Concrete crack self-repairing material based on microorganism immobilization and preparation method thereof

Abstract

The invention discloses a concrete crack self-repairing material based on microorganism immobilization and a preparation method of the concrete crack self-repairing material, and belongs to the crossing field of microorganism materials and civil engineering. The material is prepared from peptone, sodium lactate, volcanic rock, bacillus pasteurii and other raw materials through the steps of culture medium preparation, carrier modification, microorganism immobilization, microcapsule and gel protection layer formation and the like, the prepared volcanic rock-chitosan carrier provides an inhabiting environment for microorganisms, and the survival rate of the microorganisms in a high-alkali environment is increased to 70%. When the concrete cracks and the alkaline environment triggers the protective layer to disintegrate, the bacillus pasteurii and the desulfurization vibrio are subjected to a reduction reaction with sulfate through urealysis, and calcium carbonate and calcium sulfide are generated to fill cracks. The 28-day repair rate of the material is larger than or equal to 99%, the maximum crack repair width reaches 1.2 mm, the compressive strength recovery rate is larger than or equal to 85%, excellent durability and environment friendliness are achieved, and the concrete crack repair problem is effectively solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of microbial materials and civil engineering, and particularly relates to a concrete crack self-repairing material based on microbial immobilization and a preparation method thereof. BACKGROUND

[0002] As one of the most widely used materials in the field of construction, concrete is extremely common in the process of long-term use due to the influence of various factors. Under the action of load, whether it is the direct stress generated by conventional static and dynamic load or the secondary stress caused by it, it may cause cracks in concrete structures. Such cracks often occur in areas subjected to tension, shear or strong vibration, and in severe cases may even become a precursor to structural failure. Temperature changes should not be overlooked either. The thermal expansion and contraction characteristics of concrete make it prone to stress exceeding its tensile strength when its deformation is constrained under the influence of environmental temperature fluctuations or internal hydration heat, thereby forming temperature cracks. In structures such as long-span bridges, the influence of temperature stress is particularly significant. When internal constraints cause the surface concrete to bear tensile force beyond its limit, cracks will appear, presenting a crisscrossing pattern of cracks. In addition, foundation deformation, steel corrosion, frost heaving, and problems with construction materials and process quality are all potential causes of concrete cracks. In the face of concrete cracks, traditional repair methods have numerous drawbacks. The surface mortar method requires chiseling the surface of the concrete near the cracks, which is a complex process and only suitable for shallow cracks, with the repair effect not lasting long. The surface epoxy cement or epoxy glass cloth method, while enhancing the strength of the cracks to some extent, requires strict base treatment, and if the drying is not sufficient, the bonding effect will be greatly reduced. The surface strip method is mainly used for active cracks with waterproofing needs, but it has limited adaptability to crack movement range, and the sealing strip may degrade over time, reducing its waterproofing performance. The grouting method, as a commonly used repair method, requires the use of grouting equipment, which not only has high equipment costs but also makes it difficult to precisely control the injection pressure for different cracks and repair materials. High pressure may cause secondary damage to the concrete structure, while low pressure may not guarantee the repair effect. These traditional methods not only consume a large amount of manpower, material resources and time, but also often have unsatisfactory repair effects, making it difficult to fundamentally solve the problem of concrete cracks and meet the high requirements of modern architecture for structural durability and stability. In view of the difficulties of traditional repair methods, concrete self-repairing technology has emerged. Self-repairing concrete aims to mimic the self-healing properties of living organisms, enabling concrete materials to automatically heal cracks and restore structural performance through internal repair mechanisms after cracks occur. The emergence of concrete self-repairing technology has brought new hope for solving the problem of concrete cracks. Therefore, to solve the problem of changes in overall system strength caused by cracks due to stress and thermal expansion and contraction in the existing technology, the present application provides a concrete crack self-repairing material based on microbial immobilization and a preparation method thereof. SUMMARY

[0003] To solve the problem of the change of the overall system strength due to cracks caused by stress, thermal expansion and contraction.

[0004] To solve the above problems, the present application provides the following technical solutions:

[0005] A concrete crack self-repairing material based on microorganism solid carrier, comprising the following components:

[0006] 10g / L protein 1-2 parts, 3g / L sodium lactate 1-2 parts, 5g / L yeast extract 1-2 parts, 10g / L NaCl 1-2 parts, volcanic rock (1-3mm) 10-15 parts, Bacillus pasteurii 1-2 parts, Desulfovibrio 3-5 parts, glucose 1-2 parts, calcium phosphate 1-2 parts, 1% trisodium citrate 0.5-1 part, 1% sodium alginate 0.5-1 part, 1% gelatin 0.5-1 part, 1-2% sodium bicarbonate 0.5-1 part, 3-7% chitosan solution 0.5-1 part, arabic gum-malt dextrin solution.

[0007] Preferably, the specific surface area of the prepared volcanic rock-chitosan carrier is 20-30m 2 / g, and the bulk density is 100-120kg / m 3 .

[0008] Preferably, the porous structure of the modified carrier and the chitosan coating can improve the survival rate of microorganisms in the high-alkali environment of concrete to 70%, and the interlocking deposition structure is formed by the synergistic effect of Bacillus pasteurii and Desulfovibrio.

[0009] A method for preparing a concrete crack self-repairing material based on microorganism solid carrier, comprising the following steps:

[0010] S1: mixing protein, yeast extract and NaCl to obtain LB culture medium, then adding Bacillus pasteurii, and culturing at 30℃ for 24h, adjusting the concentration of the bacterial suspension to 5.0x10 8 cells / mL;

[0011] S2: mixing sodium lactate, yeast extract and ammonium sulfate to obtain anaerobic culture medium, then adding Desulfovibrio, and culturing anaerobically at 35℃ for 48h, adjusting the concentration of the bacterial suspension to 3.0x10 8 cells / mL;

[0012] S3: selecting volcanic rock with a particle size and porosity of ≥40%, soaking in hydrochloric acid, then washing to neutral, improving the degree of surface hydroxylation, then mixing with chitosan solution, and setting the inlet air temperature to 180℃, the outlet air temperature to 80℃, and the spray drying time to 30 minutes;

[0013] S4: The volcanic rock-chitosan carrier was mixed with the suspension of Bacillus pasteurianus and Desulfovibrio spp., and centrifuged for 15 min. After adsorption, it was dried at a constant temperature of 60°C for 2 h to form a bacterial complex.

[0014] S5: Using a complex coacervation method, the nutrients are mixed with a gum arabic-maltodextrin solution, and acetic acid solution is added dropwise until the pH reaches 4.5 to form microcapsules, which are then mixed evenly with the bacterial carrier;

[0015] S6: Sodium alginate, gelatin, and sodium bicarbonate are added with water to prepare a slurry, the bacteria-nutrient complex is immersed in the slurry, and cross-linked and cured with a CaCl2 solution for 1 hour to form a gel protective layer with a thickness of 50 μm. After natural curing, it is dried to a constant weight;

[0016] S7: Add the treated carrier at 12% of the weight of the concrete raw materials, then stir and shape it and then cure it. When the concrete cracks, the alkaline environment at the cracks triggers the collapse of the protective layer, and microorganisms and nutrients are released. Calcium carbonate and calcium sulfide are generated through urealysis and sulfate reduction reactions to fill the cracks.

[0017] Preferably, the calcium carbonate and calcium sulfide produced by the synergistic action of S4 Pasteurella and Desulfovibrio form an interlocking sediment structure.

[0018] Preferably, the mixture in S4 is a mixture of carrier and bibacterial suspension in a ratio of 1:5, followed by centrifugation at 3000 r / min for 15 min, and after drying, the bacterial load is measured to be ≥ 2.5 × 10 8 cells / g.

[0019] Preferably, after the nutrient microcapsules in S6 are mixed with the bacteria-carrying carrier, they are wrapped with a sodium alginate-gelatin protective layer, and the disintegration rate of the protective layer reaches 90% within 24 hours under the condition of pH=12.

[0020] Preferably, S6 introduces a pH-sensitive sodium alginate-gelatin protective layer, which directionally collapses and releases microorganisms in the alkaline environment of the crack, solving the problem of insufficient alkaline tolerance of traditional packaging materials.

[0021] Preferably, the crack repair width of S7 repair reaches a maximum of 1.2mm, an increase of 30%, the average repair width reaches 1.0mm, and the concrete compressive strength recovery rate is ≥85%, an increase of 15%.

[0022] Preferably, the repair crack closure rate in S7 is 100%, the compressive strength is restored from 45 MPa after cracking to 58 MPa, and the compressive strength loss rate is 22% after 70 cycles of sulfate attack.

[0023] The present invention provides a microbial-based concrete crack self-repairing material and its preparation method, and its effects and advantages:

[0024] 1、This patent, the method is prepared by carefully designing the raw material ratio and process, the physical properties of the material are significantly improved by making the composite carrier of volcanic rock and chitosan, after the treatment of hydrochloric acid and the compounding of chitosan, the mechanical strength of the carrier is enhanced, and the rich pore structure provides a good habitat for microorganisms, ensuring the survival and activity of microorganisms in the concrete, so that the self-repairing material has a stable physical support basis.

[0025] 2、This patent, the two kinds of microorganisms are compounded by selecting bacillus pasteurii and desulfovibrio, the urea decomposition reaction and sulfate reduction reaction are carried out, respectively, to generate calcium carbonate and calcium sulfide, when the alkaline environment triggers the disintegration of the protective layer at the concrete crack, the microorganisms and nutrients are rapidly released, and the filling material is quickly generated at the crack to effectively fill the crack and prevent water and harmful substances from entering, thereby repairing the concrete structure damage from the root and improving the durability of concrete.

[0026] 3、This patent, the microcapsules prepared by the complex coagulation method are mixed with the nutrient substances and the bacteria-carrying carrier in a scientific ratio, the release of the nutrient substances can be accurately controlled to ensure the continuous nutrient supply of the microorganisms in the repair process, the gel protective layer made of sodium alginate and gelatin can effectively isolate external interference and protect the microorganisms and nutrient substances during normal use of concrete, and when cracks occur and the alkaline environment triggers, the gel protective layer can quickly disintegrate and release the repair components to realize intelligent response repair.

[0027] 4、This patent, each experimental step parameter is clear, from the preparation of culture medium and the culture conditions of microorganisms to the treatment of carrier, microorganism adsorption and the formation of protective layer, specific temperature, time, rotation speed and other operation conditions are set, so that the preparation process is easy to control and has high repeatability, whether it is laboratory research or industrial production, the stability of product quality can be guaranteed, and the uncertainty and cost in the production process are reduced.

[0028] 5、This patent, after the self-repairing material is mixed into concrete at a reasonable proportion, the formed concrete structure has the ability of self-repairing cracks, not only reduces the cost of artificial detection and maintenance, but also effectively delays the aging of concrete structure and prolongs the service life, so that it has wide application prospect in the fields of bridge, tunnel and building, and improves the comprehensive value of concrete material in infrastructure construction. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a preparation method flow chart of a concrete crack self-repairing material based on microbial immobilization in the application;

[0030] Figure 2 It is a schematic diagram of a microbial concrete crack self-repairing material in the application;

[0031] Figure 3It is a macroscopic schematic diagram of concrete prepared by the application. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, and not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0033] It should be noted that, in this document, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between the entities or operations, and the terms “include”, “contain” or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitation, the elements defined by the statement “include” do not exclude the presence of other identical elements in the process, method, article or equipment including the elements.

[0034] Embodiment 1

[0035] This embodiment provides a preparation method of a microorganism immobilization-based concrete crack self-repairing material, which is suitable for concrete self-repairing, and the following implementation content is provided.

[0036] Experimental purposes:

[0037] Preparation of a microorganism immobilization-based concrete crack self-repairing material.

[0038] Experimental raw materials:

[0039] 10g / L proteose peptone 1 part, 3g / L sodium lactate 1 part, 5g / L yeast extract 1 part, 10g / L NaCl 1 part, volcanic rock (1-3mm) 10 parts, Bacillus pasteurii 1 part, Desulfovibrio 5 parts, glucose 1 part, calcium phosphate 1 part, 3% trisodium citrate 0.5 parts, 2% sodium alginate 0.5 parts, 1% gelatin 0.5 parts, 1% sodium bicarbonate 0.5 parts, 5% chitosan solution 0.5 parts, arabic gum-malt dextrin solution.

[0040] Experimental steps:

[0041] S1: mixed protein peptone 10 g / L, yeast extract 5 g / L, NaCl 10 g / L to obtain LB culture medium, then added Bacillus pasteurii, 30℃ oscillation culture for 24h, the concentration of bacterial suspension was adjusted to 5.0×10 8 cells / mL;

[0042] S2: mixed sodium lactate 3 g / L, yeast extract 1 g / L, ammonium sulfate 0.5 g / L to obtain anaerobic culture medium, then added Desulfovibrio, 35℃ anaerobic culture for 48h, the concentration of bacterial suspension was 3.0×10 8 cells / mL;

[0043] S3: screened the volcanic rock with particle size of 1-3mm (porosity≥40%), soaked in 10% hydrochloric acid for 2h, then washed with water to neutral, improved the degree of surface hydroxylation, then mixed with 5% chitosan solution, the weight ratio of volcanic rock to chitosan solution was 1:8, the spray drying was carried out at the inlet temperature of 180℃ and the outlet temperature of 80℃ to form the composite carrier, the bulk density reached 120kg / m 3 ;

[0044] S4: mixed the volcanic rock-chitosan carrier with Bacillus pasteurii and Desulfovibrio bacterial suspension at a weight ratio of 1:5, the centrifugal adsorption method with the rotation speed of 3000r / min was used for 15min, the carrier was dried at 35℃ for 4h after adsorption to form the bacteria-loaded composite;

[0045] S5: using complex coacervation method, mixed the nutrients with 10% arabic gum-malt dextrin solution at a weight ratio of 1:2, added 3% acetic acid solution dropwise to pH=4.5, formed the microcapsules with core material diameter of 5-10μm, mixed the bacteria-loaded carrier with the microcapsules at a weight ratio of 3:10;

[0046] S6: prepared the slurry by adding sodium alginate 2%, gelatin 1%, sodium bicarbonate 1% into water, immersed the bacteria-loaded-nutrient composite into the slurry, crosslinked and solidified for 1-2h by CaCl2 solution to form the gel protective layer with thickness of 50-100μm, after natural curing for 12h, dried at 40℃ to constant weight;

[0047] S7: mixed the treated carrier at 5-12% of the weight of concrete raw materials, then stirred at the rotation speed of 150r / min for 3min, after molding, standard curing for 28d, when the concrete cracked, the alkaline environment (pH>12) at the crack triggered the disintegration of the protective layer, the microorganisms and nutrients were released, through urea hydrolysis reaction and sulfate reduction reaction, calcium carbonate and calcium sulfide were generated to fill the cracks.

[0048] The porous structure of the modified carrier and the chitosan coating can protect the microorganisms to survive in the high-alkali environment of concrete, and the survival rate is increased to more than 70%; the crack repair width is up to 1.2 mm, and the average repair width is 0.8-1.0 mm; the compressive strength recovery rate of concrete is greater than or equal to 85%; the composite deposition product can reduce the loss of compressive strength under sulfate erosion by 40%; and the number of anti-freeze-thaw cycles is increased to more than 200 times. The slurry prepared by mixing sodium alginate and gelatin with water is a biodegradable material, and there is no secondary pollution.

[0049] Comparative Example 1

[0050] The embodiment provides an effect of a traditional concrete crack self-repairing material and a preparation method thereof, and is suitable for a field of using traditional concrete. The following implementation content is provided:

[0051] Experimental purposes:

[0052] Preparation of a traditional concrete crack self-repairing material.

[0053] Experimental raw materials:

[0054] P·O 42.5 ordinary portland cement, natural river sand as fine aggregate, fly ash (grade II), slag powder (S95 grade), epoxy resin, ettringite concrete expansive agent, polycarboxylic acid water reducer

[0055] Experimental steps:

[0056] S1: According to the experimental purposes and the related standards, the concrete with different mixing proportions is designed, for example, the water-binder ratio is 45%, the sand ratio is 38%, and different types and amounts of self-repairing materials are added;

[0057] S2: A forced mixer is used for stirring, the dry materials such as cement, aggregate and self-repairing material are first put into the mixer, and then the pre-calculated water and additive are added, and the stirring is continued for 2-3 minutes until the concrete mixture reaches a uniform and workable state;

[0058] S3: The stirred concrete mixture is quickly loaded into a 100mm×100mm×400mm rectangular test mold, and is loaded in two layers, each layer is inserted and tamped 25 times with a tamping rod and a spatula along the inner wall of the test mold to remove air bubbles, and then the surface is polished with a spatula after the mold is loaded and vibrated for 15-30 seconds with a vibration table so that the concrete surface is slurry and has no obvious air bubbles;

[0059] S4: After the test piece is formed, it is placed in a standard curing room with a temperature of 20 DEG C and a relative humidity of greater than 95% for 1-2 days, and then demolded and continued to be cured under standard curing conditions until the specified age;

[0060] S5: After the curing period, place the test piece on the pressure testing machine and slowly apply a load at a rate of 0.1 MPa / s until visible cracks appear on the test piece. Measure the crack width using a crack width observation instrument. When the crack width reaches 0.2-0.3 mm, stop loading and record the location, direction and width of the crack.

[0061] S6: For some test pieces, dry shrinkage-induced cracks can be used. Place the cured test piece in a dry environment with a temperature of 20°C and a relative humidity of 60%. Measure the length change of the test piece regularly. As the water evaporates, the concrete will shrink, and when the shrinkage stress exceeds the tensile strength of the concrete, cracks will appear on the surface of the test piece. Record the relevant information of the cracks.

[0062] The traditional concrete crack self-repairing material in Comparative Example 1 is prepared by mixing fly ash, slag powder and other mineral admixtures, and epoxy resin microcapsules, and ettringite expanding agent. Three days after cracking, the secondary hydration of the mineral admixtures generates a small amount of product, the crack width is reduced by 5-10%, and the strength recovery is less than 10%. 7-14 days later, the hydration product increases and the crack repair is 20-30% of the initial value, and the strength recovery is 15-25%. At 28 days, the average repair of cracks less than 0.2 mm is 60-70%, and the compressive strength recovery is 50-60%. However, the structure of the repair layer is loose and the interface with the matrix is weak. Its repair depends on the environmental humidity, and the effect on cracks larger than 0.3 mm is poor. The durability indicators such as impermeability and frost resistance are lower than those of the microbial self-repairing material. Moreover, the compatibility of epoxy resin with concrete is poor, the expanding agent is prone to secondary cracking, and the overall repair efficiency and effect are limited.

[0063] Comparative Example 2

[0064] A concrete self-repairing method using shape memory alloy fibers and nano calcium carbonate is provided, which is suitable for concrete scenes that need self-repairing. The following implementation content is provided:

[0065] Experimental materials:

[0066] P·O 52.5 Portland cement, machine-made sand, nickel-titanium alloy fiber, nano calcium carbonate particles, polycarboxylate superplasticizer.

[0067] Experimental purpose:

[0068] Preparation of shape memory alloy fiber and nano calcium carbonate composite concrete.

[0069] Experimental steps:

[0070] S1: The orthogonal test design method is used to determine the optimal mix proportion of the concrete. Taking water-binder ratio of 35% and sand ratio of 35-40% as the benchmark, different experimental groups of shape memory alloy fiber content and nano calcium carbonate content are set. Through the test of the fluidity, strength and self-repairing performance of the concrete, the optimal mix proportion is selected; S2: The double-shaft forced mixer is used for stirring. The cement, aggregate and nano calcium carbonate are dry mixed for 1-2 minutes to make the materials uniformly mixed, then the shape memory alloy fiber is added and dry mixed for another 0.5-1 minute to prevent the fiber from clumping, and then the pre-prepared water reducing agent and air entraining agent solution are added and stirred for 2-3 minutes until the concrete mixture has good workability and uniformity, and the slump is controlled at 120-160mm;

[0071] S3: The stirred concrete mixture is poured into a 150mmx150mmx150mm cubic test mold or a 100mmx100mmx400mm prism test mold, and is compacted by using a vibration table with a vibration time of 20-30 seconds. After the surface slurry is discharged and no air bubbles overflow, the surface is smoothed with a spatula. After the test piece is formed, it is placed in a standard curing room with a temperature of 20°C and a relative humidity of more than 95% for 1-2 days, then demolded and continuously cured under standard curing conditions until the 28-day age;

[0072] S4: The four-point bending loading test is used to induce cracks in the cured prism test piece. At different time points after the crack induction, the crack width observation instrument is used to measure the crack width change, the crack healing situation is recorded, the optical microscope and scanning electron microscope are used to observe the microstructure at the crack, and the restraining effect of the shape memory alloy fiber and the filling effect of the nano calcium carbonate are analyzed.

[0073] In the comparative example 2, through SEM observation, at the initial stage of crack generation, the crack interface is rough and there are a large number of pores and microcracks. With the passage of repair time, a small amount of tiny crystals can be seen adhering to the crack surface at 3 days, the number of crystals increases at 7 days, and they begin to connect with each other. At 14 days, a relatively continuous crystal filling layer is formed in the crack; at 28 days, the crack is almost completely filled with dense hydration products and calcium carbonate crystals, and the interface transition zone with the surrounding concrete matrix is obviously improved, and the structure is more dense. At the same time, the adhesion between the shape memory alloy fiber and the concrete matrix is good, and the fiber is uniformly distributed in the concrete, effectively enhancing the integrity of the concrete.

[0074] Reference Figure 1 , Figure 3The modified volcanic rock-chitosan composite carrier used in Example 1 has both porous adsorption and biocompatibility, avoids the patent restriction of coral calcium sand, and is combined with Bacillus pasteurii and Desulfovibrio to synergistically promote the deposition of calcium carbonate and calcium sulfide, thereby improving the repair strength and releasing the microorganisms in the alkaline environment of the cracks to solve the problem of insufficient alkaline tolerance of traditional wrapping materials.

[0075] Reference Figure 2 The concrete crack self-repairing material based on microbial immobilization in Example 1 is prepared through a series of steps such as culture medium preparation, carrier modification and microbial immobilization by carefully blending 10 g / L proteose peptone, volcanic rock, Bacillus pasteurii and other raw materials. The volcanic shell-chitosan carrier is used to improve the survival rate of microorganisms in an alkaline environment of more than 70%. When the concrete cracks, the alkaline environment triggers the disintegration of the protective layer, and the microorganisms are released after ureolysis and sulfate reduction reaction to generate calcium carbonate and calcium sulfide to fill the cracks. The repair effect is 5-10% after 3 days, the repair rate is ≥99% after 28 days, the maximum crack repair width is 1.2 mm, the average is 0.8-1.0 mm, the compressive strength recovery rate is ≥85%, and it has excellent durability and environmental friendliness.

[0076] Comparative Example 1 uses a traditional method to prepare self-repairing concrete by mixing fly ash, slag powder, epoxy resin and other raw materials based on P·O 42.5 cement. The repair is achieved by relying on the slow secondary hydration of mineral admixtures, the release of repair agents by epoxy resin microcapsules and the action of expanding agents, but the repair process is slow, the repair is only 2-5% after 3 days, and the repair is only 60-70% after 28 days. The structure of the repair layer is loose, the repair of wide cracks is poor, the compatibility of epoxy resin is poor, the expanding agent easily causes secondary cracking, and the durability is poor.

[0077] Comparative Example 2 combines shape memory alloy fibers with nano calcium carbonate, optimizes the mix ratio through orthogonal test, and prepares concrete through stirring, molding and curing. Nano calcium carbonate participates in the hydration reaction to fill the cracks, and shape memory alloy fibers constrain the crack expansion under temperature changes. The repair effect is 15-25% after 3 days and 80-90% after 28 days. Although it can improve the structure of concrete, it lacks an active repair mechanism, the repair effect is greatly affected by environmental temperature, and the repair capacity for deep cracks is limited.

[0078] Comparative Example 1, Comparative Example 1 and Comparative Example 2, Example 1 is significantly better than Comparative Examples 1 and 2 in repair efficiency and effect, and the repair rate after 28 days is 19-29 percentage points higher than that of the two. In terms of durability, it has excellent resistance to sulfate attack and freeze-thaw cycle performance, far exceeding traditional materials. At the same time, the microbial self-repairing of Example 1 is an active response type repair, which has better environmental adaptability than Comparative Example 2, and uses biodegradable materials, which is green and pollution-free. The comprehensive performance is excellent.

[0079] Those skilled in the art can understand that the modules and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized in electronic hardware or a combination of computer software and electronic hardware, and whether the functions are realized in hardware or software manner depends on the specific application and design constraints of the technical solutions, and a person skilled in the art can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0080] In addition, each functional module in each embodiment of the present application can be integrated in one processing module, or each module can exist physically alone, or two or more modules can be integrated in one module.

[0081] The above is merely specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be included in the protection scope of the present application, therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0082] Finally: the above is only the preferred embodiment of the present application, and is not used to limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection of the present application.

Claims

1. A concrete crack self-repairing material based on microbial immobilization, characterized in that: Includes the following components: 1-2 parts of 10g / L peptone, 1-2 parts of 3g / L sodium lactate, 1-2 parts of 5g / L yeast extract, 1-2 parts of 10g / L NaCl, 10-15 parts of volcanic rock (1-3mm), 1-2 parts of Bacillus pasteurianus, 3-5 parts of Desulfovibrio, 1-2 parts of glucose, 1-2 parts of calcium phosphate, 0.5-1 part of 1% trisodium citrate, 0.5-1 part of 1% sodium alginate, 0.5-1 part of 1% gelatin, 0.5-1 part of 1-2% sodium bicarbonate, 0.5-1 part of 3-7% chitosan solution, and gum arabic-maltodextrin solution.

2. A microbial-based self-repairing material for concrete cracks according to claim 1, characterized in that: The specific surface area of ​​the prepared volcanic rock-chitosan carrier reaches 20-30m 2 / g, bulk density is 100-120kg / m 3 .

3. The microbial-based self-repairing material for concrete cracks according to claim 1, characterized in that: The porous structure of the modified carrier and the chitosan coating increase the survival rate of microorganisms in the high-alkali environment of concrete to 70%, and Bacillus pasteurianus and desulfurization vibrio synergistically form an interlocking deposition structure.

4. A method for preparing a concrete crack self-repairing material based on microbial immobilization, characterized in that: The following steps are involved: S1: Mix peptone, yeast extract, and NaCl to obtain LB medium, then add Bacillus pasteurianus and culture at 30°C with shaking for 24 h. The concentration of the bacterial suspension is adjusted to 5.0 × 10 8 cells / mL; S2: Sodium lactate, yeast extract, and ammonium sulfate were mixed to obtain an anaerobic culture medium. Desulfovibrio was then added and cultured anaerobically at 35°C for 48 h. The bacterial suspension concentration was 3.0 × 10 8 cells / mL; S3: Screen volcanic rocks with a porosity of ≥40%, soak them in hydrochloric acid and then wash them with water until they are neutral to increase the degree of surface hydroxylation. Then, mix the volcanic rocks with chitosan solution and spray dry them for 30 minutes at an inlet air temperature of 180°C and an outlet air temperature of 80°C. S4: The volcanic rock-chitosan carrier was mixed with the suspension of Bacillus pasteurianus and Desulfovibrio spp., and centrifuged for 15 min. After adsorption, it was dried at a constant temperature of 60°C for 2 h to form a bacterial complex. S5: Using a complex coacervation method, the nutrients are mixed with a gum arabic-maltodextrin solution, and acetic acid solution is added dropwise until the pH reaches 4.5 to form microcapsules, which are then mixed evenly with the bacterial carrier; S6: Sodium alginate, gelatin, and sodium bicarbonate are added with water to prepare a slurry, the bacteria-nutrient complex is immersed in the slurry, and cross-linked and cured with a CaCl2 solution for 1 hour to form a gel protective layer with a thickness of 50 μm. After natural curing, it is dried to a constant weight; S7: Add the treated carrier at 12% of the weight of the concrete raw materials, then stir and shape it and then cure it. When the concrete cracks, the alkaline environment at the cracks triggers the collapse of the protective layer, and microorganisms and nutrients are released. Calcium carbonate and calcium sulfide are generated through urealysis and sulfate reduction reactions to fill the cracks.

5. The method for preparing a concrete crack self-repairing material based on microbial immobilization according to claim 4, characterized in that: The calcium carbonate and calcium sulfide produced by the synergistic action of S4 Bacillus pasteurianus and Desulfovibrio form an interlocking sedimentary structure.

6. The method for preparing a concrete crack self-repairing material based on microbial immobilization according to claim 4, characterized in that: The mixture in S4 was a mixture of carrier and bibacterial suspension in a ratio of 1:5, and then centrifuged at 3000 r / min for 15 min. After drying, the bacterial load was measured to be ≥2.5×10 8 cells / g.

7. The method for preparing a concrete crack self-repairing material based on microbial immobilization according to claim 4, characterized in that: After the nutrient microcapsules in S6 are mixed with the bacteria-carrying carrier, they are wrapped with a sodium alginate-gelatin protective layer. Under the condition of pH = 12, the disintegration rate of the protective layer reaches 90% within 24 hours.

8. The method for preparing a concrete crack self-repairing material based on microbial immobilization according to claim 4, characterized in that: S6 introduces a pH-sensitive sodium alginate-gelatin protective layer, which directionally collapses and releases microorganisms in the alkaline environment of the crack, solving the problem of insufficient alkaline tolerance of traditional packaging materials.

9. The method for preparing a concrete crack self-repairing material based on microbial immobilization according to claim 4, characterized in that: The maximum crack repair width of S7 is 1.2mm, an increase of 30%, and the average repair width is 1.0mm. The concrete compressive strength recovery rate is ≥85%, an increase of 15%.

10. The method for preparing a concrete crack self-repairing material based on microbial immobilization according to claim 4, characterized in that: The repair crack closure rate in S7 was 100%, and the compressive strength recovered from 45 MPa after cracking to 58 MPa. After 70 cycles of sulfate attack, the compressive strength loss rate was 22%.

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