Preparation method of magnetic microorganism self-repairing cement-based material

Abstract

The invention provides a preparation method of a magnetic microorganism self-repairing cement-based material, and relates to a concrete crack self-repairing technology, and the preparation method comprises the following steps: preparing a bacillus pasteurii culture medium; inoculating bacillus pasteurii, and culturing until the concentration is 1 * 10 < 8 > cell / mL to 9 * 10 < 8 > cell / mL, so as to obtain a cultured bacterial liquid; adding the second urea solution into a 15mmol / L-30mmol / L FeCl2 solution, filtering and sterilizing, and fully reacting to obtain an iron source solution; mixing the cultured bacterial liquid with an iron source solution according to a ratio of 1: 20-1: 16, and shaking uniformly to obtain a magnetic bacillus pasteurii liquid; magnetic bacillus pasteurii liquid, a plurality of nutrient substances and a mineralizer are added into cement mortar and mixed uniformly, the magnetic microorganism self-repairing cement-based material is obtained, and the ratio of the magnetic bacillus pasteurii liquid to water of the cement mortar is 15%-20%. The material prepared according to the invention can solve the problem of low utilization rate of microorganisms in concrete, significantly improve the crack repair rate, and prolong the service life of a concrete structure.

Description

Technical Field

[0001] The invention relates to the technical field of concrete crack self-repairing, and in particular to a method for preparing a magnetic microbial self-repairing cement-based material. Background Art

[0002] Concrete has been widely used in many fields such as construction, transportation, water conservancy, dams, seaports, agriculture, forestry, underground engineering, etc. due to its advantages such as low cost, easy molding, and good fire resistance. It has become the main building material in the field of civil engineering. However, concrete has the disadvantages of high brittleness and low tensile strength. In actual engineering, it is very easy to crack under the influence of complex environment such as load. Cracks provide channels for external water and corrosive media. The entry of corrosive media leads to accelerated deterioration of concrete durability, seriously affecting the service life of engineering structures. In order to effectively prevent the invasion of harmful ions, traditional repair methods such as surface treatment and grouting are currently used, but there are many problems such as the need for manual maintenance, untimely crack detection, and limited repair environment. Inspired by the phenomenon of biological diagenesis, microbial induced mineralization deposition is used to repair concrete cracks, referred to as MICP. When cracks occur, water and air enter the microorganisms to induce calcium carbonate to form, actively fill the cracks, and the calcium carbonate precipitation produced by them has good compatibility with cement-based materials. Its in-situ repair characteristics can meet the repair needs of more environments and are more environmentally friendly and economical. However, existing concrete self-repairing materials have problems such as insufficient utilization of microorganisms, resulting in a long crack repair cycle and unstable quality. How to improve the repair rate of self-repairing cement materials has become a technical problem that needs to be solved urgently. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art or related technology, and discloses a method for preparing a magnetic microbial self-repairing cement-based material. During the crack repair process, an external magnetic field is used to gather microorganisms to increase the repair speed at the cracks, thereby improving the overall repair efficiency and overcoming the limitations of traditional repair methods in the use environment.

[0004] The first aspect of the present invention discloses a method for preparing a magnetic microbial self-repairing cement-based material, comprising: preparing a Bacillus pasteurian culture medium, sterilizing and cooling to room temperature; adding a first urea solution with a volume fraction of 3% to 4% to the Bacillus pasteurian culture medium as a substrate for a urease catalytic reaction, inoculating a Bacillus pasteurian liquid with a volume fraction of 3% to 4% of the culture medium, placing the culture medium in a shaking incubator for shaking culture, and culturing the culture medium until the concentration of Bacillus pasteurian is 1×10 8 cell / mL~9×10 8 cell / mL, Bacillus pasteurianus is used to produce urease to obtain a cultured bacterial solution; the second urea solution is added to 15mmol / L to 30mmol / L FeCl2 The solution is filtered and sterilized, and a constant temperature is maintained and mechanical stirring is performed to fully react to obtain an iron source solution; the cultured bacterial solution and the iron source solution are mixed in a ratio of 1:20 to 1:16 and shaken to obtain a magnetic Bacillus pasteurianus solution; the magnetic Bacillus pasteurianus solution and a number of nutrients and mineralizers are added to cement mortar and mixed to obtain a magnetic microbial self-repairing cement-based material, and the ratio of the magnetic Bacillus pasteurianus solution to the water in the cement mortar is 25% to 30%.

[0005] In this technical solution, FeCl 2 ·4H 2 O modified Bacillus pasteurianus to make it in-situ magnetized and coated with a layer of magnetic Fe 3 O 4 Nanosheets can use an external magnetic field to achieve directional migration. During the concrete crack repair process, they use the external magnetic field to attract microorganisms to the cracks, thereby achieving the purpose of gathering microorganisms in the cracks.

[0006] The method for preparing the magnetic microbial self-repairing cement-based material disclosed in the present invention preferably further comprises: pouring the magnetic microbial self-repairing cement-based material into a mold, compacting it, placing it at room temperature for 24 to 36 hours, and then demolding it to obtain a material block.

[0007] According to the preparation method of the magnetic microbial self-repairing cement-based material disclosed in the present invention, preferably, the Bacillus pasteurianus culture medium contains 3-4 g of tryptone and 2-3 g of beef extract per 1 L.

[0008] According to the preparation method of the magnetic microbial self-repairing cement-based material disclosed in the present invention, preferably, the concentration of the first urea solution is 2 mol / L to 4 mol / L; the concentration of the second urea solution is 500 mmol / L to 700 mmol / L.

[0009] According to the preparation method of the magnetic microbial self-repairing cement-based material disclosed in the present invention, preferably, the cement mortar includes 650 parts of cement, 241-325 parts of water and 1300 parts of sand, 0-8 parts of nutrients, 1-26.15 parts of mineralizers, and 30-65 parts of magnetic Bacillus Pasteurella liquid.

[0010] According to the preparation method of the magnetic microbial self-repairing cement-based material disclosed in the present invention, preferably, the nutrients include 5 parts by weight of trypsin and 3 parts by weight of beef extract; the mineralizer includes 1 part by weight of calcium acetate and 0.3-0.4 parts by weight of urea.

[0011] According to the method for preparing the magnetic microbial self-repairing cement-based material disclosed in the present invention, preferably, the volume ratio of the first urea solution to Bacillus pasteurianus is 1:1.

[0012] According to the preparation method of the magnetic microbial self-repairing cement-based material disclosed in the present invention, preferably, the ratio of cement to water in the cement mortar is 1:0.5, and the ratio of cement to sand is 1:2.

[0013] The second aspect of the present invention also discloses a method for preparing a self-healing agent based on magnetic microorganisms, comprising: preparing a Bacillus pasteurian culture medium, sterilizing and cooling to room temperature; adding 3% to 4% by volume of a 2mol / L to 4mol / L urea solution as a substrate for urease catalysis reaction to the Bacillus pasteurian culture medium, inoculating the Bacillus pasteurian liquid at a volume fraction of 3% to 4% of the culture medium, placing the culture medium in a shaking incubator for shaking culture, and culturing until the concentration of Bacillus pasteurian is 1×10 8 cell / mL~9×10 8 cell / mL, Bacillus pasteurianus was used to produce urease to obtain a cultured bacterial solution; a urea solution with a concentration of 500mmol / L to 700mmol / L was added to a 15mmol / L to 30mmol / L FeCl 2 The solution is filtered and sterilized, and a constant temperature is maintained and mechanical stirring is performed to fully react to obtain an iron source solution; the cultured bacterial solution and the iron source solution are mixed in a ratio of 1:20 to 1:16 and shaken to obtain a magnetic Bacillus pasteurianus solution; calcium acetate and urea are mixed in a mass ratio of 1:0.3 to 1:0.4 to obtain a mineralizer; the magnetic Bacillus pasteurianus solution is mixed with the mineralizer to obtain a self-healing agent.

[0014] According to the preparation method of the magnetic microorganism-based self-repairing agent disclosed in the present invention, preferably, it also includes: preparing tryptone and beef extract according to a mass ratio of 1:0.5 to 1:0.7 to obtain nutrients; adding the nutrients to the mixture of the magnetic Bacillus Pasteurella liquid and the mineralizer.

[0015] The beneficial effects of the present invention include at least:

[0016] 1. The present invention magnetizes the microorganisms in situ to obtain microorganisms wrapped by magnetic ferroferric oxide, so that the microorganisms are protected to a certain extent in the high-alkali environment of concrete, and it is expected to increase the survival time of the microorganisms.

[0017] 2. The present invention prepares microorganisms that can migrate in a directional manner, and by applying an external magnetic field at the cracks, more microorganisms can be attracted to gather at the cracks, thereby improving the utilization rate of the microorganisms in the concrete.

[0018] 3. The present invention accelerates the speed and efficiency of crack repair through the migration of magnetic microorganisms. The repair products have good compatibility with cement-based materials and have good development prospects in the field of cement-based material self-repair. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A microscopic morphology of a magnetic microorganism according to an embodiment of the present invention is shown.

[0020] Figure 2 An EDS graph of a magnetic microorganism according to an embodiment of the present invention is shown.

[0021] Figure 3 The XRD diagram of the magnetic microorganism according to the embodiment of the present invention is shown.

[0022] Figure 4 A schematic diagram of a hysteresis loop of a magnetic microorganism according to an embodiment of the present invention is shown.

[0023] Figure 5 Shows Figure 4 Enlarged view of the origin of the hysteresis loop.

[0024] Figure 6 A microscopic morphology of a magnetic microbial mineralization product according to an embodiment of the present invention is shown.

[0025] Figure 7 The XRD diagram of the magnetic microbial mineralization product according to an embodiment of the present invention is shown.

[0026] Figure 8 An EDS graph of a magnetic microbial mineralization product according to an embodiment of the present invention is shown.

[0027] Fig. 9 The FTIR graph of the magnetic microbial mineralization product according to an embodiment of the present invention is shown.

[0028] Fig.10 A TG diagram of a magnetic microbial mineralization product according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0029] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein, and therefore, the present invention is not limited to the limitations of the specific embodiments disclosed below.

[0030] According to one embodiment of the present invention, a method for preparing a magnetic microbial self-repairing cement-based material is disclosed, comprising: preparing microorganisms; preparing a magnetic microbial self-repairing agent; preparing a cement-based material; and uniformly adding the prepared magnetic microbial self-repairing agent to the cement-based material to obtain the magnetic microbial self-repairing cement-based material. Specifically, the method comprises the following steps:

[0031] The microorganism preparation process is as follows: select Bacillus pasteurianus with high urease activity, prepare corresponding culture medium, place in a vertical pressure steam sterilizer at 120°C and 0.15MPa for sterilization for 20 to 25 minutes, cool to room temperature, inoculate Bacillus pasteurianus and urea solution (concentration is 2 to 4 mol / L) at a volume fraction of 3 to 4%, and place in a constant temperature shaker for shaking culture for 24 hours. The temperature of the shaker is 30 to 35°C and the speed is 170rpm / min. Each 1L culture medium contains 3 to 4g of tryptone and 2 to 3g of beef extract. Bacillus pasteurianus is cultured to a concentration of 1×10 8 ~9×10 8 cell / mL.

[0032] The magnetic microbial self-repairing agent includes magnetic microbial bacterial liquid (magnetic Bacillus pasteurianus), nutrients and mineralizers, wherein the nutrients include trypsin and beef extract, and the mass ratio of the trypsin:beef extract is 1:0.5-1:0.7. The mineralizer includes calcium acetate and urea, and the mass ratio of the calcium acetate:urea is 1:0.6-1:0.8.

[0033] The preparation process of magnetic microbial culture liquid specifically includes: boiling deionized water in a water bath, cooling to room temperature, adding urea and stirring thoroughly, and then pouring into the liquid containing FeCl 2 The reaction mixture is placed in a conical flask, kept at a constant temperature in a water bath and continuously mechanically stirred for 20 to 25 minutes to allow sufficient reaction to obtain an iron source solution; then it is mixed with the previously prepared Bacillus pasteurianus solution in a certain volume ratio, placed in a constant temperature shaking incubator and shaken evenly; finally, it is placed in an oven to react for 12 to 30 hours to obtain magnetic Bacillus pasteurianus (magnetic microorganism).

[0034] The preparation process of magnetic microbial self-healing cement-based materials includes: first, adding the cementitious material and the mineralizer into a stirring pot and mixing them evenly, with the mortar-sand ratio being 1:2 and the water-cement ratio being 0.5; then adding part of the water and stirring at a low speed for 20-30 seconds, then adding sand and nutrients and continuing to stir for 30-40 seconds, then switching to high-speed stirring for 30-40 seconds, adding the magnetic microbial bacterial solution, and stirring at a high speed for 90-100 seconds; pouring the evenly stirred mortar into a mold, vibrating it for 60 seconds and then smoothing it, placing it at room temperature for molding for 24-36 hours, and removing the mold to obtain a magnetic microbial self-healing cement-based material block.

[0035] According to another embodiment of the present invention, a method for preparing a magnetic microbial self-repairing cement-based material is disclosed, comprising the following steps:

[0036] S1, prepare Bacillus pasteurianus culture medium, sterilize it at high temperature and then cool it to room temperature, the sterilization conditions are 120℃, 0.15MPa, and sterilize it for 20-25min;

[0037] S2, inoculating the culture medium in step S1 with Bacillus pasteurianus and urea solution at a volume ratio of 1:1, the solubility of the urea solution is 2-4 mol / L, and the inoculation amount of the bacterial liquid and the urea solution is 3-4% of the volume fraction of the culture medium;

[0038] S3, the inoculated bacterial solution in step S2 is placed in a constant temperature shaker for shaking culture for 24-36 hours, and the shaking culture conditions are 30-35°C and 170 rpm / min, so that the concentration of Bacillus pasteurianus reaches 1×10 8 -9×10 8 cell / mL;

[0039] S4, boil the deionized water and cool it to room temperature, then add urea and stir thoroughly, the urea concentration is 500-700 mM;

[0040] S5, pour the urea solution in step S4 into the FeCl 2 In a conical flask, FeCl 2 The concentration is 10-15mM, constant temperature and continuous mechanical stirring for 5-10min to allow full reaction;

[0041] S6, mixing the Bacillus pasteurianus cultured in step S3 with the iron source solution in a certain ratio, wherein the ratio of the culture solution to the iron source solution is 1:10-1:6, and placing the mixture in a constant temperature shaking incubator and shaking well;

[0042] S7, placing the mixed solution in step S6 in a constant temperature oven (60-65° C.) for reaction for 12-30 hours to obtain magnetic Bacillus pasteurianus;

[0043] S8, mixing calcium acetate and urea in a mass ratio of 1:0.3-1:0.4 to form a mineralizer for standby use;

[0044] S9, adding the following components in order: 650 parts by weight of cement, 241-325 parts by weight of water, 0-8 parts by weight of nutrients, 0-26.15 parts by weight of mineralizer, 1300 parts by weight of sand and 0-60 parts by weight of magnetic microbial liquid into a stirring pot and mixing them evenly, wherein the nutrients are composed of 5 parts by weight of tryptone and 3 parts by weight of beef extract;

[0045] S10, pour the mortar mixed in step S9 into the mold, vibrate for 60 seconds, then scrape off the excess mortar on the mold, and place it at room temperature for 24-36 hours for demoulding.

[0046] According to the above embodiment, preferably, the percentage of magnetic microbial liquid to water is 15%-20%. This percentage range can ensure the repair effect and save the amount of additives.

[0047] According to another embodiment of the present invention, a method for preparing a self-healing agent based on magnetic microorganisms is also provided, comprising the following specific steps:

[0048] Add 400mL of deionized water, 2.5g of tryptone and 1.4g of beef extract into a 1L conical flask to prepare a liquid culture medium required for microbial growth, adjust the pH of the culture medium to 7.0, and sterilize it in a vertical pressure steam sterilizer at 120°C and 0.15MPa for 20min; after the sterilization, take it out and place it in a sterile operating table to cool to room temperature, take out the frozen bacteria, place it in a beaker for natural thawing, inoculate it with a 4% volume fraction of Bacillus pasteurianus seed solution, and add 16mL of urea solution in the culture medium with a concentration of 3mol / L as a substrate for urease catalytic reaction; finally, place the culture solution under shaking culture at 35°C and 170r / min for 24h to obtain Bacillus pasteurianus bacterial solution.

[0049] In a 200 mL beaker, boil 100 mL of deionized water in a water bath to expel the gas in the water. After cooling to room temperature, add 650 mM urea and stir thoroughly. Then pour in 18 mM FeCl 2 The reaction mixture was placed in a conical flask, kept at a constant temperature in a water bath and continuously stirred mechanically for 10 minutes to fully react, to obtain an iron source solution; then mixed with the previously prepared Bacillus pasteurianus solution at a volume ratio of 1:10, and placed in a constant temperature shaking incubator to shake well. Finally, placed in a 40°C oven to react for 12 hours, then separated with a magnet, and washed with deionized water 3-5 times to obtain magnetic Bacillus pasteurianus;

[0050] Calcium acetate and urea are mixed in a mass ratio of 1:0.34 to form a mineralizer.

[0051] The properties of the magnetic microorganisms (magnetic Bacillus Pasteurella) obtained in the above examples were tested:

[0052] Microscopic morphology of magnetic microorganisms Figure 1 As shown, a thin layer of nanosheets is embedded on the surface of the magnetic microorganism.

[0053] like Figure 2 The energy spectrum (EDS) shown shows that the element types and contents of the magnetic microorganisms mainly contain iron and oxygen, with an atomic ratio of 3:4.

[0054] The physical analysis of the constructed magnetic microorganisms showed that Figure 3 The X-ray diffraction pattern (XRD pattern) shown in Figure 2 shows that the diffraction peaks are similar to those of Fe 3 O 4The XRD spectrum of the standard card (JCPDS No.75-0449) is in good agreement, and diffraction peaks can be identified at 2θ=30.4°, 35.8°, 43.5°, 53.4°, and 57.5°, corresponding to their (2 2 0), (3 1 1), (4 0 0), (4 2 2), and (51 1) crystal planes, respectively, indicating that the surface of the magnetic microorganism is composited with well-crystallized magnetic Fe 3 O 4 .

[0055] Select FeCl 2 The concentration range is 15-30mM, and the magnetization intensity test is carried out. The hysteresis loop results are as follows Figure 4 As shown, the saturation magnetization range is 30-35emu / g. Figure 5 From the enlarged view of the origin of the hysteresis loop shown, it can be seen that the residual magnetization intensity and coercive force of the magnetic microorganisms are both low, indicating that the magnetic microorganisms have a paramagnetic tendency.

[0056] The mineralization products generated at 60°C were subjected to scanning electron microscopy, XRD, EDS, FTIR and thermogravimetric tests, and their microscopic morphology can be observed as follows: Figure 6 The mineral composition is shown in Figure 7 The elemental composition is shown in Figure 8 As shown, the infrared spectrum is Fig. 9 The thermogravimetric test results are shown in Fig.10 As shown in the scanning electron microscope image, its morphology is uniformly dispersed vaterite-type calcium carbonate, and its particle size is about 5μm. XRD results show that obvious diffraction peaks appear at 2θ of 24.9°, 27.0°, 32.8°, 43.8°, 50.1°, and 55.8°, corresponding to the (1 1

[0057] 0), (1 1 2), (1 1 4), (3 0 0), (1 1 8), (2 2 4) crystal planes. The EDS spectrum analysis results show that the magnetic microbial mineralization product is mainly composed of three elements: C, O, and Ca. The substance is CaCO 3 FTIR infrared spectrum results show that 745cm -1 、876cm -1 and 1429cm -1 The absorption peak at 600-800℃ is caused by the symmetric stretching vibration of the CO bond of calcium carbonate. The thermogravimetric results also show that there is a weight loss step of calcium carbonate at 600-800℃. In summary, the mineralization product of magnetic microorganisms is well-dispersed vaterite-type calcium carbonate.

[0058] According to another embodiment of the present invention, an experimental process of applying the magnetic microbial self-repairing agent prepared by the present invention to cement-based materials according to a certain ratio is also disclosed: the magnetic microbial self-repairing agent prepared by the present invention and cement-based materials are applied according to a certain ratio, and a blank and a common microbial group are set to compare the repair effects. Different formulas are shown in Table 1 below:

[0059]

[0060] Table 1 Mixing ratio of cement-based materials with different formulations

[0061] The experimental process includes:

[0062] 1) First, put 650g of cement into the mixing pot, then add an appropriate amount of water, then add nutrients consisting of 5g of tryptone and 3g of beef extract, then add a mineralizer consisting of 19.5g of calcium acetate and 6.65g of urea, stir at low speed for 30s, then gradually add 1300g of sand and stir at low speed for 30s, then switch to high-speed stirring for 30s to further mix the materials. Pause stirring, during which time add the microbial self-repairing agent to the mixing pot, and carefully stir the mortar at the bottom of the pot to ensure uniformity. Finally, stir at high speed for 90s to fully mix all the materials. The entire stirring process takes a total of 270s.

[0063] 2) Pour the evenly mixed mortar into the triple mold. To ensure that its density meets the requirements, use a cement mortar vibrating table to vibrate and compact it for 60 seconds. After the vibration is completed, remove the triple mold from the vibrating table and use a metal scraper to accurately scrape off the excess mortar. After completing the above steps, place the specimen at room temperature for subsequent processing.

[0064] 3) After 24 hours of molding, the mold is demolded. To avoid damage, the mold is handled with care during demolding to ensure the integrity of the specimen. After demolding, place it in water for continued curing until the specified age.

[0065] 4) For cracks of 0.05-0.1mm, the pre-buried steel wire method is used. The diameter of the pre-buried steel wire is 0.5mm and the length is 14cm. This prevents the crack from penetrating and the specimen from breaking. One steel wire is placed 1cm away from the compressive surface, and three steel wires are placed 1cm away from the tensile surface.

[0066] 5) For micro cracks of 0.05-0.1 mm, use a compression machine to suppress the cracks.

[0067] 6) For the remaining larger cracks, first use a cement electric flexural tester to break them in half, use rubber bands to tie the broken mortar specimens together, then use insect pins of different diameters to insert into the gaps, and use the TJ-FKY crack width tester to measure the width of the cracks, so as to make cracks with an average width of 0.2-0.3mm. Finally, place the mortar specimens in water for curing, and the horizontal plane covers the mortar specimens.

[0068] The self-repair performance is characterized by the area repair rate:

[0069] A digital camera was used to photograph the cracks of the specimen before and after repair, and the crack images were binarized using Fiji Image-J image processing software. The photographed images were manually processed using Weka Segmentation, and the pixels were divided into two categories according to the crack area and the non-crack area. The entire image was changed into two colors, and then converted into an 8-bit image. The noise was eliminated by noise to obtain the images before and after the crack repair. The repaired area of ​​the crack was selected for pixel statistics, and finally the area repair rate was calculated according to the ratio of the crack area pixels to the initial crack pixels after different repair times. The specific formula is as follows:

[0070]

[0071] Where: A 0 is the pixel value of the crack area before repair, A t is the pixel value of the crack area after repairing for time t.

[0072] The repair rates of different formula groups for 0.05-0.1mm cracks of different ages and areas are shown in Table 2:

[0073] Different recipes 3d 7d 14d 28d blank 7.45％ 8.32％ 9.78％ 12.41％ Common microorganisms 16.16％ 44.36％ 84.25％ 92.96％ Magnetic Microorganisms 25.12％ 66.67％ 93.70％ 97.28％

[0074] Table 2 0.05-0.1mm crack area repair rate The repair rates of different formula groups for 0.2-0.3mm cracks at different ages are shown in Table 3 below:

[0075] Different recipes 3d 7d 14d 28d blank 4.23％ 10.21％ 21.01％ 33.23％ Common microorganisms 21.46％ 54.27％ 71.01％ 95.07％ Magnetic Microorganisms 46.42％ 58.31％ 87.05％ 100.00％

[0076] Table 3 Repair rate of 0.2-0.3mm crack area

[0077] Table 2 summarizes the repair effects of different groups of cracks with a size of 0.05-0.1 mm. According to the results, the blank group showed only a slight change in crack repair with the increase of age. Compared with the ordinary microbial group, the magnetic microbial group had a crack area repair rate of more than 90%, and the repair time was accelerated from 28 days to 14 days, which doubled the rate.

[0078] Table 3 summarizes the repair effects of different groups of 0.2-0.3mm cracks. According to the results, compared with the ordinary microbial group, the area repair rate of the magnetic microbial group can reach 87.05% at 14 days, while the ordinary microbial group is only 71.01%. The area repair rate of magnetic microorganisms is 16.04% higher than that of ordinary microorganisms.

[0079] In summary, the present invention is to prepare a magnetic microbial self-repairing agent, wrap a layer of magnetic Fe 3 O 4 Nanosheets enable directional migration and are used to repair cracks in cement-based materials. They can increase the utilization rate of microorganisms in cement-based materials and improve the repair rate of cracks.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a magnetic microbial self-repairing cement-based material, characterized in that: include: Prepare Bacillus Pasteurella culture medium, sterilize and cool to room temperature; A first urea solution with a volume fraction of 3% to 4% is added to the Bacillus pasteurianus culture medium as a substrate for urease catalysis reaction, and a Bacillus pasteurianus liquid is inoculated at a volume fraction of 3% to 4% of the culture medium, and the culture is placed in a shaking table for shaking culture until the concentration of Bacillus pasteurianus is 1×10 8 cell / mL~9×10 8 cell / mL, the Bacillus pasteurianus is used to produce urease to obtain a cultured bacterial liquid; The second urea solution is added to a 15 mmol / L to 30 mmol / L FeCl2 solution, and filtered to sterilize, and the temperature is maintained constant and mechanically stirred to allow a full reaction to obtain an iron source solution; The cultured bacterial solution and the iron source solution are mixed in a ratio of 1:20 to 1:16 and shaken to obtain a magnetic Bacillus pasteurianus solution; after shaking, the mixture is placed in a constant temperature environment for reaction for 12 hours to 24 hours; The magnetic Bacillus pasteurianus liquid, several nutrients and mineralizers are added into cement mortar and mixed evenly to obtain a magnetic microbial self-repairing cement-based material. The ratio of the magnetic Bacillus pasteurianus liquid to the water in the cement mortar is 15% to 20%.

2. The method for preparing the magnetic microbial self-repairing cement-based material according to claim 1, characterized in that: Also includes: The magnetic microbial self-repairing cement-based material is poured into a mold, compacted, placed at room temperature for 24 to 36 hours, and then demolded to obtain a material block.

3. The method for preparing the magnetic microbial self-repairing cement-based material according to claim 1, characterized in that: The Bacillus Pasteurella culture medium contains 3-4g of tryptone and 2-3g of beef extract per 1L.

4. The method for preparing the magnetic microbial self-repairing cement-based material according to claim 1, characterized in that: The concentration of the first urea solution is 2 mol / L to 4 mol / L; the concentration of the second urea solution is 500 mmol / L to 700 mmol / L.

5. The method for preparing the magnetic microbial self-repairing cement-based material according to claim 1, characterized in that: The cement mortar comprises 650 parts of cement, 241-325 parts of water and 1300 parts of sand, the nutrient substance is 0-8 parts, the mineralizer is 1-26.15 parts, and the magnetic Bacillus pasteurianus liquid is 30-65 parts.

6. The method for preparing the magnetic microbial self-repairing cement-based material according to claim 5, characterized in that: The nutrient substance comprises 5 parts by weight of tryptone and 3 parts by weight of beef extract; the mineralizer comprises 1 part by weight of calcium acetate and 0.3-0.4 parts by weight of urea.

7. The method for preparing the magnetic microbial self-repairing cement-based material according to claim 1, characterized in that: The volume ratio of the first urea solution to the Bacillus pasteurianus is 1:

1.

8. The method for preparing the magnetic microbial self-repairing cement-based material according to claim 1, characterized in that: The ratio of cement to water in the cement mortar is 1:0.5, and the ratio of cement to sand is 1:

2.

9. A method for preparing a self-healing agent based on magnetic microorganisms, characterized in that: include: Prepare Bacillus Pasteurella culture medium, sterilize and cool to room temperature; A 3% to 4% volume fraction of 2 mol / L to 4 mol / L urea solution is added to the Bacillus pasteurianus culture medium as a substrate for urease catalysis reaction, and the Bacillus pasteurianus liquid is inoculated at a volume fraction of 3% to 4% of the culture medium, and the culture is placed in a shaking table for shaking culture until the concentration of Bacillus pasteurianus is 1×10 8 cell / mL~9×10 8 cell / mL, the Bacillus pasteurianus is used to produce urease to obtain a cultured bacterial liquid; A urea solution with a concentration of 500 mmol / L to 700 mmol / L is added to a FeCl2 solution with a concentration of 15 mmol / L to 30 mmol / L, and the solution is sterilized by filtration, and the temperature is kept constant and mechanical stirring is performed to allow the solution to react fully, thereby obtaining an iron source solution; The cultured bacterial solution and the iron source solution are mixed in a ratio of 1:20 to 1:16 and shaken to obtain a magnetic Bacillus pasteurianus solution; after shaking, the mixture is placed in a constant temperature environment for reaction for 12 hours to 30 hours; Mixing calcium acetate and urea in a mass ratio of 1:0.3 to 1:0.4 to obtain a mineralizer; The magnetic Bacillus pasteurianus liquid is mixed with the mineralizer to obtain a self-repairing agent.

10. The method for preparing a self-repairing agent based on magnetic microorganisms according to claim 9, characterized in that: Also includes: Prepare tryptone and beef extract in a mass ratio of 1:0.5 to 1:0.7 to obtain nutrients; The nutrient substance is added to the mixture of the magnetic Bacillus pasteurianus liquid and the mineralizer.

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