Carbonization maintenance microorganism self-repairing fiber reinforced material and preparation method thereof

Abstract

The invention discloses a carbonization maintenance microorganism self-repairing fiber reinforced material and a preparation method thereof. The preparation method of the carbonization maintenance microbial self-repairing fiber reinforced material comprises the following steps: wrapping microbial spores, urea and a growth promoter in pH responsive hydrogel to obtain pH responsive microbial composite microcapsules; uniformly mixing the gelling material rich in the calcium silicate mineral phase, the pH-responsive microbial composite microcapsule, fibers and water to obtain a mixture; and carrying out molding and carbonization maintenance on the mixture to obtain the carbonization maintenance microorganism self-repairing fiber reinforced material. According to the invention, efficient production, excellent initial mechanical properties, dynamic self-repairing and full-life-cycle carbon sequestration of the material are synchronously realized through cooperation of rapid carbonization maintenance in a manufacturing stage and microbial induced mineralization in a using stage. The method is simple in preparation process and mild in condition, and can be widely applied to the fields of building boards, components and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, and particularly relates to a carbonation curing microbial self-repairing fiber reinforced material and a preparation method thereof. BACKGROUND

[0002] As the main building and structural materials, the durability and the whole life cycle carbon emission of fiber reinforced cement-based materials are concerned. At present, the technical path to improve the sustainability of such building and structural materials mainly includes two types: one is to fix carbon in the manufacturing stage, such as using carbonation curing or using industrial solid waste to replace traditional cement-based materials; the other is to give the material self-repairing ability to prolong its service life. However, both of these two types of technologies have significant bottlenecks. The carbon fixation technology in the manufacturing stage has a high-efficiency carbon fixation behavior which is highly concentrated in the carbonation process of material forming. Although the material can still have a natural carbonation reaction with CO2 in the atmosphere in the later use, this process is very slow and inefficient, and its contribution to the whole life cycle carbon emission reduction of the material is very limited, which is essentially a static carbon fixation mode. At the same time, the microcracks generated in the long-term service of the material will accelerate its performance degradation, shorten its service life, and indirectly increase the carbon emission. In the self-repairing technology, the microbial induced calcium carbonate precipitation technology (MICP) shows great potential. However, the existing MICP application scheme has an unavoidable shortcoming: the mainstream method directly mixes the active bacteria solution into the cement-based material, and the microorganism directly faces the strong mechanical shear force, high alkaline environment (pH>12) and other harsh survival conditions in the material mixing and early curing stage, which leads to the rapid death of the microorganism and makes the self-repairing function of the material difficult to last. In addition, this method belongs to a one-time consumption strategy and cannot cope with the repeated damage of the material.

[0003] Therefore, it is urgent to develop an innovative material system and preparation method which can ensure the long-term survival of microorganisms, trigger the self-repairing mechanism on demand, and deeply integrate the self-repairing process with the whole life cycle carbon fixation. SUMMARY

[0004] The present application aims to overcome the above technical deficiencies and provides a carbonation curing microbial self-repairing fiber reinforced material and a preparation method thereof, which solves the technical problems of low carbon fixation efficiency in the later use of the material based on the carbon fixation technology in the manufacturing stage, the accelerated performance degradation caused by the microcracks generated in the long-term service of the material, and the rapid death of microorganisms in the material based on the microbial induced calcium carbonate precipitation technology, which leads to the difficulty of lasting self-repairing function and the inability to cope with the repeated damage of the material.

[0005] In a first aspect, the present application provides a preparation method of a carbonation curing microbial self-repairing fiber reinforced material, which comprises the following steps: S1, the microbial spores, urea and growth promoter are wrapped in the pH responsive hydrogel to obtain pH responsive microbial composite microcapsules; S2, the cementing material rich in calcium silicate mineral phase, the pH responsive microbial composite microcapsules, fibers and water are uniformly mixed to obtain a mixture; S3, the mixture is shaped and carbonized and cured to obtain the carbonized and cured microbial self-repairing fiber reinforced material.

[0006] In a second aspect, the present application provides a carbonized and cured microbial self-repairing fiber reinforced material, which is obtained by the preparation method of the carbonized and cured microbial self-repairing fiber reinforced material provided in the first aspect of the present application.

[0007] Compared with the prior art, the present application has the following beneficial effects: The present application uses carbonized curing as the main curing method, which not only quickly imparts initial strength to the material and realizes carbon sequestration during manufacturing, but more importantly, the weak alkaline and dense matrix environment formed thereby creates necessary conditions for long-term dormancy of microbial spores; when the material is subjected to stress and microcracks are generated, local pH changes caused by the invasion of environmental CO2 and moisture activate the built-in microorganisms in the material, absorb CO2 in the environment and induce calcium carbonate precipitation to complete material self-repairing, realizing continuous carbon sequestration and material self-repairing during use. The present application realizes efficient production of materials, excellent initial mechanical properties, dynamic self-repairing and whole life cycle carbon sequestration through the cooperation of rapid carbonized curing during manufacturing and microbial induced mineralization during use. The preparation process of the present application is simple and the conditions are mild, and the present application can be widely applied in the fields of building boards and components. DETAILED DESCRIPTION

[0008] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with reference to examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0009] In a first aspect, the present application provides a preparation method of a carbonized and cured microbial self-repairing fiber reinforced material, comprising the following steps: S1, the microbial spores, urea and growth promoter are wrapped in the pH responsive hydrogel to obtain pH responsive microbial composite microcapsules; S2, the cementing material rich in calcium silicate mineral phase, the pH responsive microbial composite microcapsules, fibers and water are uniformly mixed to obtain a mixture; S3, the mixture is shaped and carbonized and cured to obtain the carbonized and cured microbial self-repairing fiber reinforced material.

[0010] The present application utilizes the high carbonation activity of the calcium silicate mineral phase-rich cementitious material, in combination with the built-in responsive microbial composite microcapsules, to prepare a fiber-reinforced material with self-repairing and continuous carbon fixation functions. The key lies in: taking carbonation curing as the main curing method, rapidly reacting to form a matrix with calcium carbonate as the skeleton, not only quickly imparting the material with initial strength and achieving carbon fixation during manufacturing, but more importantly, the weakly alkaline and dense matrix environment created by it provides the necessary conditions for the long-term dormancy of microbial spores, which is not achievable by traditional high-alkalinity cement-based materials; when the material is damaged during use, the local acidification caused by the intrusion of CO2 and moisture at the crack will trigger the dissolution of the microcapsules and release the microbial spores, which will induce calcium carbonate precipitation to achieve self-repairing, and in the process, fix CO2 in the atmosphere to achieve continuous carbon fixation during use. The present application rapidly forms a dense matrix through carbonation curing to impart high initial strength to the material, and the self-repairing mechanism further ensures the long-term durability of the material. The entire process does not require high-temperature and high-pressure steam curing, has low energy consumption, makes full use of industrial solid waste and low-carbon cementitious materials, and has significant economic and environmental benefits.

[0011] In some embodiments, the microbial spores are bacterial spores with urease activity and the ability to induce calcium carbonate precipitation, and specifically can be one or more of Paenibacillus barellii spores, Paenibacillus barellii spores, Bacillus megaterium spores, Bacillus sphaericus spores, etc.

[0012] In some embodiments, the mass ratio of microbial spores to urea, based on the number of viable bacteria in the microbial spores, is ≥1×10 7 CFU / g, preferably 1×10 7 CFU / g-1×10 9 CFU / g, more preferably 1×10 8 CFU / g-5×10 8 CFU / g. By controlling the mass ratio of microbial spores to urea within the above range, the present application can ensure the repair efficiency of activated microorganisms.

[0013] In some embodiments, the microbial spores are provided in the form of a dry preparation; in the dry preparation, the concentration of viable bacteria is ≥1×10 8 CFU / g, preferably ≥1×10 9 CFU / g.

[0014] In some embodiments, the growth promoter is yeast extract. The present application does not limit the specific type of growth promoter, and those skilled in the art can select it according to the actual situation, for example, the growth promoter can be yeast extract produced by Sigma-Aldrich Company (Y1625).

[0015] In some embodiments, the amount of growth promoter added is 1%-5% of the mass of urea.

[0016] In some embodiments, the pH-responsive hydrogel is a sodium alginate-chitosan composite gel or a polyacrylic acid hydrogel (such as Carbopol 974P NF), which swells or dissolves in an environment with pH ≤ 7.5.

[0017] In some embodiments, microbial spores, urea, and growth promoters are encapsulated in pH-responsive hydrogels using a sharp-pore coagulation bath method or a composite coagulation method to obtain pH-responsive microbial composite microcapsules.

[0018] In some embodiments, the pH-responsive hydrogel is a sodium alginate-chitosan composite gel, and step S1 includes: Microbial spores, urea, and growth promoters were uniformly dispersed in sodium alginate solution to obtain the first mixture; Calcium chloride and chitosan were uniformly dispersed in water to obtain a second mixture; The first mixture was added dropwise to the second mixture using a sharp-hole device. After washing and drying, pH-responsive microbial composite microcapsules were obtained.

[0019] Specifically, based on the number of live bacteria in the microbial spores, the ratio of microbial spores to sodium alginate solution is ≥1×10⁻⁶. 8 CFU / 100mL, preferably 1×10 8 CFU / 100mL - 1×10 10 CFU / 100mL, more preferably 1×10 9 CFU / g-5×10 9 CFU / 100mL. This invention balances the mechanical strength of microcapsules with the reserve of repair substances by controlling the mass ratio of microbial spores to sodium alginate solution within the above range.

[0020] The sodium alginate solution contains 1%-3% by mass.

[0021] In the second mixture, the concentration of calcium chloride is 0.4-0.6 mol / L, and the mass fraction of chitosan is 0.4%-0.6%.

[0022] The volume ratio of the first mixture to the second mixture is 1:(2-10), preferably 1:(3-6).

[0023] The drying method is freeze drying.

[0024] In some embodiments, the pH-responsive hydrogel is a polyacrylic acid hydrogel, and step S1 includes: Microbial spores, urea, and growth promoters were uniformly dispersed into a polyacrylic acid hydrogel matrix to obtain a third mixture; Calcium chloride was evenly dispersed in water, and the pH was adjusted to 6.5-7.5 to obtain the fourth mixture. The third mixture was added dropwise to the fourth mixture using a sharp-hole device. After washing and drying, pH-responsive microbial composite microcapsules were obtained.

[0025] The preparation process of the polyacrylic acid hydrogel matrix is ​​as follows: the pH value of the polyacrylic acid dispersion is adjusted to 6.5-7.0 with triethanolamine to form a uniform and transparent gel matrix.

[0026] Specifically, the mass fraction of the polyacrylic acid dispersion is 1%-3%.

[0027] Specifically, based on the number of live bacteria in the microbial spores, the ratio of microbial spores to polyacrylic acid hydrogel matrix is ​​≥1×10⁻⁶. 8 CFU / 100mL, preferably 1×10 8 CFU / 100mL - 1×10 10 CFU / 100mL, more preferably 1×10 9 CFU / g-5×10 9 CFU / 100mL. This invention balances the mechanical strength of microcapsules with the reserve of repair substances by controlling the mass ratio of microbial spores to polyacrylic acid hydrogel matrix within the above range.

[0028] In the fourth mixture, the concentration of calcium chloride is 0.4-0.6 mol / L.

[0029] In this process, calcium chloride is uniformly dispersed in water, and the pH is adjusted to 6.5-7.5 using triethanolamine to obtain the fourth mixture.

[0030] The volume ratio of the third mixture to the fourth mixture is 1:(2-10), preferably 1:(3-6).

[0031] The drying method is freeze drying.

[0032] In some embodiments, the average particle size of the pH-responsive microbial composite microcapsules is 50-300 μm.

[0033] In some embodiments, the amount of pH-responsive microbial composite microcapsules added is 2%-8% of the mass of the cementitious material rich in calcium silicate mineral phase.

[0034] In some embodiments, the amount of fiber added is 5%-20% of the mass of the cementitious material rich in calcium silicate mineral phase.

[0035] In some embodiments, the amount of water added is 10%-15% of the mass of the cementitious material rich in calcium silicate mineral phase.

[0036] In some embodiments, the cementing material rich in calcium silicate mineral phase is one or more of γ-C2S powder, magnesium slag powder, or steel slag powder.

[0037] In some preferred embodiments, the calcium oxide content in the cementitious material rich in calcium silicate mineral phase is not less than 40% based on the oxide chemical composition, and the median particle size (D50) is ≤50μm.

[0038] In some preferred embodiments, the mass percentage of γ-C2S in the γ-C2S powder is ≥90%, and the median particle size is ≤50μm; the mass percentage of calcium oxide in the magnesium slag powder is ≥60%, and the median particle size is ≤50μm; and the mass percentage of calcium oxide in the steel slag powder is ≥40%, and the median particle size is ≤50μm.

[0039] In some embodiments, the fiber is one or more of pulp fiber, alkali-free glass fiber, PVA fiber, and PP fiber.

[0040] In some embodiments, the fiber length is 1-3 mm. The aforementioned chopped fibers are uniformly dispersed in the matrix and guided to form a microcrack network that facilitates microbial repair when the material is damaged.

[0041] In some specific embodiments, the pulp fibers are sulfate-pretreated wood pulp or bamboo pulp.

[0042] In some embodiments, step S2 includes: dry mixing a cementitious material rich in calcium silicate mineral phase and pH-responsive microbial composite microcapsules evenly, then adding fiber and water and stirring evenly to obtain a mixture.

[0043] The stirring temperature is ≤30℃, the stirring time is 5-10 min, and the stirring speed is 100-300 r / min.

[0044] In some embodiments, compression molding is employed, with a compression molding pressure of 10-30 MPa and a holding time of 1-3 minutes. This invention, through compression molding, can obtain components suitable for preparing sheets, blocks, or other specific shapes, depending on the final product form.

[0045] In some embodiments, the carbonization curing conditions are: carbon dioxide concentration ≥40% vol, ambient pressure 0.1-0.3 MPa, curing temperature 20-60℃, relative humidity 50%-85%, and curing time 12-24 hours. Under these carbonization curing conditions, carbonization is more complete, which is conducive to the survival of microorganisms.

[0046] This invention does not limit the source of carbon dioxide gas; those skilled in the art can choose according to actual conditions, as long as the concentration range mentioned above is met. For example, carbon dioxide gas can come from industrial flue gas, etc.

[0047] Secondly, the present invention provides a carbonized maintenance microbial self-healing fiber reinforced material, which is obtained by the preparation method of the carbonized maintenance microbial self-healing fiber reinforced material provided in the first aspect of the present invention.

[0048] Example 1 A method for preparing a carbonized, maintenance-promoting microbial self-healing fiber-reinforced material includes the following steps: (1) Weigh out the spores of *Sporosarcina pasteurii* (ATCC 11859), with a viable cell concentration of 1.5 × 10⁻⁶. 9 1.0 g of sodium alginate (CFU / g), 10.0 g of urea, and 0.3 g of yeast extract (Sigma-Aldrich, Y1625) (3% of urea mass) were uniformly dispersed in 100 mL of a 2% sodium alginate solution. This mixture was then dropwise added to 500 mL of an aqueous solution containing 0.5 M CaCl2 and 0.5% chitosan (as a coagulation bath) using a sharp-orifice device to form microcapsules. After washing with deionized water and freeze-drying, pH-responsive microbial composite microcapsules (average particle size approximately 150 μm) based on a sodium alginate-chitosan composite gel were obtained. (2) Take 100 parts of γ-C2S powder (γ-C2S content 90.2%, median particle size 22μm), mix it with 5 parts of pH-responsive microbial composite microcapsules evenly; then add 10 parts of pulp fiber (length 1-3mm) and 12 parts of water, stir at 200 r / min for 8 minutes at 25℃ to form a uniform slurry; (3) The slurry is injected into a stainless steel mold, pressed and held under a molding pressure of 10 MPa for 3 minutes to obtain a fiber-reinforced material blank; (4) Transfer the blank to a carbonization curing kettle and cure it for 24 hours under the conditions of CO2 concentration of 99% vol, pressure of 0.3 MPa, relative humidity of 70% and temperature of 40℃ to obtain self-healing fiber reinforced material.

[0049] Example 2 A method for preparing a carbonized maintenance microbial self-healing fiber-reinforced material is the same as in Example 1, except that γ-C2S powder is replaced with magnesium slag powder (wherein the chemical composition of magnesium slag contains 60.1% CaO and a median particle size of 18.3 μm).

[0050] Example 3 A method for preparing a carbonized maintenance microbial self-healing fiber reinforcement material is the same as in Example 1, except that the amount of pH-responsive microbial composite microcapsules added is 2 parts.

[0051] Example 4 A method for preparing a carbonized maintenance microbial self-healing fiber reinforcement material is the same as in Example 1, except that the amount of pH-responsive microbial composite microcapsules added is 8 parts.

[0052] Example 5 A method for preparing a carbonized maintenance microbial self-healing fiber-reinforced material, the other contents are the same as in Example 1, except that step (1) is to prepare pH-responsive microbial composite microcapsules according to the following method: Weigh out spores of *Sporosarcina pasteurii* (ATCC 11859), with a viable cell concentration of 1.5 × 10⁻⁶. 9 Prepare 1.0 g of CFU / g spores, 10.0 g of urea, and 0.3 g of yeast extract (Sigma-Aldrich, Y1625) (3% of urea mass). Slowly disperse 2.0 g of Carbopol 974P NF powder in 98 mL of deionized water, stirring continuously until completely swollen to obtain a 2% (w / w) polyacrylic acid dispersion. Then, under low-speed stirring, add triethanolamine dropwise to the dispersion until the pH of the system stabilizes at 6.5-7.0 and a uniform, transparent gel matrix is ​​formed. Uniformly disperse the prepared spores, urea, and yeast extract in the above gel matrix. Prepare 500 mL of aqueous solution containing 0.5 M CaCl2, and adjust its pH to 6.5-7.5 with triethanolamine as a coagulation bath. Subsequently, the gel containing the active substance was added to the coagulation bath through a sharp-hole device. The surface of the gel droplet stabilized and solidified after contact with the coagulation bath. After washing with deionized water and freeze-drying, pH-responsive microbial composite microcapsules based on polyacrylic acid hydrogel (average particle size of about 150 μm) were obtained.

[0053] Example 6 A method for preparing a carbonized maintenance microbial self-healing fiber-reinforced material is the same as in Example 1, except that a mixture of 5 parts PVA fiber (1-3 mm in length) and 5 parts pulp fiber (1-3 mm in length) is used.

[0054] Example 7 A method for preparing a carbonized curing microbial self-healing fiber-reinforced material is the same as in Example 1, except that the carbonization curing time is 12 hours.

[0055] Example 8 A method for preparing a carbonized curing microbial self-healing fiber-reinforced material is the same as in Example 1, except that the amount of pulp fiber added is 5 parts.

[0056] Example 9 A method for preparing a carbonized curing microbial self-healing fiber-reinforced material is the same as in Example 1, except that the amount of pulp fiber added is 20 parts.

[0057] Example 10 A method for preparing a carbonized maintenance microbial self-healing fiber-reinforced material is the same as in Example 1, except that the amount of water added is 10 parts.

[0058] Example 11 A method for preparing a carbonized maintenance microbial self-healing fiber-reinforced material is the same as in Example 1, except that the amount of water added is 15 parts.

[0059] Comparative Example 1 A method for preparing a fiber-reinforced material is the same as in Example 1, except that pH-responsive microbial composite microcapsules are not added.

[0060] Comparative Example 2 A method for preparing fiber-reinforced materials is the same as in Example 1, except that the amount of pH-responsive microbial composite microcapsules added is 12 parts.

[0061] Comparative Example 3 A method for preparing a fiber-reinforced material is the same as in Example 1, except that microencapsulation is not performed; instead, equal amounts of bacterial spores, urea, and nutrients are directly mixed with the cementitious material in powder form.

[0062] Comparative Example 4 A method for preparing a fiber-reinforced material is the same as in Example 1, except that γ-C2S powder is replaced with P·O 42.5 grade ordinary silicate cement (median particle size of 16.9μm), and standard water curing is used (temperature 20±1°C, humidity >95%, curing for 28 days) to induce a hydration reaction and generate strength.

[0063] Comparative Example 5 A method for preparing a fiber-reinforced material is the same as in Example 1, except that the carbonization curing time is shortened to 2 hours.

[0064] Comparative Example 6 A method for preparing a fiber-reinforced material is the same as in Example 1, except that no fibers are added.

[0065] Comparative Example 7 A method for preparing a fiber-reinforced material is the same as in Example 1, except that the amount of pulp fiber added is 25 parts.

[0066] Comparative Example 8 A method for preparing a fiber-reinforced material, the other contents of which are the same as in Example 1, except that the concentration of viable Bacillus pasteurellii spores is 1×10⁻⁶. 7 CFU / g.

[0067] Testing and Evaluation The samples obtained from different embodiments and comparative examples were subjected to water saturation treatment (immersion in water for 1 day), and then the porosity, water absorption rate, and saturated flexural strength of the specimens were tested according to GB / T7019-2024 "Test Methods for Fiber Cement Products". The self-healing effect was evaluated by calculating the recovery rate by comparing the flexural strength of the pre-damaged specimens before and after repair. Specific method: The specimens were subjected to three-point bending pre-damage until the crack width was 0.1-0.3 mm, and then cured for 7 days under simulated natural environmental conditions (temperature 25±2°C, humidity 95±5%, atmospheric CO2 environment). After re-saturation with water, the flexural strength was tested. Recovery rate (%) = (flexural strength after repair / initial flexural strength) × 100%. The test results are shown in Table 1.

[0068] Table 1

[0069] Please refer to Table 1. As can be seen from Table 1, the carbonized curing microbial self-healing fiber-reinforced materials provided in the embodiments of the present invention all possess good initial physical and mechanical properties, and exhibit significant self-healing capabilities (manifested as a high flexural strength recovery rate) under simulated natural environments. This verifies that the microbial "dormancy-activation" mechanism built into the material is effective. Combining the design mechanism of the present invention, namely, the repair process is triggered by the intrusion of CO2 and moisture in the environment, and microorganisms induce the formation of calcium carbonate, it is clear that this self-healing process itself is a process of utilizing and fixing atmospheric CO2. Therefore, the present invention successfully constructs a new path for dynamic carbon fixation and performance maintenance covering the entire life cycle from manufacturing to use by combining carbonization curing in the manufacturing stage with self-healing based on microbial mineralization in the usage stage.

[0070] Compared to Example 1, in Comparative Example 1, no pH-responsive microbial composite microcapsules were added. Due to the lack of microbial-induced calcium carbonate precipitation repair, the flexural strength recovery rate was 0, but the initial porosity and water absorption rate were slightly lower than those in Example 1. This may be because the introduction of microorganisms and their nutrients in Example 1 resulted in additional pores.

[0071] Compared with Example 1, in Comparative Example 2, the amount of pH-responsive microbial composite microcapsules added was too high. Although its self-repair ability was maintained, the excessive amount of additives introduced too much organic matter and non-gelling substances, which seriously damaged the compactness of the matrix, resulting in a significant increase in porosity and water absorption. The saturated flexural strength was significantly lower than that of Example 1. This shows that the amount of pH-responsive microbial composite microcapsules exceeding 8% will sacrifice the initial mechanical properties and reduce the overall benefits, which in turn confirms the rationality of the preferred range of 2%-8%.

[0072] Compared with Example 1, in Comparative Example 3, without microcapsule coating, the death or loss of microorganisms during mixing and carbonization led to the formation of defective structures inside the material. Furthermore, the uncoated powder caused non-uniformity of the matrix, resulting in a significant increase in porosity and water absorption, a decrease in saturated flexural strength, and a decrease in flexural strength recovery rate. This indicates that microcapsules play a positive role in maintaining the compactness of the matrix while protecting microorganisms.

[0073] Compared to Example 1, in Comparative Example 4, the cementitious material was silicate cement, cured with standard water, resulting in a persistently high-alkaline environment (pH>12) after long-term hydration. Under this environment, the embedded microcapsules faced a dual risk of failure: firstly, failure of the microcapsule structure itself, as the prolonged high-alkalinity and high-ionic-strength environment could erode the microcapsule wall, affecting its long-term stability, or causing alkaline media to slowly penetrate into the capsule, directly leading to microbial death; secondly, failure of the self-healing trigger mechanism, even if the microcapsule structure remained intact, when cracks appeared in the material, the invading CO2 and water, under the strong buffering effect of the highly alkaline matrix, could not lower the local pH at the crack to below the microcapsule's dissolution threshold (pH≤7.5), preventing the release and activation of microbial spores. Therefore, this comparative example material had no self-healing ability (recovery rate 0%). Although its matrix is ​​initially relatively dense due to sufficient hydration (porosity 15.7%, water absorption 9.7%), it completely loses the core benefits of the carbonization curing technology approach of this application, such as rapid high strength, creating a suitable dormant environment for microorganisms, and carbon fixation throughout the entire life cycle.

[0074] Compared with Example 1, in Comparative Example 5, the carbonization curing time was shortened to 2 hours. Due to insufficient carbonization, the matrix strength was low, the porosity was high, and the pH was not stabilized to a weakly alkaline state, resulting in a significant increase in water absorption and a decrease in saturated flexural strength. At the same time, the unstable matrix environment affected the survival of microorganisms, resulting in a low flexural strength recovery rate.

[0075] Compared to Example 1, in Comparative Example 6, no fibers were added, and the lack of fiber reinforcement significantly increased the brittleness of the matrix, leading to a tendency for a few large macroscopic cracks to form when damaged. These cracks exceeded the effective repair range of microbial-induced mineralization, resulting in weak self-healing ability (recovery rate <5%). This result contrasts sharply with the embodiments of the present invention, directly demonstrating that the introduction of fibers is not only a conventional means of improving material toughness, but also an essential technical feature for ensuring the efficient operation of the "microcrack generation - local pH triggering - microbial repair" chain, thereby achieving reliable self-healing function.

[0076] Compared to Example 1, the fiber content in Comparative Example 7 was excessively high. Excessive fiber content resulted in uneven dispersion in the matrix, leading to agglomeration and numerous defects within the material. This caused a sharp increase in porosity and water absorption, and a severe decrease in saturated flexural strength. Although the repair rate was acceptable, the initial structural properties were severely degraded. This indicates that fiber content exceeding 20% ​​will impair the material's integrity, clarifying that 5%-20% is an effective range balancing reinforcement effect and process feasibility.

[0077] Compared to Example 1, the concentration of microbial spores used in Comparative Example 8 was too low (1×10⁻⁶). 7 (CFU / g). Although the initial porosity and water absorption rate were similar to those of Example 1, indicating that the matrix structure was not significantly affected, the number of active microorganisms per unit volume was severely insufficient, and the cracks could not induce the formation of sufficient calcium carbonate precipitate, resulting in weak self-repair ability. This proves that the microbial concentration must reach a certain threshold to ensure effective repair function.

[0078] Compared with existing machinery, the beneficial effects of the present invention include: (1) This invention employs carbonization curing as the core solidification process. The calcium silicate mineral phase in the cementitious material undergoes a rapid carbonization reaction with CO2 under suitable conditions, generating a dense cementitious body with calcium carbonate as the main framework. This process shortens the autoclaving curing cycle required for traditional calcium silicate materials, enabling the material to achieve high strength within tens of hours, greatly improving production efficiency. Simultaneously, this process achieves significant absorption and solidification of CO2 during the manufacturing stage, resulting in substantial carbon sequestration benefits. Furthermore, this invention is of great significance for the resource utilization of industrial solid waste.

[0079] (2) This invention employs microencapsulation technology to construct an environment conducive to the long-term survival of microorganisms. The carbonization reaction consumes alkaline substances in the cementitious material, stabilizing the overall pH value of the matrix after carbonization curing within a weakly alkaline range (8.0±0.5), and maintaining a low free water state internally. This environment is higher than the dissolution threshold of the microcapsules, thus ensuring the stability of the microcapsules within the intact matrix and providing an ideal long-term dormancy site for the microbial spores sealed inside. This not only solves the technical bottleneck of the difficulty in the survival of microorganisms in traditional high-alkaline cement-based materials, but the physical protection of the microcapsules also avoids mechanical damage during mixing and pressing. Its on-demand triggering mechanism ensures the long-term stability and reliability of the self-healing function. Furthermore, within the preferred dosage range (e.g., 2%-8%), compared to directly adding equal amounts of microorganisms, urea, and other active substances in uncoated powder form (see Comparative Example 3), the introduction of microcapsules can significantly improve the uniformity of the mixture, reduce defects caused by powder agglomeration, and thus facilitate the formation of a denser matrix structure, resulting in lower porosity, water absorption, and higher initial mechanical strength.

[0080] (3) This invention endows the material with dynamic self-healing and secondary carbon fixation capabilities during its service life. When microcracks develop in the material due to stress during use, CO2 and moisture in the air will penetrate the cracks. CO2 dissolves in water to form carbonic acid, causing a drop in the local pH value at the crack. When the local pH drops to the response range of the microcapsules (<7.5), it triggers the microcapsules to swell and dissolve, precisely releasing microbial spores. After being activated, the microbial spores utilize their high urease activity to hydrolyze the pre-embedded urea to produce carbonate ions (CO3). 2- Carbonate ions can react with calcium ions (Ca) in the matrix. 2+ The process involves the combination of microbial metabolism and precipitation. Simultaneously, the metabolic activities of microorganisms also contribute to the absorption and fixation of atmospheric CO2. Through the combined action of these processes, calcium carbonate (CaCO3) precipitate is ultimately generated, effectively repairing microcracks. This mechanism enables the material not only to fix carbon during the manufacturing stage but also to achieve dynamic and repeated self-repair throughout its service life as damage occurs, continuously fixing atmospheric CO2 in the process and achieving full life-cycle carbon negativity.

[0081] (4) Fibers play a crucial synergistic role in this system. Not only do fibers form a three-dimensional network in the matrix, significantly improving the material's toughness and crack resistance, but more importantly, they guide stress distribution, causing the material to develop uniformly distributed microcracks when damaged, rather than a few large macrocracks. These microcracks provide ideal channels for the intrusion of moisture and CO2, acting as a "reactor" to trigger microcapsule release and microbial mineralization repair. Without fibers, the material is prone to developing wide cracks beyond the effective repair range of microorganisms, leading to a significant decrease in the reliability and efficiency of the self-healing function. Therefore, "fiber reinforcement" is a necessary technical feature to ensure the efficient realization of this self-healing mechanism.

[0082] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for the production of a carbonized, maintenance microorganism self- repairing fiber-reinforced material, characterized in that, The method comprises the following steps: S1, wrapping microbial spores, urea and growth promoters in a pH-responsive hydrogel to obtain pH-responsive microbial composite microcapsules; S2, uniformly mixing the cementing material rich in calcium silicate mineral phase, the pH-responsive microbial composite microcapsules, fibers and water to obtain a mixture; S3, molding and carbonizing and curing the mixture to obtain a carbonized and cured microbial self-repairing fiber reinforced material.

2. The preparation method of the carbonized curing microbial self-healing fiber-reinforced material according to claim 1, characterized in that, The microbial spores are one or more of Paenibacillus alvei spores, Bacillus pasteurii spores, Bacillus megaterium spores and Bacillus sphaericus spores; and / or, The growth promoter is a yeast extract.

3. The method for preparing the carbonized curing microbial self-healing fiber-reinforced material according to claim 1, characterized in that, The mass ratio of the microbial spores to urea, based on the viable bacteria in the microbial spores, is ≥ 1 x 10 7 CFU / g; and / or, The growth promoter is added in an amount of 1%-5% of the mass of the urea.

4. The preparation method of the carbonized curing microbial self-healing fiber-reinforced material according to claim 1, characterized in that, The pH-responsive hydrogel is a sodium alginate-chitosan composite gel or a polyacrylic acid hydrogel, which swells or dissolves in an environment with a pH of less than or equal to 7.5; and / or, The microbial spores, urea and growth promoters are wrapped in the pH-responsive hydrogel by means of a sharp hole-coagulation bath method or a composite coacervation method to obtain the pH-responsive microbial composite microcapsules; and / or, The average particle size of the pH-responsive microbial composite microcapsules is 50-300 μm.

5. The preparation method of the carbonized curing microbial self-healing fiber-reinforced material according to claim 1, characterized in that, The pH-responsive hydrogel is a sodium alginate-chitosan composite gel, and step S1 comprises: uniformly dispersing the microbial spores, urea and growth promoters into a sodium alginate solution to obtain a first mixed solution; uniformly dispersing calcium chloride and chitosan into water to obtain a second mixed solution; dropping the first mixed solution into the second mixed solution through a sharp hole device, and then washing and drying to obtain the pH-responsive microbial composite microcapsules; wherein, The use ratio of the microbial spores to the sodium alginate solution is ≥ 1 x 10 8 CFU / 100mL; The mass fraction of the sodium alginate solution is 1%-3%; In the second mixed solution, the concentration of calcium chloride is 0.4-0.6 mol / L, and the mass fraction of chitosan is 0.4%-0.6%; The volume ratio of the first mixed solution to the second mixed solution is 1: (2-10).

6. The preparation method of the carbonized curing microbial self-healing fiber-reinforced material according to claim 1, characterized in that, The pH-responsive hydrogel is a polyacrylic acid hydrogel, and step S1 comprises: uniformly dispersing the microbial spores, urea and growth promoters into a polyacrylic acid hydrogel matrix to obtain a third mixed solution; uniformly dispersing calcium chloride into water and adjusting the pH to 6.5-7.5 to obtain a fourth mixed solution; dropping the third mixed solution into the fourth mixed solution through a sharp hole device, and then washing and drying to obtain the pH-responsive microbial composite microcapsules; wherein, a polyacrylic acid dispersion liquid with a mass fraction of 1%-3% is adjusted to a pH value of 6.5-7.0 by triethanolamine to form a polyacrylic acid hydrogel matrix; with the polyacrylic hydrogel matrix in a ratio of ≥ 1 x 10 8 CFU / 100 mL; In the fourth mixed solution, the concentration of calcium chloride is 0.4-0.6 mol / L; The volume ratio of the third mixed solution to the fourth mixed solution is 1: (2-10).

7. The preparation method of the carbonized curing microbial self-healing fiber-reinforced material according to claim 1, characterized in that, The addition amount of the pH-responsive microbial composite microcapsules is 2%-8% of the mass of the cementing material rich in calcium silicate mineral phase; and / or, The addition amount of the fibers is 5%-20% of the mass of the cementing material rich in calcium silicate mineral phase; and / or, The water is added in an amount of 10%-15% of the mass of the cementitious material rich in calcium silicate mineral phase.

8. The preparation method of the carbonized curing microbial self-healing fiber-reinforced material according to claim 1, characterized in that, The cementitious material rich in calcium silicate mineral phase is one or more of γ-C2S powder, magnesium slag powder or steel slag powder; and / or, The calcium oxide content in the cementitious material rich in calcium silicate mineral phase is not less than 40% in terms of oxide chemical composition, and the median particle size is ≤50 μm; and / or, The fiber is one or more of paper pulp fiber, alkali-free glass fiber, PVA fiber, PP fiber; and / or, The length of the fiber is 1-3 mm.

9. The method for preparing the carbonized curing microbial self-healing fiber-reinforced material according to claim 1, characterized in that, The compaction forming is adopted, the compaction forming pressure is 10-30 MPa, and the pressure maintaining time is 1-3 minutes; and / or, The carbonation curing condition is that the carbon dioxide concentration is ≥40% vol, the environmental pressure is 0.1-0.3 MPa, the curing temperature is 20-60℃, the relative humidity is 50%-85%, and the curing time is 12-24 hours.

10. A carbonized, maintenance microorganism self-healing fiber reinforced material, characterized by, The carbonation-cured microbial self-repairing fiber reinforced material is obtained by the preparation method of the carbonation-cured microbial self-repairing fiber reinforced material in any one of claims 1-9.

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