Long-acting self-repairing low-carbon concrete suitable for coastal environment and preparation method thereof

Abstract

The application is a long-acting self-repairing low-carbon concrete suitable for a coastal environment and a preparation method thereof, and belongs to the technical field of composite material preparation.The concrete is prepared from the following components in parts by mass: cement 360-400 parts;water 145-152 parts;sand 775-785 parts;stone 1075-1085 parts;water reducing agent 3-5 parts;self-repairing biochar 20-40 parts;and corrosion-resistant additive 0.5-1 part.The application solves the three problems of strength loss under high biochar content, non-sustainable microbial self-repairing function and serious marine biological chemical corrosion.The experiment shows that the 28-day compressive strength is increased by more than 8% compared with the benchmark, the crack area repair rate is more than 77.5%, and the number of marine fouling organisms is significantly reduced, thereby providing a long-life, low-maintenance integrated material solution for coastal engineering structures.

Description

Technical Field

[0001] This invention relates to the field of composite material preparation technology, and in particular to a long-lasting self-healing low-carbon concrete suitable for coastal environments and its preparation method. Background Technology

[0002] Developing low-carbon concrete is a core pathway to addressing global climate change and promoting sustainable development in the construction industry. Incorporating biochar, converted from biomass waste, into cement-based materials not only effectively utilizes solid waste but also enables long-term carbon sequestration, providing a promising strategy for preparing low-carbon concrete for marine engineering. However, this strategy faces a series of severe and intertwined challenges in the harsh marine application environment.

[0003] First, the large-scale application of biochar is limited by its inherent material properties. Although the incorporation of biochar helps reduce the carbon footprint of concrete, its high porosity and weak interfacial bonding with the cement matrix often have a significant negative impact on the mechanical properties of composite materials when its content exceeds 5% of the cement mass. Marine engineering structures are subjected to complex wave, current impacts, and loads, placing extremely high demands on the compressive strength and durability of materials. Therefore, there is an irreconcilable contradiction between the limited biochar incorporation amount and the high dosage required to achieve significant carbon sequestration benefits in harsh marine environments.

[0004] Secondly, the marine environment poses unique biological and chemical threats to traditional concrete. Corrosive media such as sulfates and chloride ions in seawater can penetrate into the concrete, causing steel reinforcement corrosion and expansion and cracking of the cement matrix. More specifically, the abundant microorganisms in the ocean (such as sulfate-reducing bacteria and nitrifying bacteria) and their metabolic products can acid-erode concrete and promote biofilm formation, thus creating conditions for the attachment of large fouling organisms such as barnacles and mussels. The colonization of these organisms accelerates the physical erosion and chemical degradation of the concrete surface, destroys the protective layer, and significantly shortens the service life of the structure. Currently, protective measures relying on surface coatings are prone to aging and failure in harsh marine environments, and their production and maintenance processes themselves involve additional carbon emissions and environmental burdens. This makes developing the inherent and long-lasting resistance to biological erosion of concrete an urgent need for the development of low-carbon marine concrete.

[0005] Furthermore, endowing concrete with self-healing capabilities to cope with unavoidable microcracks is an ideal way to improve its durability in marine environments. Microbial-induced calcium carbonate precipitation technology is considered one of the most promising directions. However, the application of this technology in marine low-carbon concrete faces a dual bottleneck: firstly, commonly used microbial carriers (such as lightweight porous materials), while ensuring microbial survival, often damage the mechanical properties and impermeability of the matrix, failing to meet the requirements of marine structures; secondly, and more critically, there is a lack of a slow-release system that can adapt to the highly alkaline environment inside concrete and provide long-term nutrition for microorganisms. A common misconception is that biochar itself serves as a carbon source for microorganisms, but in reality, its highly stable carbon structure is difficult for microorganisms to directly utilize. Without a stable nutrient supply, microorganisms rapidly deactivate after depleting the premixed nutrients, causing the self-healing function to fail to activate when needed, making it difficult to cope with repeated erosion throughout the entire life cycle of the marine environment.

[0006] In summary, developing high-performance, low-carbon concrete suitable for marine environments urgently requires overcoming the following three challenges: the mechanical performance bottleneck under high biochar content, the durability threat posed by the harsh marine biochemical environment, and the dual lack of carrier and long-term nutrient supply in microbial self-healing technologies. Existing technological solutions often address these issues in isolation, lacking a systematic strategy that can synergistically solve material mechanics, environmental durability, and functional intelligence. This situation severely restricts the development of next-generation marine concrete technology towards low-carbon, long-life, and intelligent directions, necessitating a breakthrough through material design and technological pathways. Summary of the Invention

[0007] This invention aims to address the shortcomings of current biochar concrete, such as its limited carbon fixation capacity due to low biochar content, the lack of inherent biocorrosion protection in marine concrete, and the difficulty in balancing carrier performance and long-term nutrient supply in microbial self-healing technology. It provides a long-lasting self-healing low-carbon concrete suitable for coastal environments and its preparation method.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a long-lasting self-healing low-carbon concrete suitable for coastal environments, comprising the following components by mass proportions:

[0009] 360-400 parts cement;

[0010] 145-152 parts water;

[0011] 775-785 parts of sand;

[0012] 1075-1085 portions of pebbles;

[0013] 3-5 parts water-reducing agent;

[0014] Self-healing biochar 20-40;

[0015] The amount of corrosion-resistant additive is 0.5-1 part;

[0016] Among them, self-healing biochar is a microbial carrier material with a multi-scale composite structure, which includes: a porous biochar matrix pretreated with acid and encapsulated with nano-silica; amino functional groups grafted onto the surface of the matrix to enhance cement bonding; and Bacillus pasteurellii and organic calcium salt nutrient sources loaded in the pores, which together constitute a slow-release microsystem that can survive for a long time during the service life of concrete. After being activated by water, it achieves self-healing of cracks by inducing calcium carbonate deposition. The corrosion-resistant admixture is a composite slow-release inhibitor containing copper ions and ferrocyanate ions as active antibacterial components, with nano-calcium carbonate as the carrier and sodium metasilicate as the slow-release matrix.

[0017] Specifically, the porous biochar matrix is ​​derived from wood processing waste, and the amino functional groups are formed by the hydrolysis and grafting of γ-aminopropyltriethoxysilane onto the surface of the biochar matrix. The organic calcium salt nutrient sources include calcium lactate and calcium chloride.

[0018] Specifically, the preparation of self-healing biochar includes: the preparation of functionalized modified biochar; and the construction of a microbial sustained-release microsystem based on the functionalized modified biochar.

[0019] Specifically, functionalized modified biochar is prepared by a method including the following steps:

[0020] Acid pretreatment and modification of porous biochar matrix:

[0021] S1. The wood waste is forced to dry in an oven at 80°C for 48 hours to completely remove moisture; then it is crushed into wood chips that can pass through an 80-mesh sieve to obtain wood powder; the wood powder is soaked in a 3%-5% dilute phosphoric acid solution at 60°C for 2 hours, then filtered, washed until neutral and dried to obtain a porous primary biochar matrix.

[0022] S2. The primary biochar matrix was mixed with a 0.8 mol / L citric acid solution at a mass ratio of 1:45 and stirred at a constant temperature in a 60℃ water bath for 2 hours. The mixture was then dried at 60℃ for 24 hours and then transferred to an oven at 120℃ for 90 minutes to enhance the bonding strength. Finally, it was repeatedly washed with deionized water until neutral and dried at 105℃ to obtain the primary modified biochar.

[0023] Nano-silica encapsulation and calcium source introduction:

[0024] S3. Take 10g of the above primary modified biochar, place it in a beaker, add 400mL of anhydrous ethanol, and ultrasonically disperse for 30 minutes to allow it to fully depolymerize.

[0025] S4. Add 200 mL of anhydrous ethanol, 100 mL of distilled water, and 30 mL of ammonia to the beaker in step S3 in sequence. Stir at 300 rpm for 6 hours at room temperature. Add the above solution to 28 mL of tetraethyl orthosilicate. This mixture is denoted as solution A. In another container, mix 20 mL of distilled water, 5 mL of ammonia, and 300 mL of anhydrous ethanol evenly. This mixture is denoted as solution B.

[0026] S5. Under room temperature and continuous stirring, solution A and solution B are thoroughly mixed. Then, 40 mL of tetraethyl silicate is added first, followed by 200 mL of 1 mol / L calcium chloride solution. The mixture is stirred for 5-6 hours, rinsed clean, and the product is vacuum dried at 70°C for 12 hours to obtain intermediate biochar with nano-silica encapsulation on the surface and the initial calcium source introduced into the encapsulation.

[0027] Amino functional group grafting and low-temperature carbonization stabilization:

[0028] S6. Mix γ-aminopropyltriethoxysilane with ethanol and water at a volume ratio of 2:95:3 and hydrolyze for 30 minutes to activate the ethoxy groups on the silane to obtain a γ-aminopropyltriethoxysilane hydrolysate. Immerse the intermediate biochar from step S5 in 120mL-150mL of the γ-aminopropyltriethoxysilane hydrolysate and react at 60℃ for 4 hours to graft amino functional groups onto its surface. After the reaction is complete, wash with ethanol to remove the physically adsorbed silane and then dry to obtain functionalized biochar.

[0029] S7. The functionalized biochar obtained in step S6 is placed together with polyethylene glycol-400 in a planetary ball mill and ball-milled at 400 rpm for 1 hour. Then, the ball-milled mixture is placed in a tube furnace and heated to 400°C at 5°C / min under a nitrogen atmosphere and held for 1 hour to obtain the final functionalized modified biochar.

[0030] Specifically, the sustained-release microsystem was constructed through a microbial loading and mineralization pretreatment process including the following steps:

[0031] Preparation and activation of bacterial culture:

[0032] P1. Prepare a 2L Erlenmeyer flask. Weigh out the following ingredients according to the formula concentration: 15.0g tryptone, 5.0g soy peptone, and 5.0g sodium chloride, according to the 1L preparation volume. Pour them into the flask, add 1L of deionized water, shake well, and adjust the pH of the solution to 7.0-7.3. Then place the Erlenmeyer flask in a vertical autoclave and sterilize it at 121℃ for 1 hour. After sterilization, remove the Erlenmeyer flask from the autoclave and place it on a clean bench. Turn on the ultraviolet sterilization and ventilation buttons and wait for the temperature of the culture medium to drop to room temperature to obtain the liquid culture medium.

[0033] P2. Reactivate the lyophilized Bacillus pasteurellii powder by dissolving it in sterile water. Then, inoculate the resulting bacterial suspension into liquid culture medium in a test tube and incubate it with shaking at 30°C to obtain an activated bacterial strain. Subsequently, inoculate this activated bacterial strain into the liquid culture medium of step P1 at a volume fraction of 3%-5% and then place it in a shaker for 24 hours, wherein the shaker temperature is 36±1°C and the rotation speed is 140 r / min.

[0034] Vacuum loading and mineralization culture:

[0035] P3. Place the functionalized modified biochar obtained in step S7 into a vacuum dryer, seal it, and turn on the vacuum pump to stabilize the pressure inside the chamber at -0.085MPa for 30 minutes to completely remove air from the pores of the biochar. Then, under the condition of maintaining vacuum, inject the bacterial solution prepared in step P2 through the conduit until the liquid surface completely submerges the biochar. After maintaining the submersion state for 40 minutes, slowly open the vent valve to release the vacuum and use atmospheric pressure to forcefully press the bacterial solution into the deep pores of the biochar.

[0036] P4. Transfer the wet biochar loaded with bacterial solution to a sterile container, and inject sufficient calcium lactate solution to completely submerge it. The concentration of calcium lactate solution is 15 g / L. Continuously introduce sterile air into the solution at a rate of 0.5 L / min for 24 hours to provide initial impetus for the aerobic metabolism of Bacillus pasteurellii. Then, incubate at a constant temperature of 30℃ for 5 days. During this period, the microorganisms on the surface of the biochar use the pre-loaded nutrients to induce the formation of calcium carbonate precipitate, which is then fixed in the pores, thus forming a slow-release microsystem that can survive for a long time during the service life of the concrete. After the surface of the biochar particles is covered with a clear white product, remove them, gently rinse off the loosely attached bacteria with sterile water, and then dry them in a clean oven at 40℃ until constant weight to obtain the final self-healing biochar.

[0037] Specifically, the corrosion-resistant additive is prepared through the following steps to form a composite sustained-release inhibitor:

[0038] Dispersion of carrier and sustained-release matrix:

[0039] N1. Add 12g of nano-calcium carbonate as a carrier and 100g of water to a 500mL beaker, and stir the mixture thoroughly to form a uniform suspension.

[0040] N2. Under continuous magnetic stirring, 0.67g of sodium metasilicate as a slow-release agent is gradually added to the suspension in step N1 until it is completely dissolved.

[0041] Fixation of active antibacterial components:

[0042] N3. In another 500mL beaker, dissolve 3.1g of copper sulfate, which provides copper ions, in 50g of water and stir until completely dissolved to obtain solution C;

[0043] N4. While stirring the suspension, quickly pour solution C into it and continue stirring for 10 minutes to obtain a mixed suspension;

[0044] N5. Add 3.31g of potassium ferrocyanide (providing ferrocyanate ions) and 50g of water to another beaker and stir until completely dissolved to obtain solution D. While continuing to stir, quickly pour solution D into the mixed suspension from step N4 and stir the mixture for another 10 minutes. The reaction generates an insoluble complex precipitate, thereby fixing the active antibacterial component in the carrier-slow-release matrix system to obtain a corrosion-resistant additive.

[0045] A method for preparing long-lasting self-healing low-carbon concrete suitable for coastal environments includes the following steps:

[0046] M1. Weigh the following components by mass: 360-400 parts cement, 145-152 parts water, 775-785 parts sand, 1075-1085 parts gravel, 3-5 parts water-reducing agent, 20-40 parts self-healing biochar, and 0.5-1 parts corrosion-resistant additive.

[0047] M2. Add cement, sand, gravel, and self-healing biochar to the mixer and mix evenly for 2-3 minutes.

[0048] M3. Pour the water-reducing agent and water into a container and mix them evenly. Stir for 1-2 minutes, then add the corrosion-resistant admixture and stir for another 1-1.5 minutes to obtain fresh concrete.

[0049] M4. Pour the freshly mixed concrete obtained above into a mold for curing. Curing is carried out for 24 hours at a temperature of 22±2℃ and a humidity of 99%. After demolding, it is cured to a fixed age to obtain cured long-lasting self-healing low-carbon concrete.

[0050] The beneficial effects of this invention are:

[0051] 1. This invention overcomes the bottleneck of mechanical properties under high biochar content, achieving a synergistic effect of high strength and high carbon fixation. Through systematic acid pretreatment, nano-silica encapsulation, and silane coupling agent surface grafting of biochar, a self-healing biochar with a multi-scale composite structure is prepared. This structure fundamentally improves the interfacial bonding between biochar and the cement matrix, transforming it from an inert filler into an active reinforcing phase. Therefore, when the self-healing biochar content reaches 5%-10% of the cement mass, it not only does not weaken the mechanical properties of concrete, but also improves the 28-day compressive strength of concrete by more than 8% and simultaneously increases the splitting tensile strength by optimizing the pore structure and accelerating the hydration process, successfully resolving the contradiction between the carbon fixation capacity and mechanical properties of traditional biochar concrete.

[0052] 2. A long-term self-healing function based on a "slow-release microsystem" was constructed, achieving intelligent and continuous repair of microcracks. This invention designs self-healing biochar as a physical shelter and slow-release carrier for Bacillus pasteurellii and organic calcium salt nutrients. Its internal nano-encapsulation structure, together with pre-loaded calcium lactate and calcium chloride, constitutes a stable "slow-release microsystem." When microcracks appear in concrete due to stress and water seeps in, this system is activated. Microorganisms continuously induce calcium carbonate precipitation using the slow-release nutrients, effectively filling the cracks. Experiments show that the concrete can achieve an area repair rate of over 77.5% for cracks with a width of 0.1-0.7 mm within 28 days, achieving repeated and long-term repair of damage throughout the entire life cycle of the structure, overcoming the defect of traditional microbial self-healing technology that interrupts function due to nutrient depletion.

[0053] 3. This invention endows concrete with inherent, active, and long-lasting resistance to marine biological corrosion. By incorporating a specially formulated corrosion-resistant admixture, the invention forms a composite slow-release inhibitor within the concrete, with copper and ferrocyanate ions as active ingredients, nano-calcium carbonate as a carrier, and sodium metasilicate as a slow-release matrix. This system can slowly release antibacterial components during the service life of the concrete, effectively inhibiting the activity of sulfate-reducing bacteria, nitrifying bacteria, and other marine corrosion microorganisms, reducing microbial acid corrosion and biofilm formation at the source. Marine immersion experiments have demonstrated that this invention can reduce the number of major scaling organisms on the concrete surface by more than 55%, providing a permanent protection that penetrates the concrete itself, unlike easily aging and failing surface coatings.

[0054] 4. This invention achieves resource utilization of solid waste, resulting in significant low-carbon and environmental benefits. The core functional component (self-healing biochar) of this invention is primarily made from wood processing waste, which is transformed into high-performance engineering materials through a high-value modification process. The preparation of corrosion-resistant admixtures also utilizes common industrial raw materials. This approach treats waste with waste, significantly reducing raw material costs. Furthermore, the incorporation of biochar and the relative reduction in cement usage significantly lower net carbon emissions during concrete production, perfectly aligning with the development trend of low-carbon buildings.

[0055] 5. This invention provides a multi-functional integrated solution, comprehensively improving the service performance and lifespan of marine concrete. It is not a simple blend of multiple materials, but rather integrates enhanced mechanical properties, long-term carbon sequestration, long-term self-healing of cracks, and active inhibition of microbial corrosion into the concrete matrix through the synergistic design of "multi-scale composite self-healing biochar" and "composite slow-release corrosion-resistant admixtures." This integrated material strategy systematically and fundamentally addresses the multiple deterioration factors—mechanical, physical, and biochemical—in the harsh coastal environment, providing a material foundation for constructing low-maintenance, long-life marine engineering structures. Detailed Implementation

[0056] The present invention will be further described below with reference to embodiments:

[0057] A long-lasting, self-healing, low-carbon concrete suitable for coastal environments, comprising the following components by weight proportions:

[0058] 360-400 parts cement;

[0059] 145-152 parts water;

[0060] 775-785 parts of sand;

[0061] 1075-1085 portions of pebbles;

[0062] 3-5 parts water-reducing agent;

[0063] Self-healing biochar 20-40;

[0064] The amount of corrosion-resistant additive is 0.5-1 part;

[0065] Among them, self-healing biochar is a microbial carrier material with a multi-scale composite structure, which includes: a porous biochar matrix pretreated with acid and encapsulated with nano-silica; amino functional groups grafted onto the surface of the matrix to enhance cement bonding; and Bacillus pasteurellii and organic calcium salt nutrient sources loaded in the pores, which together constitute a slow-release microsystem that can survive for a long time during the service life of concrete. After being activated by water, it achieves self-healing of cracks by inducing calcium carbonate deposition. The corrosion-resistant admixture is a composite slow-release inhibitor containing copper ions and ferrocyanate ions as active antibacterial components, with nano-calcium carbonate as the carrier and sodium metasilicate as the slow-release matrix.

[0066] The porous biochar matrix is ​​derived from wood processing waste. The amino functional groups are formed by the hydrolysis and grafting of γ-aminopropyltriethoxysilane onto the surface of the biochar matrix. The organic calcium salt nutrient sources include calcium lactate and calcium chloride.

[0067] The preparation of self-healing biochar includes: the preparation of functionalized modified biochar; and the construction of a microbial slow-release microsystem based on the functionalized modified biochar.

[0068] Functionalized modified biochar is prepared by a method comprising the following steps:

[0069] Acid pretreatment and modification of porous biochar matrix:

[0070] S1. The wood waste is forced to dry in an oven at 80°C for 48 hours to completely remove moisture. Then, it is crushed into wood chips that can pass through an 80-mesh sieve. The wood chips are then soaked in a 3%-5% dilute phosphoric acid (H3PO4) solution at 60°C for 2 hours, then filtered, washed until neutral, and dried to obtain a porous primary biochar matrix. This step aims to initially hydrolyze the hemicellulose in the wood chips and introduce more hydroxyl groups (-OH) on its surface to provide more active sites for the subsequent silanization reaction.

[0071] S2. The primary biochar matrix was mixed with a 0.8 mol / L citric acid (C6H8O7) solution at a mass ratio of 1:45 and stirred at a constant temperature in a 60℃ water bath for 2 hours. The mixture was then dried at 60℃ for 24 hours and then transferred to an oven at 120℃ for 90 minutes to enhance the bonding strength. Finally, it was repeatedly washed with deionized water until neutral and dried at 105℃ to obtain the primary modified biochar.

[0072] Nano-silica encapsulation and calcium source introduction:

[0073] S3. Take 10g of the above primary modified biochar, place it in a beaker, add 400mL of anhydrous ethanol, and ultrasonically disperse for 30 minutes to allow it to fully depolymerize.

[0074] S4. Add 200 mL of anhydrous ethanol, 100 mL of distilled water, and 30 mL of ammonia to the beaker in step S3 in sequence. Stir at 300 rpm for 6 hours at room temperature. Add the above solution to 28 mL of tetraethyl orthosilicate. This mixture is denoted as solution A. In another container, mix 20 mL of distilled water, 5 mL of ammonia, and 300 mL of anhydrous ethanol evenly. This mixture is denoted as solution B.

[0075] S5. Under room temperature and continuous stirring, thoroughly mix solution A and solution B, then add 40 mL of tetraethyl silicate, followed by 200 mL of 1 mol / L calcium chloride solution, stir for 5-6 hours, rinse thoroughly, and vacuum dry the product at 70°C for 12 hours to obtain intermediate biochar with a surface encapsulated by nano-silica and an initial calcium source introduced into the encapsulation; at this point, a preliminary "SiO2 nanoshell" has formed on the surface of the biochar.

[0076] Amino functional group grafting and low-temperature carbonization stabilization:

[0077] S6. Mix γ-aminopropyltriethoxysilane (KH550) with ethanol and water at a volume ratio of 2:95:3, and hydrolyze for 30 minutes to activate the ethoxy groups on the silane, obtaining a γ-aminopropyltriethoxysilane hydrolysate. Immerse the intermediate biochar from step S5 in 120-150 mL of the γ-aminopropyltriethoxysilane hydrolysate and react at 60°C for 4 hours to graft amino functional groups onto its surface. After the reaction is complete, wash with ethanol to remove the physically adsorbed silane, and then dry to obtain functionalized biochar. The siloxane group at one end of KH550 will condense with the SiO2 shell on the surface of the biochar and itself to form a strong Si-O-Si chemical bond; the amino group (-NH2) at the other end will extend outward to form an active "molecular bridge".

[0078] S7. The functionalized biochar obtained in step S6 is placed together with polyethylene glycol-400 (PEG-400) in a planetary ball mill and milled at 400 rpm for 1 hour. Then, the milled mixture is placed in a tube furnace and heated to 400°C at 5°C / min under a nitrogen atmosphere and held for 1 hour to obtain the final functionalized modified biochar. This stage mainly allows the PEG and the remaining cellulose in the wood to slowly decompose and carbonize, while retaining the amino structure of KH550, thus obtaining the final functionalized modified biochar.

[0079] The sustained-release microsystem was constructed through a microbial loading and mineralization pretreatment process including the following steps:

[0080] Preparation and activation of bacterial culture:

[0081] P1. Prepare a 2L Erlenmeyer flask. Weigh out the following ingredients according to the formula concentration: 15.0g tryptone, 5.0g soy peptone, and 5.0g sodium chloride, according to the 1L preparation volume. Pour them into the flask, add 1L of deionized water, shake well, and adjust the pH of the solution to 7.0-7.3. Then place the Erlenmeyer flask in a vertical autoclave and sterilize it at 121℃ for 1 hour. After sterilization, remove the Erlenmeyer flask from the autoclave and place it on a clean bench. Turn on the ultraviolet sterilization and ventilation buttons and wait for the temperature of the culture medium to drop to room temperature to obtain the liquid culture medium.

[0082] P2. Reactivate the lyophilized Bacillus pasteurellii powder by dissolving it in sterile water. Then, inoculate the resulting bacterial suspension into liquid culture medium in a test tube and incubate it with shaking at 30°C to obtain an activated bacterial strain. Subsequently, inoculate this activated bacterial strain into the liquid culture medium of step P1 at a volume fraction of 3%-5% and then place it in a shaker for 24 hours, wherein the shaker temperature is 36±1°C and the rotation speed is 140 r / min.

[0083] Vacuum loading and mineralization culture:

[0084] P3. Place the functionalized modified biochar obtained in step S7 into a vacuum dryer, seal it, and turn on the vacuum pump to stabilize the pressure inside the chamber at -0.085MPa for 30 minutes to completely remove air from the pores of the biochar. Then, under the condition of maintaining vacuum, inject the bacterial solution prepared in step P2 through the conduit until the liquid surface completely submerges the biochar. After maintaining the submersion state for 40 minutes, slowly open the vent valve to release the vacuum and use atmospheric pressure to forcefully press the bacterial solution into the deep pores of the biochar.

[0085] P4. Transfer the wet biochar loaded with bacterial solution to a sterile container, and inject sufficient calcium lactate solution to completely submerge it. The concentration of calcium lactate solution is 15 g / L. Continuously introduce sterile air into the solution at a rate of 0.5 L / min for 24 hours to provide initial impetus for the aerobic metabolism of Bacillus pasteurellii. Then, incubate at a constant temperature of 30℃ for 5 days. During this period, the microorganisms on the surface of the biochar use the pre-loaded nutrients to induce the formation of calcium carbonate precipitate, which is then fixed in the pores, thus forming a slow-release microsystem that can survive for a long time during the service life of the concrete. After the surface of the biochar particles is covered with a clear white product, remove them, gently rinse off the loosely attached bacteria with sterile water, and then dry them in a clean oven at 40℃ until constant weight to obtain the final self-healing biochar.

[0086] Through the synergistic effect of the aforementioned acid pretreatment, nano-silica encapsulation, and silane coupling agent grafting, the obtained self-healing biochar possesses a stable multi-scale composite structure. Specifically, the nano-SiO2 shell and surface amino functional groups significantly enhance the chemical bonding with cement hydration products, which is the structural basis for overcoming the problem of weak interfaces at high dosages and achieving improved mechanical properties; while the internally constructed "slow-release microsystem" ensures the long-term effectiveness of the self-healing function.

[0087] The aforementioned biochar modification process actively and chemically integrates with cement paste through surface design. This fundamentally solves the core problem of weak interfaces between traditional biochar and cement matrix, thereby improving strength without compromising or even enhancing toughness, while simultaneously endowing biochar with dual improvements in strength and toughness, potential durability, and self-healing capabilities.

[0088] To reduce the corrosion of marine concrete by marine microorganisms, corrosion-resistant admixtures were added to the concrete. These admixtures were prepared through the following steps to form a composite slow-release inhibitor:

[0089] Dispersion of carrier and sustained-release matrix:

[0090] N1. Add 12g of nano-calcium carbonate as a carrier and 100g of water to a 500mL beaker, and stir the mixture thoroughly to form a uniform suspension.

[0091] N2. Under continuous magnetic stirring, 0.67g of sodium metasilicate as a slow-release agent is gradually added to the suspension in step N1 until it is completely dissolved.

[0092] Fixation of active antibacterial components:

[0093] N3. In another 500mL beaker, dissolve 3.1g of copper sulfate, which provides copper ions, in 50g of water and stir until completely dissolved to obtain solution C;

[0094] N4. While stirring the suspension, quickly pour solution C into it and continue stirring for 10 minutes to obtain a mixed suspension;

[0095] N5. Add 3.31g of potassium ferrocyanide (providing ferrocyanate ions) and 50g of water to another beaker and stir until completely dissolved to obtain solution D. While continuing to stir, quickly pour solution D into the mixed suspension from step N4 and stir the mixture for another 10 minutes. The reaction generates an insoluble complex precipitate, thereby fixing the active antibacterial component in the carrier-slow-release matrix system to obtain a corrosion-resistant additive.

[0096] Corrosion-resistant admixtures and self-healing biochar exist in different physical spaces and chemical microenvironments within concrete, yet they do not interfere with each other and work synergistically: the corrosion-resistant admixtures are uniformly dispersed in the concrete matrix, while the self-healing biochar encapsulates Bacillus pasteurellii within its porous structure, spatially isolating it to avoid direct contact; simultaneously, the active ingredients in the corrosion-resistant admixtures (such as copper ferrocyanide) have extremely low solubility, and the nano-calcium carbonate carrier and sodium metasilicate matrix provide pH buffering and slow-release regulation, while the physical adsorption of biochar further forms a chemical barrier. These multiple mechanisms minimize the toxicity of the antibacterial components to Bacillus pasteurellii; Bacillus pasteurellii itself has a certain tolerance to heavy metals and can evade the influence of the external chemical environment through a spore dormancy-revival mechanism; furthermore, the corrosion-resistant admixtures reduce the damage to the concrete matrix by inhibiting harmful microorganisms such as sulfate-reducing bacteria, indirectly extending the stability of the self-healing biochar microenvironment. In summary, both achieve the coexistence of "actively inhibiting corrosive microorganisms" and "passively repairing structural cracks," jointly improving the service life of concrete structures in coastal environments.

[0097] A method for preparing long-lasting self-healing low-carbon concrete suitable for coastal environments includes the following steps:

[0098] M1. Weigh the following components by mass: 360-400 parts cement, 145-152 parts water, 775-785 parts sand, 1075-1085 parts gravel, 3-5 parts water-reducing agent, 20-40 parts self-healing biochar, and 0.5-1 parts corrosion-resistant additive.

[0099] M2. Add cement, sand, gravel, and self-healing biochar to the mixer and mix evenly for 2-3 minutes.

[0100] M3. Pour the water-reducing agent and water into a container and mix them evenly. Stir for 1-2 minutes, then add the corrosion-resistant admixture and stir for another 1-1.5 minutes to obtain fresh concrete.

[0101] M4. Pour the freshly mixed concrete obtained above into a mold for curing. Curing is carried out for 24 hours at a temperature of 22±2℃ and a humidity of 99%. After demolding, it is cured to a fixed age to obtain cured long-lasting self-healing low-carbon concrete.

[0102] The material requirements for preparing the long-lasting self-healing low-carbon concrete suitable for coastal environments are as follows:

[0103] The cement is ordinary Portland cement, with a strength grade of 42.5 and an apparent density of 3150 kg / m³. 3 .

[0104] The sand is natural river sand with a fineness modulus of 2.63, a particle size distribution range of 0.15-4.75 mm, a mud content of no more than 2.0%, a mud lump content of no more than 0.5%, and an apparent density of 2650 kg / m³. 3 The bulk density is 1550 kg / m³. 3 .

[0105] The gravel is graded crushed stone with a particle size distribution range of 5-15mm, good continuous gradation, a crushing index of no more than 10%, a mud content of no more than 1.0%, a mud lump content of no more than 0.5%, an apparent density of 2690 kg / m³, and a bulk density of 1650 kg / m³. 3 .

[0106] The water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent. It is a light yellow viscous liquid with a solid content of 40% and a water reduction rate of not less than 25%.

[0107] The wood waste is pine sawdust, which comes from wood processing by-products. Before use, it is dried at 80℃ to constant weight, crushed and passed through an 80-mesh standard sieve (particle size <180um).

[0108] Citric acid, an analytical grade (AR) reagent, is a white crystalline granule, prepared into a 1 mol / L citric acid solution.

[0109] Anhydrous ethanol is an analytical grade (AR) reagent.

[0110] Ammonia is an analytical grade (AR) reagent, a colorless and transparent liquid.

[0111] Tetraethyl silicate is a chemically pure (CP) reagent, a colorless and transparent liquid.

[0112] Calcium chloride is an analytical grade (AR) reagent, a white granular or lumpy solid with the molecular formula CaCl2, prepared as a 1 mol / L calcium chloride solution.

[0113] Pasteurella multocida was preserved in lyophilized powder form; purchased from Shanghai Jiachu Bioengineering Co., Ltd.

[0114] Tryptone is a biochemical reagent, a light yellow powder, which provides nitrogen and carbon sources; it was purchased from Tianjin Suoxiang Chemical Co., Ltd.

[0115] Soy peptone is a biochemical reagent, a yellow powder, that provides nitrogen, vitamins and growth factors; purchased from Tianjin Suoxiang Chemical Co., Ltd.

[0116] Sodium chloride, analytical grade (AR), is a white crystalline solid used to maintain osmotic pressure; purchased from Tianjin Dingshengxin Chemical Co., Ltd.

[0117] Calcium lactate is a food-grade additive, a white powder, used as a calcium source and nutrient in the microbial mineralization process; purchased from Jinan Xinyue Trading Co., Ltd.

[0118] Example 1

[0119] A long-lasting, self-healing, low-carbon concrete suitable for coastal environments is composed of the following components by weight: 380 parts cement, 145 parts water, 775 parts sand, 1075 parts gravel, 4.1 parts water-reducing agent, 20 parts self-healing biochar, and 0.5 parts corrosion-resistant admixture.

[0120] A method for preparing long-lasting self-healing low-carbon concrete suitable for coastal environments includes the following steps:

[0121] M1. Weigh the following components by mass: 380 parts cement, 145 parts water, 775 parts sand, 1075 parts gravel, 4.1 parts water-reducing agent, 20 parts self-healing biochar, and 0.5 parts corrosion-resistant additive.

[0122] M2. Add cement, sand, gravel, and self-healing biochar to the mixer and mix evenly for 2-3 minutes.

[0123] M3. Pour the water-reducing agent and water into a container and mix them evenly. Stir for 1-2 minutes, then add the corrosion-resistant admixture and stir for another 1-1.5 minutes to obtain fresh concrete.

[0124] M4. Pour the freshly mixed concrete obtained above into a mold for curing. Curing is carried out for 24 hours at a temperature of 22±2℃ and a humidity of 99%. After demolding, it is cured to a fixed age to obtain cured long-lasting self-healing low-carbon concrete.

[0125] Example 2

[0126] A long-lasting self-healing low-carbon concrete suitable for coastal environments is composed of the following components by weight: 370 parts cement, 148 parts water, 778 parts sand, 1075 parts gravel, 4 parts water-reducing agent, 30 parts self-healing biochar, and 0.5 parts corrosion-resistant admixture.

[0127] A method for preparing long-lasting self-healing low-carbon concrete suitable for coastal environments includes the following steps:

[0128] M1. Weigh the following components by mass: 370 parts cement, 148 parts water, 778 parts sand, 1075 parts gravel, 4 parts water-reducing agent, 30 parts self-healing biochar, and 0.5 parts corrosion-resistant additive.

[0129] M2. Add cement, sand, gravel, and self-healing biochar to the mixer and mix evenly for 2-3 minutes.

[0130] M3. Pour the water-reducing agent and water into a container and mix them evenly. Stir for 1-2 minutes, then add the corrosion-resistant admixture and stir for another 1-1.5 minutes to obtain fresh concrete.

[0131] M4. Pour the freshly mixed concrete obtained above into a mold for curing. Curing is carried out for 24 hours at a temperature of 22±2℃ and a humidity of 99%. After demolding, it is cured to a fixed age to obtain cured long-lasting self-healing low-carbon concrete.

[0132] Example 3

[0133] A long-lasting, self-healing, low-carbon concrete suitable for coastal environments is composed of the following components by weight: 360 parts cement, 150 parts water, 780 parts sand, 1080 parts gravel, 4.2 parts water-reducing agent, 40 parts self-healing biochar, and 0.5 parts corrosion-resistant admixture.

[0134] A method for preparing long-lasting self-healing low-carbon concrete suitable for coastal environments includes the following steps:

[0135] M1. Weigh the following components by mass: 360 parts cement, 150 parts water, 780 parts sand, 1080 parts gravel, 4.2 parts water-reducing agent, 40 parts self-healing biochar, and 0.5 parts corrosion-resistant additive.

[0136] M2. Add cement, sand, gravel, and self-healing biochar to the mixer and mix evenly for 2-3 minutes.

[0137] M3. Pour the water-reducing agent and water into a container and mix them evenly. Stir for 1-2 minutes, then add the corrosion-resistant admixture and stir for another 1-1.5 minutes to obtain fresh concrete.

[0138] M4. Pour the freshly mixed concrete obtained above into a mold for curing. Curing is carried out for 24 hours at a temperature of 22±2℃ and a humidity of 99%. After demolding, it is cured to a fixed age to obtain cured long-lasting self-healing low-carbon concrete.

[0139] Example 4

[0140] A long-lasting, self-healing, low-carbon concrete suitable for coastal environments is composed of the following components by weight: 370 parts cement, 148 parts water, 778 parts sand, 1075 parts gravel, 4 parts water-reducing agent, 30 parts self-healing biochar, and 1 part corrosion-resistant admixture.

[0141] A method for preparing long-lasting self-healing low-carbon concrete suitable for coastal environments includes the following steps:

[0142] M1. Weigh the following components by mass: 370 parts cement, 148 parts water, 778 parts sand, 1075 parts gravel, 4 parts water-reducing agent, 30 parts self-healing biochar, and 1 part corrosion-resistant additive.

[0143] M2. Add cement, sand, gravel, and self-healing biochar to the mixer and mix evenly for 2-3 minutes.

[0144] M3. Pour the water-reducing agent and water into a container and mix them evenly. Stir for 1-2 minutes, then add the corrosion-resistant admixture and stir for another 1-1.5 minutes to obtain fresh concrete.

[0145] M4. Pour the freshly mixed concrete obtained above into a mold for curing. Curing is carried out for 24 hours at a temperature of 22±2℃ and a humidity of 99%. After demolding, it is cured to a fixed age to obtain cured long-lasting self-healing low-carbon concrete.

[0146] Comparative Example 1

[0147] Compared to Example 1, no self-healing biochar or corrosion-resistant additives were added in Comparative Example 1.

[0148] A long-lasting, self-healing, low-carbon concrete suitable for coastal environments is composed of the following components in parts by weight: 400 parts cement, 145 parts water, 775 parts sand, 1075 parts gravel, and 4.1 parts water-reducing agent.

[0149] A method for preparing long-lasting self-healing low-carbon concrete suitable for coastal environments includes the following steps:

[0150] M1. Weigh the following components by mass: 400 parts cement, 145 parts water, 775 parts sand, 1075 parts gravel, and 4.1 parts water-reducing agent.

[0151] M2. Add cement, sand, and gravel to the mixer and mix evenly for 2-3 minutes.

[0152] M3. Pour the water-reducing agent and water into a container and mix them evenly. Stir for 1-2 minutes to obtain fresh concrete.

[0153] M4. Pour the freshly mixed concrete obtained above into a mold for curing. Curing is carried out for 24 hours at a temperature of 22±2℃ and a humidity of 99%. After demolding, it is cured to a fixed age to obtain cured concrete.

[0154] Comparative Example 2

[0155] Compared to Example 1, Comparative Example 2 used ordinary biochar without any modification treatment.

[0156] A long-lasting, self-healing, low-carbon concrete suitable for coastal environments is composed of the following components in the indicated mass proportions: 380 parts cement, 145 parts water, 775 parts sand, 1075 parts gravel, 4.1 parts water-reducing agent, 20 parts biochar, and 0.5 parts corrosion-resistant admixture.

[0157] A method for preparing long-lasting self-healing low-carbon concrete suitable for coastal environments includes the following steps:

[0158] M1. Weigh the following components by mass: 380 parts cement, 145 parts water, 775 parts sand, 1075 parts gravel, 4.1 parts water-reducing agent, 20 parts biochar, and 0.5 parts corrosion-resistant admixture.

[0159] M2. Add cement, sand, gravel, and biochar to the mixer and mix evenly for 2-3 minutes.

[0160] M3. Pour the water-reducing agent and water into a container and mix them evenly. Stir for 1-2 minutes, then add the corrosion-resistant admixture and stir for another 1-1.5 minutes to obtain fresh concrete.

[0161] M4. Pour the freshly mixed concrete obtained above into a mold for curing. Curing is carried out for 24 hours at a temperature of 22±2℃ and a humidity of 99%. After demolding, it is cured to a fixed age to obtain cured low-carbon concrete.

[0162] Comparative Example 3

[0163] Compared to Example 3, Comparative Example 3 used ordinary biochar without any modification treatment.

[0164] A long-lasting, self-healing, low-carbon concrete suitable for coastal environments is composed of the following components in the indicated mass proportions: 360 parts cement, 150 parts water, 780 parts sand, 1080 parts gravel, 4.2 parts water-reducing agent, 40 parts biochar, and 0.5 parts corrosion-resistant admixture.

[0165] A method for preparing long-lasting self-healing low-carbon concrete suitable for coastal environments includes the following steps:

[0166] M1. Weigh the following components by mass: 360 parts cement, 150 parts water, 780 parts sand, 1080 parts gravel, 4.2 parts water-reducing agent, 40 parts biochar, and 0.5 parts corrosion-resistant admixture.

[0167] M2. Add cement, sand, gravel, and biochar to the mixer and mix evenly for 2-3 minutes.

[0168] M3. Pour the water-reducing agent and water into a container and mix them evenly. Stir for 1-2 minutes, then add the corrosion-resistant admixture and stir for another 1-1.5 minutes to obtain fresh concrete.

[0169] M4. Pour the freshly mixed concrete obtained above into a mold for curing. Curing is carried out for 24 hours at a temperature of 22±2℃ and a humidity of 99%. After demolding, it is cured to a fixed age to obtain cured low-carbon concrete.

[0170] Comparative Example 4

[0171] Compared to Example 2, Comparative Example 4 did not contain any corrosion-resistant additives.

[0172] A long-lasting, self-healing, low-carbon concrete suitable for coastal environments is composed of the following components in the indicated mass proportions: 370 parts cement, 148 parts water, 778 parts sand, 1075 parts gravel, 4 parts water-reducing agent, and 30 parts self-healing biochar.

[0173] A method for preparing long-lasting self-healing low-carbon concrete suitable for coastal environments includes the following steps:

[0174] M1. Weigh the following components by mass: 370 parts cement, 148 parts water, 778 parts sand, 1075 parts gravel, 4 parts water-reducing agent, and 30 parts self-healing biochar.

[0175] M2. Add cement, sand, gravel, and self-healing biochar to the mixer and mix evenly for 2-3 minutes.

[0176] M3. Pour the water-reducing agent and water into a container and mix them evenly. Stir for 1-2 minutes to obtain fresh concrete.

[0177] M4. Pour the freshly mixed concrete obtained above into a mold for curing. Curing is carried out for 24 hours at a temperature of 22±2℃ and a humidity of 99%. After demolding, it is cured to a fixed age to obtain cured self-healing low-carbon concrete.

[0178] The components of the long-lasting self-healing low-carbon concrete in Examples 1-4 and Comparative Examples 1-4 are shown in Table 1.

[0179] Table 1. Component ratios of self-healing low-carbon concrete in Examples 1-4 and Comparative Examples 1-4

[0180]

[0181] The compressive strength, splitting tensile strength, and mass loss rate of concrete in Examples 1-4 and Comparative Examples 1-4 were tested according to standards GB / T 50081-2019 and GB / T 50082–2009, respectively, based on freeze-thaw cycle tests.

[0182] In addition, to test the repair effect of self-healing biochar on concrete cracks, crack repair tests were conducted on the concrete in Examples 1-4 and Comparative Examples 1-4. The specific procedure is as follows:

[0183] Rectangular specimens measuring 40mm × 40mm × 160mm were prepared using concrete from Examples 1-4 and Comparative Examples 1-4. After curing the prepared specimens in water for 28 days, a three-point bending test was conducted with a loading rate of 0.05 kN / s, inducing cracking in the middle of the span of the concrete prism specimen. During the test, a crack was observed in the middle of the specimen, ensuring that the specimen did not split into two independent parts. The crack width was measured using a crack width meter, and the crack width obtained by the above testing method ranged from 0.1 mm to 0.7 mm. The crack did not extend to the entire height of the section. To prevent damage to the crack in the specimen, it was reinforced with rubber bands. Observation points along the crack path on the concrete specimen were marked with a marker at 1 cm intervals, and the initial crack width was measured and recorded using a crack width meter microscope. A total of 25 observation points were designated for each group. After recording the initial crack width using a crack width meter, the specimen was then immersed in water for repair. Cracks were observed and recorded every 7, 14, and 28 days after healing. The effectiveness of concrete crack repair was evaluated using three indicators: area repair rate, average crack repair width, and maximum crack repair width.

[0184] The evaluation method for area repair rate is as follows: Images are acquired from specimens with existing cracks that have not yet begun repair. Image processing software (ImageJ) is used to process the crack surface images, adjusting the threshold to distinguish between cracked and non-cracked areas of the concrete specimen. Then, the area of ​​the cracked area is calculated from the pixels in the cracked area.

[0185] The calculation process for the area repair rate is as follows: First, calculate the difference between the area of ​​the crack after repair and the initial area of ​​the crack before repair. Divide the difference between the two by the initial area of ​​the crack before repair to get the area repair rate.

[0186] Average crack width The calculation formula is as follows:

[0187] ;

[0188] in, It is the average crack width (mm) 28 days after the crack healed. The initial crack width (mm) at the observation points of each test group. The crack healing width (mm) of each experimental group after 28 days is given. This represents the total number of observation points in each experimental group.

[0189] In addition, in order to test the effect of corrosion-resistant admixtures on the prevention and control of scale organisms in concrete, eight sets of 100mm×100mm×400mm cuboid specimens were made using the concrete mix proportions in Examples 1-4 and Comparative Examples 1-4. The specimens were immersed at sea, and the main scale organisms on the surface of the concrete specimens after immersion for 180 days were counted to determine the total amount of marine fouling.

[0190] The test results are shown in Table 2. The compressive strength, tensile strength, freeze-thaw cycle mass loss rate, and crack repair evaluation index are the test results of a 40mm×40mm×160mm cuboid specimen after being placed in water for 28 days. The number of main scaling organisms is the test result of a 100mm×100mm×400mm cuboid specimen after being immersed in the sea for 180 days.

[0191] Table 2 Performance of long-lasting self-healing low-carbon concrete in Examples 1-4 and Comparative Examples 1-4

[0192]

[0193] By analyzing the performance results of Examples 1-4 and Comparative Examples 1-4 in Table 2, it can be found that:

[0194] 1. Mechanical properties: It completely solves the strength bottleneck under high biochar content;

[0195] The 28-day compressive strengths of Examples 1-3 (containing 5%-10% self-healing biochar) were 52.2 MPa, 55.0 MPa, and 56.5 MPa, respectively, representing significant increases of 8.1%, 13.9%, and 17.0% compared to Comparative Example 1 (48.3 MPa) without any added functional components. In stark contrast, the 28-day compressive strengths of Comparative Examples 2-3 (containing 5%-7.5% ordinary biochar) were 46.3 MPa and 45.0 MPa, respectively, compared to the comparative examples. 1 (48.3 MPa) actually decreased by 4.1% and 6.9%, and the change law of splitting tensile strength was consistent with that of compressive strength; this strong contrast directly proves that the multi-scale composite structure constructed by the present invention through "acid pretreatment-nano silica encapsulation-silane coupling agent grafting" of biochar fundamentally improves the interfacial bonding of biochar-cement matrix, transforming it from a mechanically weak point into a reinforcing phase, thus successfully achieving the goal of synergistically improving concrete strength and carbon fixation capacity at high dosage.

[0196] 2. Self-repair function: Verifies the long-lasting effect of the "slow-release microsystem";

[0197] In terms of crack area repair rate, Examples 1-3 achieved 77.5%-83.3%, an improvement of 10.6 to 11.4 times compared to Comparative Example 1. Regarding the average crack repair width, Examples 1-3 reached 0.38-0.43 mm, an increase of 2.9 to 3.3 times compared to Comparative Example 1. Conversely, in terms of crack area repair rate, Comparative Examples 2-3 only achieved 8.3%-8.8%, showing no substantial improvement compared to Comparative Example 1. Regarding the average crack repair width, Comparative Examples 2-3 achieved 0.12 mm, at the same level as Comparative Example 1. This difference demonstrates that ordinary biochar does not possess self-repairing capabilities. This invention designs modified biochar as a physical shelter and slow-release nutrient carrier for microorganisms. Its internally pre-loaded nutrients (calcium lactate, calcium chloride) and nano-coating layer form a stable nutrient reservoir that continuously nourishes Bacillus pasteurellii, inducing the generation of a large amount of calcium carbonate precipitate, thereby achieving repeated and long-term repair of microcracks and completely solving the defect of traditional microbial self-repair technology that leads to functional interruption due to nutrient depletion.

[0198] 3. Resistance to biocorrosion: This confirms the effectiveness of the "composite slow-release inhibitor";

[0199] Regarding the number of major scaling organisms, Examples 1-3 showed 0.12-0.14 organisms / cm³. 2 Compared to Comparative Example 1, the number of cells decreased significantly by 55%-61%, and in Example 4, it further decreased to 0.1 cells / cm. 2 The reduction rate reached 68%. This proves that the concrete prepared by this invention has excellent resistance to marine biological corrosion. This data directly proves that the internally added corrosion-resistant admixture can form an effective antibacterial microenvironment inside the concrete. The active ingredients, such as copper ions and ferrocyanate ions, contained therein, under the regulation of sodium metasilicate as a slow-release matrix, can inhibit sulfate-reducing bacteria and other corrosive microorganisms for a long time, providing an active protection capability that is self-generated and distinct from surface coatings.

[0200] 4. Freeze-resistant durability: Demonstrates the comprehensive performance improvement brought about by multi-functional synergy;

[0201] Regarding the concrete mass loss rate after 300 freeze-thaw cycles, Examples 1-3 showed a loss of 3.88%-4.02%, an improvement of 13%-16% compared to Comparative Example 1. In contrast, Comparative Examples 2-3 showed a mass loss rate of 4.95%-5.15%, a deterioration of 8%-12% compared to Comparative Example 1. This demonstrates that the self-healing biochar of this invention, through its unique modification process and microbial mineralization products, not only avoids exacerbating freeze-thaw damage due to its porous nature, but also significantly improves the freeze-thaw resistance of concrete by refining pores and strengthening interfaces. This contrasts sharply with the negative effects of ordinary biochar, further highlighting the advantage of the multifunctional components of this invention in synergistically enhancing overall durability.

[0202] In summary, by comparing the performance results of Examples 1-4 with those of Comparative Examples 1-4, it can be found that the present invention, through the synergy of two functional components, simultaneously achieves enhanced mechanical properties, long-term self-healing, improved freeze resistance, and resistance to bio-corrosion in an integrated material, systematically solving a variety of durability challenges in marine environments.

[0203] The present invention has been described above by way of example. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any improvements made by adopting the inventive concept and technical solution of the present invention, or direct application to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A long-lasting, self-healing, low-carbon concrete suitable for coastal environments, characterized in that... It is composed of the following components in parts by mass: 360-400 parts cement; 145-152 parts water; 775-785 parts of sand; 1075-1085 portions of pebbles; 3-5 parts water-reducing agent; 20-40 parts of self-healing biochar; The amount of corrosion-resistant additive is 0.5-1 part; Among them, self-healing biochar is a microbial carrier material with a multi-scale composite structure, which includes: a porous biochar matrix pretreated with acid and encapsulated with nano-silica; amino functional groups grafted onto the surface of the matrix to enhance cement bonding; and Bacillus pasteurellii and organic calcium salt nutrient sources loaded in the pores, which together constitute a slow-release microsystem that can survive for a long time during the service life of concrete. After being activated by water, it achieves self-healing of cracks by inducing calcium carbonate deposition; the corrosion-resistant admixture is a composite slow-release inhibitor containing copper ions and ferrocyanate ions as active antibacterial components, with nano-calcium carbonate as the carrier and sodium metasilicate as the slow-release matrix; The corrosion-resistant additive is prepared through the following steps to form a composite sustained-release inhibitor: Dispersion of carrier and sustained-release matrix: N1. Add 12g of nano-calcium carbonate as a carrier and 100g of water to a 500mL beaker, and stir the mixture thoroughly to form a uniform suspension. N2. Under continuous magnetic stirring, 0.67 g of sodium metasilicate as a slow-release agent is gradually added to the suspension in step N1 until it is completely dissolved. Fixation of active antibacterial components: N3. In another 500 mL beaker, dissolve 3.1 g of copper sulfate, which provides copper ions, in 50 g of water and stir until completely dissolved to obtain solution C; N4. While stirring the suspension, quickly pour solution C into it and continue stirring for 10 minutes to obtain a mixed suspension; N5. Add 3.31g of potassium ferrocyanide (providing ferrocyanate ions) and 50g of water to another beaker and stir until completely dissolved to obtain solution D. While continuing to stir, quickly pour solution D into the mixed suspension from step N4 and stir the mixture for another 10 minutes. The reaction generates an insoluble complex precipitate, thereby fixing the active antibacterial component in the carrier-slow-release matrix system to obtain a corrosion-resistant additive.

2. The long-lasting self-healing low-carbon concrete suitable for coastal environments according to claim 1, characterized in that, The porous biochar matrix is ​​derived from wood processing waste. The amino functional groups are formed by the hydrolysis and grafting of γ-aminopropyltriethoxysilane onto the surface of the biochar matrix. The organic calcium salt nutrient sources include calcium lactate and calcium chloride.

3. The long-lasting self-healing low-carbon concrete suitable for coastal environments according to claim 2, characterized in that, The preparation of self-healing biochar includes: the preparation of functionalized modified biochar; and the construction of a microbial slow-release microsystem based on the functionalized modified biochar.

4. The long-lasting self-healing low-carbon concrete suitable for coastal environments according to claim 3, characterized in that, Functionalized modified biochar is prepared by a method comprising the following steps: Acid pretreatment and modification of porous biochar matrix: S1. The wood waste is forced to dry in an oven at 80°C for 48 hours to completely remove moisture; then it is crushed into wood chips that can pass through an 80-mesh sieve to obtain wood powder; the wood powder is soaked in a 3%-5% dilute phosphoric acid solution at 60°C for 2 hours, then filtered, washed until neutral and dried to obtain a porous primary biochar matrix. S2. The primary biochar matrix was mixed with a 0.8 mol / L citric acid solution at a mass ratio of 1:45 and stirred at a constant temperature in a 60℃ water bath for 2 hours. The mixture was then dried at 60℃ for 24 hours and then transferred to an oven at 120℃ for 90 minutes to enhance the bonding strength. Finally, it was repeatedly washed with deionized water until neutral and dried at 105℃ to obtain the primary modified biochar. Nano-silica encapsulation and calcium source introduction: S3. Take 10g of the above primary modified biochar, place it in a beaker, add 400mL of anhydrous ethanol, and ultrasonically disperse for 30 minutes to allow it to fully depolymerize. S4. Add 200 mL of anhydrous ethanol, 100 mL of distilled water, and 30 mL of ammonia to the beaker in step S3 in sequence. Stir at 300 rpm for 6 hours at room temperature. Add the solution to 28 mL of tetraethyl orthosilicate. This mixture is denoted as solution A. In another container, mix 20 mL of distilled water, 5 mL of ammonia, and 300 mL of anhydrous ethanol evenly. This mixture is denoted as solution B. S5. Under room temperature and continuous stirring, solution A and solution B are thoroughly mixed. Then, 40 mL of tetraethyl silicate is added first, followed by 200 mL of 1 mol / L calcium chloride solution. The mixture is stirred for 5-6 hours, rinsed clean, and the product is vacuum dried at 70°C for 12 hours to obtain intermediate biochar with nano-silica encapsulation on the surface and the initial calcium source introduced into the encapsulation. Amino functional group grafting and low-temperature carbonization stabilization: S6. Mix γ-aminopropyltriethoxysilane with ethanol and water at a volume ratio of 2:95:3 and hydrolyze for 30 minutes to activate the ethoxy groups on the silane to obtain a γ-aminopropyltriethoxysilane hydrolysate. Immerse the intermediate biochar from step S5 in 120mL-150mL of the γ-aminopropyltriethoxysilane hydrolysate and react at 60℃ for 4 hours to graft amino functional groups onto its surface. After the reaction is complete, wash with ethanol to remove the physically adsorbed silane and then dry to obtain functionalized biochar. S7. Place the functionalized biochar obtained in step S6 together with polyethylene glycol-400 in a planetary ball mill and ball mill at 400 rpm for 1 hour. Then place the ball-milled mixture in a tube furnace and heat it to 400°C at 5°C / min under a nitrogen atmosphere and hold for 1 hour to obtain the final functionalized modified biochar.

5. The long-lasting self-healing low-carbon concrete suitable for coastal environments according to claim 4, characterized in that, The sustained-release microsystem was constructed through a microbial loading and mineralization pretreatment process including the following steps: Preparation and activation of bacterial culture: P1. Prepare a 2L Erlenmeyer flask. Weigh out the following ingredients according to the formula concentration: 15.0 g tryptone, 5.0 g soy peptone, and 5.0 g sodium chloride, according to the 1L preparation volume. Pour them into the flask, add 1L of deionized water, shake well, and adjust the pH of the solution to 7.0-7.

3. Then place the Erlenmeyer flask in a vertical autoclave and sterilize it at 121℃ for 1 hour. After sterilization, remove the Erlenmeyer flask from the autoclave and place it on a clean bench. Turn on the ultraviolet sterilization and ventilation buttons and wait for the temperature of the culture medium to drop to room temperature to obtain the liquid culture medium. P2. Reactivate the lyophilized Bacillus pasteurellii powder by dissolving it in sterile water. Then, inoculate the resulting bacterial suspension into liquid culture medium in a test tube and incubate it with shaking at 30°C to obtain an activated bacterial strain. Subsequently, inoculate this activated bacterial strain into the liquid culture medium of step P1 at a volume fraction of 3%-5% and then place it in a shaker for 24 hours, wherein the shaker temperature is 36±1°C and the rotation speed is 140 r / min. Vacuum loading and mineralization culture: P3. Place the functionalized modified biochar obtained in step S7 into a vacuum dryer, seal it, and turn on the vacuum pump to stabilize the pressure inside the chamber at -0.085 MPa for 30 minutes to completely remove air from the pores of the biochar. Then, under the condition of maintaining vacuum, inject the bacterial solution prepared in step P2 through the conduit until the liquid surface completely submerges the biochar. After maintaining the submersion state for 40 minutes, slowly open the vent valve to release the vacuum and use atmospheric pressure to forcefully press the bacterial solution into the deep pores of the biochar. P4. Transfer the wet biochar loaded with bacterial solution to a sterile container and inject sufficient calcium lactate solution to completely submerge it. The concentration of calcium lactate solution is 15 g / L. Sterile air is continuously introduced into the solution at a rate of 0.5 L / min for 24 hours to provide initial impetus for the aerobic metabolism of Bacillus pasteurellii. Subsequently, it is statically cultured in a constant temperature environment of 30℃ for 5 days. During this period, the microorganisms on the surface of the biochar use the pre-loaded nutrients to induce the formation of calcium carbonate precipitate and fix it in the pores, thereby forming a slow-release microsystem that can survive for a long time during the service life of concrete. After the surface of the biochar particles is covered with a clear white product, it is taken out, rinsed with sterile water to remove the loosely attached bacteria on the surface, and then placed in a clean oven at 40℃ to dry to constant weight, thus obtaining the final self-healing biochar.

6. A method for preparing long-lasting self-healing low-carbon concrete suitable for coastal environments according to any one of claims 1-5, characterized in that, Includes the following steps: M1. Weigh the following components by mass: 360-400 parts cement, 145-152 parts water, 775-785 parts sand, 1075-1085 parts gravel, 3-5 parts water-reducing agent, 20-40 parts self-healing biochar, and 0.5-1 parts corrosion-resistant additive. M2. Add cement, sand, gravel, and self-healing biochar to the mixer and mix evenly for 2-3 minutes. M3. Pour the water-reducing agent and water into a container and mix them evenly. Stir for 1-2 minutes, then add the corrosion-resistant admixture and stir for another 1-1.5 minutes to obtain fresh concrete. M4. Pour the freshly mixed concrete obtained above into a mold for curing. Curing is carried out for 24 hours at a temperature of 22±2℃ and a humidity of 99%. After demolding, it is cured to a fixed age to obtain cured long-lasting self-healing low-carbon concrete.

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