阅读说明：本技术 一种多层核壳结构自修复微球及其制备方法和应用 (Multilayer core-shell structure self-repairing microsphere and preparation method and application thereof ) 是由 詹其伟 董婉莹 傅昌皓 周娟兰 潘志宏 于 2021-10-21 设计创作，主要内容包括：本发明公开了一种多层核壳结构自修复微球,包括内核、包覆在内核表面的外核、以及包覆在外核表面的外壳,所述内核成分为复合微生物菌剂和硫酸铝的混合物,所述外核成分为磁性功能组份,所述外壳成分为水泥。本发明所述的多层核壳结构自修复微球用于水泥基材料裂缝修复,通过耦合微生物诱导矿化和钙矾石形成填充、封堵水泥基材料裂缝,硫酸铝与基体中氢氧化钙反应形成钙矾石,钙矾石形成过程中体积膨胀、颗粒较大,在裂缝填充中起到骨架的作用,固碳微生物捕获环境中二氧化碳诱导矿化形成方解石,在裂缝区起到胶凝材料的作用,从而大幅改善裂缝修复的宽度和深度,解决了单一微生物诱导矿化修复深度不足的难题。(The invention discloses a multilayer core-shell structure self-repairing microsphere which comprises an inner core, an outer core and a shell, wherein the outer core is coated on the surface of the inner core, the shell is coated on the surface of the outer core, the inner core is a mixture of a composite microbial agent and aluminum sulfate, the outer core is a magnetic functional component, and the shell is cement. The multilayer core-shell structure self-repairing microspheres are used for repairing cracks of cement-based materials, the cracks of the cement-based materials are filled and blocked by coupling microbe induced mineralization and ettringite formation, aluminum sulfate reacts with calcium hydroxide in a matrix to form ettringite, the ettringite is expanded in volume and large in particle size in the formation process and plays a role of a skeleton in crack filling, carbon-fixing microbes capture carbon dioxide in the environment to induce mineralization to form calcite, and the calcite plays a role of a cementing material in a crack area, so that the width and the depth of crack repair are greatly improved, and the problem of insufficient depth of single microbe induced mineralization repair is solved.)

1. The multilayer core-shell structure self-repairing microsphere is characterized by comprising an inner core, an outer core and a shell, wherein the outer core is coated on the surface of the inner core, the shell is coated on the surface of the outer core, the inner core is a mixture of a composite microbial agent and aluminum sulfate, the outer core is a magnetic functional component, and the shell is cement.

2. The self-repairing microsphere with the multilayer core-shell structure according to claim 1, wherein the magnetic functional component is attapulgite and/or ferroferric oxide.

3. The multilayer core-shell structure self-repairing microsphere of claim 1, wherein the composite microbial agent is prepared from yeast and a carbon-fixing microbial strain according to a ratio of 1: 10-15, and the mass ratio of the composite microbial agent to aluminum sulfate is 1: 1-5.

4. The multilayer core-shell structure self-repairing microsphere of claim 1, wherein the particle size of the inner core is 2.0-2.5mm, the thickness of the outer core is 0.1-0.5mm, and the thickness of the outer shell is 1.0-1.5 mm.

5. The preparation method of the multilayer core-shell structure self-repairing microsphere of claims 1 to 4, which is characterized by comprising the following steps:

s1: inoculating the carbon-fixing microbial strains into a corresponding culture medium A, carrying out constant-temperature shaking culture for 24-48 hours to obtain a culture solution A, adding a spore efficient conversion agent into the culture solution A to obtain a microbial spore culture solution A, and carrying out spray drying to prepare a powdery microbial agent A; respectively inoculating the yeast strains into corresponding culture media B, carrying out constant-temperature shaking culture for 24-48 hours to obtain a culture solution B, adding a spore efficient conversion agent into the culture solution B to obtain a microbial spore culture solution B, preparing a powdery microbial agent B by spray drying, and mixing the two to obtain a composite microbial bacterium;

s2: adding the compound microbial agent and aluminum sulfate into a sugar-coating machine according to a proportion, uniformly spraying an ethanol solution in a rotating process to prepare spherical particles, and taking the spherical particles as an inner core of the self-repairing microspheres;

s3: adding magnetic functional components into a sugar coating machine, uniformly spraying ethanol solution in the rotating process, and coating a layer of magnetic components on the surface layer of the inner core of the self-repairing microsphere as the outer core of the self-repairing microsphere;

s4: adding cement into the sugar coating machine, uniformly spraying deionized water in the rotating process, coating a layer of cement on the surface layer of the outer core of the self-repairing microsphere, taking the cement as the shell of the self-repairing microsphere, and finally maintaining.

6. The method according to claim 5, wherein the carbon-fixing microorganism strain in step S1 is one or more of Bacillus mucilaginosus, Bacillus lysinate, Arthrobacter and photosynthetic bacteria; the mass ratio of the inoculation amount of the carbon-fixing microbial strain to the culture medium is 1-2: 100, and the culture medium is 1000mL of deionized water, 8-12g of sucrose and Na₂HPO₄·12H₂O 2-3g、MgSO₄ 0.4-0.6g、CaCO₃ 0.5-1.5g、KC1 0.1-0.2g、(NH₄)₂SO₄0.4-0.6 g; the mass ratio of the inoculation amount of the yeast in the step S1 to the culture medium is 1-2: 100, and the culture medium comprises 1000mL of deionized water, 30-40g of potato powder, 5-10g of glucose and 5-10g of agar.

7. The preparation method according to claim 5, wherein the efficient transforming agent for spores in the step S1 is manganese chloride, and the addition amount is 1-5 g/L.

8. The method as claimed in claim 5, wherein the spray drying temperature in step S1 is 105 ℃ and the speed is 5-20mL/min, the coating machine rotation speed in step S2 is 10-50r/min, and the liquid spraying amount is 10-20 mL/min.

9. The method according to claim 5, wherein the standard conditions for curing in step S4 are humidity 90% -95%, temperature 20-23 ℃, and time 3-14 days.

10. The application of the multilayer core-shell structure self-repairing microspheres of claims 1-4 in the field of repairing cracks of cement-based materials.

Technical Field

The invention belongs to crossed scientific technologies in multiple fields of microbiology, materials science and civil engineering, and particularly relates to a multilayer core-shell structure self-repairing microsphere as well as a preparation method and application thereof.

Background

In recent years, with the rapid development of economy in China, the urbanization process is accelerated continuously, large-scale urban infrastructure is under construction or planning construction, and a huge amount of building materials are urgently needed. Cement-based materials have been the main building materials used in civil engineering because of their outstanding advantages such as superior durability to common steel and wood, convenience in construction with different structural sizes and shapes, easy availability of raw materials, and low cost. However, the increasingly complex composition, increased fluidity, and accelerated early strength development of the material properties, lead to increased shrinkage; the problems of shrinkage and cracking of the long-span, large-volume and strong-constraint modern structure and severe construction environments such as high temperature and dryness are obvious, and the durability of the structure is seriously influenced. Therefore, considering that the cement-based material is a material with high brittleness and low tensile strength, how to inhibit the generation of cracks is a key problem for realizing large-scale application of the cement-based material.

For repairing the crack of the cement-based material, researchers at home and abroad develop research with rich success. The traditional repairing mode is mainly manual repairing, time and labor are consumed, and manual repairing is difficult to realize if the microcracks are invisible to naked eyes or are in positions which are difficult to touch. With the progress of building materials and structural intelligence, the self-repairing of cement-based material cracks becomes a focus of attention in academic and engineering circles. After the cement-based material is cracked, unhydrated cement particles in the crack area continue to hydrate, the product expands and CaCO₃And Ca (OH)₂The crystal deposition can play a certain repairing role, the self-repairing is only limited to tiny cracks, the repairing speed is slow, and the engineering requirements cannot be met. Therefore, the research and development of the cement-based material with the self-repairing function are urgently needed, which is beneficial to greatly reducing the repairing and maintaining cost, obviously improving the engineering durability and the service life, and having obvious economic value and wide application prospect.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a multilayer core-shell structure self-repairing microsphere which is low in crack repairing cost, high in speed, good in effect and good in compatibility; the invention also aims to provide a preparation method and application of the multilayer core-shell structure self-repairing microsphere.

The technical scheme is as follows: the invention relates to a multilayer core-shell structure self-repairing microsphere which comprises an inner core, an outer core and a shell, wherein the outer core is coated on the surface of the inner core, the shell is coated on the surface of the outer core, the inner core is a mixture of a compound microbial agent and aluminum sulfate, the outer core is a magnetic functional component, and the shell is cement.

Further, the magnetic functional component is attapulgite and/or ferroferric oxide.

Further, the compound microbial agent is prepared from yeast and carbon-fixing microbial strains according to the proportion of 1: 10-15, and the mass ratio of the compound microbial agent to aluminum sulfate is 1: 1-5.

Furthermore, the grain diameter of the inner core is 2.0-2.5mm, the thickness of the outer core is 0.1-0.5mm, and the thickness of the outer shell is 1.0-1.5 mm.

The preparation method of the multilayer core-shell structure self-repairing microsphere comprises the following steps:

s1: inoculating the carbon-fixing microbial strains into a corresponding culture medium A, carrying out constant-temperature shaking culture for 24-48 hours to obtain a culture solution A, adding a spore efficient conversion agent into the culture solution A to obtain a microbial spore culture solution A, and carrying out spray drying to prepare a powdery microbial agent A; respectively inoculating the yeast strains into corresponding culture media B, carrying out constant-temperature shaking culture for 24-48 hours to obtain a culture solution B, adding a spore efficient conversion agent into the culture solution B to obtain a microbial spore culture solution B, preparing a powdery microbial agent B by spray drying, and mixing the two to obtain a composite microbial bacterium;

s2: adding the composite microbial agent and aluminum sulfate into a sugar-coating machine according to a ratio, uniformly spraying an ethanol solution in a rotating process to prepare spherical particles, and taking the spherical particles as an inner core of the self-repairing microspheres;

s3: adding magnetic functional components into a sugar coating machine, uniformly spraying ethanol solution in the rotating process, and coating a layer of magnetic components on the surface layer of the inner core of the self-repairing microsphere as the outer core of the self-repairing microsphere;

s4: adding cement into the sugar coating machine, uniformly spraying deionized water in the rotating process, coating a layer of cement on the surface layer of the outer core of the self-repairing microsphere, taking the cement as the shell of the self-repairing microsphere, and placing under standard conditions for maintenance.

Further, the carbon-fixing microbial strains in the step S1 are one or more of bacillus mucilaginosus, bacillus lysinate, arthrobacter and photosynthetic bacteria;

the mass ratio of the inoculation amount of the carbon-fixing microbial strain to the culture medium is 1-2: 100, and the culture medium is 1000mL of deionized water, 8-12g of sucrose and Na₂HPO₄·12H₂O 2-3g、MgSO₄ 0.4-0.6g、CaCO₃ 0.5-1.5g、KCl 0.1-0.2g、(NH₄)₂SO₄ 0.4-0.6g；

The mass ratio of the inoculation amount of the yeast in the step S1 to the culture medium is 1-2: 100, and the culture medium comprises 1000mL of deionized water, 30-40g of potato powder, 5-10g of glucose and 5-10g of agar.

Further, the efficient spore transforming agent in the step S1 is manganese chloride, and the addition amount is 1-5 g/L;

further, the spray drying temperature in the step S1 is 105-.

Further, the standard conditions of the maintenance in the step S4 are that the humidity is 90-95%, the temperature is 20-23 ℃, and the time is 3-14 days.

The multilayer core-shell structure self-repairing microsphere is applied to the field of repairing cement-based material cracks.

The application method comprises the following steps: the product is prepared by adopting the multilayer core-shell structure self-repairing microspheres to replace part of sand and adding a proper amount of calcium source to keep the water-cement ratio unchanged.

Furthermore, the replacement rate of the multilayer core-shell structure self-repairing microspheres for replacing part of sand is 1% -10%;

further, the calcium source is one or more of calcium nitrate, calcium chloride and calcium lactate;

further, the addition amount of the calcium source is 1-5% of the cement of the cementing material;

furthermore, the crack is a through crack with a width of 200-.

Further, preparing a test piece with the size of 300mm multiplied by 30mm, curing the test piece at normal temperature for 24-26 hours, curing the test piece at normal temperature water environment for 7 days, then manually manufacturing cracks through a press, placing the cracked test piece in water environment, and monitoring the crack repairing effect of the cracked test piece.

Has the advantages that: compared with the traditional passive repair method, the multilayer core-shell structure self-repairing microsphere provided by the invention has the following beneficial effects that: (1) the method has the advantages that the method creatively leads mineralization and ettringite to form, fill and plug cement base material cracks through coupling microorganisms, aluminum sulfate reacts with calcium hydroxide in a base body to form ettringite, the ettringite is expanded in volume and large in particle size in the forming process and plays a role of a framework in crack filling, carbon dioxide in a carbon-fixing microorganism capture environment is induced and mineralized to form calcite, and the calcite plays a role of a cementing material in a crack area, so that the width and the depth of crack repair are greatly improved, and the problem of insufficient depth of single microorganism induced mineralization repair is solved; (2) the saccharomycetes decompose ethanol added in the preparation process of the microspheres to provide a carbon source for calcite deposition; (3) the outer core magnetic component in the multilayer core-shell structure self-repairing microsphere can effectively enrich calcium ions in a crack region, avoid the calcium ions from running out of the crack region, and improve the deposition amount of calcite and ettringite; (4) the shell protective layer in the multilayer core-shell structure self-repairing microsphere is prepared by cement, has excellent compatibility with a cement-based material substrate, and has no negative influence.

Drawings

FIG. 1 is a representation of the morphology of self-healing microspheres of the present invention;

FIG. 2 XRD spectra of fracture zone products;

FIG. 3 SEM image of fracture zone product;

FIG. 4 shows the crack repair rate of the self-repairing microspheres of the present invention.

Detailed Description

For a further understanding of the present invention, reference will now be made in detail to the embodiments illustrated in the drawings.

Example 1

A preparation method and application of a multilayer core-shell structure self-repairing microsphere are disclosed, wherein the method comprises the following steps:

(1) inoculating bacillus mucilaginosus into a culture medium A, wherein the mass ratio of the inoculation amount to the culture medium A is 1: 100, and the culture medium A is 1000mL of deionized water, 8g of cane sugar and Na₂HPO₄·12H₂O 2g、MgSO₄ 0.4g、CaCO₃ 0.5g、KCl 0.1g、(NH₄)₂SO₄0.4g, carrying out constant-temperature shaking culture for 24 hours to obtain a culture solution A, adding a spore efficient transforming agent manganese chloride into the culture solution A, wherein the adding amount is 1g/L to obtain a microbial spore culture solution A, and carrying out spray drying to prepare a powdery microbial agent A; inoculating the yeast strain into a culture medium B, wherein the mass ratio of the inoculation amount to the culture medium B is 1: 100, the culture medium B is 1000mL of deionized water, 30g of potato powder, 5g of glucose and 5g of agar, and carrying out constant-temperature shaking culture for 24 hours to obtain a culture solution B; adding a spore efficient transforming agent manganese chloride into the culture solution B, wherein the addition amount is 1g/L to obtain a microbial spore culture solution B, preparing a powdery microbial agent B through spray drying, and mixing the microbial agent A and the microbial agent B to obtain a compound microbial bacterium; the spray drying temperature is 105 ℃, the speed is 5mL/min, and the composite microbial agent is prepared from saccharomycete powder and bacillus mucilaginosus powder according to the proportion of 1: 10;

(2) adding the composite microbial agent and aluminum sulfate into a sugar-coating machine according to equal mass ratio, uniformly spraying ethanol solution in the rotating process to prepare spherical particles, wherein the rotating speed of the sugar-coating machine is 10r/min, the liquid spraying amount is 10ml/min, and screening to obtain particles with the particle size of 2.0-2.5mm as an inner core 1 of the self-repairing microspheres;

(3) adding ferroferric oxide serving as a magnetic functional component into a sugar coating machine, uniformly spraying ethanol solution in the rotation process, wherein the rotation speed of the sugar coating machine is 10r/min, the liquid spraying amount is 10ml/min, and coating a layer of magnetic component on the surface layer of the inner core of the self-repairing microsphere with the coating thickness of 0.1-0.5mm to serve as the outer core 2 of the self-repairing microsphere;

(4) adding cement into the sugar coating machine, uniformly spraying deionized water in the rotating process, coating a layer of cement with the thickness of 1.0-1.5mm on the surface layer of the outer core of the self-repairing microsphere, taking the cement as the shell 3 of the self-repairing microsphere, and maintaining for 3 days at the humidity of 90-95% and the temperature of 20-23 ℃.

(5) The method comprises the steps of replacing part of sand with multilayer core-shell structure self-repairing microspheres with the replacement rate of 1%, adding a proper amount of calcium source calcium nitrate, keeping the water cement ratio unchanged, preparing a 300mm multiplied by 30mm test piece, curing the test piece at normal temperature for 24 hours, curing the test piece at normal temperature for 7 days, then manually manufacturing a through crack with the crack width of 200 mu m through a press machine, placing the cracked test piece in a water environment, and monitoring the crack repairing effect of the cracked test piece.

Example 2

A preparation method and application of a multilayer core-shell structure self-repairing microsphere are disclosed, wherein the method comprises the following steps:

(1) inoculating bacillus mucilaginosus into a culture medium A, wherein the mass ratio of the inoculation amount to the culture medium A is 2: 100, and the culture medium A is 1000mL of deionized water, 12g of cane sugar and Na₂HPO₄·12H₂O 3g、MgSO₄ 0.6g、CaCO₃ 1.5g、KCl 0.2g、(NH₄)₂SO₄0.6g, carrying out constant-temperature shaking culture for 24 hours to obtain a culture solution A, adding a spore efficient transforming agent manganese chloride into the culture solution A, wherein the adding amount is 1g/L to obtain a microbial spore culture solution A, and carrying out spray drying to prepare a powdery microbial agent A; inoculating a yeast strain into a culture medium B, wherein the mass ratio of the inoculation amount to the culture medium B is 2: 100, the culture medium B is 1000mL of deionized water, 40g of potato powder, 10g of glucose and 10g of agar, carrying out constant-temperature oscillation culture for 24 hours to obtain a culture solution B, adding a spore efficient conversion agent manganese chloride into the culture solution B, wherein the addition amount is 5g/L to obtain a microbial spore culture solution B, carrying out spray drying to prepare a powdery microbial agent B, and mixing the microbial agent A and the microbial agent B to obtain a composite microbial bacterium; the spray drying temperature is 110 ℃, the speed is 20mL/min, and the composite microbial agent is prepared from saccharomycete powder and bacillus mucilaginosus powder according to the proportion of 1: 15;

(2) adding the compound microbial agent and aluminum sulfate into a sugar-coating machine according to the mass ratio of 1: 5, uniformly spraying an ethanol solution in the rotating process to prepare spherical particles, wherein the rotating speed of the sugar-coating machine is 50r/min, the liquid spraying amount is 20ml/min, and sieving to obtain particles with the particle size of 2.0-2.5mm as an inner core 1 of the self-repairing microspheres;

(3) adding ferroferric oxide serving as a magnetic functional component into a sugar coating machine, uniformly spraying ethanol solution in the rotating process, wherein the rotating speed of the sugar coating machine is 50r/min, the liquid spraying amount is 20ml/min, and coating a layer of magnetic component on the surface layer of the inner core of the self-repairing microsphere with the coating thickness of 0.1-0.5mm to serve as the outer core 2 of the self-repairing microsphere;

(4) adding cement into the sugar coating machine, uniformly spraying deionized water in the rotating process, coating a layer of cement with the thickness of 1.0-1.5mm on the surface layer of the outer core of the self-repairing microsphere, taking the cement as the shell 3 of the self-repairing microsphere, and maintaining for 14 days at the humidity of 90-95% and the temperature of 20-23 ℃.

(5) The method comprises the steps of replacing part of sand with multilayer core-shell structure self-repairing microspheres with a substitution rate of 10%, adding a proper amount of calcium source calcium nitrate, keeping a cement ratio of cement to be 5% of that of a cementing material, preparing a 300mm multiplied by 30mm test piece, curing the test piece at normal temperature for 24 hours, curing the test piece at normal temperature for 7 days, manually manufacturing a through crack with a crack width of 500 mu m through a press, placing the cracked test piece in a water environment, and monitoring a crack repairing effect of the cracked test piece.

Example 3

A preparation method and application of a multilayer core-shell structure self-repairing microsphere are disclosed, wherein the method comprises the following steps:

(1) inoculating bacillus mucilaginosus into a culture medium A, wherein the mass ratio of the inoculation amount to the culture medium A is 2: 100, and the culture medium A is 1000mL of deionized water, 10g of cane sugar and Na₂HPO₄·12H₂O 3g、MgSO₄ 0.5g、CaCO₃ 1.0g、KCl 0.2g、(NH₄)₂SO₄0.5g, carrying out constant-temperature shaking culture for 24 hours to obtain a culture solution A, adding a spore efficient transforming agent manganese chloride into the culture solution A, wherein the adding amount is 1g/L to obtain a microbial spore culture solution A, and carrying out spray drying to prepare a powdery microbial agent A; inoculating yeast strain into culture medium B, and inoculating and culturingThe mass ratio of the culture medium B is 2: 100, the culture medium B is 1000mL of deionized water, 40g of potato powder, 10g of glucose and 10g of agar, and the culture solution B is obtained after the culture is performed with constant temperature shaking culture for 24 hours; adding a spore efficient transforming agent manganese chloride into the culture solution B, wherein the addition amount is 2g/L to obtain a microbial spore culture solution B, and preparing a powdery microbial agent B by spray drying; mixing the microbial agent A and the microbial agent B to obtain a compound microbial bacterium; the spray drying temperature is 110 ℃, the speed is 10mL/min, and the composite microbial agent is prepared from saccharomycete powder and bacillus mucilaginosus powder according to the proportion of 1: 12;

(2) adding the compound microbial agent and aluminum sulfate into a sugar-coating machine according to the mass ratio of 1: 2, uniformly spraying an ethanol solution in the rotating process to prepare spherical particles, wherein the rotating speed of the sugar-coating machine is 30r/min, the liquid spraying amount is 15ml/min, and sieving to obtain particles with the particle size of 2.0-2.5mm as an inner core 1 of the self-repairing microspheres;

(3) adding ferroferric oxide serving as a magnetic functional component into a sugar coating machine, uniformly spraying ethanol solution in the rotating process, wherein the rotating speed of the sugar coating machine is 30r/r/min, the liquid spraying amount is 15ml/min, and coating a layer of magnetic component on the surface layer of the inner core of the self-repairing microsphere, wherein the coating thickness is 0.1-0.5mm, so that the magnetic component is used as the outer core 2 of the self-repairing microsphere;

(4) adding cement into the sugar coating machine, uniformly spraying deionized water in the rotating process, coating a layer of cement with the thickness of 1.0-1.5mm on the surface layer of the outer core of the self-repairing microsphere, taking the cement as the shell 3 of the self-repairing microsphere, and maintaining for 14 days at the humidity of 90-95% and the temperature of 20-23 ℃.

(5) The method comprises the steps of replacing part of sand with multilayer core-shell structure self-repairing microspheres with the replacement rate of 5%, adding a proper amount of calcium source calcium nitrate, keeping the water cement ratio unchanged, preparing a 300mm multiplied by 30mm test piece, curing the test piece at normal temperature for 24 hours, curing the test piece at normal temperature for 7 days, then manually manufacturing a through crack with the crack width of 300 mu m through a press machine, placing the cracked test piece in a water environment, and monitoring the crack repairing effect of the cracked test piece.

FIG. 1 shows the morphology of the self-repairing microsphere of the present invention, wherein the self-repairing microsphere cracks with crack cracking and releases the repairing components inside the microsphere during the use process.

FIG. 2 is an XRD spectrum of the fracture zone product; fig. 3 is an SEM image of the fracture zone product, showing that the fracture zone formed mineralized products, including calcite and ettringite, to fill the fracture during fracture repair.

Fig. 4 shows the crack repairing rate of the self-repairing microspheres of the invention, and the detection and comparison of the repairing effect of the crack in the test piece prepared in example 3 show that the repairing effect is gradually enhanced with the extension of the repairing time, and the area repairing rate and the water seepage resisting repairing rate are both close to 100% when the test piece is repaired for 28 days.