High-strength self-repairing concrete and preparation method thereof

Abstract

The application discloses a kind of strength promotion type self-repairing concrete and its preparation method, to solve the problem of existing concrete crack repair technology that microbial self-repairing agent is reduced in high-alkali environment Active, carrier material reduces concrete strength, by mixing admixture optimization microbial survival environment and ensure its long-term activity, while improving concrete strength;Its technical scheme includes selecting specific admixture and mixing microbial self-repairing agent, to prepare the concrete with self-repairing function and strength promotion;When crack occurs, microorganisms can automatically locate and metabolize to produce calcium carbonate to fill cracks, significantly improve the strength and durability of concrete structure;It is mainly used for water conservancy projects and other concrete structures that need to bear complex environmental factors for a long time, prolong the service life of the project, improve the safety performance of structure;The concrete preparation method process is simple, cost controllable, suitable for large-scale production and application, and is expected to become an important development direction in the field of building materials in the future.

Description

Technical Field

[0001] This invention relates to the field of concrete crack repair technology in building materials, and particularly to a high-strength self-healing concrete and its preparation method. Background Technology

[0002] Concrete, as the most widely used man-made building material in the world, has extensive applications in various fields such as water conservancy projects and civil engineering. However, in practical applications, concrete is often affected by factors such as water erosion, chemical corrosion, and changes in temperature and humidity, resulting in defects such as cracking, honeycombing, pitting, and hollowing on its interior or surface. Especially in water conservancy projects, such as concrete dams and concrete panels, once cracks appear, they provide channels for moisture and corrosive ions to diffuse into the interior of the concrete. This not only accelerates the reduction of the strength and durability of hydraulic concrete, but also seriously affects the operational safety of water conservancy projects, thereby shortening their service life.

[0003] Extensive research has been conducted by scholars both domestically and internationally on the repair of concrete cracks, leading to the development of a self-healing technology that can automatically locate cracks at their source. This technology utilizes microbial self-healing agents to achieve self-healing of cracks in hydraulic concrete, offering advantages such as precise location, enhanced strength and durability of the concrete structure, and long-term repair capabilities. The basic principle of microbial self-healing technology is that the metabolic processes of microorganisms (such as Bacillus pasteurellii) produce mineralized substances like calcium carbonate, which fill the concrete cracks, thereby achieving the repair purpose.

[0004] However, existing microbial self-healing technologies still have some problems in application. First, the highly alkaline environment inside concrete can inhibit the activity of microorganisms or even kill them, thus affecting the self-healing effect. To solve this problem, existing technologies usually use immobilization technology to protect microorganisms, that is, immobilizing microorganisms on a carrier material and then incorporating them into the concrete. For example, CN114956737A discloses a self-healing concrete using foamed concrete as a carrier, which is composed of concrete ingredients, microbial-carrying foamed concrete, and nutrients; wherein, the microbial-carrying foamed concrete consists of a carbonized modified foamed concrete carrier and Bacillus subtilis loaded on the foamed concrete carrier. This invention utilizes carbonized modified waste foamed concrete as a carrier to immobilize microorganisms. The abundant pores and rough surface of foamed concrete facilitate microbial attachment. Furthermore, vacuum adsorption significantly increases the microbial load on the carrier, effectively enhancing the self-healing efficiency of cracks. The modified foamed concrete also exhibits good mechanical properties, minimizing its negative impact on the mechanical properties of concrete when added to the mix. While this invention uses a carrier material to immobilize and protect microorganisms, improving their survival rate and activity, examples and comparative studies show that the concrete strength decreases significantly after incorporating the carrier material, severely affecting its mechanical properties. This invention, by adding admixtures, greatly mitigates the strength reduction caused by the carrier material. However, this method also has drawbacks; the carrier material often has low strength, which can significantly reduce the concrete strength after incorporation.

[0005] Secondly, although the addition of admixtures can improve certain properties of concrete, in existing microbial self-healing concrete, the impact of admixtures on the microbial survival environment and concrete strength is often not fully considered. Therefore, how to improve concrete strength while ensuring microbial activity has become an urgent technical problem to be solved in the field of microbial self-healing concrete.

[0006] In view of this, the present invention aims to provide a strength-enhancing self-healing concrete and its preparation method. By using admixtures, the living environment of microorganisms is optimized and their long-term activity is ensured, thereby achieving long-term self-healing of cracks. At the same time, it improves the compressive strength and splitting tensile strength of concrete, and improves the situation where the concrete strength is reduced due to the introduction of carrier materials. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a high-strength self-healing concrete and its preparation method, thereby solving the problems in existing concrete crack repair technologies, such as the reduced activity of microbial self-healing agents due to high alkaline environments and the reduction of concrete strength by carrier materials.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a strength-enhancing self-healing concrete, which is made by mixing raw materials including water, cementitious materials, aggregates, reaction substrates and admixtures, and then adding admixtures and coated particles. The cementitious materials include cement and fly ash, the aggregates include gravel and sand, the reaction substrates include calcium lactate and urea, and the admixtures include water-reducing agents and air-entraining agents. The raw materials are mixed in the following mass proportions: water 6.7%~6.9%, cement 11.2%~11.8%, fly ash 2.7%~3%, gravel 47%~47.5%, sand 30.8%~31.2%, calcium lactate 0.28%~0.3%, urea 0.05%~0.07%, water-reducing agent 0.08%~0.1%, and air-entraining agent 0.095%~0.0105%.

[0009] In a preferred embodiment, the raw materials are mixed according to the following mass ratios: water 6.86%, cement 11.55%, fly ash 2.89%, gravel 47.23%, sand 31.02%, calcium lactate 0.29%, urea 0.06%, water-reducing agent 0.09%, and air-entraining agent 0.01%.

[0010] In a preferred embodiment, the admixture is one of phosphogypsum, magnesium oxide, or aluminum oxide.

[0011] In a preferred embodiment, when the admixture is either phosphogypsum or alumina, its dosage is 1%, 3%, 5%, or 7% of the mass of the cementitious material.

[0012] In a preferred embodiment, when the admixture is magnesium oxide, its dosage is 1% or 3% of the mass of the cementitious material.

[0013] In a preferred embodiment, the coating particles account for 15% of the volume of the self-healing concrete and include expanded perlite, metakaolin, and Bacillus pasteurellii.

[0014] In a preferred embodiment, the cement in the cementitious material is PO42.5 ordinary Portland cement with a specific surface area of ​​420. The fly ash is classified as Grade II fly ash.

[0015] In the preferred embodiment, the sand in the aggregate is medium sand; the gravel used is small gravel of 5-20mm and medium gravel of 20-40mm.

[0016] In a preferred embodiment, the water-reducing agent of the admixture is a polycarboxylic acid water-reducing agent, and the air-entraining agent is an AIR202 type air-entraining agent.

[0017] In a preferred embodiment, the calcium lactate in the reaction substrate is analytical grade calcium lactate; the urea is analytical grade urea, and the purity of both calcium lactate and urea is 99%.

[0018] A method for preparing strength-enhancing self-healing concrete, comprising using any one of the strength-enhancing self-healing concretes described above, wherein the preparation method is as follows:

[0019] Step 1: Prepare liquid culture medium according to the nutritional components required by Bacillus pasteurellis, and then autoclave and sterilize it with ultraviolet light.

[0020] Step 2: Add NaOH solution to the sterilized liquid culture medium to adjust the pH to 11, and then dispense it into sterile Erlenmeyer flasks;

[0021] Step 3: Inoculate Pasteurella multocida into Erlenmeyer flasks for large-scale culture;

[0022] Step 4: Centrifuge the cultured bacterial solution to obtain bacterial sludge, and dilute the bacterial sludge to the required concentration for the experiment to obtain a bacterial suspension; use vacuum impregnation method to adsorb the bacterial suspension onto the surface and internal pores of expanded perlite, and dry it to constant weight;

[0023] Step 5: Mix metakaolin with sodium silicate aqueous solution and then spray the bacterial expanded perlite with the mixture. Repeat the process 3 to 4 times to obtain coated particles.

[0024] Step 6: Pour the prepared coated particles, cementitious materials, aggregates, reaction substrates, and admixtures into a mixer and mix at low speed until homogeneous. During the mixing process, add water, water-reducing agent, and air-entraining agent into the mixer in three batches. After mixing, pour the concrete into a mold, vibrate to compact it, and then place it in a curing chamber to wait for molding. Set the temperature of the curing chamber to 20±2℃. After curing the specimens for one to two days and nights, demold them and then immerse the specimens in water in the curing chamber, with the water level 2cm above the specimens, to obtain the self-healing concrete.

[0025] The present invention provides a high-strength self-healing concrete and its preparation method, which have the following beneficial effects:

[0026] 1. This invention solves two major problems in existing concrete crack repair technologies: first, the activity of microbial self-healing agents decreases in a high-alkali environment; second, the addition of carrier materials leads to a decrease in concrete strength.

[0027] 2. This invention, through the external admixture (such as phosphogypsum, alumina, magnesium oxide, etc.), not only optimizes the living environment of microorganisms and ensures their long-term activity, thus achieving long-term self-repair of cracks, but also improves the compressive strength and splitting tensile strength of concrete, effectively improving the phenomenon of reduced concrete strength caused by the addition of carrier materials.

[0028] 3. The self-healing technology of this invention utilizes the microbial metabolic process to produce calcium carbonate, which reduces dependence on harmful chemicals, has low energy consumption, and can reduce greenhouse gas emissions, making it an environmentally friendly and energy-saving crack repair method.

[0029] 4. The phosphogypsum, alumina or magnesium oxide incorporated in this invention can reduce the pH value of the internal environment of concrete, which is beneficial to increasing the activity of Bacillus pasteurellii urease and enhancing the mineralization deposition ability, thereby further improving the compressive strength and splitting tensile strength of concrete.

[0030] 5. This invention uses industrial solid waste stockpiles (such as phosphogypsum, alumina, magnesium oxide, etc.) as raw materials for preparing self-healing concrete, providing a new way to consume these solid wastes, protecting the environment, and saving land resources.

[0031] 6. This invention uses sand and small stones as aggregates, reducing the amount of cement used and increasing the slump of the concrete, which is beneficial for producing denser concrete. Simultaneously, the concrete mold is vibrated using a vibrating table, further improving the density of the concrete.

[0032] 7. The addition of an air-entraining agent in this invention can introduce small air bubbles during the concrete pouring process. These small air bubbles become small pores after the concrete hardens, providing a reaction space for the mineralization and deposition of Bacillus pasteurellii, thereby improving the strength and impermeability of the concrete.

[0033] 8. This invention uses expanded perlite and metakaolin to immobilize and encapsulate microorganisms, protecting their integrity during mechanical mixing and vibration, and ensuring that microorganisms can be released and repaired in a timely manner when concrete cracks.

[0034] 9. The strength-enhancing self-healing concrete of the present invention has been verified by detailed experimental data. The experimental results show that the crack width is significantly reduced within a period of time after the cracks are generated, the concrete strength is effectively restored, and the long-term performance is stable. This not only proves that the activity of the microbial self-healing agent is enhanced in the high-alkali environment of concrete, but also proves that the admixtures significantly improve the mechanical properties of concrete.

[0035] 10. Through a series of innovative technologies, this invention successfully solves the problems existing in the current concrete crack repair technology, and provides an environmentally friendly, energy-saving, high-strength concrete material with long-term self-healing function, which has broad application prospects and important practical value. Attached Figure Description

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0037] Figure 1 This is a flowchart of the preparation method of the present invention;

[0038] Figure 2 This is a diagram illustrating the crack repair process in Example 3;

[0039] Figure 3 This is a diagram illustrating the crack repair process in Example 4;

[0040] Figure 4 This is a diagram illustrating the crack repair process in Example 5;

[0041] Figure 5 This is a diagram illustrating the crack repair process in Example 6;

[0042] Figure 6 This is a diagram illustrating the crack repair process in Example 7;

[0043] Figure 7 This is a diagram illustrating the crack repair process in Example 8;

[0044] Figure 8 This is a diagram illustrating the crack repair process in Example 9;

[0045] Figure 9 This is a diagram illustrating the crack repair process in Example 10;

[0046] Figure 10 This is a diagram illustrating the crack repair process in Example 11;

[0047] Figure 11 This is a diagram illustrating the crack repair process in Example 12;

[0048] Figure 12 This is a diagram of the crack repair process in Example 13. Detailed Implementation

[0049] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments:

[0050] Example 1

[0051] A type of strength-enhancing self-healing concrete is made by mixing raw materials including water, cementitious materials, aggregates, reactive substrates, and admixtures, and then adding admixtures and coated particles. The cementitious materials include cement and fly ash, the aggregates include gravel and sand, the reactive substrates include calcium lactate and urea, and the admixtures include water-reducing agents and air-entraining agents. The raw materials are mixed in the following mass proportions: water 6.7%~6.9%, cement 11.2%~11.8%, fly ash 2.7%~3%, gravel 47%~47.5%, sand 30.8%~31.2%, calcium lactate 0.28%~0.3%, urea 0.05%~0.07%, water-reducing agent 0.08%~0.1%, and air-entraining agent 0.095%~0.0105%.

[0052] In this embodiment, the raw materials are mixed according to the following mass ratios: water 6.86%, cement 11.55%, fly ash 2.89%, gravel 47.23%, sand 31.02%, calcium lactate 0.29%, urea 0.06%, water-reducing agent 0.09%, and air-entraining agent 0.01%.

[0053] Furthermore, the admixture is one of phosphogypsum, magnesium oxide, or aluminum oxide.

[0054] Furthermore, when the admixture is either phosphogypsum or alumina, its dosage is 1%, 3%, 5%, or 7% of the mass of the cementitious material.

[0055] Furthermore, when the admixture is magnesium oxide, its dosage is 1% or 3% of the mass of the cementitious material.

[0056] Furthermore, the coating particles account for 15% of the volume of the self-healing concrete and include expanded perlite, metakaolin, and Bacillus pasteurellii.

[0057] Furthermore, the cement in the cementitious material is PO42.5 ordinary Portland cement with a specific surface area of ​​420. The fly ash is classified as Grade II fly ash.

[0058] Furthermore, the sand in the aggregate is medium sand; the gravel used is small stone of 5-20mm and medium stone of 20-40mm.

[0059] Furthermore, the water-reducing agent in the admixture is a polycarboxylate water-reducing agent, and the air-entraining agent is an AIR202 type air-entraining agent.

[0060] Furthermore, the calcium lactate in the reaction substrate is analytical grade calcium lactate; the urea is analytical grade urea, and the purity of both calcium lactate and urea is 99%.

[0061] Example 2

[0062] In another preferred embodiment, based on Embodiment 1 above, a method for preparing strength-enhancing self-healing concrete is to use any one of the strength-enhancing self-healing concretes described above, and the preparation method is as follows:

[0063] Step 1: Prepare liquid culture medium according to the nutrient composition required by Bacillus pasteurellis. Place the prepared liquid culture medium into an autoclave, cover the liquid culture medium with kraft paper, set the sterilization temperature to 121℃ and the sterilization time to 20min.

[0064] Step 2: Take out the sterilized liquid culture medium and place it in the ultraviolet irradiation of the laminar flow hood for 15 minutes for sterilization. Add NaOH solution to the sterilized liquid culture medium to adjust it to 1:1. Dispense the prepared liquid culture medium into sterile conical flasks, 150ml in each conical flask.

[0065] Step 3: Inoculate Pasteurella multocida into Erlenmeyer flasks for expansion culture. Seal the Erlenmeyer flasks with gauze and place them in a water bath constant temperature shaking incubator (30℃, 120r / min) for 36h.

[0066] Step 4: Centrifuge the cultured bacterial solution at 4500 rpm for 15 minutes. Wash the resulting bacterial sludge with purified water and set aside. Dilute the sludge to the required concentration for the experiment to obtain a bacterial suspension. Use a vacuum impregnation method to adsorb the bacterial suspension onto the surface and internal pores of expanded perlite. Place the adsorbed expanded perlite in a 10°C container. o Dry in oven C until constant weight;

[0067] Step 5: Mix metakaolin with sodium silicate aqueous solution in a ratio of 53% metakaolin, 23% water and 24% sodium silicate solution. Pour the mixture into the spray gun barrel and spray it onto one side of the bacteria-loaded expanded perlite. After spraying, flip the bacteria-loaded particles over and spray again to complete the first coating treatment. Repeat this process 3 to 4 times to obtain the coated particles for the test.

[0068] Step 6: Pour the prepared coated granules, cementitious materials, aggregates, reaction substrates, and admixtures into a mixer and mix at low speed until homogeneous. During the mixing process, add water, water-reducing agent, and air-entraining agent to the mixer in three batches. After mixing, pour the concrete into molds that have been pre-applied with release agent. Place the molds on a vibrating table to compact the concrete, then place them in a curing chamber to await shaping. Set the curing chamber temperature to 20°C. 2 o C. After curing the specimens for one to two days and nights, they are demolded and then immersed in water in a curing chamber with the water level 2 cm above the specimens to obtain the self-healing concrete.

[0069] Example 3

[0070] In another preferred embodiment, based on the above embodiments 1 and 2, this embodiment 3 provides a high-strength self-healing concrete composed of the following raw materials in the following mass percentages: water 6.86%, cement 11.55%, fly ash 2.89%, aggregate 47.23%, sand 31.02%, calcium lactate 0.29%, urea 0.06%, water-reducing agent 0.09%, and air-entraining agent 0.01%; in addition, the admixture is phosphogypsum, and the amount of phosphogypsum accounts for 1% of the mass of the cementitious materials.

[0071]

[0072] Example 4

[0073] In another preferred embodiment, based on Example 3, a high-strength self-healing concrete is prepared with a phosphogypsum content of 3%, and the other components are the same as in Example 3, and the preparation method is the same as in Example 2.

[0074]

[0075] Example 5

[0076] In another preferred embodiment, based on Example 3, a high-strength self-healing concrete is prepared with 5% phosphogypsum content, and the other components are the same as in Example 3, and the preparation method is the same as in Example 2.

[0077]

[0078] Example 6

[0079] In another preferred embodiment, based on Example 3, a high-strength self-healing concrete is prepared with 7% phosphogypsum content, and the other components are the same as in Example 3, and the preparation method is the same as in Example 2.

[0080]

[0081] Example 7

[0082] In another preferred embodiment, based on the above embodiments 1 and 2, the high-strength self-healing concrete of this embodiment 7 is composed of the following raw materials in the following mass percentages: water 6.86%, cement 11.55%, fly ash 2.89%, aggregate 47.23%, sand 31.02%, calcium lactate 0.29%, urea 0.06%, water-reducing agent 0.09%, and air-entraining agent 0.01%; in addition, the admixture is magnesium oxide, and the amount of magnesium oxide accounts for 1% of the mass of the cementitious materials.

[0083]

[0084] Example 8

[0085] In another preferred embodiment, based on Example 7, a high-strength self-healing concrete is prepared with a magnesium oxide content of 3%, and the other components are the same as in Example 7, and the preparation method is the same as in Example 2.

[0086]

[0087] Example 9

[0088] In another preferred embodiment, based on the above embodiments 1 and 2, the high-strength self-healing concrete of this embodiment 9 is composed of the following raw materials in the following mass percentages: water 6.86%, cement 11.55%, fly ash 2.89%, aggregate 47.23%, sand 31.02%, calcium lactate 0.29%, urea 0.06%, water-reducing agent 0.09%, and air-entraining agent 0.01%; in addition, the admixture is alumina, and the alumina content accounts for 1% of the mass of the cementitious material.

[0089]

[0090] Example 10

[0091] In another preferred embodiment, based on Example 9, a high-strength self-healing concrete is prepared with an alumina content of 3%, and the other components are the same as in Example 9, and the preparation method is the same as in Example 2.

[0092]

[0093] Example 11

[0094] In another preferred embodiment, based on Example 9, a high-strength self-healing concrete is prepared with an alumina content of 5%, and the other components are the same as in Example 9, and the preparation method is the same as in Example 2.

[0095]

[0096] Example 12

[0097] In another preferred embodiment, based on Example 9, a high-strength self-healing concrete is prepared with an alumina content of 7%, and the other components are the same as in Example 9, and the preparation method is the same as in Example 2.

[0098]

[0099] Example 13

[0100] In another preferred embodiment, based on Examples 3-12, a high-strength self-healing concrete has an admixture dosage of 0, except that the other components are the same as in Examples 3-12, and the preparation method is the same as in Example 2.

[0101]

[0102] The performance of the concrete prepared in Examples 3-13 above was tested:

[0103] The self-healing concrete prepared in Examples 3-13 was used to prepare 100mm thick sheets. 100mm 100mm test blocks were prepared, and the concrete was cured for 28 days according to SL / T 352-2020 "Test Procedures for Hydraulic Concrete". The compressive strength test of the self-healing concrete was performed using a YE-W2000kN pressure testing machine, in accordance with SL / T 352-2020 "Test Procedures for Hydraulic Concrete". The compressive strength of the self-healing concrete was... It can be calculated by formula (1). The arithmetic mean of the compressive strength of the three specimens in each group is taken as the compressive strength value of that group. If the difference between a measured value and the median value exceeds 15%, the median value is taken as the compressive strength result. If the difference between two measured values ​​and the median value exceeds 15%, the result is considered invalid. Considering the 100mm 100mm The 100mm cube specimen is a non-standard specimen, so the compressive strength calculation needs to be multiplied by a conversion factor of 0.95.

[0104] (1)

[0105] In the formula, The compressive strength of the self-healing concrete specimen is given in MPa. The failure load of the self-healing concrete specimen is expressed in kN. The bearing surface area of ​​the self-healing concrete specimen is given in units of: .

[0106] The splitting tensile strength test of self-healing concrete was performed using a YE-W2000kN compression testing machine, in accordance with GB / T50061-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The splitting compressive strength of self-healing concrete was also tested. The splitting tensile strength value is calculated using formula (2) and taken as the arithmetic mean of the three specimens in each group. The median value is used as the evaluation criterion. If the difference between a measured value and the median value exceeds 15%, the median value is taken as the splitting tensile strength result; if the difference between two measured values ​​and the median value exceeds 15%, the result is considered invalid. Considering the 100mm... 100mm The 100mm cube specimen is a non-standard specimen, so a conversion factor of 0.85 is required when calculating the splitting tensile strength.

[0107] (2)

[0108] In the formula, Splitting tensile strength of the specimen, unit: MPa; The failure load of the specimen is expressed in N. The area of ​​the splitting surface of the specimen, in units of: .

[0109] The specific test results are shown in Table 12:

[0110]

[0111] As can be seen from the comparison of Examples 3 to 13, the self-healing concrete modified with phosphogypsum, magnesium oxide and alumina has higher compressive strength and splitting tensile strength.

[0112] Self-healing tests were conducted on the concrete prepared in Examples 3-13 above:

[0113] The marked points were observed using a ZW-C3600 image microscope, and the entire microbial concrete crack surface at each age was recorded by taking pictures. The crack area repair rate was calculated. The crack and non-crack areas were distinguished by software, and the crack area was calculated by a self-written program. The crack area repair rate of the specimen at each age was obtained by substituting the program into formula (3).

[0114] (3)

[0115] In the formula, The crack area repair rate; To repair the crack area of ​​the specimen after 0 days of curing; For repair and maintenance The crack area of ​​specimen d.

[0116] The specific test results are shown in Table 13:

[0117]

[0118] As can be seen from the comparison of Examples 3 to 13, the self-healing concrete modified with phosphogypsum, magnesium oxide and alumina has a better repair effect and a higher repair rate for cracks.

[0119] By adjusting the type and dosage of admixtures, the mechanical properties, self-healing effect, and environmental adaptability of self-healing concrete can be further explored and optimized. Each embodiment independently demonstrates the influence of different admixtures on concrete performance, providing strong support for the diversity and practicality of technical features.

[0120] In a preferred embodiment, the admixture is one of phosphogypsum, magnesium oxide, or aluminum oxide. This configuration not only significantly improves the strength and durability of the material but also effectively regulates its setting time and workability, meeting the application requirements under various complex construction conditions, thereby improving project quality and construction efficiency.

[0121] In a preferred embodiment, when the admixture is either phosphogypsum or alumina, its dosage is 1%, 3%, 5%, or 7% of the mass of the cementitious material; when the admixture is magnesium oxide, its dosage is 1% or 3% of the mass of the cementitious material. These settings can significantly improve the crack resistance and durability of concrete, making it particularly suitable for large-volume concrete and structures requiring long-term load bearing. Simultaneously, the magnesium oxide dosage at this level can effectively regulate the heat of hydration of concrete, reducing the risk of temperature cracks.

[0122] In a preferred embodiment, the coating particles account for 15% of the volume of the self-healing concrete and include expanded perlite, metakaolin, and Bacillus pasteurellii. This configuration allows Bacillus pasteurellii to activate and produce calcium carbonate when cracks occur in the concrete. This calcium carbonate works in conjunction with the microstructure of expanded perlite and metakaolin to effectively fill and strengthen the cracked area, thereby improving the durability and self-healing efficiency of the concrete.

[0123] In a preferred embodiment, the cement in the cementitious material is PO42.5 ordinary Portland cement with a specific surface area of ​​420. The fly ash is Class II fly ash; the above settings ensure that the cementitious material has good physical properties and chemical stability; in addition, an appropriate amount of slag powder is added as an auxiliary cementitious material, which further improves the overall strength and durability, making the final product perform better.

[0124] In the preferred embodiment, the sand in the aggregate is medium sand; the gravel used is small stone of 5-20mm and medium stone of 20-40mm; the above settings enable the concrete to have sufficient strength while maintaining good workability, such as fluidity and pumpability; at the same time, through reasonable gradation, the porosity is reduced, and the density and durability of the concrete are improved.

[0125] In a preferred embodiment, the water-reducing agent of the admixture is a polycarboxylate water-reducing agent, and the air-entraining agent is an AIR202 type air-entraining agent. The above configuration can effectively improve the fluidity and workability of concrete. At the same time, the AIR202 type air-entraining agent can introduce an appropriate amount of micro air bubbles, enhance the freeze-thaw resistance of concrete, make concrete more durable, and meet the construction needs of various complex environments.

[0126] In the preferred embodiment, the calcium lactate in the reaction substrate is analytical grade calcium lactate; the urea is analytical grade urea, and the purity of both calcium lactate and urea is 99%. The above settings ensure the controllability of the reaction conditions and the stability of the product quality. In addition, deionized water is used as the reaction solvent to reduce interference from impurities, and all raw materials are accurately weighed before use to ensure that the reaction proceeds according to the predetermined stoichiometric ratio.

[0127] In summary, this invention provides a high-strength self-healing concrete and its preparation method. This method modifies the self-healing concrete by introducing admixtures such as phosphogypsum, magnesium oxide, or alumina. The addition of these admixtures not only optimizes the survival environment of the microorganism *Pasteurella multocida*, ensuring its long-term activity and thus achieving long-term self-healing of cracks, but also effectively improves the reduction in concrete strength caused by the addition of load-bearing materials (such as expanded perlite and metakaolin). This invention is the first to propose mixing these admixtures with conventional concrete materials (such as water, cement, fly ash, sand, and gravel), and obtaining coated particles by externally adding expanded perlite, metakaolin, and *Pasteurella multocida*. These particles play a crucial role in the concrete, promoting the survival of microorganisms and the formation of calcium carbonate. In the preparation process, a liquid culture medium is first prepared according to the nutrient composition required by Bacillus pasteurellii, and then sterilized using a high-pressure steam sterilizer to ensure the purity and activity of the microorganisms. Then, during concrete preparation, admixtures, coating particles, and other materials are mixed with conventional concrete materials. Through specific mixing processes and curing conditions, self-healing concrete is produced. This self-healing mechanism mainly utilizes the metabolic process of Bacillus pasteurellii and other microorganisms in concrete to produce calcium carbonate, achieving automatic repair of cracks, thereby reducing dependence on harmful chemicals and lowering energy consumption and greenhouse gas emissions. This invention successfully produces a high-strength self-healing concrete, further expanding the application scope of existing self-healing concrete and possessing broad practical application value. The concrete preparation method is simple, cost-controllable, and suitable for large-scale production and application, and is expected to become an important development direction in the future building materials field, promoting the realization of green building and sustainable development goals. Furthermore, this self-healing concrete exhibits good durability and environmental adaptability, maintaining stable repair effects under different climatic and geological conditions, providing strong support for extending the service life of buildings and reducing maintenance costs.

Claims

1. A strength-enhancing self-healing concrete, characterized in that, It is made by mixing raw materials including water, cementitious materials, aggregates, reaction substrates, and admixtures, and then adding admixtures and coated particles. The cementitious materials include cement and fly ash, the aggregates include gravel and sand, the reaction substrates include calcium lactate and urea, and the admixtures include water-reducing agents and air-entraining agents. The proportions of each raw material are as follows: water 6.7%~6.9%, cement 11.2%~11.8%, fly ash 2.7%~3%, gravel 47%~47.5%, sand 30.8%~31.2%, calcium lactate 0.28%~0.3%, and urea 0.05%. The mixture comprises ~0.07% by mass of water-reducing agent, 0.08%~0.1% by mass of air-entraining agent, and 0.095%~0.0105% by mass of phosphogypsum, magnesium oxide, or aluminum oxide. When the admixture is phosphogypsum or aluminum oxide, its dosage is 1%, 3%, 5%, or 7% of the mass of cementitious material. When the admixture is magnesium oxide, its dosage is 1% or 3% of the mass of cementitious material. The coating particles account for 15% of the volume of self-healing concrete and include expanded perlite, metakaolin, and Bacillus pasteurellii.

2. The strength-enhancing self-healing concrete according to claim 1, characterized in that: The raw materials are mixed according to the following mass ratios: water 6.86%, cement 11.55%, fly ash 2.89%, gravel 47.23%, sand 31.02%, calcium lactate 0.29%, urea 0.06%, water-reducing agent 0.09%, and air-entraining agent 0.01%.

3. The strength-enhancing self-healing concrete according to claim 1, characterized in that: The cement in the cementitious material is PO42.5 ordinary Portland cement with a specific surface area of ​​420. The fly ash is classified as Grade II fly ash.

4. The strength-enhancing self-healing concrete according to claim 1, characterized in that: The sand in the aggregate is medium sand; the gravel used is small gravel of 5-20mm and medium gravel of 20-40mm.

5. The strength-enhancing self-healing concrete according to claim 1, characterized in that: The water-reducing agent in the admixture is a polycarboxylate water-reducing agent, and the air-entraining agent is an AIR202 type air-entraining agent.

6. A method for preparing strength-enhancing self-healing concrete, characterized in that, The strength-enhancing self-healing concrete according to any one of claims 1 to 5 is prepared by the following method: Step 1: Prepare liquid culture medium according to the nutritional components required by Bacillus pasteurellis, and then autoclave and sterilize it with ultraviolet light. Step 2: Add NaOH solution to the sterilized liquid culture medium to adjust the pH to 11, and then dispense it into sterile Erlenmeyer flasks; Step 3: Inoculate Pasteurella multocida into Erlenmeyer flasks for large-scale culture; Step 4: Centrifuge the cultured bacterial solution to obtain bacterial sludge, and dilute the bacterial sludge to the required concentration for the experiment to obtain a bacterial suspension; use vacuum impregnation method to adsorb the bacterial suspension onto the surface and internal pores of expanded perlite, and dry it to constant weight; Step 5: Mix metakaolin with sodium silicate aqueous solution and then spray the bacterial expanded perlite with the mixture. Repeat the process 3 to 4 times to obtain coated particles. Step 6: Pour the prepared coated particles, cementitious materials, aggregates, reaction substrates, and admixtures into a mixer and mix at low speed until homogeneous. During the mixing process, add water, water-reducing agent, and air-entraining agent into the mixer in three batches. After mixing, pour the concrete into a mold, vibrate to compact it, and then place it in a curing chamber to wait for molding. Set the temperature of the curing chamber to 20±2℃. After curing the specimens for one to two days and nights, demold them and then immerse the specimens in water in the curing chamber, with the water level 2cm above the specimens, to obtain the self-healing concrete.

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