Self-repairing concrete based on gellan gum-microorganism composite carrier as well as preparation method and application of self-repairing concrete

Abstract

The invention discloses self-repairing concrete based on a gellan gum-microorganism composite carrier as well as a preparation method and application of the self-repairing concrete. Relates to the concrete field. The concrete comprises a concrete base material and a gellan gum-microorganism composite carrier dispersed in the concrete base material, the gellan gum-microorganism composite carrier comprises gellan gum, urease-producing bacteria, calcium salt and a calcium-containing nutrient source. The gellan gum is used for replacing a traditional carrier (such as sodium alginate and epoxy resin), the gellan gum is anionic polysaccharide generated by fermentation of sphingomonas paucimobilis, a molecular chain contains carboxylic acid groups, and the gellan gum is stable in the pH range of 3-13, so that the gellan gum-microorganism composite carrier is prevented from being degraded due to alkali corrosion, and long-term protection is provided for microorganisms. In addition, the gellan gum is high in gel strength and can resist shear stress in the concrete stirring process, and the situation that microorganisms are released too early due to the fact that the gellan gum-microorganism composite carrier is broken in advance is avoided.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and in particular to a self-healing concrete based on gellan gum-microbial composite carrier, its preparation method, and its application. Background Technology

[0002] Concrete, as the most widely used building material globally, is brittle, making it inevitable that microcracks will form during its use. These cracks not only detract from the structure's aesthetics but also become channels for moisture and harmful substances to penetrate, leading to a series of problems such as steel corrosion and freeze-thaw damage, significantly reducing the structure's durability and service life.

[0003] Traditional repair methods, such as grouting and epoxy resin coatings, while capable of solving problems in the short term, have insurmountable limitations. Long construction cycles, high costs, and unsustainable repair effects severely hinder their practical application. To overcome these bottlenecks, self-healing concrete technology has emerged, with microbial self-healing technology becoming a research hotspot due to its dual advantages of environmental friendliness and economy. This technology works by pre-embedding microorganisms and their nutrient sources into the concrete. When cracks appear, the microorganisms are activated, producing minerals such as calcium carbonate through metabolism, thereby achieving self-repair of the cracks.

[0004] However, microbial self-healing technology has encountered many challenges in practical applications. Microorganisms have a low survival rate in highly alkaline concrete environments, and the mechanical strength of the carrier material is also insufficient. Specifically, existing technologies have the following problems:

[0005] First, the carrier has poor alkali resistance. Systems using sodium alginate as a carrier are easily degraded in the highly alkaline environment of concrete (pH>13), resulting in a microbial survival rate typically below 30%, significantly limiting their long-term repair capabilities. Simultaneously, while the double-layer coating structure can delay microbial release, the sodium alginate gel has low strength (<200 g / cm³). 2 Internal stress in concrete can easily lead to premature cracking of the carrier, causing microorganisms to be released too early and resulting in unstable repair efficiency. In addition, the process is complex, requiring the preparation of a core layer, a first coating layer, and a second coating layer in steps, which not only results in high production costs but also makes industrialization difficult.

[0006] Secondly, complete self-repair is not possible. Some existing technologies require manual injection of emulsified repair materials, which cannot achieve complete self-repair and leads to low construction efficiency. Furthermore, nanofibers have poor dispersibility and are prone to agglomeration, affecting the uniformity of the repair material and the crack filling effect. The interface between calcium alginate and calcium carbonate is easily delaminated under stress, resulting in insufficient long-term durability.

[0007] Third, the use of repair capsules is limited; some capsules cannot be reused after rupture and can only address single cracks. Additionally, additives such as sodium dodecyl sulfonate may interfere with cement hydration, affecting the early strength of concrete. Furthermore, these technologies rely on the reaction of calcium oxide with water for energy, resulting in a long repair cycle and slow repair speed (typically requiring more than 14 days).

[0008] Furthermore, current technologies for self-healing microbial concrete mainly include sodium alginate-microbial carrier systems and epoxy resin microcapsule systems. Sodium alginate carrier systems mix Bacillus pasteurellii with sodium alginate to form gel microspheres, which release microorganisms for repair when cracks leak water, offering advantages such as good biocompatibility and low cost. However, they have poor alkali resistance, with a microbial survival rate of less than 30% in highly alkaline environments, and low mechanical strength, making them prone to premature breakage. Epoxy resin microcapsule systems achieve rapid repair by encapsulating chemical repair agents, but can only perform single-use repairs and cannot encapsulate living microorganisms. In practical applications, these technologies all exhibit problems such as unstable repair efficiency and limited repair effects, severely restricting the engineering application of self-healing microbial concrete.

[0009] Therefore, there is an urgent need to develop a type of concrete with good alkali resistance, high mechanical strength, and self-healing function. Summary of the Invention

[0010] The purpose of this invention is to develop a microbial carrier system that is resistant to high alkali, has high mechanical strength, can be targeted for release, and supports multiple repairs, so as to improve the repair efficiency, microbial survival rate, and long-term durability of self-healing concrete.

[0011] The first aspect of the present invention is:

[0012] A type of concrete is provided.

[0013] The second aspect of the present invention is as follows:

[0014] A method for preparing concrete is provided.

[0015] The third aspect of the present invention is:

[0016] The application of the concrete.

[0017] Specifically, the technical solution adopted according to the first aspect of the present invention is as follows:

[0018] A type of concrete includes a concrete substrate and a gellan gum-microbial composite carrier dispersed in the concrete substrate; the gellan gum-microbial composite carrier comprises gellan gum, urease-producing bacteria, calcium salts, and a calcium-containing nutrient source.

[0019] According to embodiments of the present invention, one of the technical solutions has at least one of the following advantages or beneficial effects:

[0020] Gellan gum is an anionic polysaccharide produced by the fermentation of *Sphingomonas sphingosine monocytogenes*. Its molecular chain contains carboxylic acid groups (-COO-), and it is stable within a pH range of 3-13. This invention uses gellan gum to replace traditional carriers (such as sodium alginate and epoxy resin), preventing the gellan gum-microbial composite carrier from degrading due to alkali corrosion and providing long-term protection for microorganisms. Furthermore, gellan gum has high gel strength, resisting shear stress during concrete mixing, preventing premature rupture of the gellan gum-microbial composite carrier and thus preventing premature release of microorganisms.

[0021] Gellan gum's -COO- and Ca in concrete substrate 2+ The concrete forms a cross-linked structure. During concrete use, when cracks appear, moisture seeps in, causing cement hydration at the cracks. The products of cement hydration dissolve, leading to the release of calcium into the cracks. 2+ Localized increase in concentration, high Ca2 + Environmental factors promote external Ca2 + The internal Ca of the concrete bonding agent-microbial composite carrier 2+ Competition for COO- binding causes some cross-linking points to break, accompanied by gellan gum swelling due to water absorption, which expands the gellan gum pore size from about 50 nm to about 200 nm, triggering the gradient release of microorganisms and nutrients.

[0022] Microorganisms diffuse into the cracks and metabolize to produce CaCO3, thereby repairing the cracks. The nutrient source provides the energy needed for the microorganisms' metabolism, further improving the repair effect of the microorganisms.

[0023] According to one embodiment of the present invention, the gellan gum is an anionic polysaccharide produced by microbial fermentation, which is a linear tetrasaccharide repeating unit polymer composed of glucose, glucuronic acid and rhamnose in a ratio of 2-3:1-2:1.

[0024] According to one embodiment of the present invention, the gellan gum is an anionic polysaccharide produced by microbial fermentation, which is a linear tetrasaccharide repeating unit polymer composed of glucose, glucuronic acid and rhamnose in a ratio of 2:1:1.

[0025] According to one embodiment of the present invention, the gel strength of the gellan gum is ≥265 g / cm³. 2 .

[0026] According to one embodiment of the present invention, the gel strength of the gellan gum is ≥500 g / cm³. 2 .

[0027] According to one embodiment of the present invention, the gellan gum accounts for 1.0-2.0% of the mass of the gellan gum-microbial composite carrier. When the mass percentage is less than 1.0%, the gel strength of the gellan gum is insufficient and cannot resist the shear force of concrete mixing. When the mass percentage is greater than 2.0%, the excessive density of the gellan gum gel will reduce the release rate of microorganisms in the gellan gum-microbial composite carrier by more than 50%, thus extending the repair cycle of concrete cracks to more than 14 days.

[0028] According to one embodiment of the present invention, the gellan gum accounts for 1.5-1.9% of the mass of the gellan gum-microbial composite carrier.

[0029] According to one embodiment of the present invention, the urease-producing bacteria includes Bacillus pasteurellii. The high urease activity of Bacillus pasteurellii can efficiently catalyze the decomposition of urea into calcium carbonate, thereby increasing the crack repair rate.

[0030] According to one embodiment of the present invention, the calcium salt comprises at least one of calcium chloride and calcium nitrate; and / or, the calcium-containing nutrient source comprises calcium lactate. The calcium salt is used for cross-linking, and the calcium-containing nutrient source is used for microbial metabolism. The present invention specifies that the calcium-containing nutrient source includes calcium lactate because it simultaneously provides calcium. 2+ In addition to energy, calcium lactate avoids insufficient repair efficiency caused by a single nutrient source, whereas traditional nutrient sources like glucose only provide energy.

[0031] According to one embodiment of the present invention, the calcium-containing nutrient source accounts for 8-10% of the mass of the gellan gum-microbial composite carrier.

[0032] According to one embodiment of the present invention, the mass of the gellan gum-microbial composite carrier is 1-3% of the mass of cement in the concrete substrate. The present invention limits the amount of composite carrier added to avoid excessive loss of concrete strength due to excessive carrier.

[0033] According to one embodiment of the present invention, the gellan gum-microbial composite carrier has a spherical shape with a diameter of 1-1.2 mm.

[0034] According to one embodiment of the present invention, the concrete substrate comprises cement, aggregate and water-reducing agent.

[0035] According to one embodiment of the present invention, the cement comprises P·O42.5 ordinary Portland cement.

[0036] According to one embodiment of the present invention, the aggregate comprises crushed stone with a particle size of 5-20 mm and medium sand with a fineness modulus of about 2.6.

[0037] According to one embodiment of the present invention, the water-reducing agent includes a polycarboxylate-based water-reducing agent.

[0038] Specifically, the technical solution adopted according to the second aspect of the present invention is as follows:

[0039] A method for preparing the concrete includes the following steps:

[0040] The gellan gum, urease-producing bacterial spores, calcium salts, and calcium-containing nutrient sources were mixed with water, and then frozen and dried to obtain the gellan gum-microbial composite carrier.

[0041] The concrete is obtained by mixing the gellan gum-microbial composite carrier and the concrete substrate.

[0042] According to one embodiment of the present invention, the temperature of the water is 50-60°C.

[0043] According to one embodiment of the present invention, the freezing temperature is -40°C to -45°C; and / or, the drying is vacuum drying.

[0044] According to one embodiment of the present invention, the drying time is 48-50 hours.

[0045] According to one embodiment of the present invention, the mixture of gellan gum, urease-producing bacterial spores, and calcium-containing nutrient source is mixed with water at a temperature of 50-60°C.

[0046] Another aspect of the invention relates to the application of the concrete in marine engineering. This includes the concrete described in the first aspect of the embodiment above. Since this application employs all the technical solutions described above for the concrete, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments.

[0047] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the discovery. Detailed Implementation

[0048] The terms "preferred," "more preferred," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0049] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0050] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of the present invention.

[0051] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0052] In the examples and comparative examples, gellan gum is an anionic polysaccharide produced by microbial fermentation. It is a linear tetrasaccharide repeating unit polymer composed of glucose, glucuronic acid and rhamnose in a ratio of 2:1:1. It was purchased from McCrae and its CAS number is 71010-52-1.

[0053] In the comparative example, the epoxy resin microcapsules were purchased from BASF, model number MasterSeal M 865.

[0054] In the examples and comparative examples, the concrete substrate components include P·O42.5 ordinary Portland cement, crushed stone with a particle size of 5-20mm, medium sand with a fineness modulus of 2.6, and polycarboxylate superplasticizer.

[0055] Example 1

[0056] A type of concrete includes a concrete substrate and a gellan gum-microbial composite carrier dispersed in the concrete substrate, wherein the mass of the gellan gum-microbial composite carrier is 1% of the concrete substrate; the gellan gum-microbial composite carrier comprises gellan gum, Bacillus pasteurellii spores, calcium chloride, and calcium lactate.

[0057] In the gellan gum-microbial composite carrier, the mass percentage of gellan gum is 1.0%;

[0058] In the gellan gum-microbial composite carrier, calcium lactate accounts for 8% by mass;

[0059] The concentration of Bacillus pasteurellii spores in the gellan gum-microbial composite carrier was 10. 7 CFU / g.

[0060] A method for preparing the concrete includes the following steps:

[0061] Gellan gum was added to 60℃ deionized water and stirred until completely dissolved. Pasteurella spores, calcium chloride, and calcium lactate were added and ultrasonically dispersed for 10 min to obtain a mixed solution. 0.1M CaCl2 solution at 4℃ was added dropwise to the mixed solution using a syringe and allowed to stand for cross-linking for 30 min to form gel microspheres with a diameter of 0.5-1 mm. After freezing at -40℃ for 24 h, the microspheres were vacuum dried for 48 h to obtain the gellan gum-microbial composite carrier.

[0062] The concrete is obtained by mixing the gellan gum-microbial composite carrier and the concrete substrate.

[0063] Example 2

[0064] The difference between Example 2 and Example 1 is that the mass percentage of gellan gum in Example 2 is 1.5%.

[0065] Specifically:

[0066] A type of concrete includes a concrete substrate and a gellan gum-microbial composite carrier dispersed in the concrete substrate, wherein the mass of the gellan gum-microbial composite carrier is 1% of the concrete substrate; the gellan gum-microbial composite carrier comprises gellan gum, Bacillus pasteurellii spores, calcium chloride, and calcium lactate.

[0067] In the gellan gum-microbial composite carrier, the mass percentage of gellan gum is 1.5%.

[0068] In the gellan gum-microbial composite carrier, calcium lactate accounts for 8% by mass;

[0069] The concentration of Bacillus pasteurellii spores in the gellan gum-microbial composite carrier was 10. 7 CFU / g.

[0070] A method for preparing the concrete includes the following steps:

[0071] Gellan gum was added to 60℃ deionized water and stirred until completely dissolved. Pasteurella spores, calcium chloride, and calcium lactate were added and ultrasonically dispersed for 10 min to obtain a mixed solution. 0.1M CaCl2 solution at 4℃ was added dropwise to the mixed solution using a syringe and allowed to stand for cross-linking for 30 min to form gel microspheres with a diameter of 0.5-1 mm. After freezing at -40℃ for 24 h, the microspheres were vacuum dried for 48 h to obtain the gellan gum-microbial composite carrier.

[0072] The concrete is obtained by mixing the gellan gum-microbial composite carrier and the concrete substrate.

[0073] Example 3

[0074] The difference between Example 3 and Example 1 is that the mass percentage of gellan gum in Example 3 is 2.0%.

[0075] Specifically:

[0076] A type of concrete includes a concrete substrate and a gellan gum-microbial composite carrier dispersed in the concrete substrate, wherein the mass of the gellan gum-microbial composite carrier is 1% of the concrete substrate; the gellan gum-microbial composite carrier comprises gellan gum, Bacillus pasteurellii spores, calcium chloride, and calcium lactate.

[0077] In the gellan gum-microbial composite carrier, the mass percentage of gellan gum is 2.0%;

[0078] In the gellan gum-microbial composite carrier, calcium lactate accounts for 8% by mass;

[0079] The concentration of Bacillus pasteurellii spores in the gellan gum-microbial composite carrier was 10. 7 CFU / g.

[0080] A method for preparing the concrete includes the following steps:

[0081] Gellan gum was added to 60℃ deionized water and stirred until completely dissolved. Pasteurella spores, calcium chloride, and calcium lactate were added and ultrasonically dispersed for 10 min to obtain a mixed solution. 0.1M CaCl2 solution at 4℃ was added dropwise to the mixed solution using a syringe and allowed to stand for cross-linking for 30 min to form gel microspheres with a diameter of 0.5-1 mm. After freezing at -40℃ for 24 h, the microspheres were vacuum dried for 48 h to obtain the gellan gum-microbial composite carrier.

[0082] The concrete is obtained by mixing the gellan gum-microbial composite carrier and the concrete substrate.

[0083] Example 4

[0084] The difference between Example 4 and Example 2 is that in Example 4, the static crosslinking time is 20 minutes.

[0085] Specifically:

[0086] A type of concrete includes a concrete substrate and a gellan gum-microbial composite carrier dispersed in the concrete substrate, wherein the mass of the gellan gum-microbial composite carrier is 1% of the concrete substrate; the gellan gum-microbial composite carrier comprises gellan gum, Bacillus pasteurellii spores, calcium chloride, and calcium lactate.

[0087] In the gellan gum-microbial composite carrier, the mass percentage of gellan gum is 1.5%.

[0088] In the gellan gum-microbial composite carrier, calcium lactate accounts for 8% by mass;

[0089] The concentration of Bacillus pasteurellii spores in the gellan gum-microbial composite carrier was 10. 7 CFU / g.

[0090] A method for preparing the concrete includes the following steps:

[0091] Gellan gum was added to 60℃ deionized water and stirred until completely dissolved. Pasteurella spores, calcium chloride, and calcium lactate were added and ultrasonically dispersed for 10 min to obtain a mixed solution. 0.1M CaCl2 solution at 4℃ was added dropwise to the mixed solution using a syringe and allowed to stand for cross-linking for 20 min to form gel microspheres with a diameter of 0.5-1 mm. After freezing at -40℃ for 24 h, the microspheres were vacuum dried for 48 h to obtain the gellan gum-microbial composite carrier.

[0092] The concrete is obtained by mixing the gellan gum-microbial composite carrier and the concrete substrate.

[0093] Example 5

[0094] The difference between Example 5 and Example 2 is that in Example 5, the static crosslinking time is 40 minutes.

[0095] Specifically:

[0096] A type of concrete includes a concrete substrate and a gellan gum-microbial composite carrier dispersed in the concrete substrate, wherein the mass of the gellan gum-microbial composite carrier is 1% of the concrete substrate; the gellan gum-microbial composite carrier comprises gellan gum, Bacillus pasteurellii spores, calcium chloride, and calcium lactate.

[0097] In the gellan gum-microbial composite carrier, the mass percentage of gellan gum is 1.5%.

[0098] In the gellan gum-microbial composite carrier, calcium lactate accounts for 8% by mass;

[0099] The concentration of Bacillus pasteurellii spores in the gellan gum-microbial composite carrier was 10. 7 CFU / g.

[0100] A method for preparing the concrete includes the following steps:

[0101] Gellan gum was added to deionized water at 60°C and stirred until completely dissolved. Pasteurella spores, calcium chloride, and calcium lactate were added and ultrasonically dispersed for 10 min to obtain a mixed solution. 0.1 M CaCl2 solution at 4°C was added dropwise to the mixed solution using a syringe and allowed to stand for cross-linking for 40 min to form gel microspheres with a diameter of 0.5-1 mm. After freezing at -40°C for 24 h, the microspheres were vacuum dried for 48 h to obtain the gellan gum-microbial composite carrier.

[0102] The concrete is obtained by mixing the gellan gum-microbial composite carrier and the concrete substrate.

[0103] Example 6

[0104] The difference between Example 6 and Example 2 is that in Example 6, the bacterial cells in the gellan gum-microbial composite carrier are replaced with Bacillus subtilis.

[0105] Specifically:

[0106] A type of concrete includes a concrete substrate and a gellan gum-microbial composite carrier dispersed in the concrete substrate, wherein the mass of the gellan gum-microbial composite carrier is 1% of the concrete substrate; the gellan gum-microbial composite carrier comprises gellan gum, Bacillus subtilis spores, calcium chloride, and calcium lactate.

[0107] In the gellan gum-microbial composite carrier, the mass percentage of gellan gum is 1.5%.

[0108] In the gellan gum-microbial composite carrier, calcium lactate accounts for 8% by mass;

[0109] The concentration of Bacillus subtilis spores in the gellan gum-microbial composite carrier was 10. 7 CFU / g.

[0110] A method for preparing the concrete includes the following steps:

[0111] Gellan gum was added to 60℃ deionized water and stirred until completely dissolved. Bacillus subtilis spores, calcium chloride, and calcium lactate were added and ultrasonically dispersed for 10 min to obtain a mixed solution. 0.1M CaCl2 solution at 4℃ was added dropwise to the mixed solution using a syringe and allowed to stand for cross-linking for 30 min to form gel microspheres with a diameter of 0.5-1 mm. After freezing at -40℃ for 24 h, the microspheres were vacuum dried for 48 h to obtain the gellan gum-microbial composite carrier.

[0112] The concrete is obtained by mixing the gellan gum-microbial composite carrier and the concrete substrate.

[0113] Example 7

[0114] The difference between Example 7 and Example 2 is that Example 7 does not use the operation of freezing at -40°C for 24 hours and then vacuum drying for 48 hours, but instead uses natural drying.

[0115] Specifically:

[0116] A type of concrete includes a concrete substrate and a gellan gum-microbial composite carrier dispersed in the concrete substrate, wherein the mass of the gellan gum-microbial composite carrier is 1% of the concrete substrate; the gellan gum-microbial composite carrier comprises gellan gum, Bacillus pasteurellii spores, calcium chloride, and calcium lactate.

[0117] In the gellan gum-microbial composite carrier, the mass percentage of gellan gum is 1.5%.

[0118] In the gellan gum-microbial composite carrier, calcium lactate accounts for 8% by mass;

[0119] The concentration of Bacillus pasteurellii spores in the gellan gum-microbial composite carrier was 10. 7 CFU / g.

[0120] A method for preparing the concrete includes the following steps:

[0121] Gellan gum was added to deionized water at 60°C and stirred until completely dissolved. Pasteurella spores, calcium chloride, and calcium lactate were added and ultrasonically dispersed for 10 minutes to obtain a mixed solution. 0.1M CaCl2 solution at 4°C was added dropwise to the mixed solution using a syringe and allowed to stand for cross-linking for 30 minutes to form gel microspheres with a diameter of 0.5-1 mm. After natural drying at 25°C, the gellan gum-microbial composite carrier was obtained.

[0122] The concrete is obtained by mixing the gellan gum-microbial composite carrier and the concrete substrate.

[0123] Comparative Example 1

[0124] The difference between Comparative Example 1 and Example 2 is that in Comparative Example 1, gellan gum was replaced with sodium alginate.

[0125] Specifically:

[0126] A type of concrete includes a concrete substrate and a sodium alginate-microbial composite carrier dispersed in the concrete substrate, wherein the sodium alginate-microbial composite carrier comprises 1% by mass of the concrete substrate; the sodium alginate-microbial composite carrier comprises sodium alginate, Bacillus pasteurellii spores, calcium chloride, and calcium lactate.

[0127] In the sodium alginate-microbial composite carrier, the mass percentage of sodium alginate is 1.5%;

[0128] In the sodium alginate-microbial composite carrier, calcium lactate accounts for 8% by mass;

[0129] The sodium alginate-microbial composite carrier contains 10% Bacillus pasteurellium spores. 7 CFU / g.

[0130] A method for preparing the concrete includes the following steps:

[0131] Sodium alginate was added to deionized water at 60℃ and stirred until completely dissolved. Bacillus pasteurellii spores, calcium chloride, and calcium lactate were added and ultrasonically dispersed for 10 min to obtain a mixed solution. 0.1 MCaCl2 solution at 4℃ was added dropwise to the mixed solution using a syringe and allowed to stand for cross-linking for 30 min to form gel microspheres with a diameter of 0.5-1 mm. After freezing at -40℃ for 24 h, the microspheres were vacuum dried for 48 h to obtain sodium alginate-microbial composite carrier.

[0132] The concrete is obtained by mixing the sodium alginate-microbial composite carrier and the concrete substrate.

[0133] Comparative Example 2

[0134] The difference between Comparative Example 2 and Example 2 is that in Comparative Example 2, gellan gum was replaced with epoxy resin microcapsules.

[0135] Specifically:

[0136] A type of concrete includes a concrete substrate and an epoxy resin microcapsule-microbial composite carrier dispersed in the concrete substrate, wherein the mass of the epoxy resin microcapsule-microbial composite carrier is 1% of the concrete substrate; the epoxy resin microcapsule-microbial composite carrier comprises epoxy resin microcapsules, Bacillus pasteurellii spores, calcium chloride, and calcium lactate.

[0137] In the epoxy resin microcapsule-microbial composite carrier, the epoxy resin microcapsules account for 1.5% by mass.

[0138] In the epoxy resin microcapsule-microbial composite carrier, calcium lactate accounts for 8% by mass;

[0139] The concentration of Bacillus pasteurellii spores in the epoxy resin microcapsule-microbial composite carrier is 10. 7 CFU / g.

[0140] A method for preparing the concrete includes the following steps:

[0141] Epoxy resin microcapsules were added to deionized water at 60℃ and stirred until completely dissolved. Bacillus pasteurellii spores, calcium chloride, and calcium lactate were added and ultrasonically dispersed for 10 min to obtain a mixed solution. 0.1 M CaCl2 solution at 4℃ was added dropwise to the mixed solution using a syringe and allowed to stand for cross-linking for 30 min to form gel microspheres with a diameter of 0.5-1 mm. After freezing at -40℃ for 24 h, the microspheres were vacuum dried for 48 h to obtain the epoxy resin microcapsule-microbial composite carrier.

[0142] The epoxy resin microcapsule-microbial composite carrier and concrete substrate are mixed to obtain the concrete.

[0143] Comparative Example 3

[0144] The difference between Comparative Example 3 and Example 2 is that calcium lactate was replaced with glucose in Comparative Example 3.

[0145] Specifically:

[0146] A type of concrete includes a concrete substrate and a gellan gum-microbial composite carrier dispersed in the concrete substrate, wherein the mass of the gellan gum-microbial composite carrier is 1% of the mass of the concrete substrate; the gellan gum-microbial composite carrier comprises gellan gum, Bacillus pasteurellii spores, and glucose.

[0147] In the gellan gum-microbial composite carrier, the mass percentage of gellan gum is 1.5%.

[0148] In the gellan gum-microbial composite carrier, glucose accounts for 8% by mass;

[0149] The concentration of Bacillus pasteurellii spores in the gellan gum-microbial composite carrier was 10. 7 CFU / g.

[0150] A method for preparing the concrete includes the following steps:

[0151] Gellan gum was added to 60℃ deionized water and stirred until completely dissolved. Pasteurella spores and glucose were added and ultrasonically dispersed for 10 min to obtain a mixed solution. 0.1M CaCl2 solution at 4℃ was added dropwise to the mixed solution using a syringe and allowed to stand for cross-linking for 30 min to form gel microspheres with a diameter of 0.5-1 mm. After freezing at -40℃ for 24 h, the microspheres were vacuum dried for 48 h to obtain the gellan gum-microbial composite carrier.

[0152] The concrete is obtained by mixing the gellan gum-microbial composite carrier and the concrete substrate.

[0153] Performance testing:

[0154] The concrete prepared in Examples 1-3 was tested, and the results are shown in Table 1. The gel strength was tested using a texture analyzer. The 7-day repair rate test method for 0.3mm cracks was based on GB / T 50082-2024, "Standard for Test Methods of Long-Term Performance and Durability of Concrete". The 6-month microbial survival rate test method involved culturing and counting microorganisms in the concrete, comparing the initial microbial count with the microbial count after 6 months, and calculating the survival rate.

[0155] Table 1

[0156] Gellan gum concentration <![CDATA[Gel strength (g / cm 2 )]]> 0.3mm crack repair rate in 7 days 6-month microbial survival rate Example 1 1.0wt% 280±15 78％ 45％ Example 2 1.5wt% 520±20 91％ 62％ Example 3 2.0wt% 650±25 85％ 38％

[0157] As shown in Table 1, when the gellan gum concentration is 1.5 wt%, the repair capacity of concrete reaches its optimal level, with a repair rate of >90% and a survival rate of >60%.

[0158] The concrete prepared in Examples 2 and 4-5 were tested, and the test results are shown in Table 2. During the testing process, particle size uniformity was tested using a laser particle size analyzer, and porosity was tested using mercury intrusion porosimetry.

[0159] Table 2

[0160] <![CDATA[Crosslinking time of CaCl2]]> Average particle size (μm) Porosity Calcium lactate release rate within 7 days Example 4 20min 550±50 52％ 98% (Too fast) Example 2 30min 500±25 40％ 95％ Example 5 40min 480±20 32％ 80% (too slow)

[0161] As shown in Table 2, the calcium lactate release rate reaches its optimal level after 7 days when the CaCl2 cross-linking time is 30 min.

[0162] Thermogravimetric analysis (TGA) was performed on the concrete prepared in Examples 2 and 6. Sample preparation was as follows: cylindrical samples with a diameter of approximately 10 mm and a height of approximately 10 mm were drilled or cut from the concrete of Examples 2 and 6, with three parallel samples taken from each group. The samples were placed in a standard curing chamber (temperature 20±2℃, humidity ≥95%) for 7 days to simulate a crack repair environment. After curing, the samples were crushed into fine powder, passed through a 100-mesh sieve, and the powder passing through the sieve was used as the test sample (approximately 5-10 mg), ensuring the powder was uniform and free of impurities. Subsequently, a mechanical loading method was used, applying a three-point bending load to the concrete specimen using a universal testing machine, and a crack with a width of 0.3 mm was prefabricated at the mid-span to simulate cracking.

[0163] Tests revealed that the 7-day calcium carbonate formation rate in the concrete of Example 2 was 1.8 g / cm³. 3 In Example 6, the 7-day calcium carbonate formation rate in the concrete was only 0.9 g / cm³. 3 This indicates that adding Pasteurella multocida to concrete is the optimal choice.

[0164] The concrete prepared in Example 2 and Comparative Example 1 were tested, and the results are shown in Table 3. The 6-month survival rate test method involved simulating the actual use environment of concrete for 6 months in a laboratory, and periodically sampling and testing the number of microorganisms. Concrete specimens were first cured under standard curing conditions (temperature 20±2℃, humidity ≥95%) for 6 months. Then, the specimens were broken, and the microorganisms were counted using the plate count method. The percentage of surviving microorganisms relative to the initial number of microorganisms was calculated to determine the 6-month survival rate. Crack repair rate and compressive strength loss tests were conducted according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".

[0165] Table 3

[0166] index Example 2 (using gellan glue) Comparative Example 1 (using sodium alginate) 6-month survival rate 62％ 28％ Repair rate of 0.3mm cracks (7 days) 91％ 68％ 28-day compressive strength loss 3.3％ 6.1％

[0167] As shown in Table 3, when gellan gum is replaced with sodium alginate, the concrete strength of Comparative Example 1 decreases due to the weak alkali resistance of sodium alginate.

[0168] The concrete prepared in Example 2 and Comparative Example 2 were tested, and the results are shown in Table 4. The single-repair rate test was performed according to GB / T 50081-2019, "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The secondary repair capability test method was as follows: after completing the single-repair rate test, a 0.3mm crack was pre-fabricated on the repaired specimen, and the curing and crack width measurement steps were repeated to calculate the repair rate after secondary repair. If the repair rate was not 0 and reached a certain effective repair standard (e.g., a secondary repair rate of 88% for gellan gum carrier), it was determined to have secondary repair capability; if, for example, the epoxy resin microcapsule carrier could not be repaired due to rupture, and the repair rate was 0, it was determined not to have secondary repair capability. The biocompatibility test method was as follows: biocompatibility was determined by observing the effect of the carrier on microbial growth and metabolism. Microorganisms were inoculated into culture media containing different carriers (gellan gum, epoxy resin microcapsules), cultured under suitable conditions, and the growth status of the microorganisms (e.g., growth rate, activity, etc.) was observed. If microorganisms can grow and metabolize normally in the environment where the carrier exists, then the carrier has good biocompatibility, such as gellan gum which can encapsulate live bacteria; if it can only accommodate chemical remediation agents and microorganisms cannot survive, then the biocompatibility is poor.

[0169] Table 4

[0170] index Example 2 (using gellan glue) Comparative Example 2 (using epoxy resin microcapsules) Single-shot repair rate (0.3mm) 91％ 95％ Secondary repair capability Supported (88% repair rate) Not supported (capsule breakage). Biocompatibility Live bacteria can be encapsulated Chemical repair agents only

[0171] As can be seen from Table 4, when gellan glue is replaced with epoxy resin microcapsules, the concrete will lose its ability to be repaired.

[0172] The concrete prepared in Examples 2 and 7 were tested, and the results are shown in Table 5. The 6-month microbial survival rate test method involved culturing and counting microorganisms in the concrete, comparing the initial microbial count with the number of microorganisms after 6 months, and calculating the survival rate. The particle redissolution time test method involved removing gellan gum-microbial composite carrier particles from the concrete specimens after 6 months of curing, placing them in 100 mL of deionized water at 20°C, and using a stopwatch to record the time from particle placement to complete dissolution; this was the particle redissolution time.

[0173] Table 5

[0174] Drying method Microbial survival rate (6 months) Particle resolution time Example 2 (Freeze-drying) 62％ <30s Example 7 (natural drying) 22％ >5min

[0175] As shown in Table 5, freezing and drying treatment can further improve the survival rate of microorganisms in concrete.

[0176] The concrete prepared in Example 2 and Comparative Example 3 were tested, and the results are shown in Table 6. The calcium carbonate formation was determined using TGA thermogravimetric analysis. The crack repair rate was tested according to the following standard: GB / T50082-2009.

[0177] Table 6

[0178] Calcium source type Calcium carbonate formation (7 days) Crack repair rate Example 2 (using calcium lactate) <![CDATA[1.8g / cm 3 ]]> 91％ Comparative Example 3 (using glucose) <![CDATA[0.7g / cm 3 ]]> 43％

[0179] As can be seen from Table 6, calcium lactate can simultaneously provide Ca... 2+ As for energy, glucose only provides energy and requires exogenous calcium, therefore the concrete in Example 2 has a better crack repair rate.

[0180] The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A type of concrete, characterized in that: It includes a concrete substrate and a gellan gum-microbial composite carrier dispersed in the concrete substrate; the gellan gum-microbial composite carrier contains gellan gum, urease-producing bacteria, calcium salts, and calcium-containing nutrient sources.

2. The concrete according to claim 1, characterized in that: The gellan gum is an anionic polysaccharide produced by microbial fermentation, which is a linear tetrasaccharide repeating unit polymer composed of glucose, glucuronic acid and rhamnose in a ratio of 2-3:1-2:

1.

3. The concrete according to claim 1, characterized in that: The gellan gum accounts for 1.0-2.0% of the mass of the gellan gum-microbial composite carrier.

4. The concrete according to claim 3, characterized in that: The gellan gum accounts for 1.5-1.9% of the mass of the gellan gum-microbial composite carrier.

5. The concrete according to claim 1, characterized in that: The urease-producing bacteria include Bacillus pasteurellii.

6. The concrete according to claim 1, characterized in that: The calcium salt includes at least one of calcium chloride and calcium nitrate; and / or, the calcium-containing nutrient source includes calcium lactate.

7. The concrete according to claim 1, characterized in that: The concrete substrate comprises cement, aggregates, and water-reducing agents.

8. A method for preparing concrete as described in any one of claims 1 to 7, characterized in that: Includes the following steps: The gellan gum, urease-producing bacterial spores, calcium salts, and calcium-containing nutrient sources were mixed with water, and then frozen and dried to obtain the gellan gum-microbial composite carrier. The concrete is obtained by mixing the gellan gum-microbial composite carrier and the concrete substrate.

9. The method according to claim 8, characterized in that: The freezing temperature is -40°C to -45°C; and / or the drying is vacuum drying.

10. The application of concrete in marine engineering as described in any one of claims 1 to 8.