Self-repairing polymer concrete, its preparation method and application

Abstract

The application discloses a kind of self-repairing polymer concrete and its preparation method and application, belong to building material technical field. Including the following weight parts of component: cement 300~350 parts, fly ash 100~150 parts, branched amylopectin 1.5~3 parts, load bacteria lotus root residue cellulose 1~2 parts, natural river sand 0~715.5 parts, copper residue fine aggregate 200~1030 parts, basalt coarse aggregate 1290~1340 parts, steel fiber 70~90 parts, water 100~140 parts, water reducing agent 2~3 parts, urea 2~3 parts, calcium lactate 2~3 parts. By copper residue fine aggregate replaces traditional natural fine aggregate, and introduces lotus root residue cellulose and pasteur's bacillus microbial mineralization system, two kinds of solid waste are converted into functional enhanced components;Realize the synergistic enhancement of two kinds of solid waste. When microcrack is generated, external moisture intrusion activates dormant spores, bacteria decomposes urea to generate carbonate ions, combine with calcium ions in environment to precipitate calcite crystal, realize the self-repair of crack.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a self-healing geopolymer concrete, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Geopolymer concrete is a three-dimensional network inorganic polymer formed from aluminosilicate industrial waste (such as fly ash and slag) through activation with an alkali activator. It requires no cement and possesses characteristics such as high strength, corrosion resistance, and high density.

[0004] Although geopolymer concrete has become an important development direction for green building materials due to its advantages such as low carbon, high strength and corrosion resistance, it is inherently brittle and suffers from severe shrinkage cracking. Furthermore, when using solid waste such as copper slag as aggregate, there is a problem of weak interfacial bonding. Existing microbial self-healing technology has low survival rate of microorganisms and random distribution of mineral products in the high alkaline environment of geopolymers, making it difficult to simultaneously solve the multiple needs of improving toughness, strengthening the interface and self-healing cracks. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a self-healing geopolymer concrete, its preparation method, and its application. This invention improves mechanical properties by adding high-density and low-water-absorption copper slag, forms an internal fiber network by adding lotus root residue cellulose, and enhances initial strength and self-healing capabilities by adding specific microbial agents.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a self-healing geopolymer concrete, comprising the following components in parts by weight: 300-350 parts cement, 100-150 parts fly ash, 1.5-3 parts amylopectin, 1-2 parts cellulose from lotus root residue with bacterial growth, 0-715.5 parts natural river sand, 200-1030 parts copper slag fine aggregate, 1290-1340 parts basalt coarse aggregate, 70-90 parts steel fiber, 100-140 parts water, 2-3 parts water-reducing agent, 2-3 parts urea, and 2-3 parts calcium lactate; Among them, the cellulose in lotus root residue loaded with bacteria is cellulose in lotus root residue loaded with Bacillus pasteurellii, with a loading amount of 0.5~1.5wt%.

[0007] Secondly, the preparation method of the aforementioned self-healing geopolymer concrete includes the following steps: Lotus root residue cellulose was soaked in a bacterial solution of Bacillus pasteurellii to obtain bacterial-loaded lotus root residue cellulose; urea and calcium lactate were dispersed in a set amount of water and used to soak copper slag fine aggregate to obtain wet copper slag fine aggregate; then cement, fly ash, natural river sand and basalt coarse aggregate were dry-mixed and added to the wet copper slag fine aggregate and mixed; branched-chain starch and bacterial-loaded lotus root residue cellulose were added and mixed to obtain dry mix; the remaining water and water-reducing agent were added and mixed; steel fibers were added and mixed; and the mixture was poured and cured to obtain the self-healing geopolymer concrete.

[0008] Thirdly, the aforementioned self-healing geopolymer concrete is used in bridges, high-rise buildings, nuclear power plants, or protective engineering projects.

[0009] The beneficial effects of this invention are as follows: This invention achieves high-value-added resource utilization of industrial solid waste and agricultural by-products, significantly reducing the carbon footprint of concrete. By replacing traditional natural fine aggregate with copper slag fine aggregate and introducing lotus root residue cellulose and Bacillus pasteurization microbial mineralization system, both types of solid waste are transformed into functional reinforcing components, achieving synergistic enhancement of the two types of solid waste. Copper slag fine aggregate itself has high hardness and high strength, and its rough, angular particle shape forms excellent mechanical interlocking with cement paste; lotus root residue cellulose, as a bacterial carrier and internal curing agent, not only protects the activity of the bacteria together with amylopectin, but also improves the internal humidity field of concrete through its hygroscopic and slow-release properties; Bacillus pasteurization bacteria tend to attach to rough or porous surfaces—that is, the surface of the pretreated copper slag fine aggregate and the cavity inside the lotus root residue cellulose. Microbial mineralization at room temperature endows concrete with excellent self-healing capabilities for cracks. When microcracks develop in concrete due to load or environmental factors, external moisture intrusion activates dormant spores, causing bacteria to revive and restart their metabolic activities. They continuously decompose urea to generate carbonate ions, which combine with calcium ions in the environment to precipitate calcite crystals. This process occurs in situ at the crack, and the newly formed calcite crystals gradually fill the crack, achieving self-healing. Attached Figure Description

[0010] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0011] Figure 1 This is a schematic diagram showing the relationship between flexural strength, self-shrinkage, and the amount of copper slag fine aggregate in a specific embodiment of the present invention; Figure 2 This is a schematic diagram showing the relationship between drying shrinkage rate, chloride ion diffusion coefficient and copper slag fine aggregate content in a specific embodiment of the present invention. Figure 3 This is a schematic diagram showing the relationship between the compressive strength and flexural strength of concrete with different components when the amount of copper slag fine aggregate added is fixed in a specific embodiment of the present invention. Figure 4 This is a schematic diagram showing the relationship between the drying shrinkage rate and chloride ion diffusion coefficient of concrete with different components when the amount of copper slag fine aggregate added is fixed in a specific embodiment of the present invention. Detailed Implementation

[0012] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0013] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0014] A typical embodiment of the present invention provides a self-healing geopolymer concrete, comprising the following components in parts by weight: 300-350 parts cement, 100-150 parts fly ash, 1.5-3 parts amylopectin, 1-2 parts cellulose from lotus root residue with bacterial growth, 0-715.5 parts natural river sand, 200-1030 parts copper slag fine aggregate, 1290-1340 parts basalt coarse aggregate, 70-90 parts steel fiber, 100-140 parts water, 2-3 parts water-reducing agent, 2-3 parts urea, and 2-3 parts calcium lactate; Among them, the cellulose in lotus root residue loaded with bacteria is cellulose in lotus root residue loaded with Bacillus pasteurellii, with a loading amount of 0.5~1.5wt%.

[0015] Among the above components, a three-dimensional mineral network is constructed at the interface between copper slag fine aggregate and lotus root residue cellulose through microbial-induced mineralization technology: During the concrete hydration process, bacteria metabolize and decompose urea to generate carbonate ions, which combine with calcium ions provided by calcium lactate to precipitate calcite crystals in situ. These calcite crystals have angular geometric shapes and will continue to grow and overlap, eventually forming a three-dimensional mineral skeleton network between the copper slag fine aggregate and cellulose. This mineral network is a three-dimensional structure with mechanical interlocking effect, which "roughens" the surface of the copper slag fine aggregate while rooting into the porous wall of cellulose, thereby firmly "stitching" the copper slag fine aggregate and lotus root residue cellulose together, significantly improving the weak links in the interface transition zone, and greatly improving the overall mechanical properties and structural integrity of the concrete. When microcracks occur in the concrete due to load or environmental effects, external moisture intrusion activates dormant spores, which can achieve self-repair of cracks based on the same principle and restore mechanical properties.

[0016] Optionally, the fine aggregate of copper slag has a particle size range of 0.075~4.75mm and a density of 3.8 g / cm³. 3 It has a water absorption rate of 0.18% and a fineness modulus of 3.5.

[0017] Optionally, the natural river sand serves as fine aggregate, with the selected natural river sand having a specific gravity of 2.65, a fineness modulus of 2.80, and a particle diameter of 0.075~4.75mm.

[0018] Optionally, the basalt coarse aggregate has a particle size of 5-20 mm; the basalt has a specific gravity of 3.1 and a density of 3.1 g / cm³. 3 Its elastic modulus is 50±20 GPa and its Poisson's ratio is 0.25.

[0019] Optionally, the specific surface area of ​​the fly ash is greater than 450 m². 2 / kg, density approximately 2.31 g / cm³ 3 .

[0020] Optionally, the cement is silicate cement or ordinary silicate cement with a strength grade of 42.5 or 42.5R.

[0021] Optionally, the steel fiber is a straight brass-galvanized steel fiber, approximately 20 mm in length, approximately 0.22 mm in diameter, with a tensile strength greater than 2800 MPa, an elastic modulus of 200 GPa, and a density of 7.9 g / cm³. 3 .

[0022] Optionally, the lotus root residue cellulose is a white powder, tasteless and odorless, with a density of 1.5 g / cm³. 3 ;(C 12 H 20 O 10 ) n The structural formula is: n is 700-1200.

[0023] Optionally, the molecular formula of amylopectin is C 30 H 52 O 26 The structural formula is: .

[0024] Amylopectin, with its large molecular weight and highly branched structure, exhibits high viscosity and strong adhesion in its aqueous solution, acting as a binder throughout the system. In the initial stirring stages, amylopectin molecules adsorb onto the surface of lotus root residue cellulose, forming a hydrophilic film. This film prevents direct contact and aggregation between cellulose molecules through steric hindrance. The numerous hydroxyl groups (-OH) on the amylopectin molecular chains can form hydrogen bonds or coordination bonds with metal oxides (such as Fe2O3 and SiO2) on the surface of copper slag fine aggregate, thus adsorbing onto the surface. When amylopectin simultaneously adsorbs onto both copper slag fine aggregate and cellulose, a flexible and highly adhesive "molecular bridge" is established between them. Mineral crystals can grow on the starch film, upgrading physical adsorption to chemical interlocking and greatly strengthening the interfacial transition zone. Furthermore, the gel layer formed by amylopectin on the cellulose surface provides a physical barrier for bacteria attached to it, buffering drastic changes in external alkalinity and osmotic pressure. Although Bacillus pasteurellii mainly utilizes urea and calcium as sources, amylopectin, as a polysaccharide, can serve as a slowly released carbon source. In the early stages of concrete hardening, when bacteria are in a dormant or slow metabolic state, the degradation products of amylopectin can maintain their basic activity, helping them to survive the most difficult phase and successfully form spores, thereby improving the survival rate of the strain.

[0025] Of the above components, urea and calcium lactate promote the transformation of the "bioactivity" of Bacillus pasteurellii into "mineral deposition"; because they first soak the copper slag fine aggregate, they can enrich Ca on the surface of the copper slag fine aggregate. 2+ Then the CO3 released by bacterial metabolism 2- Priority with Ca 2+ The calcite crystals combine to form calcite, meaning they grow from the surface of the fine aggregate in the copper slag outwards, while simultaneously reacting with the metabolic products of microorganisms (CO3) that overflow from the cellulose channels. 2- When the two minerals meet, a three-dimensional interlocking mineral skeleton is formed between the copper slag fine aggregate and cellulose, realizing the directional, controllable, and in-situ growth of the mineralization network, and achieving the toughening of the copper slag fine aggregate-cellulose interface and the self-healing function of concrete.

[0026] Optionally, the water-reducing agent is a polycarboxylate-based high-performance water-reducing agent.

[0027] A typical embodiment of the present invention provides a method for preparing the above-mentioned self-healing geopolymer concrete, comprising the following steps: Lotus root residue cellulose was soaked in a bacterial solution of Bacillus pasteurellii to obtain bacterial-loaded lotus root residue cellulose; urea and calcium lactate were dispersed in a set amount of water and used to soak copper slag fine aggregate to obtain wet copper slag fine aggregate; then cement, fly ash, natural river sand and basalt coarse aggregate were dry-mixed and added to the wet copper slag fine aggregate and mixed; branched-chain starch and bacterial-loaded lotus root residue cellulose were added and mixed to obtain dry mix; the remaining water and water-reducing agent were added and mixed; steel fibers were added and mixed; and the mixture was poured and cured to obtain the self-healing geopolymer concrete.

[0028] Optionally, the OD600 of the bacterial solution is 1.5~2.5, and 5~15mL of bacterial solution is adsorbed per kilogram of lotus root residue cellulose.

[0029] Optionally, the copper slag fine aggregate is sequentially subjected to crushing, magnetic separation, washing, and drying; it is preferentially soaked in a urea and calcium lactate solution. Since copper slag contains components such as CaO, SiO2, and Al2O3, after crushing and washing, micron-level scratches and pits appear on the surface. These surfaces are rich in silanol groups (≡Si-OH) and iron hydroxyl groups (≡Fe-OH), which can undergo deprotonation reactions, giving the surface of the copper slag fine aggregate a stable negative charge. This state can capture Ca during the soaking process. 2+ , making Ca 2+ Calcite is enriched on the surface of copper slag fine aggregate, which in turn causes calcite to preferentially form on the surface of copper slag fine aggregate; thus transforming copper slag fine aggregate from "inert aggregate" into "active anchoring base of mineral network".

[0030] Optionally, urea and calcium lactate can be dispersed in water that accounts for 75-85% of the total water volume.

[0031] A typical embodiment of the present invention provides the application of the above-mentioned self-healing geopolymer concrete in bridges, high-rise buildings, nuclear power plants or protective engineering projects.

[0032] Optional applications include: core tubes or load-bearing components of high-rise buildings, waterproof and seepage-proof structures for subway tunnels or underground parking lots, and marine or cold-region projects; copper slag fine aggregate has dense particles, low internal porosity, and a water absorption rate far lower than that of natural aggregates, fundamentally reducing the total porosity and number of harmful pores in concrete, constructing the first barrier against the intrusion of moisture and corrosive media; the addition of lotus root residue cellulose physically blocks the path of microcracks; the microbially induced calcite mineral network not only strengthens the interface but also further blocks capillary pores and optimizes the pore structure, forming multiple densification effects with the pozzolanic active products (CSH gel) of copper slag fine aggregate. The triple compounding effect significantly enhances the impermeability, freeze-thaw resistance, carbonation resistance, and chemical erosion resistance of concrete, enabling it to maintain excellent volume stability and ultra-long service life even in harsh environments (such as marine environments and de-icing salt erosion sections), making it particularly suitable for structures with high waterproof and seepage-proof requirements such as subway tunnels and underground parking lots.

[0033] The present invention will be further described below with reference to specific embodiments.

[0034] Preparation Example 1 A copper slag fine aggregate, the preparation method includes: The copper slag raw material is coarsely crushed using a jaw crusher to reduce its particle size. Then, a cone crusher is used for secondary fine crushing, mechanically breaking down large pieces of copper slag into smaller particles, increasing the specific surface area, which is beneficial for subsequent screening and processing. The crushed copper slag is then graded using a drum screen to a particle size range of 0.075~4.75mm. The resulting fine aggregate of copper slag is then processed using an electromagnetic separator to remove residual metallic impurities, thereby improving the purity of the fine aggregate.

[0035] Copper slag fine aggregate that has not undergone magnetic separation may contain heavy metal particles that inhibit bacterial activity; the magnetic field strength is set at 8000 Gauss and the magnetic separation time is 5 minutes.

[0036] Afterwards, use a spiral washing machine to wash for 10 minutes to remove dust and adhering substances from the surface of the copper slag, reduce the impact of surface dust and impurities, and improve the quality of subsequent processing.

[0037] After cleaning, the fine copper slag aggregate is placed in a drum dryer for drying. The drying temperature is set at 150℃ and the drying time is set at 2 hours to reduce the moisture content of the fine copper slag aggregate.

[0038] Preparation Example 2 A method for preparing a bacterial-loaded lotus root residue cellulose includes: The lotus root residue was dried in an oven at 65 ℃. After drying, it was pulverized. The obtained powder was added to pure water at a material-to-liquid ratio of 1:10, and 0.2 wt% amylase was added. After water bathing at 55 ℃ for 4 h, the starch in the lotus root residue was removed. After testing with iodine solution and finding no blue color, the temperature was raised to 90 ℃ and water bathed for 2 h to inactivate the amylase. The residue was then centrifuged at 4500 r / min for 15 min, and the precipitate was dried and stored at 50 ℃.

[0039] 10 g of precipitate, 300 mL of 5% sodium hydroxide solution and 37.8 g of sodium sulfite were mixed and stirred at 80 °C for 120 min. The mixture was then filtered and washed until neutral. This process was repeated three times. After that, the mixture was bleached with 4 wt% hydrogen peroxide solution at 80 °C, washed until neutral, and then freeze-dried under vacuum to obtain pretreated lotus root residue. The residue was then stored in sealed bags for later use.

[0040] Mix 10 g of pretreated lotus root residue with raw material mass at a ratio of 1:30 (g / mL). -1The material-to-liquid ratio was adjusted, and 300 mL of 5wt% sodium hydroxide solution and 37.82 g of sodium sulfite (NaOH concentration of 1.25 M and Na2SO3 concentration of 1 M) were added. The mixture was extracted at 80 ℃ for 120 min with the water bath temperature as the variable to obtain lotus root residue cellulose.

[0041] Use commercially available Pasteurella multocida ( Sporosarcina pasteurii Dilute the concentrated bacterial solution with sterile water to OD600≈2.0. Mix the bacterial solution according to the ratio of 10mL of bacterial solution to cellulose adsorption per kilogram of lotus root residue. Soak under normal pressure for 30 minutes, stirring slightly during the process to ensure that the bacterial solution is fully loaded into the fiber pores. Use sterile gauze to squeeze out excess liquid until the cellulose reaches a saturated and surface-dry state (it can be clumped when squeezed, but crumbles when lightly pressed).

[0042] Example 1 A self-healing geopolymer concrete comprises the following components in parts by weight: The ingredients included 337.1 parts cement, 137.9 parts fly ash, 2.375 parts amylopectin, 1.425 parts cellulose from lotus root residue obtained in Preparation Example 2, 205.2 parts copper slag fine aggregate obtained in Preparation Example 1, 572.4 parts natural river sand, 1317.5 parts basalt coarse aggregate, 79 parts straight brass galvanized steel fiber, 118.75 parts water, 2.575 parts water-reducing agent, 2.375 parts urea, and 2.375 parts calcium lactate.

[0043] The cement used is silicate cement with a strength grade of 42.5.

[0044] The specific surface area of ​​fly ash is greater than 450 m². 2 / kg, density approximately 2.31 g / cm³ 3 .

[0045] The molecular formula of amylopectin is Ca 30 H 52 O 26 The structural formula is: .

[0046] Natural river sand serves as fine aggregate, with a specific gravity of 2.65, a fineness modulus of 2.80, and a particle size of 0.075~4.75mm.

[0047] The coarse basalt aggregate has a particle size of 5-20 mm; the specific gravity of basalt is 3.1, and its density is 3.1 g / cm³. 3 Its elastic modulus is 50±20GPa and its Poisson's ratio is 0.25.

[0048] The steel fibers are straight, brass-galvanized steel fibers, approximately 20 mm in length and 0.22 mm in diameter, with a tensile strength greater than 2800 MPa, an elastic modulus of 200 GPa, and a density of 7.9 g / cm³. 3 .

[0049] The water-reducing agent is a polycarboxylate-based high-performance water-reducing agent.

[0050] Urea and calcium lactate are added in granular or powder form, respectively.

[0051] Preparation methods include: Using a mixer as a container, urea and calcium lactate were dissolved in 80% of the mixing water to obtain a soaking solution. Copper slag fine aggregate was added to the soaking solution and stirred and soaked for 30 seconds. Add cement, fly ash, natural river sand and basalt coarse aggregate to a mixer and mix at 70±55 rpm (low speed) for 3 minutes to mix the raw materials evenly and thoroughly. Evenly sprinkle amylopectin and cellulose from lotus root residue loaded with bacteria into a mixer and continue mixing for 15 seconds to disperse the cellulose and prevent agglomeration. Then start the mixer and keep it at a low speed. Slowly add the remaining water and water-reducing agent, and continue mixing for 3 minutes until the slurry is uniform and there is no dry powder. Mix at 160±5 rpm (medium speed). After the concrete has good fluidity, slowly add steel fibers through a square-hole sieve. Maintain a moderate mixing speed to ensure that the steel fibers are evenly distributed in the cement. After mixing at 360±55 rpm (high-speed mixing) for 1-2 minutes, pour the mixture into shape and cure it to the specified age.

[0052] Example 2 A self-healing geopolymer concrete comprises the following components in parts by weight: 337.1 parts cement, 137.9 parts fly ash, 2.375 parts branched-chain starch, 1.425 parts cellulose from lotus root residue with bacterial growth, 410.4 parts copper slag fine aggregate, 429.3 parts natural river sand, 1317.5 parts basalt coarse aggregate, 79 parts straight brass galvanized steel fiber, 118.75 parts water, 2.575 parts water-reducing agent, 2.375 parts urea, and 2.375 parts calcium lactate.

[0053] The requirements for each raw material and the preparation method are the same as in Example 1.

[0054] Example 3 A self-healing geopolymer concrete comprises the following components in parts by weight: 337.1 parts cement, 137.9 parts fly ash, 2.375 parts amylopectin, 1.425 parts cellulose from lotus root residue with bacterial growth, 615.6 parts copper slag fine aggregate, 286.2 parts natural river sand, 1317.5 parts basalt coarse aggregate, 79 parts straight brass galvanized steel fiber, 118.75 parts water, 2.575 parts water-reducing agent, 2.375 parts urea, and 2.375 parts calcium lactate.

[0055] The requirements for each raw material and the preparation method are the same as in Example 1.

[0056] Example 4 A self-healing geopolymer concrete comprises the following components in parts by weight: 337.1 parts cement, 137.9 parts fly ash, 2.375 parts branched-chain starch, 1.425 parts cellulose from lotus root residue with bacterial growth, 820.8 parts copper slag fine aggregate, 143.1 parts natural river sand, 1317.5 parts basalt coarse aggregate, 79 parts straight brass galvanized steel fiber, 118.75 parts water, 2.575 parts water-reducing agent, 2.375 parts urea, and 2.375 parts calcium lactate.

[0057] The requirements for each raw material and the preparation method are the same as in Example 1.

[0058] Example 5 A self-healing polymer concrete comprises the following components in parts by weight: 337.1 parts cement, 137.9 parts fly ash, 2.375 parts branched-chain starch, 1.425 parts cellulose from lotus root residue with bacterial growth, 1026 parts copper slag fine aggregate, 1317.5 parts basalt coarse aggregate, 79 parts straight brass galvanized steel fiber, 118.75 parts water, 2.575 parts water-reducing agent, 2.375 parts urea, and 2.375 parts calcium lactate.

[0059] The requirements for raw materials and preparation methods are the same as in Example 1, but natural river sand is not added.

[0060] Comparative Example 1 A type of ordinary concrete comprises the following components in parts by weight: The composition includes 337.1 parts cement, 137.9 parts fly ash, 2.375 parts amylopectin, 1.425 parts lotus root residue cellulose, 715.5 parts natural river sand, 1317.5 parts basalt coarse aggregate, 79 parts straight brass-galvanized steel fiber, 118.75 parts water, and 2.575 parts water-reducing agent. The difference from Example 1 is that copper slag fine aggregate, urea, and calcium lactate are not added.

[0061] Comparative Example 2 A type of ordinary concrete comprises the following components in parts by weight: The composition includes 337.1 parts cement, 137.9 parts fly ash, 410.4 parts copper slag fine aggregate, 429.3 parts natural river sand, 1317.5 parts basalt coarse aggregate, 79 parts straight brass galvanized steel fiber, 118.75 parts water, and 2.575 parts water-reducing agent. The difference from Example 1 is that branched-chain starch, bacterial-loaded lotus root residue cellulose, urea, and calcium lactate are not added.

[0062] Comparative Example 3 A type of ordinary concrete comprises the following components in parts by weight: The composition includes 337.1 parts cement, 137.9 parts fly ash, 1.426 parts uninfected lotus root residue cellulose, 410.4 parts copper slag fine aggregate, 429.3 parts natural river sand, 1317.5 parts basalt coarse aggregate, 79 parts straight brass-galvanized steel fiber, 118.75 parts water, and 2.575 parts water-reducing agent. The difference from Example 1 is that it does not contain amylopectin, urea, or calcium lactate, and the lotus root residue cellulose is uninfected.

[0063] Comparative Example 4 A type of ordinary concrete comprises the following components in parts by weight: The composition includes 337.1 parts cement, 137.9 parts fly ash, 2.375 parts amylopectin, 1.426 parts uninfected lotus root residue cellulose, 410.4 parts copper slag fine aggregate, 429.3 parts natural river sand, 1317.5 parts basalt coarse aggregate, 79 parts straight brass-galvanized steel fiber, 118.75 parts water, and 2.575 parts water-reducing agent. The difference from Example 1 is that it does not contain urea or calcium lactate, and the lotus root residue cellulose is uninfected.

[0064] Comparative Example 5 A self-healing ordinary concrete comprises the following components by weight: 337.1 parts cement, 137.9 parts fly ash, 2.375 parts amylopectin, 1.425 parts uninoculated lotus root residue cellulose, 205.2 parts copper slag fine aggregate, 572.4 parts natural river sand, 1317.5 parts basalt coarse aggregate, 79 parts straight brass galvanized steel fiber, 118.75 parts water, 2.575 parts water-reducing agent, 2.375 parts urea, and 2.375 parts calcium lactate. It also contains the same amount of bacterial solution as in Example 1, but differs in that the bacterial solution is directly mixed with the slurry in the step of adding the water-reducing agent, instead of loading the bacteria into the lotus root residue cellulose.

[0065] Comparative Example 6 A self-healing geopolymer concrete differs from Example 1 in that its preparation method includes: placing cement, fly ash, copper slag fine aggregate, natural river sand and basalt coarse aggregate in a mixer and mixing at 70±55 rpm (low speed mixing) for 3 minutes to uniformly and fully mix the raw materials into a dry mix. Evenly sprinkle amylopectin and cellulose from lotus root residue loaded with bacteria into the dry mixture, and continue to dry mix for about 15 seconds to disperse the cellulose and prevent agglomeration, thus obtaining the dry mixture. Dissolve urea and calcium lactate in 80% of the mixing water, stir until dissolved, pour into the mixer, then start the mixer and keep stirring at low speed. Slowly add the remaining water and water-reducing agent, and continue stirring for 3 minutes until the slurry is uniform and there is no dry powder. Mix at 160±5 rpm (medium speed). After the concrete has good fluidity, slowly add steel fibers through a square-hole sieve. Maintain a moderate mixing speed to ensure that the steel fibers are evenly distributed in the cement. After mixing at 360±55 rpm (high speed) for 1-2 minutes, pour the mixture into shape and cure it to the specified age.

[0066] Test case The ultra-high performance concrete of the above embodiments and comparative examples were subjected to conventional mechanical performance tests. Mechanical performance tests were conducted according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" GB / T 50081-2019, and durability performance tests were conducted according to the "Standard for Test Methods of Long-Term Performance and Durability of Concrete" GB / T50082-2024. The results are shown in Table 1. Figure 1 This is a schematic diagram showing the relationship between flexural strength, self-shrinkage, and the amount of copper slag fine aggregate in a specific embodiment of the present invention; Figure 2 This is a schematic diagram showing the relationship between drying shrinkage rate, chloride ion diffusion coefficient and copper slag fine aggregate content in a specific embodiment of the present invention. Figure 3 This is a schematic diagram showing the relationship between the compressive strength and flexural strength of concrete with different components when the amount of copper slag fine aggregate added is fixed in a specific embodiment of the present invention. Figure 4 This is a schematic diagram showing the relationship between the drying shrinkage rate and chloride ion diffusion coefficient of concrete with different components when the amount of copper slag fine aggregate added is fixed in a specific embodiment of the present invention.

[0067] Table 1. Test results of mechanical properties and durability

[0068] The following analysis can be drawn from the data in Table 1: Compared to Comparative Example 2, Comparative Example 3 added uninfected lotus root residue cellulose to the concrete. In terms of strength, the compressive strength of Comparative Example 3 increased by 5.2% and the flexural strength increased by 10.8% compared to 85.4 MPa in Comparative Example 2. In terms of durability, the drying shrinkage rate of Comparative Example 3 decreased by 8.5% and the chloride ion diffusion coefficient decreased by 12.5% ​​compared to Comparative Example 2. This shows that adding lotus root residue cellulose can effectively improve the mechanical properties and durability of concrete. As a physical fiber network, lotus root residue cellulose inhibits microcrack propagation and improves toughness through bridging. Furthermore, comparing Comparative Example 4 with Comparative Example 3, Comparative Example 4 added amylopectin to the concrete. It can be seen that the compressive strength and flexural strength of Comparative Example 4 both increased to varying degrees, with the compressive strength increasing by 3.9% and the flexural strength increasing by 3.3%. Durability also improved, with the drying shrinkage rate decreasing by 6.8% and the chloride ion permeability coefficient decreasing by 12.9%. This indicates that the addition of amylopectin can have a synergistic effect with lotus root residue cellulose. As an auxiliary binder, amylopectin improves the interfacial affinity between cellulose and the matrix, enhances fiber dispersion and anchoring, and effectively improves the strength of concrete.

[0069] Compared to Example 1, Comparative Example 5 involved mixing the bacterial solution with the stirred slurry, rather than loading the bacteria onto lotus root residue cellulose. Observing its mechanical and durability properties, Example 1 showed an 11.6% increase in compressive strength, a 6.0% increase in flexural strength, a 28.5% decrease in drying shrinkage, and a 34.7% decrease in chloride ion permeability compared to Comparative Example 5. This demonstrates that the method of bacterial loading is crucial to its performance. Direct mixing leads to significant bacterial inactivation during concrete mixing and hardening due to multiple stresses such as high alkali, shear, and heat of hydration. Mineralized products are randomly dispersed, failing to form an effective three-dimensional mineral network at the copper slag fine aggregate-cellulose interface. Therefore, the improvement in mechanical properties is limited, self-healing function is essentially lost, and durability is not significantly improved. However, using lotus root residue cellulose as a bacterial carrier utilizes the porous structure of the fiber to protect the bacteria, while amylopectin improves fiber dispersion and calcium lactate forms a calcium-rich layer on the surface of the copper slag fine aggregate. This achieves multiple effects, including directional bacterial colonization, preferential growth of mineralized products, interface strengthening, and synergistic internal curing.

[0070] Comparing Example 2 with Comparative Example 4, the difference lies in the addition of bacterial-loaded lotus root residue cellulose in Example 2. The compressive strength of Example 2 increased by 21.5% and the flexural strength increased by 13.7% compared to Comparative Example 4. The drying shrinkage rate of Example 2 decreased by 28.6% and the chloride ion permeability coefficient decreased by 21.0% compared to Comparative Example 4. This demonstrates that the addition of bacterial-loaded lotus root residue cellulose significantly improves the mechanical properties and durability of concrete. This is because Bacillus pasteurellii bacteria tend to attach to rough or porous surfaces—namely, the surface of the pretreated copper slag fine aggregate and the interior of the lotus root residue cellulose cavities. The lotus root residue cellulose acts as a bacterial carrier, providing a sanctuary for the bacteria and simultaneously providing internal curing. During concrete hydration, bacteria metabolize and decompose urea to generate carbonate ions, which combine with calcium ions provided by calcium lactate, precipitating in situ to form calcite crystals. These calcite crystals have angular geometric shapes and continuously grow and overlap, ultimately forming a three-dimensional mineral skeleton network between the copper slag fine aggregate and the cellulose. This mineral network "roughens" the smooth surface of the copper slag fine aggregate while simultaneously embedding itself into the porous walls of the cellulose in a root-like manner, thus firmly "stitching" the copper slag fine aggregate and lotus root residue cellulose together, significantly improving the weak points in the interface transition zone. The synergistic effect of fiber bridging at the physical level and the mineral network at the chemical level makes the internal structure of the concrete denser and stress transfer more efficient, thereby greatly improving mechanical properties and durability.

[0071] All five embodiments showed varying degrees of improvement in various mechanical and durability tests, with Embodiment 2 exhibiting the best overall performance. In terms of compressive strength, Embodiment 2 reached 113.4 MPa, significantly higher than Comparative Example 1's 81.5 MPa. The elastic modulus also increased with the increase in the proportion of copper slag fine aggregate to the total fine aggregate (including copper slag fine aggregate and natural river sand), with Embodiment 2 reaching an elastic modulus of 37.6 GPa, the highest among all embodiments, indicating a significant improvement in stiffness characteristics. Embodiment 2 also achieved a flexural strength of 10.8 MPa, demonstrating superior crack resistance and toughness. Furthermore, Embodiment 2 reduced its drying shrinkage to 265 με and its chloride ion permeability coefficient to 1.54 × 10⁻⁶. -12 m 2This is due to the fact that the active components in the copper slag fine aggregate can react with the cement hydration product Ca(OH)2 to generate more dense calcium silicate hydrate (CSH) gel, further blocking capillary pores and optimizing the pore structure. Furthermore, the copper slag fine aggregate itself possesses high hardness and high strength; its rough, angular particle shape forms excellent mechanical interlocking with the cement paste, significantly optimizing the interfacial transition zone (ITZ) structure, thereby improving the compressive and flexural strength of the concrete. The highly branched molecular structure of amylopectin forms a gel-like protective layer on the surface of lotus root residue cellulose, providing a physical barrier for Bacillus pasteurellii, buffering the direct stress of the highly alkaline environment of concrete on the bacteria, and significantly improving bacterial survival rate. Secondly, as a slow-release carbon source, amylopectin can be slowly metabolized and utilized by bacteria, maintaining the basic metabolic activity of bacteria in the early stage of concrete hardening and before the urea substrate has fully diffused, helping them to form spores smoothly. In addition, the strong water absorption of amylopectin can regulate the humidity and osmotic pressure of the cellulose-bacterial microenvironment, avoiding bacterial inactivation due to local water shortage. At the same time, its hydrogen bonding with the surface of copper slag fine aggregate confines bacterial metabolic activity to the interface region that needs enhancement, allowing the limited nutrient substrate (urea, calcium lactate) to serve the mineralization reaction more efficiently, thereby indirectly improving the mineralization efficiency of microorganisms and the orderly distribution of products. Meanwhile, lotus root residue cellulose is uniformly distributed in three dimensions within the matrix, forming a highly efficient fiber network. Through its excellent "bridging effect," it inhibits the initiation and propagation of microcracks, and works synergistically with amylopectin to give concrete excellent crack resistance and ductility.

[0072] As the proportion of copper slag fine aggregate in the total fine aggregate increases, the strength and durability of the concrete gradually decrease. The compressive strength decreases from 113.4 MPa in Example 2 to 88.4 MPa in Example 5, and the chloride ion permeability coefficient decreases from 1.54 × 10⁻⁶. -12 m 2 / s increased to 1.77×10 -12 m 2 / s. This is because the water absorption rate of copper slag fine aggregate is lower than that of natural river sand, leading to an increase in the free water content in the mixture, which affects the sufficiency of the hydration reaction and thus reduces the overall strength of the concrete. In Example 2, the reinforcing effect of copper slag fine aggregate and the interface defects achieve an optimal balance.

[0073] Compared to Comparative Example 2, Example 2 removed amylopectin and cellulose from lotus root residue, unlike Example 2. The compressive strength of Example 2 increased by 28.3% and the flexural strength increased by 30.1% compared to the Comparative Example. This demonstrates that the addition of amylopectin and cellulose from lotus root residue is beneficial for improving the mechanical properties of concrete, such as compressive strength. This is because cellulose from lotus root residue is a natural fiber; its high strength and toughness allow it to form a fiber network in concrete, dispersing stress and delaying crack propagation through a "bridging" effect, while simultaneously improving the tensile properties and fracture toughness of the concrete. Amylopectin improves the bonding ability of the concrete cementitious material, further reducing crack formation; its polymer structure creates a special viscosity that helps maintain the closure of microcracks in the concrete. The combined effect of these two materials allows for better filling of voids within the concrete, significantly improving its durability, mechanical strength, and self-healing properties.

[0074] Compared with the all-natural sand Comparative Example 1, Example 2 achieved a strength improvement of nearly 40%, which fully demonstrates the synergistic effect of the triple composite system of copper slag fine aggregate replacement + lotus root residue cellulose + microbial mineralization: copper slag fine aggregate provides a high-hardness skeleton, lotus root residue cellulose provides physical bridging and microbial carrier, amylopectin improves fiber dispersion, and microbial mineralization constructs a mineral network at the interface, "stitching" the components into a whole.

[0075] Comparative Example 6 did not pre-treat the copper slag fine aggregate with urea and calcium lactate during preparation. Compared to Example 1, the compressive strength of Comparative Example 6 decreased by 9.8%, and the flexural strength decreased by 3.4%. This indicates that the combined treatment with urea and calcium lactate plays a crucial role in improving the interfacial bonding performance of copper slag fine aggregate and cement matrix. This is because the surface of copper slag is rich in silanol and ferrool groups, which become negatively charged after deprotonation in aqueous solution. The Ca released after the urea and calcium lactate dissolve... 2+ It preferentially adsorbs onto the surface of fine aggregates in copper slag, forming a stable calcium-rich layer through electrostatic interaction. During subsequent microbial mineralization, *Bacillus pasteurellii* metabolizes urea to generate CO3. 2- With the Ca enriched on the surface of copper slag fine aggregate 2+ Combined, angular calcite crystals are generated in situ. These crystals continuously grow and overlap, constructing a three-dimensional mineral framework network that "roughens" the smooth surface of the copper slag fine aggregate and embeds it into the cement stone, upgrading the interfacial bonding from physical adsorption to chemical interlocking. In contrast, the untreated comparative example 6 lacks this calcium-rich layer, resulting in randomly dispersed mineralized products, high porosity in the interfacial transition zone, and a significant decrease in mechanical properties.

[0076] Overall, Example 2 exhibits the best comprehensive performance, demonstrating outstanding mechanical and durability properties. It is suitable for engineering applications with high requirements for strength, toughness, and durability. Excessive copper slag fine aggregate can lead to a decrease in concrete strength.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A self-healing geopolymer concrete, characterized in that, It consists of the following components in parts by weight: 300-350 parts cement, 100-150 parts fly ash, 1.5-3 parts amylopectin, 1-2 parts cellulose from lotus root residue with bacterial growth, 0-715.5 parts natural river sand, 200-1030 parts copper slag fine aggregate, 1290-1340 parts basalt coarse aggregate, 70-90 parts steel fiber, 100-140 parts water, 2-3 parts water-reducing agent, 2-3 parts urea, and 2-3 parts calcium lactate; Among them, the cellulose in lotus root residue loaded with bacteria is lotus root residue cellulose loaded with Bacillus pasteurella, with a loading of 0.5~1.5 wt%; The preparation method includes the following steps: Lotus root residue cellulose was soaked in a bacterial solution of Bacillus pasteurellii to obtain bacterial-loaded lotus root residue cellulose; urea and calcium lactate were dispersed in a set amount of water and used to soak copper slag fine aggregate to obtain wet copper slag fine aggregate; then cement, fly ash, natural river sand and basalt coarse aggregate were dry-mixed and added to the wet copper slag fine aggregate and mixed; branched-chain starch and bacterial-loaded lotus root residue cellulose were added and mixed to obtain dry mix; the remaining water and water-reducing agent were added and mixed; steel fibers were added and mixed; and the mixture was poured and cured to obtain the self-healing geopolymer concrete.

2. The self-healing geopolymer concrete as described in claim 1, characterized in that, The particle size range of copper slag fine aggregate is 0.075~4.75mm; the particle size of basalt coarse aggregate is 5~20mm.

3. The self-healing geopolymer concrete as described in claim 1, characterized in that, The cement is silicate cement or ordinary silicate cement with a strength grade of 42.5 or 42.5R. The steel fibers are straight brass-galvanized steel fibers; The water-reducing agent is a polycarboxylate-based high-performance water-reducing agent.

4. The self-healing geopolymer concrete as described in claim 1, characterized in that, The molecular formula of amylopectin is Ca 30 H 52 O 26 .

5. The self-healing geopolymer concrete as described in claim 1, characterized in that, The molecular formula of cellulose in lotus root residue is (C 12 H 20 O 10 ) n n is 700-1200.

6. A method for preparing self-healing geopolymer concrete as described in any one of claims 1-5, characterized in that, Including the following steps: Lotus root residue cellulose was soaked in a bacterial solution of Bacillus pasteurellii to obtain bacterial-loaded lotus root residue cellulose; urea and calcium lactate were dispersed in a set amount of water and used to soak copper slag fine aggregate to obtain wet copper slag fine aggregate; then cement, fly ash, natural river sand and basalt coarse aggregate were dry-mixed and added to the wet copper slag fine aggregate and mixed; branched-chain starch and bacterial-loaded lotus root residue cellulose were added and mixed to obtain dry mix; the remaining water and water-reducing agent were added and mixed; steel fibers were added and mixed; and the mixture was poured and cured to obtain the self-healing geopolymer concrete.

7. The method for preparing self-healing geopolymer concrete as described in claim 6, characterized in that, The OD600 of the bacterial solution is 1.5~2.5, and 5~15mL of bacterial solution is adsorbed per kilogram of lotus root residue cellulose.

8. The method for preparing self-healing geopolymer concrete as described in claim 6, characterized in that, The copper slag fine aggregate is subjected to crushing, magnetic separation, washing and drying processes in sequence.

9. The method for preparing self-healing geopolymer concrete as described in claim 6, characterized in that, Disperse urea and calcium lactate in water that accounts for 75-85% of the total water volume.

10. The application of a self-healing geopolymer concrete as described in any one of claims 1-5 in bridges, high-rise buildings, nuclear power plants, or protective engineering projects.

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