Thermal insulation type self-repairing cement-based material based on paraffin-encapsulated hollow microsphere immobilized microorganisms and preparation method of thermal insulation type self-repairing cement-based material

Abstract

The invention provides a thermal insulation type self-repairing cement-based material based on paraffin encapsulated hollow microsphere immobilized microorganisms and a preparation method thereof, and belongs to the technical field of building materials. The preparation method of the heat preservation type microbial self-healing agent comprises the following steps: mixing and soaking a bacterial liquid and a carrier, drying the soaked carrier to constant weight, mixing with liquid paraffin, performing vacuum impregnation, and drying to obtain the heat preservation type microbial self-healing agent. The addition amount of the thermal insulation type microbial self-healing agent is 5-10 wt% of the total mass of the thermal insulation type microbial self-healing agent and the standard sand, the water-cement ratio of the thermal insulation type self-repairing cement-based material is 0.5, and the sand-cement ratio is 2.0. Under the conditions of low temperature and freeze-thaw cycle, the thermal insulation type self-repairing cement-based material based on paraffin encapsulated microorganisms has a wide application prospect in seasonal frozen area engineering application.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a heat-insulating self-repairing cement-based material based on paraffin-encapsulated hollow microbeads carrying microorganisms and a preparation method thereof. Background Art

[0002] Concrete is one of the most widely used engineering materials in the world, and is mainly used in infrastructure fields such as building structures, bridge engineering, and road engineering. During the service process, concrete cracks appear due to its own brittleness, easy plastic shrinkage, and low tensile strength. Especially when the concrete structure is in service in the seasonally frozen environment, the temperature fluctuates greatly, causing the concrete to easily expand in volume under the action of osmotic pressure and freezing pressure, resulting in internal stress and bending cracks, making it easy for a large amount of water, oxygen, and chloride ions to enter the concrete, which will not only seriously affect the performance of the concrete, but also accelerate the corrosion process inside the concrete, reducing the bearing capacity of the concrete structure.

[0003] At present, the technologies for repairing micro cracks in concrete components mainly include physical healing, chemical healing and biological healing. Physical healing and chemical healing usually involve sealing the cracks from the outside and repairing them with chemicals after detecting the cracks. These technologies require a lot of time and repair costs, and chemical agents are harmful to the environment and may affect the durability of concrete. Therefore, it is of great significance to study greener and more convenient biological healing methods.

[0004] Biological healing refers to the use of microbial induced calcium carbonate precipitation (MICP) technology for self-healing. The basic principle of MICP is that microbial spores are introduced into concrete in advance. When cracks appear in concrete, external oxygen and water penetrate into the cracks to activate the spores to transform into bacteria and generate structurally stable CaCO3 precipitation during metabolism, thereby filling the cracks and achieving self-healing of the cracks. The optimal temperature range for microbial metabolism is usually 20-30℃. Most researchers studying the MICP effect in cement matrix usually control the healing temperature at 30℃. After the specimens are cured for a certain age in a low temperature or negative temperature environment, they are placed at an ideal temperature of 30℃ for healing-related research. Yan et al. studied the use of expanded perlite as a carrier to immobilize microorganisms to explore the effects of durability and frost resistance under freeze-thaw cycles. The results showed that after 100 freeze-thaw cycles, compared with other microorganisms not wrapped by expanded perlite, the microorganisms wrapped by expanded perlite can still have higher activity, and the maximum crack width of repair can reach 643μm. Yifan et al. prepared a microbial self-healing agent using expanded perlite as a carrier and confirmed that the addition of expanded perlite can increase the maximum number of freeze-thaw cycles from 150 to 700 times, and that the secondary hydration reaction of the cement matrix itself is difficult to heal cracks with a width of more than 200 μm. The maximum crack healing width of the specimens with the addition of the self-healing agent can reach 1000 μm.

[0005] However, although there are products of self-healing microorganisms in the prior art, they only have good self-healing properties after returning to normal temperature healing temperature environment after freeze-thaw damage, and cannot achieve self-healing in low temperature environment or freeze-thaw cycle damage process. To this end, the present invention proposes a heat-insulating self-healing cement-based material based on paraffin-encapsulated hollow microspheres immobilized with microorganisms and a preparation method thereof. Summary of the invention

[0006] In order to solve the above technical problems, the present invention proposes a heat-insulating self-healing cement-based material based on paraffin-encapsulated hollow microspheres immobilizing microorganisms and a preparation method thereof. The present invention uses hollow microspheres to immobilize microorganisms, and after the self-healing agent is wrapped with the heat-insulating material paraffin, it is prepared into a new type of self-healing agent with a certain resistance to low temperature and extreme temperature destruction temperature, thereby preparing a heat-insulating self-healing cement-based material.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] One of the technical solutions of the present invention:

[0009] A method for preparing a heat-insulating microbial self-healing agent comprises the following steps: mixing bacterial liquid with a carrier and soaking them, drying the soaked carrier to a constant weight, then mixing the carrier with liquid paraffin and vacuum impregnating the carrier, and drying the carrier to obtain the heat-insulating microbial self-healing agent.

[0010] Furthermore, the bacterial liquid is a Bacillus pseudofirmus liquid.

[0011] Furthermore, the optical density OD of the bacterial culture solution is 600 is 0.6; and / or,

[0012] The carrier is fly ash hollow microbeads, which are low-cost, light-weight, thin-walled and hollow, and can well protect the survival of bacterial spores in the cement matrix.

[0013] Further, the bacterial liquid is mixed with the carrier and soaked for 24 hours, and the soaked hollow microbead carrier is dried at 40° C. to a constant weight; and / or,

[0014] The vacuum impregnation time is 20 minutes.

[0015] Furthermore, the liquid paraffin is obtained by heating paraffin in a 60° C. water bath to a liquid state.

[0016] The second technical solution of the present invention:

[0017] A heat-insulating microbial self-healing agent is prepared according to the above preparation method.

[0018] The third technical solution of the present invention:

[0019] A heat-insulating self-repairing cement-based material based on paraffin-encapsulated hollow microspheres immobilized with microorganisms, wherein the raw materials include the heat-insulating microbial self-healing agent and calcium lactate, and the addition amount of the heat-insulating microbial self-healing agent is 5wt% to 10wt% of the total mass of the heat-insulating microbial self-healing agent and standard sand; and / or,

[0020] The water-cement ratio (the mass ratio of water to cement) is 0.5, and the sand-cement ratio (the mass ratio of standard sand, thermal insulation type microbial self-healing agent to cement) is 2.0.

[0021] Calcium lactate is added to the mortar as a bacterial nutrient.

[0022] Furthermore, the raw materials include, by weight, 500 parts of water, 10 parts of calcium lactate, 1000 parts of cement and 1800 to 2000 parts of standard sand, preferably 500 parts of water, 10 parts of calcium lactate, 1000 parts of cement and 1800 to 1900 parts of standard sand.

[0023] The fourth technical solution of the present invention:

[0024] A method for preparing a heat-insulating self-repairing cement-based material based on paraffin-encapsulated hollow microspheres immobilizing microorganisms comprises the following steps:

[0025] After cement, standard sand, heat-insulating microbial self-healing agent and calcium lactate are mixed and stirred, water is added and stirring is continued to obtain a mortar slurry, and then the mortar slurry is molded, standardly cured and demolded to obtain the heat-insulating self-healing cement-based material based on paraffin-encapsulated hollow microspheres immobilizing microorganisms.

[0026] Furthermore, the standard curing temperature is 23±1°C and the curing time is 24h.

[0027] Compared with the prior art, the present invention has the following advantages and technical effects:

[0028] (1) The present invention uses paraffin-encapsulated hollow microspheres as a new type of thermal insulation self-healing agent, which can improve the survival efficiency of bacteria in low temperature or even negative temperature environments, enhance the effect of MICP under extreme temperatures, and is more conducive to the self-healing of microcracks in seasonally frozen areas.

[0029] (2) The study on the healing ability of the novel thermal insulation self-healing agent of the present invention under different healing environments found that the healing ability of the specimens without thermal insulation self-healing agent in the low temperature 4°C healing environment was reduced by 37.36% to 37.92% compared with that at room temperature, while the healing ability of the specimens using the thermal insulation self-healing agent was only reduced by 3.00% to 4.83%. In the -20 / 20°C freeze-thaw cycle environment, the healing rate of the ordinary self-healing agent decreased by 61.37% to 62.52%, while the healing rate of the novel thermal insulation self-healing agent of the present invention was only reduced by 25.12% to 26.06%. It is confirmed that the novel thermal insulation self-healing agent of the present invention provides protection for bacterial spores in the extreme destructive temperature environment, allowing more bacterial spores to survive. Under low temperature and freeze-thaw cycle conditions, the thermal insulation self-healing cement-based material based on paraffin-encapsulated microorganisms has broad application prospects in seasonally frozen area engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0031] Figure 1 This is a schematic diagram of the preparation of the heat-insulating microbial self-healing agent in Example 1 of the present invention;

[0032] Figure 2 The results of the determination of the healing rate of the cracks of the cement-based material specimens prepared in Example 1, Example 2 and Comparative Examples 1-3 after curing at a low temperature of 4°C for 28 days;

[0033] Figure 3 This is the crack healing image of the cement-based material specimen of Example 2 at the healing age of day 0;

[0034] Figure 4This is the crack healing image of the cement-based material specimen of Example 2 at the 28th day of healing age;

[0035] Figure 5 The results of the determination of the healing rate of the cracks of the cement-based material specimens prepared in Example 1, Example 2 and Comparative Examples 1-3 after 28 days of curing under the conditions of -20 / 20°C freeze-thaw cycle damage;

[0036] Figure 6 This is a scanning electron microscope image of the heat-insulating microbial self-healing agent prepared in Example 1;

[0037] Figure 7 This is a scanning electron microscope image of the thermal insulation self-repairing cement-based material prepared in Example 1 after 28 days of healing and curing at the extreme damage temperature of -20 / 20°C;

[0038] Figure 8 This is a scanning electron microscope image of the thermal insulation self-repairing cement-based material prepared in Comparative Example 2 after healing and curing at the extreme damage temperature of -20 / 20°C for 28 days.

[0039] Fig. 9 This is a scanning electron microscope image of the thermal insulation self-repairing cement-based material prepared in Example 2 after 28 days of healing and curing at the extreme damage temperature of -20 / 20°C;

[0040] Fig.10 This is a scanning electron microscope image of the thermal insulation self-repairing cement-based material prepared in Comparative Example 3 after 28 days of healing and curing at the extreme damage temperature of -20 / 20°C. DETAILED DESCRIPTION

[0041] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0042] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0043] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0044] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0045] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0046] The embodiment of the present invention provides a method for preparing a heat-insulating microbial self-healing agent, comprising the following steps: mixing a bacterial liquid with a carrier and soaking them, drying the soaked carrier to a constant weight, then mixing it with liquid paraffin and vacuum impregnating it, and obtaining the heat-insulating microbial self-healing agent after drying.

[0047] In a preferred embodiment of the present invention, the bacterial culture liquid is a Bacillus pseudofirmus culture liquid, and the optical density OD 600 is 0.6; and / or,

[0048] The carrier is fly ash hollow microbeads, which are low-cost, light-weight, thin-walled and hollow, and can well protect the survival of bacterial spores in the cement matrix.

[0049] In a preferred embodiment of the present invention, the bacterial liquid is mixed with the hollow microbead carrier and soaked for 24 hours, and the soaked hollow microbead carrier is placed at 40° C. and dried to constant weight; and / or,

[0050] The vacuum impregnation time is 20 minutes.

[0051] In a preferred embodiment of the present invention, the liquid paraffin is obtained by heating paraffin in a 60° C. water bath to a liquid state.

[0052] In a preferred embodiment of the present invention, the preparation method of the bacterial liquid used includes: transplanting the bacterial strain into a liquid culture medium, and using a shaker to culture at 25°C and 120 rpm for 48 hours, wherein the liquid culture medium used contains beef extract, peptone, sodium chloride and pure water, wherein the mass fraction of beef extract in pure water is 0.5%, the mass fraction of peptone in pure water is 0.3%, and the mass fraction of sodium chloride in pure water is 0.5%.

[0053] The embodiment of the present invention also provides a heat-insulating microbial self-healing agent, which is prepared according to the above preparation method.

[0054] The embodiment of the present invention also proposes a thermal insulation self-healing cement-based material based on paraffin-encapsulated hollow microspheres immobilized microorganisms, the raw materials include the thermal insulation microbial self-healing agent and calcium lactate, the addition amount of the thermal insulation microbial self-healing agent is 5wt% to 10wt% of the total mass of the thermal insulation microbial self-healing agent and standard sand; the water-cement ratio (the mass ratio of water to cement) is 0.5, and the sand-binder ratio (the mass ratio of standard sand, thermal insulation microbial self-healing agent and cement) is 2.0. Preferably, the water-cement ratio is 0.5, and the sand-binder ratio is 2.0.

[0055] In a preferred embodiment of the present invention, the raw materials of the thermal insulation self-healing cement-based material include, by weight, 500 parts of water, 10 parts of calcium lactate, 1000 parts of cement and 1800 to 2000 parts of standard sand, preferably 500 parts of water, 10 parts of calcium lactate, 1000 parts of cement and 1800 to 1900 parts of standard sand.

[0056] The embodiment of the present invention also proposes a method for preparing the heat-insulating self-repairing cement-based material based on hollow microspheres encapsulated with paraffin and immobilized with microorganisms, comprising the following steps:

[0057] After cement, standard sand, heat-insulating microbial self-healing agent and calcium lactate are mixed and stirred, water is added and stirring is continued to obtain a mortar slurry, and then the mortar slurry is molded, standardly cured and demolded to obtain the heat-insulating self-healing cement-based material based on paraffin-encapsulated hollow microspheres immobilizing microorganisms.

[0058] In a preferred embodiment of the present invention, the standard curing temperature is 23±1° C. and the time is 24 hours.

[0059] The raw materials used in the examples of the present invention are all commercially available, wherein the Bacillus pseudofirmus used is obtained from the China Industrial Culture Collection (CICC) with the collection number DSM8715.

[0060] In the embodiments of the present invention, "normal temperature" refers to "25±2°C".

[0061] The embodiment of the present invention has no restriction on the amount of bacterial liquid and liquid paraffin used for "immersion" and "vacuum impregnation", and it is only necessary to immerse the hollow microbead carrier.

[0062] In the following examples, the “high-speed stirring” is 1000 rpm; the “low-speed stirring” is 150 rpm.

[0063] The particle size of the fly ash hollow microspheres used in the following examples is 1-2 mm, and the water absorption rate is 143.2%.

[0064] The cement type used in the following examples is PO42.5.

[0065] The technical solution of the present invention is further illustrated by the following embodiments.

[0066] Example 1

[0067] (1) Bacillus pseudofirmus bacterial solution (optical density OD 600 =0.6) and fly ash hollow microspheres and soaked for 24 hours, the soaked fly ash hollow microspheres were placed at 40°C and dried to constant weight, paraffin was heated in a 60°C water bath to liquid to obtain liquid paraffin, the dried fly ash hollow microspheres and liquid paraffin were mixed and vacuum impregnated, and after drying, a heat-insulating microbial self-healing agent was obtained. The preparation schematic diagram is shown in Figure 1 ;

[0068] (2) Weigh the following raw materials according to the following weight proportions: 500 parts of water, 10 parts of calcium lactate, 1000 parts of cement and 1900 parts of standard sand. The amount of thermal insulation type microbial self-healing agent added is 5wt% (100 parts) of the total mass of the thermal insulation type microbial self-healing agent and standard sand (water-cement ratio is 0.5, sand-binder ratio is 2.0);

[0069] (3) Cement, standard sand, the heat-insulating microbial self-healing agent prepared in step (1) and calcium lactate are placed in a stirring pot and stirred at a low speed for 30 seconds, and then water is added and stirred at a low speed for 120 seconds. After high-speed stirring for 180 seconds, a mortar slurry is obtained. The mortar slurry obtained by stirring is then poured into a mold with a size of 50×50×50 mm and placed on a vibrating table to expel the air in the mortar slurry. The mold is covered with a polyethylene film and placed in a standard curing box. After curing at 23±1°C for 24 hours, the mold is demolded to obtain a heat-insulating self-healing cement-based material based on paraffin-encapsulated hollow microspheres with immobilized microorganisms.

[0070] Example 2

[0071] (1) Add the Bacillus pseudofirmus bacterial solution (concentration OD 600=0.6) and fly ash hollow microspheres, and soaked for 24 hours, the soaked fly ash hollow microspheres were placed at 40°C and dried to constant weight, paraffin was heated in a 60°C water bath to liquid to obtain liquid paraffin, the dried fly ash hollow microspheres and liquid paraffin were mixed and vacuum impregnated, and after drying, a heat-insulating microbial self-healing agent was obtained;

[0072] (2) Weigh the following raw materials according to the following weight proportions: 500 parts of water, 10 parts of calcium lactate, 1000 parts of cement and 1800 parts of standard sand. The amount of thermal insulation type microbial self-healing agent added is 10wt% (200 parts) of the total mass of the thermal insulation type microbial self-healing agent and standard sand (water-cement ratio is 0.5, sand-binder ratio is 2.0);

[0073] The rest of the preparation method of step (3) is the same as that of Example 1.

[0074] Comparative Example 1

[0075] (1) Weigh the following raw materials in parts by weight: 500 parts of water, 1000 parts of cement and 2000 parts of standard sand (water-cement ratio is 0.5, sand-binder ratio is 2.0);

[0076] (2) Place cement and standard sand in a mixing pot and stir at a low speed for 30 seconds. Then add water and stir at a low speed for 120 seconds. After stirring at a high speed for 180 seconds, a mortar slurry is obtained. The mortar slurry is then poured into a mold with a size of 50×50×50 mm and placed on a vibrating table to expel the air in the mortar slurry. The mold is covered with a polyethylene film and placed in a standard curing box. After curing at 23±1°C for 24 hours, the mold is demolded to obtain a cement-based material.

[0077] Comparative Example 2

[0078] (1) Bacillus pseudofirmus bacterial solution (optical density OD 600 =0.6) and fly ash hollow microspheres and soaked for 24 hours, and the soaked fly ash hollow microspheres were placed at 40° C. and dried to constant weight to obtain a microbial self-healing agent;

[0079] The addition amount of the heat preservation type microbial self-healing agent is 5wt% of the total mass of the heat preservation type microbial self-healing agent and the standard sand;

[0080] The rest of the preparation method of step (2) and step (3) is the same as that of Example 1.

[0081] Comparative Example 3

[0082] The same as comparative example 2, except that the addition amount of the heat-insulating microbial self-healing agent is 10wt% of the total mass of the heat-insulating microbial self-healing agent and the standard sand.

[0083] Performance Testing

[0084] After the cracks of the cement-based material specimens prepared in Examples 1-2 and Comparative Examples 1-3 were cured at low temperature of 4°C for 28 days, the healing rates were calculated based on microscopic crack observation and image binarization (the same below). The results are shown in Tables 1 and Figure 2 The results of the healing rate determination after 28 days of healing and curing at room temperature are shown in Table 1. The crack healing images of the cement-based material specimens of Example 2 at the healing age of 0 day and 28 day under low temperature 4°C are shown in Table 1. Figure 3 and Figure 4 .

[0085] Table 1 Crack healing rate test results of examples 1-2 and comparative examples 1-3

[0086] Under low temperature conditions of 4℃ Under normal temperature conditions sample Healing rate (%) Healing rate (%) Example 1 85.26 88.26 Example 2 88.78 93.61 Comparative Example 1 9.74 29.88 Comparative Example 2 55.70 93.06 Comparative Example 3 62.08 100

[0087] Compare Table 1 and Figure 2 It can be seen from the data that the crack healing rate of the specimens obtained after adding the thermal insulation type microbial self-healing agent is higher than that of the specimens without adding the thermal insulation type microbial self-healing agent, and under the low temperature 4°C curing condition, the crack healing rate of the specimens with the addition of paraffin encapsulated self-healing agent is significantly higher than the crack healing rate without the addition of paraffin encapsulated self-healing agent. Therefore, the thermal insulation type self-repairing cement-based material based on paraffin encapsulated microorganisms in Example 1 has good crack self-healing ability under low temperature 4°C conditions.

[0088] The results of the healing rate determination of the cracks of the cement-based material specimens prepared in Examples 1-2 and Comparative Examples 1-3 after 28 days of curing under -20 / 20°C freeze-thaw cycle damage conditions are shown in Tables 2 and Figure 5 .

[0089] Table 2 Crack healing rate test results of Example 1-2 and Comparative Example 1-3

[0090]

[0091]

[0092] Compare Table 2 and Figure 5 It can be seen from the data that the crack healing rate of the specimens after adding the thermal insulation type microbial self-healing agent is higher than that of the specimens without adding the self-healing agent. This indicates that the microorganisms still have a certain activity after 28 days under the extreme destruction temperature conditions, and under the extreme destruction temperature of -20 / 20℃ curing conditions, the crack healing rate of the specimens with the addition of paraffin encapsulated self-healing agent is significantly higher than the crack healing rate without the addition of paraffin encapsulated self-healing agent. Therefore, the thermal insulation type self-repairing cement-based material based on paraffin encapsulated microorganisms in Example 1-2 still has good crack self-healing ability under the extreme destruction temperature of -20 / 20℃.

[0093] Combining the data in Table 1 and Table 2, it can be seen that the specimens (Comparative Example 2 and Comparative Example 3) without adding the heat-insulating self-healing agent in the low-temperature 4°C healing environment have a healing ability reduced by 37.36% to 37.92% compared to that at room temperature, while the healing ability of the specimens (Example 1 and Example 2) using the heat-insulating self-healing agent is only reduced by 3.00% to 4.83% compared to that at room temperature. Under a -20 / 20°C freeze-thaw cycle environment, the healing rate of the specimens (Comparative Example 2 and Comparative Example 3) without adding the heat-insulating self-healing agent decreased by 61.37% to 62.52%, and the healing rate of the specimens (Example 1 and Example 2) using the heat-insulating self-healing agent of the present invention decreased by only 25.12% to 26.06%. It is confirmed that the heat-insulating self-healing agent of the present invention provides a protective effect for bacterial spores in an extreme damage temperature environment, allowing more bacterial spores to survive. Under low temperature and freeze-thaw cycle conditions, the thermal insulation self-healing cement-based materials based on paraffin-encapsulated microorganisms have broad application prospects in engineering applications in seasonally frozen areas.

[0094] The scanning electron microscope image of the heat-insulating microbial self-healing agent prepared in Example 1 is shown in Figure 6 ,Depend on Figure 6 It can be observed that there are a large number of free bacilli in the lower layer of the paraffin in the test piece of Example 1, which indicates that the paraffin encapsulation technology does not affect the survival of bacteria.

[0095] After 28 days of curing at the extreme damage temperature of -20 / 20°C, the scanning electron microscope image of the thermal insulation self-repairing cement-based material prepared in Example 1 is shown in FIG. Figure 7 The SEM image of the cement-based material prepared in Comparative Example 2 is shown in Figure 8 ,Depend on Figure 7 and Figure 8 It can be seen that under the extreme damage temperature curing condition of -20 / 20℃, compared with the self-healing agent specimen without paraffin encapsulation (Comparative Example 2), the calcium carbonate crystals formed by the self-healing agent encapsulated with paraffin (Example 1) are denser, while the specimen without paraffin encapsulation (Comparative Example 2) is observed to have a large amount of complete calcium carbonate generation. This shows that more microorganisms survive in the paraffin-encapsulated specimens at the extreme damage temperature of -20 / 20℃, and the normal metabolism completes the healing of microcracks, which also shows the effectiveness of the heat-insulating self-repairing cement-based material prepared by the present invention in protecting microorganisms from exerting MICP in seasonally frozen areas.

[0096] After 28 days of curing at the extreme damage temperature of -20 / 20°C, the scanning electron microscope image of the thermal insulation self-repairing cement-based material prepared in Example 2 is shown in FIG. Fig. 9 The SEM image of the cement-based material prepared in Comparative Example 3 is shown in Fig.10 ,Depend on Fig. 9 and Fig.10It can be seen that under the curing condition of the extreme destruction temperature of -20 / 20°C, under the condition of the same dosage of the self-healing agent, the calcium carbonate crystals formed by the self-healing agent specimen encapsulated with paraffin (Example 2) are more complete in morphology and smoother in surface than those of the self-healing agent specimen without paraffin encapsulation (Comparative Example 3), which indicates that more microorganisms survive in the self-healing agent encapsulated with paraffin at the extreme destruction temperature of -20 / 20°C, and the metabolism occurs normally to complete the healing of microcracks. Compared with Example 1, with the increase of the dosage of the thermal insulation self-healing agent (from 5wt% to 10wt%), the calcium carbonate crystals are more complete and denser in number, which also indicates the effectiveness of the thermal insulation self-repairing cement-based material prepared by the present invention in protecting microorganisms in seasonally frozen areas to play the role of MICP.

[0097] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a heat-insulating microbial self-healing agent, characterized in that: The following steps are involved: The bacterial liquid is mixed with the carrier and soaked, the soaked carrier is dried to a constant weight, then mixed with liquid paraffin and vacuum impregnated, and the heat-insulating microbial self-healing agent is obtained after drying.

2. The method for preparing the heat-insulating microbial self-healing agent according to claim 1, characterized in that: The bacterial culture liquid is a Bacillus pseudofirmus culture liquid; and / or, The carrier is fly ash hollow microbeads.

3. The method for preparing the heat-insulating microbial self-healing agent according to claim 2, characterized in that: The optical density OD of the bacterial culture 600 is 0.

6.

4. The method for preparing the heat-insulating microbial self-healing agent according to claim 1, characterized in that: Mix the bacterial liquid and the carrier and soak them for 24 hours, and dry the soaked carrier at 40°C to a constant weight; and / or, The vacuum impregnation time is 20 minutes.

5. A heat-insulating microbial self-healing agent, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 4.

6. A heat-insulating self-repairing cement-based material based on paraffin-encapsulated hollow microspheres immobilized with microorganisms, characterized in that: The raw materials include the heat-insulating microbial self-healing agent according to claim 5 and calcium lactate, wherein the addition amount of the heat-insulating microbial self-healing agent is 5wt% to 10wt% of the total mass of the heat-insulating microbial self-healing agent and the standard sand; and / or, The thermal insulation self-repairing cement-based material has a water-cement ratio of 0.5 and a sand-cement ratio of 2.

0.

7. The heat-insulating self-repairing cement-based material based on paraffin-encapsulated hollow microspheres immobilized with microorganisms according to claim 6, characterized in that: The raw materials, calculated by weight, include: 500 parts of water, 10 parts of calcium lactate, 1000 parts of cement and 1800 to 2000 parts of standard sand.

8. A method for preparing a heat-insulating self-repairing cement-based material based on paraffin-encapsulated hollow microspheres immobilized with microorganisms according to any one of claims 6 to 7, characterized in that: The following steps are involved: After cement, standard sand, heat-insulating microbial self-healing agent and calcium lactate are mixed and stirred, water is added and stirring is continued to obtain a mortar slurry, and then the mortar slurry is molded, standardly cured and demolded to obtain the heat-insulating self-healing cement-based material based on paraffin-encapsulated hollow microspheres immobilizing microorganisms.

9. The preparation method according to claim 8, characterized in that: The standard curing temperature is 23±1°C and the curing time is 24h.

Images