A method for extending the life of a concrete material in a harsh environment

Abstract

This invention discloses a method for extending the service life of concrete materials in harsh environments, belonging to the field of concrete repair technology. The method involves adding a concrete repair agent, which is a compound of microbial agents, mineralized substrates, carrier materials, and auxiliary additives in a specific ratio. In this method, microbial metabolic activity induces a mineralization reaction to generate stable calcium carbonate crystals, which can quickly fill corrosion cracks and pores in concrete. The repair agent exhibits high bonding strength and good compatibility with the concrete matrix, effectively blocking the intrusion of external corrosive media, significantly improving the mechanical properties and durability of corroded concrete. This achieves the effect of extending the service life of concrete materials under harsh environments, and the repair process is green, environmentally friendly, and produces no secondary pollution.

Description

Technical Field

[0001] This invention belongs to the field of concrete repair technology, specifically relating to a method for extending the service life of concrete materials in harsh environments. Background Technology

[0002] Concrete, as the world's most widely used building material, is widely used in various engineering projects such as industrial buildings, municipal engineering, water conservancy facilities, bridges and tunnels, and offshore platforms due to its advantages such as high strength, low cost, and easy availability. However, during long-term service in harsh environments such as corrosive environments, freeze-thaw cycles, alternating wet and dry conditions, and chemical erosion, concrete structures will inevitably be corroded and require repair.

[0003] Currently, repair techniques for corroded concrete are mainly divided into two categories: physical repair methods and chemical repair methods. Physical repair methods mainly include surface coating methods, adhesive reinforcement methods, and replacement methods. Among them, the surface coating method involves applying a protective coating to the concrete surface to isolate the corrosive medium from contact with the concrete substrate. However, it suffers from problems such as low adhesion strength between the coating and the substrate, easy aging and peeling, and short-lasting repair effects. Chemical repair methods mainly use chemical grouting materials and inorganic cementitious materials for repair, such as epoxy resin, polyurethane, and cement-based grouting materials. Although these repair agents can fill cracks and improve concrete strength in the short term, they have problems such as poor environmental performance, poor compatibility with the concrete substrate, and easy generation of secondary pollution.

[0004] In recent years, microbial induced mineralization (MICP) technology has gradually become a research hotspot in the field of concrete repair due to its advantages such as being environmentally friendly, having a long-lasting repair effect, and good compatibility with the matrix. Microbial induced mineralization refers to the use of microbial metabolic activities to convert soluble ions in the environment into insoluble minerals (mainly calcium carbonate), thereby achieving the purpose of crack filling and structural reinforcement. Existing technologies include some research on concrete repair agents based on microbial induced mineralization, but there are still many shortcomings: First, the mineralization efficiency of a single microbial strain is low, and the repair speed is slow, making it difficult to meet the repair needs of actual engineering projects; second, the survival rate of microorganisms in the corrosive environment of concrete is low, and they are easily affected by factors such as acidity, alkalinity, temperature, and corrosive ions, making it difficult for the mineralization reaction to continue and resulting in insufficient repair durability; third, the composition of the repair agent is unreasonable, the carrier material has a poor protective effect on microorganisms, the utilization rate of the mineralization substrate is low, and the bond strength between the repair agent and the concrete matrix needs to be improved; fourth, the existing repair agents have a narrow range of applications, making it difficult to adapt to the concrete repair needs under different corrosion levels and environmental conditions, and the application methods are complex and the construction efficiency is low.

[0005] Furthermore, traditional microbial remediation agents suffer from problems such as uneven crystallization of mineralized products and incomplete pore filling during application, failing to effectively block the intrusion of external corrosive media. This results in the repaired concrete structure still being susceptible to secondary corrosion. Additionally, some remediation agents contain chemical reagents that can cause environmental pollution, contradicting the principles of green building. Therefore, developing a concrete life-extending method with high mineralization efficiency, high microbial survival rate, long-lasting repair effects, environmental friendliness, simple construction, and adaptability to various corrosion scenarios is of significant practical importance and engineering application value. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned shortcomings in the prior art and provide a method for extending the service life of concrete materials in harsh environments, solving the technical problems of low mineralization efficiency of repair agents, low survival rate of microorganisms, poor repair effect, insufficient durability, poor environmental performance and complex construction in existing concrete repair technologies.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for extending the service life of concrete materials in harsh environments includes the following steps: S1. Pretreatment: Clean the corroded concrete surface to remove surface slag, loose layer and corrosion products, rinse with a high-pressure water gun and let it dry until there is no obvious water accumulation on the surface; for cracks with a width ≥0.1mm, use a wire brush to clean the debris inside the crack to ensure that the crack is unobstructed. S2. Preparation of repair agent: Mix the microbial agent, mineralized substrate, carrier material and auxiliary additives evenly, add deionized water, adjust the water-to-material ratio to 0.3-0.5:1, and stir to make a uniform paste-like repair agent; S3. Apply / Grouting: Apply the prepared repair agent evenly to the corroded concrete surface, with a thickness of 0.5-2mm. For cracked areas, use grouting to fill the cracks with the repair agent until the cracks are completely filled. S4. Curing: Place the repaired concrete in an environment with a temperature of 20-30℃ and a relative humidity of 70%-90% for 7-28 days. Spray deionized water during the curing period to keep the surface moist.

[0008] In one specific embodiment, the repair agent in step S2, by mass parts, includes the following components: 10-25 parts of microbial agent, 30-60 parts of mineralized substrate, 15-35 parts of carrier material, and 5-15 parts of auxiliary additives.

[0009] The microbial agent is a mixture of sporocysts of *Sporosarcina pasteurii* and *Pseudomonas aeruginosa*, with a concentration ratio of 8-12:1 and a total sporocyst concentration of 9 × 10⁻⁶. 8 -6×10 10 cells / ml; Bacillus pasteurellii is a urea-degrading strain that can efficiently decompose urea to generate carbonate ions, while Pseudomonas aeruginosa is a denitrifying strain that can induce mineralization reactions through anaerobic respiration in hypoxic environments. The synergistic effect of the two can significantly improve mineralization efficiency and repair effect, adapt to the hypoxic environment deep in concrete cracks, and achieve comprehensive repair.

[0010] The mineralization substrate is a mixture of urea and calcium nitrate tetrahydrate in a mass ratio of 1:1-2. Urea provides carbon and nitrogen sources for microbial metabolism and decomposes to generate carbonate ions, while calcium nitrate tetrahydrate provides calcium ions. Under the induction of microorganisms, carbonate ions and calcium ions combine to form calcium carbonate crystals, which fill concrete cracks and pores.

[0011] The carrier material is porous ceramic particles modified with silane coupling agent KH-550, with a particle size of 0.5-2 mm and a porosity of 35%-55%. The modified porous ceramic particles have good adsorption performance and stability, providing a stable habitat for microorganisms, protecting them from the influence of external corrosive environments, and improving their survival rate. At the same time, their porous structure can adsorb mineralized substrates, enabling the slow release of mineralized substrates and prolonging the mineralization reaction time.

[0012] The auxiliary additives include nutrients, dispersants, and water-retaining agents, with a mass ratio of 5-8:2-4:1-3. The nutrients are a mixture of yeast extract, ammonium nitrate, and inosine, with a mass ratio of 18-20:8-10:0.5-1. This provides sufficient nutrition for microbial metabolism, promotes microbial growth and reproduction, and improves mineralization efficiency. The dispersant is sodium polynaphthalene sulfonate, which improves the dispersibility of the components of the repair agent, prevents clumping, and enhances the uniformity of the repair agent. The water-retaining agent is sodium polyacrylate, which locks in the moisture in the repair agent, providing a stable moisture environment for microbial metabolism and mineralization reactions, while also improving the bond strength between the repair agent and the concrete substrate.

[0013] Further, the preparation method of the microbial agent is as follows: Bacillus pasteurellii (strain number: ATCC 11859) and Pseudomonas aeruginosa (strain number: ATCC 27853) are cultured separately using LB medium. The culture conditions are: temperature 30℃, rotation speed 180 r / min, culture for 24-48 h. After the strains enter the stationary phase, they are centrifuged at 8000 r / min and 4℃ for 15 min to collect the bacterial cells. The cells are washed three times with sterile physiological saline and then freeze-dried at -50℃ and 0.08 MPa for 24 h to prepare spores. The spores are then mixed at a concentration ratio of 8-12:1 and sterile physiological saline is added to prepare a spore suspension, which yields the microbial agent.

[0014] Furthermore, the modification method of the carrier material is as follows: porous ceramic particles are placed in an ethanol solution of silane coupling agent KH-550 with a mass fraction of 3%-5%, ultrasonically dispersed for 30-60 minutes with an ultrasonic power of 200W, and then dried at 60-80℃ to constant weight and cooled to room temperature to obtain modified porous ceramic particles; the addition of silane coupling agent can improve the compatibility of porous ceramic particles with other components of the repair agent, and at the same time enhance its adsorption performance and stability.

[0015] Further, the optimal composition by mass is as follows: 18 parts microbial inoculant, 45 parts mineralized substrate, 25 parts carrier material, and 12 parts auxiliary additives; the concentration ratio of Bacillus pasteurellii to Pseudomonas aeruginosa in the microbial inoculant is 10:1, and the total concentration of spores is 3 × 10⁻⁶. 9 The mass ratio of urea to calcium nitrate tetrahydrate in the mineralization substrate is 1:1.5; the mass ratio of nutrients, dispersant and water-retaining agent in the auxiliary additives is 6:3:2; this optimal ratio can achieve the best balance of microbial mineralization efficiency, repair effect, durability and environmental protection.

[0016] Furthermore, in step S2, the stirring speed is 300-500 r / min and the stirring time is 10-20 min; in step S4, deionized water is sprayed 3-4 times a day for the first 3 days of curing, and the amount of water sprayed each time should be enough to moisten the surface without water accumulation; after 3 days, it is sprayed 1-2 times a day until the curing is completed.

[0017] Furthermore, the concrete material life extension method can be used to repair and extend the life of various concrete structures that are subjected to chemical corrosion, microbial corrosion or physical erosion, such as industrial sewage tanks, bridge piers, underground integrated pipe corridors, and offshore platforms. It has a wide range of applications and can meet the repair needs under different corrosion levels and environmental conditions.

[0018] The beneficial effects of this invention are as follows: 1. This invention discloses a method for extending the service life of concrete materials in harsh environments, mainly achieved by adding a concrete repair agent. The concrete repair agent is composed of microbial agents, mineralizing substrates, carrier materials, and auxiliary additives in a specific ratio. The microbial agents utilize the synergistic effect of Bacillus pasteurellii and Pseudomonas aeruginosa, which exert their mineralization effects under aerobic and anaerobic environments respectively. This allows them to adapt to different environments on the concrete surface and deep within cracks, achieving comprehensive and efficient mineralization repair, with a mineralization efficiency more than 30% higher than that of a single strain.

[0019] 2. The concrete repair agent uses porous ceramsite modified with silane coupling agent as a carrier material, which can provide a stable habitat for microorganisms, protect microorganisms from the effects of corrosive media, increase the survival rate of microorganisms to more than 85%, and at the same time realize the slow release of mineralized substrates, prolong the mineralization reaction time, and ensure the long-lasting repair effect. 3. The concrete repair agent has a reasonable combination of components. The addition of auxiliary additives not only provides sufficient nutrition for microorganisms, but also improves the dispersibility and water retention of the repair agent, and increases the bonding strength between the repair agent and the concrete matrix. The bonding strength can reach more than 2.5 MPa. 4. The method provided by this invention is green and environmentally friendly in its repair process. No toxic or harmful substances are generated during the microbial metabolism and mineralization reaction, and there is no secondary pollution, which is in line with the development concept of green building. 5. The repair agent prepared by the method provided by this invention is simple to prepare, easy to apply, has high construction efficiency, low cost, and wide applicability. It can effectively repair concrete structures with different degrees of corrosion and under different environmental conditions. After repair, the compressive strength, impermeability, and corrosion resistance of the concrete are significantly improved, which can greatly extend the service life of the concrete structure. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The described embodiments are only some preferred embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise specified, the experimental methods used in the embodiments are conventional or common methods in the art, and the materials and reagents used are commercially available unless otherwise specified.

[0022] The raw materials used in the examples and comparative examples are described below: The *Pasteurella multocida* strain used was ATCC 11859, and the *Pseudomonas aeruginosa* strain was ATCC27853, both purchased from the China General Microbiological Culture Collection Center. The silane coupling agent KH-550, sodium polynaphthalene sulfonate, and sodium polyacrylate were all commercially available analytical grade reagents. The porous ceramic granules were commercially available, with a particle size of 0.5-2 mm and a porosity of 35%-55%. The yeast extract, ammonium nitrate, and inosine in the nutrients were all commercially available biological reagents.

[0023] Unless otherwise specified, all components and raw materials used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0024] Preparation method of microbial inoculant: Bacillus pasteurellii and Pseudomonas aeruginosa were cultured separately on LB medium under the following conditions: 30℃, 180 r / min, for 36 h. After the strains entered the stationary phase, they were centrifuged at 8000 r / min and 4℃ for 15 min to collect the bacterial cells. The cells were washed three times with sterile physiological saline and then freeze-dried at -50℃ and 0.08 MPa for 24 h to prepare spores. The spores were then mixed according to the set concentration ratio and sterile physiological saline was added to prepare a spore suspension, which yielded the microbial inoculant.

[0025] Modification method of carrier material: Porous ceramsite is placed in an ethanol solution of 4% KH-550 silane coupling agent by mass, ultrasonically dispersed for 45 min at an ultrasonic power of 200 W, and then dried at 70℃ to constant weight and cooled to room temperature to obtain modified porous ceramsite.

[0026] Example 1

[0027] A method for extending the service life of concrete materials in harsh environments includes the following steps: S1. Pretreatment: Clean the corroded concrete surface to remove surface slag, loose layer and corrosion products, rinse with a high-pressure water gun and let it dry until there is no obvious water accumulation on the surface; for cracks with a width ≥0.1mm, use a wire brush to clean the debris inside the crack to ensure that the crack is unobstructed. S2. Preparation of repair agent: Mix the above components evenly, add deionized water, adjust the water-to-material ratio to 0.3:1, stir at 300r / min for 10min to make a uniform paste-like repair agent; S3. Apply / Grouting: Apply the repair agent evenly to the corroded concrete surface to a thickness of 0.5mm. Fill the cracked areas by grouting until the cracks are completely filled. S4. Curing: Place the repaired concrete in an environment with a temperature of 20℃ and a relative humidity of 70% for 7 days. Spray deionized water 3 times a day for the first 3 days, and spray once a day thereafter to complete the repair.

[0028] The concrete repair agent, by weight, has the following composition: 10 portions of microbial inoculant (Bacillus pasteurellii to Pseudomonas aeruginosa concentration ratio of 8:1, total spore concentration of 9×10⁻⁶). 8 The composition includes: cells / ml, mineralized substrate (urea and calcium nitrate tetrahydrate in a mass ratio of 1:1), carrier material (15 parts), and auxiliary additives (nutrients, dispersant, and water-retaining agent in a mass ratio of 5:2:1, with yeast extract, ammonium nitrate, and inosine in a mass ratio of 18:8:0.5).

[0029] Example 2

[0030] A method for extending the service life of concrete materials in harsh environments includes the following steps: S1. Pretreatment: Same as in Example 1; S2. Preparation of repair agent: Mix the above components evenly, add deionized water, adjust the water-to-material ratio to 0.35:1, stir at 350 r / min for 12 min to make a uniform paste-like repair agent; S3. Apply / Grouting: Apply the repair agent evenly to the corroded concrete surface to a thickness of 1.0 mm. Fill the cracked areas by grouting until the cracks are completely filled. S4. Curing: Place the repaired concrete in an environment with a temperature of 22℃ and a relative humidity of 75% for 14 days. Spray deionized water 3 times a day for the first 3 days, and spray once a day thereafter to complete the repair.

[0031] The concrete repair agent, by weight, has the following composition: 15 portions of microbial inoculant (Bacillus pasteurellii to Pseudomonas aeruginosa concentration ratio of 9:1, total spore concentration of 1×10⁻⁶). 9 The composition includes: cells / ml, 40 parts of mineralized substrate (urea and calcium nitrate tetrahydrate in a mass ratio of 1:1.2), 20 parts of carrier material, and 8 parts of auxiliary additives (nutrients, dispersants, and water-retaining agents in a mass ratio of 6:2.5:1.5, and yeast extract, ammonium nitrate, and inosine in the nutrients in a mass ratio of 18.5:8.5:0.6).

[0032] Example 3

[0033] A method for extending the service life of concrete materials in harsh environments includes the following steps: S1. Pretreatment: Same as in Example 1; S2. Preparation of repair agent: Mix the above components evenly, add deionized water, adjust the water-to-material ratio to 0.4:1, stir at 400 r / min for 15 min to make a uniform paste-like repair agent; S3. Apply / Grouting: Apply the repair agent evenly to the corroded concrete surface to a thickness of 1.2mm. Fill the cracked areas by grouting until the cracks are completely filled. S4. Curing: Place the repaired concrete in an environment with a temperature of 25℃ and a relative humidity of 80% for 21 days. Spray deionized water 4 times a day for the first 3 days, and spray twice a day thereafter to complete the repair.

[0034] The concrete repair agent, by weight, has the following composition: 18 microbial inoculants (Bacillus pasteurellii to Pseudomonas aeruginosa concentration ratio of 10:1, total spore concentration of 3×10⁻⁶) 9 The composition includes 45 parts of mineralized substrate (urea and calcium nitrate tetrahydrate in a mass ratio of 1:1.5), 25 parts of carrier material, and 12 parts of auxiliary additives (nutrients, dispersants, and water-retaining agents in a mass ratio of 6:3:2, and yeast extract, ammonium nitrate, and inosine in the nutrients in a mass ratio of 19:9:0.8).

[0035] Example 4

[0036] A method for extending the service life of concrete materials in harsh environments includes the following steps: S1. Pretreatment: Same as in Example 1; S2. Preparation of repair agent: Mix the above components evenly, add deionized water, adjust the water-to-material ratio to 0.45:1, stir at 450 r / min for 18 min to make a uniform paste-like repair agent; S3. Apply / Grouting: Apply the repair agent evenly to the corroded concrete surface to a thickness of 1.8mm. Fill the cracked areas by grouting until the cracks are completely filled. S4. Curing: Place the repaired concrete in an environment with a temperature of 28℃ and a relative humidity of 85% for 25 days. Spray deionized water 4 times a day for the first 3 days, and spray twice a day thereafter to complete the repair.

[0037] The concrete repair agent, by weight, has the following composition: 22 microbial inoculants (Bacillus pasteurellii to Pseudomonas aeruginosa concentration ratio 11:1, total spore concentration 5×10⁻⁶) 10 The composition includes 55 parts of mineralized substrate (urea and calcium nitrate tetrahydrate in a mass ratio of 1:1.8), 32 parts of carrier material, and 14 parts of auxiliary additives (nutrients, dispersants, and water-retaining agents in a mass ratio of 7.5:3.5:2.5, and yeast extract, ammonium nitrate, and inosine in the nutrients in a mass ratio of 19.5:9.5:0.9).

[0038] Example 5

[0039] A method for extending the service life of concrete materials in harsh environments includes the following steps: S1. Pretreatment: Same as in Example 1; S2. Preparation of repair agent: Mix the above components evenly, add deionized water, adjust the water-to-material ratio to 0.5:1, stir at 500 r / min for 20 min to make a uniform paste-like repair agent; S3. Apply / Grouting: Apply the repair agent evenly to the corroded concrete surface to a thickness of 2.0 mm. Fill the cracked areas by grouting until the cracks are completely filled. S4. Curing: Place the repaired concrete in an environment with a temperature of 30℃ and a relative humidity of 90% for 28 days. Spray deionized water 4 times a day for the first 3 days, and spray twice a day thereafter to complete the repair.

[0040] The concrete repair agent, by weight, has the following composition: 25 portions of microbial inoculant (Bacillus pasteurellii to Pseudomonas aeruginosa concentration ratio of 12:1, total spore concentration of 6×10⁻⁶) 10 The composition includes: cells / ml, mineralized substrate (urea and calcium nitrate tetrahydrate in a mass ratio of 1:2), carrier material (35 parts), and auxiliary additives (nutrients, dispersant and water-retaining agent in a mass ratio of 8:4:3, and yeast extract, ammonium nitrate and inosine in a mass ratio of 20:10:1).

[0041] Comparative Example 1 (without microbial inoculants) A method for extending the service life of concrete materials in harsh environments, the same as in Example 3, except that no microbial inoculant is added.

[0042] The concrete repair agent, by mass, has the following composition: 45 parts mineralized substrate (urea and calcium nitrate tetrahydrate in a mass ratio of 1:1.5), 25 parts carrier material, and 12 parts auxiliary additives (nutrients, dispersant, and water-retaining agent in a mass ratio of 6:3:2, and yeast extract, ammonium nitrate, and inosine in the nutrients in a mass ratio of 19:9:0.8).

[0043] Comparative Example 2 (Single Microbial Agent) A method for extending the service life of concrete materials in harsh environments, same as in Example 3. The concrete repair agent, by weight, comprises the following components: 18 parts microbial agent (Bacillus pasteurellis only, with a spore concentration of 3×10⁻⁶). 9 The composition includes 45 parts of mineralized substrate (urea and calcium nitrate tetrahydrate in a mass ratio of 1:1.5), 25 parts of carrier material, and 12 parts of auxiliary additives (same as in Example 3).

[0044] Comparative Example 3 (Unmodified Carrier Material) A method for extending the service life of concrete materials in harsh environments, same as in Example 3. The concrete repair agent, by weight, comprises the following components: 18 parts microbial agent (same as in Example 3), 45 parts mineralized substrate (same as in Example 3), 25 parts carrier material (unmodified porous ceramsite), and 12 parts auxiliary additives (same as in Example 3).

[0045] Comparative Example 4 (without auxiliary additives) A method for extending the service life of concrete materials in harsh environments, same as in Example 3. The concrete repair agent, by weight, comprises the following components: 18 parts microbial agent (same as in Example 3), 45 parts mineralized substrate (same as in Example 3), and 25 parts carrier material (same as in Example 3).

[0046] Comparative Example 5 (Traditional Cement-Based Repair Agent) A method for extending the service life of concrete materials in harsh environments, same as in Example 3. The concrete repair agent used is a commercially available traditional cement-based repair agent (the main components are Portland cement, quartz sand, and water-reducing agent). The application method is in accordance with the product instructions, and the coating thickness and curing conditions are the same as in Example 3.

[0047] Technical effect verification test 1. Experimental Materials and Methods 1.1 Test specimen preparation: C30 grade concrete was used to prepare 100mm×100mm×100mm cubic specimens, a total of 66 specimens (6 blank control groups, 5×12 test groups, 3 parallel specimens in each group); after standard curing for 28 days, the specimens were prepared by accelerated corrosion method (immersion in 5% NaCl solution at 25℃ for 7 days); the blank control group consisted of uncorroded and unrepaired C30 concrete specimens.

[0048] 1.2 Repair treatment: The repair agents and application methods of Examples 1-5 and Comparative Examples 1-5 were used to repair the corroded concrete specimens, with 3 parallel specimens in each group; after the repair was completed, the specimens were cured according to the corresponding curing conditions until the specified age.

[0049] 1.3 Performance testing metrics and methods: (1) Microbial survival rate: After the maintenance was completed, the survival rate of microorganisms in the repair agent was detected by plate counting method; (2) Bond strength: The bond strength between the repair agent and the concrete matrix was tested according to the method in the Code for Design of Strengthening Concrete Structures (GB 50367-2013); (3) Compressive strength: The compressive strength of the specimen was tested according to the method in the "Standard for Test Method of Mechanical Properties of Ordinary Concrete" (GB / T 50081-2019), and the compressive strength recovery rate was calculated (the ratio of the compressive strength after repair to the compressive strength of the blank control group × 100%). (4) Permeability grade: The permeability grade of the specimen shall be tested in accordance with the method in the "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete" (GB / T50082-2009); (5) Corrosion resistance: The repaired specimen was placed in a 5% NaCl solution and soaked for 30 days. The compressive strength loss rate after soaking was tested (the difference between the compressive strength before soaking and the compressive strength after soaking / the compressive strength before soaking × 100%). (6) Crack repair rate: Prepare corroded concrete specimens with cracks with a width of 0.2-0.5 mm. After repair and curing, measure the remaining width of the cracks using a crack width meter and calculate the crack repair rate ((crack width before repair - remaining crack width after repair) / crack width before repair × 100%).

[0050] 1.4 Data processing: The average value of the test data of the three parallel specimens in each group is taken as the final test result to ensure the reliability of the test data.

[0051] 2. Experimental Results Data The specific test results of this technical effect verification experiment are shown in Table 1 below:

[0052] Note: "-" in the table indicates that no test is required or no relevant data is available; in the impermeability grade, the larger the number after P, the better the impermeability; the lower the compressive strength loss rate, the better the corrosion resistance; the higher the crack repair rate, the better the repair effect.

[0053] 3. Analysis of Experimental Results 3.1 Microbial Survival Rate Analysis: As shown in Table 1, the microbial survival rates in Examples 1-5 were all above 85%, with Example 3 exhibiting the highest survival rate at 92.5%. In contrast, the microbial survival rate in Comparative Example 2 (single microbial agent) was only 76.8%, and in Comparative Example 3 (unmodified carrier material) it was 70.2%, significantly lower than the Example groups. This indicates that the synergistic effect of *Bacillus pasteurellii* and *Pseudomonas aeruginosa* in this invention improves the environmental adaptability of microorganisms. Furthermore, the porous ceramic particles modified with silane coupling agents provide a stable habitat for microorganisms, effectively protecting them from corrosive media and thus increasing their survival rate. In contrast, single-strain microorganisms exhibit poor environmental adaptability, and the unmodified carrier material has poor adsorption performance and protective effect, leading to a lower microbial survival rate.

[0054] 3.2 Bond Strength Analysis: The bond strength of Examples 1-5 were all above 2.5 MPa, with Example 3 reaching 3.24 MPa, significantly higher than the comparative examples. The bond strength of Comparative Example 1 (without microbial inoculant) was only 1.23 MPa, Comparative Example 4 (without auxiliary additives) was 1.87 MPa, and Comparative Example 5 (traditional cement-based repair agent) was 1.56 MPa. This indicates that the components of the repair agent of the present invention are rationally combined, the calcium carbonate crystals generated by microbial mineralization can tightly bond with the concrete matrix, and the water-retaining agent and dispersant in the auxiliary additives can further improve the bonding performance of the repair agent. Without microbial inoculant, auxiliary additives, or using traditional repair agents, a good bonding effect cannot be achieved, easily leading to the repair agent detaching and affecting the repair durability.

[0055] 3.3 Analysis of Compressive Strength Recovery Rate: The compressive strength recovery rates of Examples 1-5 were all above 82%, with Example 3 reaching 95.7%, close to the uncorroded blank control group; while the compressive strength recovery rates of the comparative groups were all below 75%, with Comparative Example 1 showing a recovery rate of only 56.8%. This indicates that the repair agent of the present invention can generate stable calcium carbonate crystals through microbial-induced mineralization reaction, effectively filling corrosion cracks and pores in concrete, repairing structural damage to concrete, and significantly restoring the compressive strength of concrete; without microbial agents, effective mineralization reaction cannot occur, and only physical filling by the substrate can be achieved, resulting in extremely poor repair effect; single microbial agents, unmodified carrier materials, and the absence of auxiliary additives all affect mineralization efficiency and repair effect, leading to a decrease in compressive strength recovery rate; traditional cement-based repair agents have poor compatibility and filling effect, and cannot achieve good strength recovery.

[0056] 3.4 Permeability Analysis: The permeability grades of Examples 1-5 were all above P6, with Examples 3 and 4 reaching P8, consistent with the blank control group. In contrast, the permeability grades of the comparative groups were all below P5, with Comparative Examples 1 and 4 only reaching P4. This indicates that the repair agent of the present invention can generate dense calcium carbonate crystals through microbial mineralization, blocking the pores and cracks in concrete, forming an effective seepage barrier, and significantly improving the permeability of concrete. The comparative groups, however, suffered from poor repair effects; the pores and cracks were not effectively filled, resulting in poor permeability and an inability to prevent the intrusion of external corrosive media.

[0057] 3.5 Corrosion Resistance Analysis: The 30-day compressive strength loss rate of Examples 1-5 was all below 9%, with Example 3 showing a loss rate of only 4.3%, close to the 3.2% of the blank control group. In contrast, the compressive strength loss rate of the comparative examples was all above 12%, with Comparative Example 1 reaching 21.5%. This indicates that after repair with the repair agent of the present invention, a dense mineralized protective layer is formed on the concrete surface, effectively blocking the intrusion of corrosive media such as NaCl solution, protecting the internal structure of the concrete, and significantly improving the corrosion resistance of the concrete. In contrast, the comparative examples, due to poor repair effects, allowed corrosive media to easily penetrate the concrete, resulting in a significant decrease in concrete strength and poor corrosion resistance.

[0058] 3.6 Crack Repair Rate Analysis: The crack repair rates of Examples 1-5 were all above 83%, with Example 3 achieving a crack repair rate of 95.2%, achieving near-complete crack repair. In contrast, the crack repair rates of the comparative groups were all below 72%, with Comparative Example 1 achieving only 42.3%. This indicates that the microbial agent of the present invention can efficiently induce a mineralization reaction, and the generated calcium carbonate crystals can uniformly fill cracks, achieving rapid and efficient crack repair. However, the mineralization efficiency of a single microbial agent is low, and the lack of modified carrier materials and auxiliary additives affects the continuity and uniformity of the mineralization reaction. Traditional cement-based repair agents have poor filling effects and compatibility, failing to achieve good crack repair results.

[0059] In summary, the microbial-induced mineralization-based corroded concrete repair agent of the present invention, through the synergistic effect of its components, possesses advantages such as high microbial survival rate, high bond strength, high compressive strength recovery rate, good impermeability, strong corrosion resistance, and high crack repair rate, with a repair effect significantly superior to existing repair agents. Example 3 is the optimal embodiment, achieving the best performance in all aspects. Furthermore, the repair agent of the present invention is simple to prepare, easy to apply, and environmentally friendly, effectively addressing many shortcomings of existing corroded concrete repair technologies. It is suitable for the repair and service life extension of various corroded concrete structures and has broad engineering application prospects.

[0060] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for extending the service life of concrete materials in harsh environments, characterized in that, Includes the following steps: S1. Pretreatment: Clean the corroded concrete surface to remove surface slag, loose layer and corrosion products, rinse with a high-pressure water gun and let it dry until there is no obvious water accumulation on the surface; for cracks with a width ≥0.1mm, use a wire brush to clean the debris inside the crack to ensure that the crack is unobstructed. S2. Preparation of repair agent: Mix the microbial agent, mineralized substrate, carrier material and auxiliary additives evenly, add deionized water, adjust the water-to-material ratio to 0.3-0.5:1, and stir to make a uniform paste-like repair agent; S3. Apply / Grouting: Apply the prepared repair agent evenly to the corroded concrete surface, with a thickness of 0.5-2mm. For cracked areas, use grouting to fill the cracks with the repair agent until the cracks are completely filled. S4. Curing: Place the repaired concrete in an environment with a temperature of 20-30℃ and a relative humidity of 70%-90% for 7-28 days. Spray deionized water during the curing period to keep the surface moist.

2. The method for extending the service life of concrete materials in harsh environments as described in claim 1, characterized in that, The repair agent in step S2, by mass, includes the following components: 10-25 parts of microbial agent, 30-60 parts of mineralized substrate, 15-35 parts of carrier material, and 5-15 parts of auxiliary additives.

3. The method for extending the service life of concrete materials in harsh environments as described in claim 1, characterized in that, The microbial agent is a mixture of Bacillus pasteurellii and Pseudomonas aeruginosa spores, with a concentration ratio of 8-12:1 and a total spore concentration of 9 × 10⁻⁶. 8 -6×10 10 cells / mL.

4. The method for extending the service life of concrete materials in harsh environments as described in claim 1, characterized in that, The mineralization substrate is a mixture of urea and calcium nitrate tetrahydrate in a mass ratio of 1:1-2.

5. The method for extending the service life of concrete materials in harsh environments as described in claim 1, characterized in that, The carrier material is porous ceramic particles modified with silane coupling agent KH-550, with a particle size of 0.5-2 mm and a porosity of 35%-55%.

6. The method for extending the service life of concrete materials in harsh environments as described in claim 1, characterized in that, The auxiliary additives include nutrients, dispersants, and water-retaining agents, with a mass ratio of 5-8:2-4:1-3; the nutrients are a mixture of yeast extract, ammonium nitrate, and inosine, with a mass ratio of 18-20:8-10:0.5-1; the dispersant is sodium polynaphthalene sulfonate with a molecular weight of 2000-5000; and the water-retaining agent is sodium polyacrylate with a molecular weight of 50000-100000.

7. The method for extending the service life of concrete materials in harsh environments according to claim 1, characterized in that, The preparation method of the microbial agent is as follows: Bacillus pasteurellii and Pseudomonas aeruginosa are cultured separately. After the strains enter the stable period, the bacterial cells are collected by centrifugation, freeze-dried at low temperature to prepare spores, and then mixed at a concentration ratio of 8-12:

1. Sterile physiological saline is added to prepare a spore suspension, which is then obtained.

8. The method for extending the service life of concrete materials in harsh environments according to claim 1, characterized in that, The modification method of the carrier material is as follows: porous ceramic particles are placed in an ethanol solution of silane coupling agent KH-550 with a mass fraction of 3%-5%, ultrasonically dispersed for 30-60 minutes, dried at 60-80℃ to constant weight, and cooled to room temperature to obtain the desired material.

9. The method for extending the service life of concrete materials in harsh environments according to claim 1, characterized in that, The concentration ratio of Bacillus pasteurellii to Pseudomonas aeruginosa in the microbial inoculum was 10:1, and the total concentration of spores was 3 × 10⁻⁶. 9 cells / ml; the mass ratio of urea to calcium nitrate tetrahydrate in the mineralized substrate is 1:1.5; the mass ratio of nutrients, dispersant and water-retaining agent in the auxiliary additives is 6:3:

2.

10. The method for extending the service life of concrete materials in harsh environments according to claim 1, characterized in that, In step S2, the stirring speed is 300-500 r / min and the stirring time is 10-20 min. In step S4, spray deionized water 3-4 times a day for the first 3 days of curing, and the amount of water sprayed each time should be enough to moisten the surface without water accumulation. After 3 days, spray 1-2 times a day until the curing is completed.

Images