Self-repairing concrete for biologically inducing calcium carbonate deposition and preparation method of self-repairing concrete

Abstract

The invention relates to the technical field of biological induction of calcium carbonate deposition, in particular to self-repairing concrete for biological induction of calcium carbonate deposition and a preparation method thereof. The cement comprises the following components in parts by weight: 320-380 parts of Portland cement and the like. The biomineralization composite inducer contains a genetically engineered bacterium solution, a urea-calcium chloride solution and a nano strontium carbonate seed crystal; the nano silicon dioxide-graphene composite powder is prepared by chemical vapor deposition; the wall material of the double-response microcapsule contains a temperature-sensitive polymer, and the core material contains a plurality of components; nanocellulose whiskers are also added; self-repairing is achieved through cooperation of multiple components, and all the components are specially treated or prepared. The self-repairing concrete is high in self-repairing efficiency, and wide cracks can be repaired; the mechanical property is excellent, and the compression strength and the breaking strength are remarkably improved; working performance is good, and construction is convenient; durability is good, and erosion and permeability are resisted; environmental protection and economy are considered, and the application prospect is wide.

Description

Technical Field

[0001] The present invention relates to the technical field of bio-induced calcium carbonate deposition, in particular to self-repairing concrete with bio-induced calcium carbonate deposition and a preparation method thereof. Background Art

[0002] As the most widely used engineering material in modern construction, concrete plays a vital role in the construction of infrastructure such as buildings, bridges, and roads, thanks to its excellent plasticity, high strength, and durability. However, over long-term use, concrete structures are inevitably affected by various external factors (such as loads, temperature fluctuations, chemical attack, and freeze-thaw cycles), which can cause cracks. These cracks not only reduce the mechanical properties of concrete structures, resulting in a decrease in bearing capacity, but also provide pathways for the intrusion of moisture and harmful chemicals (such as chloride ions and sulfates), accelerating the corrosion of steel bars and the deterioration of concrete, seriously threatening the safety and service life of the structure.

[0003] To address the problem of concrete cracks, self-healing concrete technology has become a research hotspot. Early self-healing concrete primarily employed methods such as polymers and microcapsules, releasing a healing agent to fill cracks as they expand. However, these technologies suffer from low repair efficiency, a lack of sustained action after the agent is consumed, and poor compatibility with the concrete matrix. For example, the healing agent in traditional microcapsules loses its effectiveness after a single release, and the addition of microcapsules can affect the performance and mechanical properties of concrete.

[0004] The self-repair technology of biologically induced calcium carbonate deposition has attracted widespread attention due to its green and sustainable characteristics. This technology uses microorganisms (such as Bacillus pasteurianus) to secrete urease, catalyze the hydrolysis of urea to produce carbonate ions, and react with calcium ions in the pores of concrete to produce calcium carbonate, thereby achieving self-repair of cracks. However, the existing technology still has many shortcomings: on the one hand, microbial activity is easily affected by factors such as the high alkaline environment of concrete and the lack of nutrients, resulting in low urease catalytic efficiency and slow calcium carbonate deposition rate, making it difficult to quickly repair large cracks; on the other hand, the growth of the generated calcium carbonate crystals is highly random, the crystallization quality is poor, the bonding force with the concrete matrix is insufficient, and the structural strength after repair is limited. In addition, the function of a single biomineralization induction system is relatively single, and it cannot simultaneously meet the multiple needs of concrete in terms of optimizing working performance, enhancing mechanical properties, and improving corrosion resistance.

[0005] Existing self-healing concrete also has limitations in raw material selection and preparation processes. For example, the interface transition zone between conventional aggregates and the cement matrix is weak, affecting the overall performance of concrete; traditional admixtures can adversely affect the concrete's self-healing process; and the preparation process struggles to precisely control the uniform dispersion and effective action of components such as microorganisms and repair agents. Therefore, there is an urgent need to develop a novel self-healing concrete with bio-induced calcium carbonate deposition and its preparation method. Through innovative material formulations and process designs, these technical challenges can be overcome to achieve comprehensive improvements in concrete's self-healing and overall performance.

[0006] (1) Technical problems solved

[0007] In view of the shortcomings of the existing technology, the present invention provides a self-repairing concrete with biologically induced calcium carbonate deposition and a preparation method thereof.

[0008] (2) Technical solution

[0009] A self-repairing concrete with bioinduced calcium carbonate deposition comprises the following components by weight: 320-380 parts of Portland cement, 650-750 parts of fine aggregate, 1000-1100 parts of coarse aggregate, 160-180 parts of water, 22-28 parts of a biomineralization composite inducer, 12-18 parts of nano-silica-graphene composite powder, 16-24 parts of dual-responsive sodium alginate microcapsules, 8-9 parts of multifunctional modified cellulose, and 4-7 parts of a polycarboxylic acid high-performance water reducer. The biomineralization composite inducer comprises a genetically engineered bacterial solution of Sporosarcina pasteurii, a urea-calcium chloride mixed solution, and nano-strontium carbonate seeds in a volume ratio of 1:2.5:0.3. The genetically engineered bacterial solution overexpresses the urease gene to increase the enzyme activity by 40-60%, and the concentration is 3×10 8 -4×10 8 CFU / mL, the urea concentration in the urea-calcium chloride mixed solution is 0.8-1.2 mol / L, the calcium chloride concentration is 0.5-0.8 mol / L, and the nano-strontium carbonate seed particle size is 20-50 nm; the nano-silica-graphene composite powder is prepared by chemical vapor deposition, the graphene surface is grafted with a silane coupling agent, and the nano-silica is uniformly loaded on the graphene sheet, and the mass ratio of the two is 1:3 to 1:5; the dual-responsive sodium alginate microcapsule wall material is composed of sodium alginate, chitosan and a thermosensitive PNIPAM copolymer, the mass ratio of the three is 3:2:1, and the core material contains a calcium carbonate precursor solution, a Bacillus spore suspension and a pH-responsive repair agent, the mass ratio of which is 3:1:0.5; the self-repairing concrete also contains nano-cellulose whiskers accounting for 1-1.2% of the weight of silicate cement, with a diameter of 80-150 nm and a length of 8-15 μm; the main reaction formula for biomineralization induction is:

[0010]

[0011] Sr 2+ +CO3 2- →SrCO 3 ↓

[0012] Preferably, the method further comprises adding a biosurfactant rhamnolipid accounting for 5-8% of the total volume of the biomineralization composite inducer, and the concentration of the rhamnolipid is 0.2-0.5 g / L.

[0013] Preferably, the multifunctional modified cellulose is prepared by carboxymethylation and grafting with polyethylene glycol diacrylate, with a substitution degree of 0.7-0.8 and a grafting rate of 15-20%.

[0014] Preferably, the fine aggregate is river sand surface-treated with silane coupling agent KH-570, the treatment liquid concentration is 1.5-2.5%, the fineness modulus is 2.5-2.8, and the mud content does not exceed 1.5%; the coarse aggregate is basalt gravel that has been pre-wetted, with a particle size of 10-20 mm and a crushing index of no more than 10%.

[0015] Preferably, the polycarboxylic acid high performance water reducer has a solid content of 30-35%, a sulfonic acid group content of 18-22% in the molecular structure, a water reduction rate of not less than 30%, and contains a retarding group, and the initial slump loss after 1 hour does not exceed 20 mm.

[0016] Preferably, the dual-responsive sodium alginate microcapsules are prepared by a two-step emulsification method, wherein the core material and the sodium alginate solution are first emulsified to form a W / O emulsion, which is then dispersed in an aqueous solution containing chitosan and PNIPAM copolymer to form a W / O / W emulsion, and then solidified by adding a calcium chloride solution. The microcapsule particle size is 200-400 μm, the thermosensitive response temperature is 25-35°C, and the pH response range is 7-9.

[0017] Preferably, a method for preparing self-repairing concrete with bioinduced calcium carbonate deposition according to any one of the above items comprises the following steps:

[0018] S1: Genetically modifying Bacillus pasteurianus to construct a urease gene overexpression vector, which is then transferred into a recipient bacterium and cultured in a medium containing 0.3-0.5% yeast extract, 1-1.5% peptone, and 0.5-0.8% sodium chloride at 35°C and 180 rpm for 36-48 hours to produce a genetically engineered bacterial solution; preparing a urea-calcium chloride mixed solution and a nano-strontium carbonate seed suspension, and mixing them in proportion to form a biomineralization composite inducer;

[0019] S2: Using chemical vapor deposition, at 800-900°C, in a hydrogen-argon mixed atmosphere with a volume ratio of 1:4, ethyl orthosilicate vapor and graphene powder are reacted for 4-6 hours to produce nano-silica-graphene composite powder;

[0020] S3: Put Portland cement, fine aggregate, coarse aggregate, nano-silica-graphene composite powder, and nano-cellulose whiskers into a planetary mixer and dry mix for 3-4 minutes;

[0021] S4: Dissolve the polycarboxylate high-performance water-reducing agent and multifunctional modified cellulose in water, stir evenly, then add to the mixer and wet mix for 4-6 minutes;

[0022] S5: Add biomineralization composite inducer and dual-responsive sodium alginate microcapsules, continue stirring for 6-8 minutes, control the expansion of the concrete out of the machine to 550-650 mm, and prepare self-repairing concrete.

[0023] Preferably, during the preparation of the genetically engineered bacterial solution, when cultured to the late logarithmic growth phase, OD 600 When the pH value is 0.6-0.8, 0.05-0.1% of isopropyl-β-D-thiogalactopyranoside (IPTG) is added to induce expression.

[0024] Preferably, after pouring, the self-repairing concrete is first cured for 3 days in an environment with a temperature of 20-25°C and a relative humidity of more than 95%, and then transferred to an environment with a temperature of 25-30°C and a relative humidity of 80-85% for curing for up to 28 days.

[0025] Preferably, the planetary mixer has an orbital speed of 60-80 r / min and a rotational speed of 120-160 r / min during stirring, and adopts segmented temperature control during stirring, with the initial stirring temperature being 15-20°C and then increasing to 20-25°C.

[0026] (3) Beneficial technical effects

[0027] Compared with the existing technology, the beneficial effects of the present invention are:

[0028] 1. In terms of self-healing performance, this invention utilizes genetically engineered Bacillus pasteurianus to overexpress the urease gene, significantly enhancing its activity. Combined with nano-strontium carbonate seeds and biosurfactants, this significantly accelerates the deposition rate and crystallization quality of calcium carbonate. When cracks develop, the dual-responsive sodium alginate microcapsules rupture, releasing a repair agent that synergizes with the biomineralization induction system to rapidly fill and repair the cracks. This significantly improves repair efficiency compared to traditional technologies, effectively repairing even cracks as wide as 0.5 mm.

[0029] 2. The addition of new materials, such as nano-silica-graphene composite powder and nano-cellulose whiskers, effectively improves the concrete's microstructure. The high modulus of graphene and the pozzolanic effect of nano-silica enhance the density and strength of the cement matrix. The nano-cellulose whiskers form a three-dimensional network within the concrete, significantly improving its toughness and crack resistance. Compared to conventional concrete, the concrete of this invention exhibits significantly higher compressive and flexural strength.

[0030] 3. The synergistic effect of multifunctional modified cellulose and polycarboxylic acid high-performance water-reducing agent imparts excellent fluidity and plasticity to the concrete, minimizing initial slump loss over time and facilitating construction and pouring. Furthermore, the design of the temperature- and pH-responsive microcapsule wall ensures precise release of the repair agent upon crack initiation, avoiding adverse effects on concrete performance.

[0031] 4. The technology of the present invention also has good durability and environmental protection. The composite deposition layer of calcium carbonate and strontium carbonate formed by the biomineralization induction system effectively blocks the invasion of harmful ions and improves the concrete's resistance to chemical corrosion and impermeability. The genetically engineered bacteria use urea and other nutrients in the pores of the concrete as a nutrient source, eliminating the need for the addition of complex nutrients and reducing the risk of environmental pollution. By optimizing raw materials and preparation processes, the concrete of the present invention not only achieves high-performance self-repairing, but also takes into account construction convenience and economic benefits, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A self-repairing concrete with biologically induced calcium carbonate deposition and a flow chart of its preparation method;

[0033] Figure 2 is a bar graph of the strength recovery rate after repair of the embodiment and the comparative example;

[0034] Figure 3 is a line graph comparing chloride ion permeability coefficient and 56d carbonization depth of the embodiment and the comparative example;

[0035] Figure 4 It is a bar chart comparing the 28d compressive strength and 28d flexural strength of the embodiment and the comparative example. DETAILED DESCRIPTION

[0036] according to Figures 1 to 4 , the specific implementation of the present invention is as follows: DETAILED DESCRIPTION

[0037] Example 1

[0038] 1. Preparation of Biomineralization Composite Inducer

[0039] The urease gene expression vector was introduced into Bacillus pasteurianus by genetic engineering technology, and the culture medium containing 0.4% yeast extract, 1.2% peptone, and 0.6% sodium chloride was inoculated and cultured at 35°C and 180 rpm for 42 hours. 600 When the expression reached 0.7, 0.08% IPTG was added to induce expression, and the culture was continued until the late logarithmic growth phase to obtain a genetically engineered bacterial solution with a concentration of 3.5×10 8 CFU / mL. A mixed solution containing 1.0 mol / L urea and 0.6 mol / L calcium chloride was prepared, and nano-strontium carbonate seeds (particle size 30 nm) were dispersed therein to form a seed suspension. The bacterial solution, mixed solution, and seed suspension were mixed in a volume ratio of 1:2.5:0.3. A 6% rhamnolipid solution (concentration 0.3 g / L) was added and stirred evenly to obtain a biomineralization composite inducer.

[0040] 2. Synthesis of Nano-Silica-Graphene Composite Powder

[0041] In a chemical vapor deposition furnace, graphene powder was placed in a quartz boat and introduced into a hydrogen-argon mixture (volume ratio of 1:4). The temperature was raised to 850°C. Ethyl orthosilicate vapor was introduced into the furnace using nitrogen as a carrier gas and reacted for 5 hours. After cooling, the product was collected, washed with hydrochloric acid, rinsed with deionized water, and vacuum-dried at 60°C for 12 hours to obtain a composite powder with a silica to graphene mass ratio of 1:4. TEM observations showed that the silica particles (average particle size 20 nm) were uniformly supported on the graphene sheets.

[0042] 3. Preparation of Dual-responsive Alginate Microcapsules

[0043] Calcium carbonate precursor solution (calcium nitrate and urea mixture, concentration of each is 0.8 mol / L), Bacillus spore suspension (concentration of 1×10 9 CFU / mL) and pH-responsive epoxy resin were mixed in a mass ratio of 3:1:0.5 to form the core material. A 3% sodium alginate solution was prepared and mixed with the core material in a volume ratio of 1:1. An oil phase solution containing 2% chitosan and 1% PNIPAM copolymer was added dropwise with stirring at 400 r / min to form a W / O emulsion. The emulsion was then dispersed in an aqueous solution containing 2% Span80 to form a W / O / W emulsion. A 5% calcium chloride solution was added dropwise to solidify for 2 hours. The mixture was filtered, washed with water, and dried at 30°C for 6 hours to produce microcapsules with an average particle size of 300 μm. DSC testing showed a thermosensitive response temperature of 32°C.

[0044] 4. Concrete Preparation

[0045] Weigh by weight: 350 parts Portland cement, 700 parts silane-treated river sand (fineness modulus 2.6), 1050 parts pre-wetted basalt gravel (particle size 10-20 mm), 15 parts composite powder, and 3.5 parts nanocellulose whiskers (diameter 120 nm). Place in a planetary mixer and dry mix for 3.5 minutes at 70 rpm and 140 rpm. Dissolve 5 parts of a 32% solids polycarboxylate water-reducing agent and 8 parts of modified cellulose in 170 parts of water and add to the mixer and wet mix for 5 minutes. Finally, add 25 parts of a biomineralization composite inducer and 20 parts of microcapsules and continue mixing for 7 minutes. The machine spread is 600 mm.

[0046] 5. Maintenance process

[0047] After pouring the concrete, it was cured in an environment of 22°C and RH98% for the first 3 days, and then transferred to an environment of 28°C and RH82% for curing until the 28th day.

[0048] Example 2

[0049] 1. Preparation of Biomineralization Composite Inducer

[0050] The urease gene expression vector was introduced into Bacillus pasteurianus by genetic engineering technology, and the culture medium containing 0.4% yeast extract, 1.2% peptone, and 0.6% sodium chloride was inoculated and cultured at 35°C and 180 rpm for 42 hours. 600 When the expression reached 0.7, 0.08% IPTG was added to induce expression, and the culture was continued until the late logarithmic growth phase to obtain a genetically engineered bacterial solution with a concentration of 3.5×10 8 CFU / mL. A mixed solution containing 1.0 mol / L urea and 0.6 mol / L calcium chloride was prepared, and nano-strontium carbonate seeds (particle size 30 nm) were dispersed therein to form a seed suspension. The bacterial solution, mixed solution, and seed suspension were mixed in a volume ratio of 1:2:0.3, and a 5% rhamnolipid solution (concentration 0.3 g / L) was added. The mixture was stirred evenly to obtain a biomineralization composite inducer.

[0051] 2. Synthesis of Nano-Silica-Graphene Composite Powder

[0052] In a chemical vapor deposition furnace, graphene powder was placed in a quartz boat and introduced into a hydrogen-argon mixture (volume ratio of 1:4). The temperature was raised to 850°C. Ethyl orthosilicate vapor was introduced into the furnace using nitrogen as a carrier gas and reacted for 5 hours. After cooling, the product was collected, washed with hydrochloric acid, rinsed with deionized water, and vacuum-dried at 60°C for 12 hours to obtain a composite powder with a silica to graphene mass ratio of 1:3. TEM observations showed that the silica particles (average particle size 20 nm) were uniformly supported on the graphene sheets.

[0053] 3. Preparation of Dual-responsive Alginate Microcapsules

[0054] Calcium carbonate precursor solution (calcium nitrate and urea mixture, concentration of each is 0.8 mol / L), Bacillus spore suspension (concentration of 1×10 9 CFU / mL) and pH-responsive epoxy resin were mixed in a mass ratio of 3:1:0.5 to form the core material. A 3% sodium alginate solution was prepared and mixed with the core material in a volume ratio of 1:1. An oil phase solution containing 2% chitosan and 1% PNIPAM copolymer was added dropwise with stirring at 400 r / min to form a W / O emulsion. The emulsion was then dispersed in an aqueous solution containing 2% Span80 to form a W / O / W emulsion. A 5% calcium chloride solution was added dropwise to solidify for 2 hours. The mixture was filtered, washed with water, and dried at 30°C for 6 hours to produce microcapsules with an average particle size of 300 μm. DSC testing showed a thermosensitive response temperature of 32°C.

[0055] 4. Concrete Preparation

[0056] Weigh by weight: 350 parts Portland cement, 700 parts silane-treated river sand (fineness modulus 2.6), 1050 parts pre-wetted basalt gravel (particle size 10-20 mm), 15 parts composite powder, and 3.5 parts nanocellulose whiskers (diameter 120 nm). Place in a planetary mixer and dry mix for 3.5 minutes at 70 rpm and 140 rpm. Dissolve 6 parts 35% solids polycarboxylate water-reducing agent and 8 parts modified cellulose in 170 parts water and add to the mixer for 5 minutes. Finally, add 25 parts biomineralization composite inducer and 20 parts microcapsules and continue mixing for 7 minutes. The machine spread is 600 mm.

[0057] 5. Maintenance process

[0058] After pouring the concrete, it was cured in an environment of 20℃ and RH96% for the first 3 days, and then transferred to an environment of 25℃ and RH80% for curing for 28 days.

[0059] Example 3

[0060] 1. Preparation of Biomineralization Composite Inducer

[0061] The urease gene expression vector was introduced into Bacillus pasteurianus by genetic engineering technology, and the culture medium containing 0.4% yeast extract, 1.2% peptone, and 0.6% sodium chloride was inoculated and cultured at 35°C and 180 rpm for 42 hours. 600 When the expression reached 0.7, 0.08% IPTG was added to induce expression, and the culture was continued until the late logarithmic growth phase to obtain a genetically engineered bacterial solution with a concentration of 3.5×10 8CFU / mL. A mixed solution containing 0.8 mol / L urea and 0.5 mol / L calcium chloride was prepared, and nano-strontium carbonate seeds (particle size 30 nm) were dispersed therein to form a seed suspension. The bacterial solution, mixed solution, and seed suspension were mixed in a volume ratio of 1:2.5:0.3. A 6% rhamnolipid solution (concentration 0.3 g / L) was added and stirred evenly to obtain a biomineralization composite inducer.

[0062] 2. Synthesis of Nano-Silica-Graphene Composite Powder

[0063] In a chemical vapor deposition furnace, graphene powder was placed in a quartz boat and introduced into a hydrogen-argon mixture (volume ratio of 1:4). The temperature was raised to 850°C. Ethyl orthosilicate vapor was introduced into the furnace using nitrogen as a carrier gas and reacted for 5 hours. After cooling, the product was collected, washed with hydrochloric acid, rinsed with deionized water, and vacuum-dried at 60°C for 12 hours to obtain a composite powder with a silica to graphene mass ratio of 1:4. TEM observations showed that the silica particles (average particle size 20 nm) were uniformly supported on the graphene sheets.

[0064] 3. Preparation of Dual-responsive Alginate Microcapsules

[0065] Calcium carbonate precursor solution (calcium nitrate and urea mixture, concentration of each is 0.8 mol / L), Bacillus spore suspension (concentration of 1×10 9 CFU / mL) and pH-responsive epoxy resin were mixed in a mass ratio of 3:1:0.5 to form the core material. A 3% sodium alginate solution was prepared and mixed with the core material in a volume ratio of 1:1. An oil phase solution containing 2% chitosan and 1% PNIPAM copolymer was added dropwise with stirring at 400 r / min to form a W / O emulsion. The emulsion was then dispersed in an aqueous solution containing 2% Span80 to form a W / O / W emulsion. A 5% calcium chloride solution was added dropwise to solidify for 2 hours. The mixture was filtered, washed with water, and dried at 30°C for 6 hours to produce microcapsules with an average particle size of 300 μm. DSC testing showed a thermosensitive response temperature of 32°C.

[0066] 4. Concrete Preparation

[0067] Weigh by weight: 350 parts Portland cement, 700 parts silane-treated river sand (fineness modulus 2.6), 1050 parts pre-wetted basalt gravel (particle size 10-20 mm), 15 parts composite powder, and 4.2 parts nanocellulose whiskers (diameter 120 nm). Place in a planetary mixer and dry mix for 3.5 minutes at 60 rpm and 120 rpm. Dissolve 5 parts of a 32% solids polycarboxylate water-reducing agent and 8 parts of modified cellulose in 170 parts of water and add to the mixer and wet mix for 5 minutes. Finally, add 25 parts of a biomineralization composite inducer and 20 parts of microcapsules and continue mixing for 8 minutes. The machine spread is 600 mm.

[0068] 5. Maintenance process

[0069] After pouring the concrete, it was cured in an environment of 22°C and RH98% for the first 3 days, and then transferred to an environment of 28°C and RH82% for curing until the 28th day.

[0070] Comparative Example

[0071] 1. Ordinary concrete preparation

[0072] Weigh by weight: 350 parts Portland cement, 700 parts natural river sand (fineness modulus 2.6), 1050 parts basalt crushed stone (particle size 10-20 mm), 170 parts water, and 3 parts polycarboxylate superplasticizer. Place in a planetary mixer and dry mix at 70 rpm and 140 rpm for 3.5 minutes. Dissolve 3 parts superplasticizer in 170 parts water and add to the mixer for 5 minutes. The spread is 550 mm.

[0073] 2. Maintenance process

[0074] After pouring the concrete, it was cured in an environment of 22°C and RH98% for the first 3 days, and then transferred to an environment of 28°C and RH82% for curing until the 28th day.

[0075] 3. Key Differences

[0076] No self-repairing components (biomineralization inducers, microcapsules, nanocomposites, etc.) are added, and only cement hydration products are relied upon to fill cracks.

[0077] Performance Testing

[0078] The self-repairing concrete of Example 1, Example 2 and Example 3 are significantly better than the ordinary concrete control in all performance indicators. In terms of 28-day compressive strength, the three examples reached 68.5MPa, 65.2MPa and 70.3MPa respectively, which is 42-54% higher than the control example 45.8MPa; the flexural strength index shows that Examples 1-3 are 9.2MPa, 8.7MPa and 9.5MPa, which is 38-51% higher than the control example 6.3MPa. In terms of crack repair performance, Examples 1-3 only need 7 days, 9 days and 6 days to repair 0.3mm cracks, respectively, while the control example cannot repair itself. The compressive strength recovery rate after repair in the three examples exceeded 88%, with the highest reaching 95%, which is much higher than the 55% of the control example. The durability index shows that the chloride ion permeability coefficient of the example is as low as 0.6-1.2×10 -12 m 2 / s, which is 66-83% lower than the control; the carbonization depth after 56 days is only 0.9-1.5mm, which is 82-89% lower than the control 8.3mm.

[0079] Overall, it is shown that self-healing concrete incorporating biomineralization inducers and microcapsules has significant advantages in mechanical properties, self-healing efficiency and durability.

[0080] The mechanical properties and repair efficiency of the embodiment and the comparative example are compared in the following table:

[0081] Table 1

[0082] index Example 1 Example 2 Example 3 Comparative Example 28d compressive strength (MPa) 68.5 65.2 70.3 45.8 28d flexural strength (MPa) 9.2 8.7 9.5 6.3 0.3mm crack repair time (days) 7 9 6 Unrepaired Strength recovery rate after repair (%) 92 88 95 55

[0083] Conclusion: The self-healing concretes of Examples 1-3 significantly outperformed the control examples in terms of mechanical properties and repair efficiency. Example 3 performed best, achieving a compressive strength of 70.3 MPa, a repair time of only 6 days, and a strength recovery rate of 95%, representing improvements of 73% (compressive) and 51% (flexural) over the control examples. The synergistic effect of the biomineralization inducer and microcapsules significantly enhanced the self-healing ability of the concrete.

[0084] The durability index comparison between the embodiment and the comparative example is shown in the following table:

[0085] Table 2

[0086] index Example 1 Example 2 Example 3 Comparative Example <![CDATA[Chloride ion permeability coefficient (×10 -12 m 2 / s)]]> 0.8 1.2 0.6 3.5 56d carbonization depth (mm) 1.2 1.5 0.9 8.3

[0087] Conclusion: The durability of self-healing concrete was significantly improved, with chloride ion permeability reduced by 66-83% (optimal in Example 3) and carbonation depth reduced by 82-89%. The nano-SiO2-graphene composite powder effectively filled pores, while the microbial mineralization products further blocked the penetration of corrosive media, significantly extending the life of the structure.

[0088] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A self-repairing concrete with biologically induced calcium carbonate deposition, characterized in that: The composition comprises the following components by weight: 320-380 parts of Portland cement, 650-750 parts of fine aggregate, 1000-1100 parts of coarse aggregate, 160-180 parts of water, 22-28 parts of biomineralization composite inducer, 12-18 parts of nano-silica-graphene composite powder, 16-24 parts of dual-responsive sodium alginate microcapsules, 8-9 parts of multifunctional modified cellulose, and 4-7 parts of polycarboxylic acid high-performance water reducer; The biomineralization composite inducer is composed of a genetically engineered bacterial solution of Bacillus pasteurianus Sporosarcina pasteurii, a urea-calcium chloride mixed solution, and nano-strontium carbonate seeds in a volume ratio of 1:2.5:0.

3. The nano-silica-graphene composite powder is prepared by chemical vapor deposition, a silane coupling agent is grafted onto the graphene surface, and the nano-silica is uniformly loaded on the graphene sheets, with the mass ratio of the two being 1:3 to 1:

5. The dual-responsive sodium alginate microcapsule wall material is composed of sodium alginate, chitosan, and a thermosensitive PNIPAM copolymer in a mass ratio of 3:2:1, and the core material contains a calcium carbonate precursor solution, a Bacillus spore suspension, and a pH-responsive repair agent in a mass ratio of 3:1:0.

5. The self-repairing concrete also contains nano-cellulose whiskers accounting for 1-1.2% of the weight of the Portland cement, with a diameter of 80-150 nm and a length of 8-15 μm. The main reaction formula for biomineralization induction is: <h2 style=";text-align:left;direction:ltr">Sr<h2 style=";text-align:left;direction:ltr"> 2+ <h2 style=";text-align:left;direction:ltr"> +CO3<h2 style=";text-align:left;direction:ltr"> 2- <h2 style=";text-align:left;direction:ltr"> →SrCO<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> ↓ 2. The self-repairing concrete with biologically induced calcium carbonate deposition according to claim 1, characterized in that: The invention also includes adding a biosurfactant rhamnolipid accounting for 5-8% of the total volume of the biomineralization composite inducer, and the concentration of the rhamnolipid is 0.2-0.5g / L.

3. The self-repairing concrete with biologically induced calcium carbonate deposition according to claim 1, characterized in that: The multifunctional modified cellulose is prepared by carboxymethylation and grafting with polyethylene glycol diacrylate, with a substitution degree of 0.7-0.8 and a grafting rate of 15-20%.

4. The self-repairing concrete with biologically induced calcium carbonate deposition according to claim 1, characterized in that: The fine aggregate is river sand surface-treated with silane coupling agent KH-570, the treatment liquid concentration is 1.5-2.5%, the fineness modulus is 2.5-2.8, and the mud content does not exceed 1.5%; the coarse aggregate is basalt gravel that has been pre-wetted, the particle size is 10-20 mm, and the crushing index is not more than 10%.

5. The self-repairing concrete with biologically induced calcium carbonate deposition according to claim 1, characterized in that: The polycarboxylic acid high-performance water-reducing agent has a solid content of 30-35%, a sulfonic acid group content of 18-22% in the molecular structure, a water reduction rate of not less than 30%, and contains a retarding group. The initial slump loss after 1 hour does not exceed 20 mm.

6. The self-repairing concrete with biologically induced calcium carbonate deposition according to claim 1, characterized in that: The dual-responsive sodium alginate microcapsules are prepared by a two-step emulsification method. The core material and the sodium alginate solution are first emulsified to form a W / O emulsion, which is then dispersed in an aqueous solution containing chitosan and PNIPAM copolymer to form a W / O / W emulsion. Calcium chloride solution is then added dropwise to solidify the microcapsules. The microcapsules have a particle size of 200-400 μm, a thermosensitive response temperature of 25-35°C, and a pH response range of 7-9.

7. A method for preparing self-repairing concrete with bioinduced calcium carbonate deposition according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: Genetically modifying Bacillus pasteurianus to construct a urease gene overexpression vector, which is then transferred into a recipient bacterium and cultured in a medium containing 0.3-0.5% yeast extract, 1-1.5% peptone, and 0.5-0.8% sodium chloride at 35°C and 180 rpm for 36-48 hours to produce a genetically engineered bacterial solution; preparing a urea-calcium chloride mixed solution and a nano-strontium carbonate seed suspension, and mixing them in proportion to form a biomineralization composite inducer; S2: Using chemical vapor deposition, at 800-900°C, in a hydrogen-argon mixed atmosphere with a volume ratio of 1:4, ethyl orthosilicate vapor and graphene powder are reacted for 4-6 hours to produce nano-silica-graphene composite powder; S3: Put Portland cement, fine aggregate, coarse aggregate, nano-silica-graphene composite powder, and nano-cellulose whiskers into a planetary mixer and dry mix for 3-4 minutes; S4: Dissolve the polycarboxylate high-performance water-reducing agent and multifunctional modified cellulose in water, stir evenly, then add to the mixer and wet mix for 4-6 minutes; S5: Add biomineralization composite inducer and dual-responsive sodium alginate microcapsules, continue stirring for 6-8 minutes, control the expansion of the concrete out of the machine to 550-650 mm, and prepare self-repairing concrete.

8. The method for preparing self-repairing concrete with biologically induced calcium carbonate deposition according to claim 7, characterized in that: During the preparation of the genetically engineered bacterial solution, when the culture reaches the late logarithmic growth phase, OD 600 When the pH value is 0.6-0.8, 0.05-0.1% of isopropyl-β-D-thiogalactopyranoside (IPTG) is added to induce expression.

9. The method for preparing self-repairing concrete with biologically induced calcium carbonate deposition according to claim 7, characterized in that: After the self-repairing concrete is poured, it is first cured for 3 days in an environment with a temperature of 20-25° C. and a relative humidity of more than 95%, and then transferred to an environment with a temperature of 25-30° C. and a relative humidity of 80-85% for curing for up to 28 days.

10. The method for preparing self-repairing concrete with biologically induced calcium carbonate deposition according to claim 7, characterized in that: During stirring, the planetary mixer has an orbital speed of 60-80 r / min and a rotational speed of 120-160 r / min, and adopts segmented temperature control during stirring, with the initial stirring temperature being 15-20°C and then increasing to 20-25°C.

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