A curing agent with biological self-healing ability and preparation method thereof

Abstract

The present invention discloses a method for preparing a curing agent with biological self-healing ability, which comprises the following steps: first preparing a bacillus pasteurianus liquid, then preparing an endospore solution, then immersing a polyvinyl alcohol fiber in a sodium alginate / endospore solution, taking it out and immediately immersing it in a calcium acetate solution, drying it, obtaining a core fiber with a hydrogel coating, immediately immersing it in a chloroform solution of a polystyrene and polylactic acid polymer blend, drying it, obtaining a coated microbial liquid, pre-mixing urea and glucose, adding them to magnesium phosphate cement, stirring them evenly, then adding the coated microbial liquid, stirring them evenly, and obtaining the product. The present invention adopts phosphate cement as a curing agent, which has the advantages of high strength, short setting time, strong durability, low alkalinity, good biocompatibility, etc. Compared with the curing agent in the prior art, the curing agent not only has a good curing effect, but also has a crack self-healing function, and is particularly suitable for reinforcing foundation soil.

Description

Technical Field

[0001] The present invention belongs to the field of geotechnical technology, and in particular relates to a curing agent with biological self-healing ability and a preparation method thereof. Background Art

[0002] With the continued economic development and accelerated urbanization in my country, infrastructure construction is expanding, and stability issues are becoming increasingly prominent. There is an urgent need for curing agents to ensure the long-term stability of foundations, preventing them from gradually deteriorating under external loads or changes in the natural environment, leading to instability such as sliding and collapse. The traditional curing agent is ordinary Portland cement, but its production process is energy-intensive and emits large amounts of carbon dioxide, which has a serious impact on the environment. In recent years, with the widespread adoption of environmental protection concepts, the environmental pollution caused by traditional soil curing agents during construction has received increasing attention.

[0003] Against this backdrop, the demand for bio-self-healing curing agents, a new type of environmentally friendly soil curing agent, is particularly urgent. Bio-self-healing curing agents are soil curing agents made using biotechnology or biomaterials. Their mechanism of action is to stimulate the activity of microorganisms in the soil or introduce specific microorganisms to promote biochemical reactions between soil particles, thereby improving the engineering properties of the soil. Bio-self-healing curing agents can effectively solidify various types of weak foundation soils, improve land utilization, and help alleviate the current shortage of land resources. Infrastructure construction is placing increasing demands on rapid construction and long-term stability of foundation treatment technologies. Bio-self-healing curing agents offer the advantages of simple construction, fast construction, and high early strength, meeting the needs of rapid construction. At the same time, their self-healing properties ensure the stability of the foundation soil during long-term use, reducing subsequent maintenance costs.

[0004] On the other hand, magnesium phosphate cement offers a wide range of advantages compared to other cementitious materials: MPC has the ability to set and harden rapidly, meaning it can develop structural strength very quickly after construction, accelerating construction schedules; it has high early strength (compressive strength can reach 28 MPa in 1 hour and over 40 MPa in 3 hours); it can set quickly in low-temperature environments; it has high wear resistance, resisting the effects of wear and freeze-thaw cycles, making it suitable for structures exposed to harsh environments; it has a low drying shrinkage, meaning it develops fewer cracks during hardening, thereby improving structural integrity and durability; it has good fire resistance, maintaining its structural integrity even at high temperatures, an important feature for buildings with high fire protection requirements; it has a low coefficient of thermal expansion, meaning it experiences less volume change with temperature changes, thereby reducing stress and cracking caused by temperature fluctuations; and it also has low alkalinity and good biocompatibility. However, its limited long-term strength and durability significantly limit its application in practical engineering, and as a result, it is not a commonly used curing agent.

[0005] Based on this, the present invention intends to combine bio-self-healing technology with magnesium phosphate cement to provide a curing agent with bio-self-healing ability, thereby improving the long-term strength and durability of magnesium phosphate cement through bio-self-healing technology and expanding its application range. Summary of the Invention

[0006] The purpose of the present invention is to address the deficiencies of the prior art and provide a curing agent with biological self-healing ability and a preparation method thereof. The prepared curing agent has good curing effect and also has crack self-healing function.

[0007] The present invention uses low-alkalinity and biocompatible phosphate cement, to which are added coated Bacillus pasteurianus endospores, glucose, and urea. When the solidified material breaks, the microbial coating comes into contact with moisture, automatically releasing the bacterial endospores. The bacterial endospores are automatically activated upon contact with moisture and nutrients, thereby hydrolyzing urea to produce calcium carbonate minerals, thereby repairing cracks. In addition, the present invention also uses biofiber as a biological agent carrier, which can introduce crack growth control capabilities into the curing agent, not only producing a crack bridging effect, but also improving the mechanical properties after curing. The specific scheme of the present invention is as follows:

[0008] A method for preparing a curing agent with biological self-healing ability comprises the following steps:

[0009] (1) Activating Bacillus pasteurianus and inoculating it into a liquid culture medium, culturing it at 35°C and 150 rpm for 1 day to obtain a Bacillus pasteurian culture liquid, transferring the Bacillus pasteurian culture liquid to a solid culture medium containing calcium ions and phosphate, heat shocking it, and continuing to culture it at 30-37°C. After the culture is completed, scraping the bacterial lawn, suspending it with sterile water, and collecting endospores by centrifugation to obtain an endospore solution;

[0010] (2) adding sodium alginate to the endospore solution to obtain a sodium alginate / endospore solution, immersing a polyvinyl alcohol fiber in the sodium alginate / endospore solution, taking it out and immediately immersing it in a calcium acetate solution, drying it to obtain a core fiber with a hydrogel coating, and immediately immersing the core fiber with the hydrogel coating in a chloroform solution of a polystyrene and polylactic acid polymer blend, drying it and obtaining a coated microbial culture liquid;

[0011] (3) Urea and glucose are pre-mixed and added to magnesium phosphate cement. After stirring evenly, the coated microbial liquid is slowly added and stirred evenly to obtain a curing agent with biological self-healing ability.

[0012] Furthermore, in step (1), the liquid culture medium formula is: 15-20 g / L casein peptone, 5-10 g / L soy peptone, 5-10 g / L sodium chloride, 15-20 g / L urea, pH = 7.3; the solid culture medium formula is: yeast extract 5-10 g / L, tryptone 5-10 g / L, sodium chloride 5-10 g / L, agar 15-20 g / L, CaCl2·2H2O (0.5-0.8) g / L, K2HPO4 (0.1-0.2) g / L.

[0013] Furthermore, in step (1), the temperature of the heat shock treatment is 50-65° C. and the duration is 2 h.

[0014] Furthermore, in step (2), the length of the polyvinyl alcohol fiber is 25-35 mm and the diameter is 600-650 μm.

[0015] Furthermore, in step (2), the concentration of sodium alginate in the sodium alginate / endospore solution is (5-10) g / L.

[0016] Furthermore, in step (2), the concentration of the calcium acetate solution is 0.22-0.25 mol / L.

[0017] Furthermore, in step (2), the mass concentration of the chloroform solution of the polystyrene and polylactic acid polymer blend is 1%; the preparation method of the chloroform solution of the polystyrene and polylactic acid polymer blend is as follows: polystyrene is added to chloroform, stirred and heated to 50-80°C to obtain a polystyrene solution, and then polylactic acid is added, the mass ratio of polystyrene to polylactic acid is 1:1.2, and stirred until completely dissolved to obtain a chloroform solution of the polystyrene and polylactic acid polymer blend.

[0018] Furthermore, in step (3), the mass ratio of urea, glucose, coated microbial culture liquid and magnesium phosphate cement is (1-2): (0.5-1): (1-2): (95-97.5), more preferably 1.6:0.8:1.6:96.

[0019] The curing agent with biological self-healing ability is prepared by the method.

[0020] Beneficial effects of the present invention: The present invention discloses a method for preparing a curing agent with biological self-healing ability. The curing agent is prepared by mixing low-alkalinity and highly biocompatible phosphate cement with bacterial endospores coated with bacteria. Compared with curing agents in the prior art, the present invention has the following advantages:

[0021] 1) The curing agent of the present invention not only has a good curing effect, but also has a crack self-healing function.

[0022] 2) The present invention uses cross-linked alginate as a carrier of bacterial endospores, which can release bacterial endospores when exposed to water. Alginate is a hydrophilic polymer that absorbs water and swells when it encounters water. This hydration can cause the cross-linked alginate network structure to become loose, so the cross-linked alginate has the ability to release bacterial endospores when exposed to water.

[0023] 3) This invention uses polyvinyl alcohol (PVA) fiber as the core fiber to transport endospores. PVA fiber has high strength, high modulus, low elongation, abrasion resistance, acid and alkali resistance, and good weather resistance. It also has good affinity and binding properties with substrates such as cement and gypsum. This invention uses biofiber to deliver a bio-healing agent containing bacterial endospores into quasi-brittle materials such as concrete. When cracks appear in the solidified material, the bacterial endospores are activated and repair these cracks through their growth and metabolic activity, thereby endowing the concrete with self-healing properties.

[0024] 4) The present invention utilizes a mixture of polystyrene and polylactic acid copolymers as the outer impermeable layer. Polystyrene has excellent transparency and insulation properties, but is not easily degraded, which puts pressure on the environment. Polylactic acid, on the other hand, is a biodegradable plastic derived from renewable resources such as corn starch. It can be decomposed by microorganisms under certain conditions, making it environmentally friendly and commonly used in food packaging, medical implants, 3D printing materials, and the like. The present invention blends polystyrene and polylactic acid copolymers. The addition of polylactic acid improves the material's environmental friendliness, partially resolving the difficulty of polystyrene degradation. Polystyrene can also improve certain physical properties of polylactic acid, such as its impact resistance and mechanical strength. The shell is designed to withstand the soil solidification process without any rupture or unnecessary release of biological agents, breaking only when the solidified soil breaks and reaches each biofiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The ratio of calcium carbonate in the solid residue at different ages after cracks are generated in the curing agent prepared in Example 1;

[0026] Figure 2 The unconfined compressive strength test results of the curing agents of Example 1 and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments.

[0028] To clearly illustrate the present invention, in the following examples, the Bacillus pasteurianus used was purchased from Shanghai Preservation Biotechnology Center; the liquid culture medium formula used was: the liquid culture medium formula: (15-20) g / L casein peptone, (5-10) g / L soy peptone, 5-10 g / L sodium chloride, 15-20 g / L urea, pH = 7.3; the solid culture medium formula used was: yeast extract 5-10 g / L, tryptone 5-10 g / L, sodium chloride 5-10 g / L, agar 15-20 g / L, CaCl2·2H2O (0.5-0.8) g / L, K2HPO4 (0.1-0.2) g / L. The mass concentration of the chloroform solution of the polystyrene and polylactic acid polymer blend used is 1%. The preparation method of the chloroform solution of the polystyrene and polylactic acid polymer blend comprises the following steps: adding polystyrene to chloroform, stirring and heating to 50-80°C to obtain a polystyrene solution, then adding polylactic acid with a mass ratio of polystyrene to polylactic acid of 1:1.2, stirring until completely dissolved, and obtaining a chloroform solution of the polystyrene and polylactic acid polymer blend.

[0029] Example 1

[0030] A method for preparing a curing agent with biological self-healing ability comprises the following steps:

[0031] (1) After activation, Bacillus pasteurianus was inoculated into liquid culture medium and cultured at 35°C and 150 rpm for 1 day to obtain Bacillus pasteurianus liquid. The bacterial concentration was measured by absorbance test method, and the number of bacteria per milliliter was 6.57×10 7 The Bacillus pasteurianus culture liquid was transferred to a solid culture medium containing calcium ions and phosphate, and heat-shocked at 60°C for 2 hours. After the heat treatment, the culture was continued at 30-37°C. After the culture was completed, the bacterial moss was scraped, suspended with sterile water, and the endospores were collected by centrifugation to obtain an endospore solution (the concentration of the spore solution was measured to be 5.26×10 per milliliter). 7 );

[0032] (2) Sodium alginate is added to the endospore solution to obtain a sodium alginate / endospore solution, wherein the sodium alginate concentration in the sodium alginate / endospore solution is 8 g / L, and polyvinyl alcohol fibers (30 mm in length and 611 μm in diameter) are immersed in the sodium alginate / endospore solution, taken out and immediately immersed in a 0.24 mol / L calcium acetate solution, and dried at 23±1°C and a relative humidity of 30±5% for 24 hours to obtain a core fiber with a hydrogel coating, and the core fiber with the hydrogel coating is immediately immersed in a chloroform solution of a polystyrene and polylactic acid polymer blend (the mass concentration of the polystyrene and polylactic acid polymer blend is 1%), taken out and dried at 23±1°C and a relative humidity of 30±5% for 2 hours to obtain a coated microbial bacterial liquid.

[0033] (3) First prepare magnesium phosphate cement: 1) Based on the total mass of MgO, granulated blast furnace slag, ammonium dihydrogen phosphate and fly ash as 100%, add 40% MgO, 10% granulated blast furnace slag and 0.03% retarder (the retarder consists of sodium bicarbonate and sodium tripolyphosphate in a mass ratio of 1:1) into a mixer and dry mix at low speed for 2 minutes; 2) Add 20% ammonium dihydrogen phosphate, 30% fly ash and 0.03% retarder (the retarder consists of sodium bicarbonate and sodium tripolyphosphate in a mass ratio of 1:1) into a second mixer and dry mix at the same low speed for 2 minutes; 3) Slowly add 20% water into the first mixer and 15% water into the second mixer, and fully wet mix them at high speed for 2 minutes to homogenize the slurry; 4) Quickly mix the two components together and stir at high speed for 30 seconds to obtain magnesium phosphate cement;

[0034] 10 g of urea and 5 g of glucose were premixed and added to 600 g of magnesium phosphate cement, and the mixture was stirred and mixed evenly. 10 g of the coated microbial liquid prepared in step (2) was slowly added and stirred evenly to obtain a curing agent with biological self-healing ability.

[0035] The prepared curing agent with biological self-healing ability was poured into 20mm and 40mm cubes, cured in air, and then demolded. The samples were then further cured in air (temperature 20℃±2℃, humidity 60%±5%) for 28 days. After the curing was completed, some samples were taken for unconfined compressive strength testing. The test method was based on the GB-T50123-2019 geotechnical test method standard. In addition, cracks were made in some samples (before the cement hardened, a crack was pre-cut on the cement surface. The crack width was 2mm, the crack length was 10mm, and the crack depth was 5mm). A knife was used to gently scrape the sample inside the crack, and the calcium carbonate content was determined by infrared spectroscopy. The calcium carbonate content in the crack was then measured every seven days. The unconfined compressive strength was measured after healing for 28 days (GB-T50123-2019 geotechnical test method standard).

[0036] Comparative Example 1

[0037] Ordinary Portland cement was used as a comparative example.

[0038] Ordinary Portland cement was poured into 20 mm and 40 mm cubes, allowed to cure in air, and then demolded. The samples were then further cured in air (temperature 20°C ± 2°C, humidity 60% ± 5%) for 28 days. Their unconfined compressive strength was measured according to GB-T50123-2019 Geotechnical Test Methods.

[0039] Figure 1 The ratio of calcium carbonate in the solid residue at different ages after cracks are generated in the curing agent prepared in Example 1; Figure 1 It can be seen that over time, the content of calcium carbonate in the solid residues in the samples taken from the cracks has increased. This shows that microorganisms induce the production of calcium carbonate minerals, proving that the bio-self-healing curing agent has excellent biomineralization ability and strong self-healing ability.

[0040] Figure 2 The unconfined compressive strength test results of the curing agents of Example 1 and Comparative Example 1 are as follows: Figure 2 As can be seen, the unconfined compressive strength of Example 1 is 114 MPa, while the unconfined compressive strength of Comparative Example 1 is only 51 MPa, demonstrating that the curing agent prepared in Example 1 of the present invention has excellent strength properties. When cracks were artificially created in the curing agent prepared in Example 1 and then biohealed for 28 days, the results showed that the unconfined compressive strength after 28 days of self-healing was 100 MPa. Compared to the unconfined compressive strength without the cracks, it has recovered approximately 90%, demonstrating the excellent biohealing ability of the curing agent prepared in Example 1 of the present invention.

Claims

1. A method for preparing a curing agent with biological self-healing ability, characterized in that: The steps include: (1) Activating Bacillus pasteurianus and inoculating it into a liquid culture medium, culturing it at 35°C and 150 rpm for 1 day to obtain a Bacillus pasteurian culture liquid, transferring the Bacillus pasteurian culture liquid to a solid culture medium containing calcium ions and phosphate, and subjecting it to heat shock treatment. After the end of the heat shock treatment, the culture is continued at 30-37°C. After the culture is completed, the bacterial moss is scraped, suspended with sterile water, and endospores are collected by centrifugation to obtain an endospore solution; (2) adding sodium alginate to the endospore solution to obtain a sodium alginate / endospore solution, immersing a polyvinyl alcohol fiber in the sodium alginate / endospore solution, taking it out and immediately immersing it in a calcium acetate solution, drying it to obtain a core fiber with a hydrogel coating, and immediately immersing the core fiber with the hydrogel coating in a chloroform solution of a polystyrene and polylactic acid polymer blend, drying it and obtaining a coated microbial culture liquid; (3) Urea and glucose are pre-mixed and added to magnesium phosphate cement. After stirring evenly, the coated microbial liquid is slowly added and stirred evenly to obtain a curing agent with biological self-healing ability.

2. The method for preparing a curing agent having biological self-healing ability according to claim 1, wherein: In step (1), the liquid culture medium formula is: 15-20 g / L casein peptone, 5-10 g / L soy peptone, 5-10 g / L sodium chloride, 15-20 g / L urea, pH = 7.3; the solid culture medium formula is: yeast extract 5-10 g / L, tryptone 5-10 g / L, sodium chloride 5-10 g / L, agar 15-20 g / L, CaCl2·2H2O (0.5-0.8) g / L, K2HPO4 (0.1-0.2) g / L.

3. The method for preparing a curing agent having biological self-healing ability according to claim 1, characterized in that In step (1), the temperature of the heat shock treatment is 50-65° C. and the duration is 3 h.

4. The method for preparing a curing agent having biological self-healing ability according to claim 1, wherein: In step (2), the length of the polyvinyl alcohol fiber is 25-35 mm and the diameter is 600-650 μm.

5. The method for preparing a curing agent having biological self-healing ability according to claim 1, characterized in that In step (2), the concentration of sodium alginate in the sodium alginate / endospore solution is (5-10) g / L.

6. The method for preparing a curing agent having biological self-healing ability according to claim 1, characterized in that In step (2), the concentration of the calcium acetate solution is 0.22-0.25 mol / L.

7. The method for preparing a curing agent with biological self-healing ability according to claim 1, wherein: The mass concentration of the chloroform solution of the polystyrene and polylactic acid polymer blend is 1%. The preparation method of the chloroform solution of the polystyrene and polylactic acid polymer blend comprises the following steps: adding polystyrene to chloroform, stirring and heating to 50-80° C. to obtain a polystyrene solution, then adding polylactic acid with a mass ratio of polystyrene to polylactic acid of 1:1.2, stirring until completely dissolved, and obtaining a chloroform solution of the polystyrene and polylactic acid polymer blend.

8. The method for preparing a curing agent having biological self-healing ability according to any one of claims 1 to 7, characterized in that: In step (3), the mass ratio of the urea, glucose, coated microbial culture liquid and magnesium phosphate cement is (1-2): (0.5-1): (1-2): (95-97.5).

9. A curing agent with biological self-healing ability prepared by the method according to any one of claims 1 to 8.

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