacillus pasteurellis (No.: BNCC337394) from BNCC Beina Biotechnology. The colonies are 1-2 mm in diameter, round, with neat edges, opaque, grayish-white on the front, raised in the center, smooth and bright, and moist in texture. It belongs to the bacillus family and is of pure purity. The microbial nutrient used is Ruipu brand calcium lactate, with the molecular formula C6H. 10 CaO·5H2O, with a purity of approximately 99% and a density of approximately 12.26 g / ml, is a white powder that is easily soluble in water, has high solubility, and dissolves quickly.

[0065] The microbial self-healing shell concrete comprises the following raw materials by weight:

[0066] 100 parts shell sand;

[0067] 7 portions of microbial inoculum solution;

[0068] 88 portions of microbial nutrients;

[0069] 50 parts of P·O 52.5 silicate cement produced by Jiangsu Xinning New Building Materials Co., Ltd.

[0070] 30 portions of tap water from Nanjing City;

[0071] 0.5 parts of polycarboxylate high-performance water-reducing agent produced by Shanxi Feike New Material Technology Co., Ltd.

[0072] 0.08 parts of XP-2 type mortar defoamer produced by Shanxi Feike New Material Technology Co., Ltd.

[0073] The preparation of the microbial self-healing shell concrete includes the following steps:

[0074] The collected waste seashells are washed, crushed, ground, and sieved to obtain the desired seashell sand;

[0075] Prepare and preserve microbial culture;

[0076] Weigh out the following ingredients according to weight proportions: shell sand, microbial inoculum, microbial nutrients, P·O 52.5 silicate cement, tap water, polycarboxylate high-performance water-reducing agent, and XP-2 type mortar defoamer.

[0077] Using shell sand as a carrier, microbial inoculum and microbial nutrients are immobilized in the shell sand;

[0078] P·O 52.5 silicate cement, tap water, polycarboxylate high-performance water-reducing agent, XP-2 type mortar defoamer, and shell sand (with microbial inoculum and microbial nutrients already immobilized) are mixed evenly to obtain a mixture.

[0079] The mixture is cured to obtain microbial self-healing shell concrete;

[0080] The preset crack width is 0.3 mm.

[0081] The preparation and preservation of microbial culture includes the following steps:

[0082] The experimental equipment and culture medium were placed in a high-pressure steam sterilizer for high-temperature sterilization at 120°C for 20 minutes.

[0083] The culture medium was prepared according to the following ratio: 5.0 g peptone, 3.0 g beef extract, 20.0 g urea, and 1.0 L distilled tap water.

[0084] Open the ampoule and use a sterile pipette to add about 0.3 mL of culture medium into the opened ampoule;

[0085] Add the lyophilized bacterial culture powder to the ampoule containing the culture medium, and shake to dissolve the lyophilized bacterial culture powder into a suspension to obtain a bacterial suspension.

[0086] Use a pipette to draw up the bacterial suspension and inoculate it into a sterilized culture medium centrifuge tube. Place the tube in a constant temperature of 30℃ for 24 h to activate the culture and obtain the original strain.

[0087] Using a sterile pipette, the original strain obtained above was inoculated into the sterilized culture medium on a clean bench and placed in a constant temperature shaker for 24 h (30℃) to obtain the required microbial culture solution.

[0088] The cultured microbial solution was placed into test tubes and stored.

[0089] The process involves using shell sand as a carrier to immobilize microbial inoculum and nutrients within it. The specific steps are as follows:

[0090] Place the shell sand carrier inside a vacuum pot and seal it.

[0091] After starting the vacuum pump and reducing the pressure inside the pot to -0.06 MPa through the air intake, immerse the tubing connected to the air inlet valve into the bacterial liquid storage tank.

[0092] Slowly open the air inlet valve to allow the bacterial solution to be drawn into the container under negative pressure. During this process, the pressure inside the container must be dynamically maintained at -0.06 MPa.

[0093] After the bacterial solution is completely absorbed, close all valves and allow for static adsorption for 15 minutes.

[0094] After the adsorption process is completed, the carrier is filtered through a sieve to remove residual bacterial liquid, and then dried in a 40℃ constant temperature oven until the mass is constant.

[0095] The process involves uniformly mixing P·O 52.5 silicate cement, tap water, polycarboxylate high-performance water-reducing agent, XP-2 type mortar defoamer, and shell sand (with immobilized microbial inoculum and microbial nutrients). The steps include: first, pouring P·O 52.5 silicate cement, tap water, polycarboxylate high-performance water-reducing agent, and XP-2 type mortar defoamer into a mixer and mixing at low speed for 30 seconds; then, uniformly adding the immobilized shell sand during the second 30 seconds; finally, mixing at high speed for 30 seconds, stopping for 90 seconds, and simultaneously scraping the mortar from the blades, pot walls, and pot bottom into the pot with a scraper; and then mixing at high speed for another 60 seconds to obtain the mixture.

[0096] The curing of the mixture includes the following steps:

[0097] The mixture was poured into a mold, placed on a vibration table and vibrated for 120 seconds. After curing at room temperature for 24 hours, the mold was removed and the demolded specimens were subjected to standard curing.

[0098] Example 2

[0099] This embodiment provides a microbial self-healing shell concrete and its preparation method. The only difference from Embodiment 1 is that the width of the preset crack is 0.5 mm, while the other steps and conditions are the same.

[0100] Example 3

[0101] This embodiment provides a microbial self-healing shell concrete and its preparation method. The only difference from Embodiment 1 is that the width of the preset crack is 1.0 mm, while the other steps and conditions are the same.

[0102] Comparative Example 1

[0103] This comparative example provides a common shell concrete and its preparation method, which differs from Example 1 only in that it does not incorporate microbial inoculum and microbial nutrients. All other steps and conditions are the same.

[0104] Comparative Example 2

[0105] This comparative example provides a common shell concrete and its preparation method. The only difference from Comparative Example 1 is that the width of the preset crack is 0.5 mm, while the other steps and conditions are the same.

[0106] Comparative Example 3

[0107] This comparative example provides a common shell concrete and its preparation method. The only difference from Comparative Example 1 is that the width of the preset crack is 1.0 mm, while the other steps and conditions are the same.

[0108] The differences in mix design schemes of microbial self-healing shell concrete in the three examples and three comparative examples are shown in Table 1.

[0109] Table 1: Mix design scheme for microbial self-healing shell concrete.

[0110]

[0111] The preparation and curing of various types of concrete were carried out in accordance with GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)". Each group consisted of three prisms with dimensions of 40 mm × 40 mm × 160 mm. The concrete test blocks were formed by vibrating on a vibrating table for 120 seconds.

[0112] The steel plate insertion and extraction method was used to pre-determine crack widths for different specimens. Before the test, both sides of the steel plate were coated with lubricating oil. The plate was then inserted during concrete pouring, and the cracks were obtained by inserting and extracting the steel plate every 30 minutes after the initial setting and before the final setting of the concrete. The crack repair and strength recovery capabilities of the concrete after different repair ages were analyzed and determined.

[0113] Crack Repair Capacity Analysis: Crack Repair Width and Repair Rate of Microbial Self-Healing Shell Concrete at Different Repair Ages Figure 2 As shown, Figure 2The crack repair width and repair rate of Example 3 and Comparative Example 3 were compared at 7 days, 14 days, 28 days, and 56 days (the preset crack widths of Examples 1 and 2 were smaller, and the cracks were repaired within 14 to 28 days of repair age, resulting in less data and insufficient information to explore the crack repair pattern; therefore, only Example 3 and Comparative Example 3 were analyzed). In Example 3, the crack could continuously repair itself, with a final repair rate approaching 100%. Comparative Example 3, however, had no repair function, and the crack width remained essentially unchanged. The main reason is that Example 3 utilizes microbial mineralization reactions to continuously generate CaCO3 crystals to fill the cracks, essentially achieving self-repair, while Comparative Example 3 relies solely on its own hydration reaction to generate hydration products, which is insufficient for self-repair. This indicates that Example 3 possesses effective crack self-repair capabilities.

[0114] Strength recovery capability analysis: Compressive strength and recovery rate of microbial self-healing shell concrete at different repair ages, as shown in the figure. Figure 3 As shown, the flexural strength and recovery rate of microbial self-healing shell concrete at different repair ages are as follows: Figure 4 As shown, Figure 3 and Figure 4 The mechanical properties and recovery rates of the shell concrete in three sets of examples and three sets of comparative examples were compared at repair ages of 3 days, 7 days, and 28 days. Examples 1-3 showed faster recovery of mechanical properties such as compressive and flexural strength, with recovery rates exceeding 30% at 3 days and approximately 60% at 28 days. In contrast, the compressive and flexural strengths of comparative examples 1-3 remained essentially unchanged. The main reason for this is that examples 1-3 utilized microbial mineralization to generate CaCO3 crystals that filled the cracks, effectively compensating for the strength defects caused by the cracks. In contrast, comparative examples 1-3 only involved incompletely hydrated cement particles undergoing hydration to generate hydration products, resulting in limited filling effect and virtually no strength recovery. This demonstrates that examples 1-3 possess effective strength recovery capabilities.

[0115] Based on the above analysis, it can be seen that the microbial self-healing shell concrete prepared by using shell sand made from waste shells as raw material can effectively self-repair cracks compared with ordinary concrete, thereby improving the mechanical properties and durability of concrete.

[0116] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A microbial self-healing shell concrete, characterized in that, Listed by weight, it includes the following components: 95-105 parts shell sand; 7-8 portions of microbial inoculum solution; 85-90 parts of microbial nutrients; 55-58 parts cement; 28-30 parts water; Water-reducing agent: 0.4~0.6 parts; Defoamer 0.07~0.09 parts.

2. The microbial self-healing shell concrete according to claim 1, characterized in that, The shell sand is obtained by crushing waste shells.

3. The microbial self-healing shell concrete according to claim 1, characterized in that, The microorganism in question is *Pasteurella multocida*.

4. The microbial self-healing shell concrete according to claim 1, characterized in that, The microbial nutrients have the molecular formula C6H. 10 Calcium lactate of CaO·5H2O.

5. The microbial self-healing shell concrete according to claim 1, characterized in that, The cement is silicate cement; the water is tap water; the water-reducing agent is polycarboxylate water-reducing agent; and the defoamer is XP-2 type defoamer.

6. A method for preparing microbial self-healing shell concrete according to any one of claims 1-5, characterized in that, Includes the following steps: The collected waste seashells are cleaned, crushed, ground, and screened to obtain seashell sand with the target particle size. Prepare and preserve microbial culture; Weigh out the following ingredients according to their weight proportions: shell sand, microbial inoculum, microbial nutrients, cement, water, water-reducing agent, and defoamer. Using shell sand as a carrier, microbial inoculum and microbial nutrients are immobilized in the shell sand; Cement, water, water-reducing agent, defoamer, and shell sand that has been immobilized with microbial inoculum and microbial nutrients are mixed to obtain a mixture. The mixture was cured to obtain microbial self-healing shell concrete.

7. The method for preparing microbial self-healing shell concrete according to claim 6, characterized in that, The curing of the mixture to obtain microbial self-healing shell concrete includes the following steps: The mixture was poured into a mold, placed on a vibrating table and vibrated for 120 seconds. After curing at room temperature for 24 hours, the mold was removed. The demolded specimens were then subjected to standard curing to obtain microbial self-healing shell concrete.

8. The method for preparing microbial self-healing shell concrete according to claim 6, characterized in that, The preparation and preservation of microbial culture includes the following steps: The experimental equipment and culture medium were placed in a high-pressure steam sterilizer for high-temperature sterilization at 120°C for 20 minutes. The culture medium was prepared according to the following ratio: 5.0 g peptone, 3.0 g beef extract, 20.0 g urea and 1 L distilled water. Open the ampoule and use a sterile pipette to add 0.3-0.5 mL of culture medium into the opened ampoule; Shaking dissolves the freeze-dried bacterial powder, causing it to suspend in a state, thus obtaining a bacterial suspension. Use a pipette to draw up the bacterial suspension and inoculate it into a sterilized culture medium centrifuge tube. Place the tube in a constant temperature of 30℃ for 24 h to activate the culture and obtain the original strain. Using a sterile pipette, the original strain obtained above was inoculated into the sterilized culture medium on a clean bench and placed in a constant temperature shaker at 30°C for 24 h to obtain a microbial culture solution with a concentration of 200 μL / L. The cultured microbial solution was placed into test tubes and stored.

9. The method for preparing microbial self-healing shell concrete according to claim 6, characterized in that, The specific steps for immobilizing microbial inoculum and microbial nutrients in shell sand are as follows: Place the shell sand carrier inside a vacuum pot and seal it. After starting the vacuum pump and reducing the pressure inside the pot to -0.06 MPa through the air intake, immerse the conduit connected to the air intake valve into the microbial liquid storage tank. Open the air inlet valve to allow the microbial liquid to be drawn into the container under negative pressure, and dynamically maintain the pressure inside the container at -0.06 MPa during this process. After the bacterial solution is completely absorbed, close all valves and allow for static adsorption for 15 minutes. After the adsorption of the shell sand carrier is completed, it is filtered through a sieve to remove residual microbial liquid, and then dried in a constant temperature oven at 40℃ until the quality is constant.

10. The method for preparing microbial self-healing shell concrete according to claim 6, characterized in that, The process of mixing cement, water, water-reducing agent, defoamer, and shell sand that has been immobilized with microbial inoculum and microbial nutrients to obtain a mixture includes the following steps: First, pour cement, water, water-reducing agent, and defoamer into the mixer and mix at low speed for 30 seconds. In the second 30 seconds, evenly add shell sand that has been immobilized with microbial liquid and microbial nutrients. Then mix at high speed for 30 seconds, stop mixing for 90 seconds, and at the same time use a scraper to scrape the mortar from the blades, pot walls, and pot bottom into the pot. Then mix at high speed for 60 seconds to obtain the mixture.

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