Self-repairing foam concrete and a method for preparing the same

Abstract

The application provides a self-repairing foam concrete and a preparation method thereof, and belongs to the technical field of concrete. Hydroxyl stone powder is obtained by hydroxyl treatment of stone powder, a graft copolymer is obtained by modification of sodium alginate with a silane coupling agent, and the hydroxyl stone powder, the graft copolymer and nano silicon dioxide are compounded as a composite carrier, and bacillus pasteurii is inoculated on the composite carrier; 300-400 parts of cement, 100-150 parts of the composite carrier inoculated with bacillus pasteurii, 1 part of a composite foaming agent and 10 parts of urea are mixed in a water-binder ratio of 0.35-0.45 to obtain the self-repairing foam concrete. The self-repairing foam concrete is prepared by the innovative microbial carrier design and the composite repair mechanism in a one-step method, and the problem that the microbial inoculation and the self-repairing foaming need to be performed in steps in the composite concrete in the prior art is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of concrete, and particularly relates to a self-repairing foam concrete and a preparation method thereof. BACKGROUND

[0002] As a light-weight and porous building material, the foam concrete has excellent heat insulation performance, low density and good construction performance, and is widely applied to the fields of building walls, roof insulation and filling engineering.

[0003] The self-repairing concrete has become a research hotspot in the field of building materials due to its characteristics of autonomously repairing micro-cracks and prolonging the service life of structures. The self-repairing technology based on microbial-induced carbonate precipitation (MICP) has attracted much attention due to its environmental friendliness and high efficiency.

[0004] In the prior art, the foam concrete and the self-repairing concrete belong to two independent research directions, and are fragmented in function. In the self-repairing concrete, the microbial carrier is only used for repairing, and cannot realize the foaming function. Therefore, the preparation of the composite self-repairing foam concrete needs to be carried out in steps, that is, the foam concrete is prepared first, and then the microbial population is injected into the foam concrete, which is relatively complex in process.

[0005] Therefore, it is necessary to provide a self-repairing foam concrete and a preparation method thereof to solve the above problems. SUMMARY

[0006] The application provides a self-repairing foam concrete and a preparation method thereof. Hydroxyl stone powder, grafted copolymer and nano-silicon dioxide are compounded as a composite carrier, and Bacillus pasteurii is inoculated on the composite carrier. Through innovative microbial carrier design and composite repair mechanism, the self-repairing foam concrete is prepared by one-step method, and the problem that the microbial inoculation and self-repairing foaming need to be carried out in steps in the composite concrete in the prior art is solved, so that at least one technical problem in the background art can be effectively solved.

[0007] To solve the above technical problems, the application is implemented as follows:

[0008] A preparation method of a self-repairing foam concrete, comprising the following steps:

[0009] In step S2, the stone powder is subjected to hydroxylation treatment to obtain hydroxyl stone powder, the silane coupling agent is used to modify sodium alginate to obtain grafted copolymer, and the hydroxyl stone powder, the grafted copolymer and nano-silicon dioxide are compounded as a composite carrier, and Bacillus pasteurii is inoculated on the composite carrier.

[0010] Step S3, according to the mass fraction, 300-400 parts of cement, 100-150 parts of the compound carrier inoculated with Bacillus pasteurii, 1 part of the compound foaming agent and 10 parts of urea are mixed at a water-binder ratio of 0.35-0.45 to obtain the self-repairing foam concrete, wherein the compound foaming agent is prepared by mixing the compound high-molecular cement foaming agent SDS and L-cysteine hydrochloride at a mass ratio of 5:1, and the compound high-molecular cement foaming agent SDS comprises sodium fatty alcohol polyoxyethylene ether sulfate, ninal and water.

[0011] As a preferred improvement, the preparation process of the hydroxyl stone powder comprises the following steps:

[0012] Step S211, the stone powder is treated with ultrasonic in 0.1 mol / L hydrochloric acid for 15 minutes, and then washed with deionized water until neutral;

[0013] Step S212, the stone powder activated by hydrochloric acid in step S211 is immersed in an ethanol suspension containing 5 wt% nano-hydroxyapatite and 1 wt% KH-550, and ultrasonic treatment is performed to uniformly disperse the nanoparticles; then, reaction is carried out at 60°C for 90 min, and finally, drying is carried out at 60°C until the weight is constant, to obtain the hydroxyl stone powder.

[0014] As a preferred improvement, the stone powder is argillaceous siltstone powder, and the mass content of quartz is 60-70%, and the balance is calcite and dolomite.

[0015] As a preferred improvement, the preparation process of the graft copolymer comprises the following steps:

[0016] KH-550 is dissolved in a pH=5, 5wt% acetic acid-sodium acetate buffer solution, and pre-hydrolysis is carried out at 60°C for 30 min; sodium alginate is dissolved in a pH=5, 3wt% acetic acid-sodium acetate buffer solution, and pre-heating is carried out at 60°C to reduce viscosity; the hydrolyzed KH-550 solution is added to the sodium alginate solution at a mass ratio of 1:3, and stirring reaction is carried out at 60°C for 2 h, to finally form the graft copolymer.

[0017] As a preferred improvement, the inoculation process of Bacillus pasteurii specifically comprises the following steps:

[0018] 10 8 The Bacillus pasteurii bacterial solution with a CFU / mL of 10 is mixed with the graft copolymer solution at a volume ratio of 1:1, and nano-silicon dioxide is added to form a mixed solution; then, the mixed solution is immersed in the hydroxyl stone powder at a vacuum degree of -0.095 MPa for 30 min; then, 2wt% sterile CaCl2 solution is sprayed, and standing is carried out for 20 min, to complete the microencapsulation and fixation of Bacillus pasteurii, wherein the doping amount of nano-silicon dioxide is 1-3% of the mass of the hydroxyl stone powder, and the amount of CaCl2 solution is 5% of the mass of the stone powder.

[0019] As a preferred improvement, step S3 specifically comprises the following process:

[0020] According to the mass fraction, 300-400 parts of 350 kg / m 3 of ordinary Portland cement is mixed with 100-150 parts of 120 kg / m 3 of Bacillus pasteurii inoculated composite carrier by double shaft forced mixer for 3 minutes of dry material; according to the water-binder ratio of 0.35-0.45, the water solution containing 0.1wt% retarder is added, and the slurry is continuously stirred for 3 minutes until it is uniform, 1 part of composite foaming agent and 10 parts of urea are added, foaming is carried out according to the dilution ratio of 1:30, the foaming machine pressure is 0.6 MPa, and the foaming machine is injected into the concrete initial mixing material at a speed of 50 L / m 3 , and the planetary stirring is adopted, the mixing time is controlled within 1 minute, the layer pouring and plug-in vibration are adopted, and the polyethylene film is covered on the surface to prevent evaporation of moisture, so as to obtain the self-repairing foam concrete.

[0021] As a preferred improvement, the obtained self-repairing foam concrete is cured according to the following conditions:

[0022] Stage I: 0-24h, temperature 20±1℃, relative humidity RH≥95%;

[0023] Stage II: 24-72h, temperature 25±2℃, relative humidity RH≥90%;

[0024] Stage III: after 72h, natural curing, control the temperature below 40℃.

[0025] As a preferred improvement, step S2 further comprises the following steps:

[0026] Step S1, preparing liquid medium, and cultivating Bacillus pasteurii on the liquid medium.

[0027] As a preferred improvement, the preparation process of the liquid medium comprises the following steps:

[0028] Step S111, adding proteose peptone, sodium chloride and soybean peptone to ultrapure water to obtain a mixed solution, and the concentration of each component in the mixed solution is: proteose peptone 0.015 g / mL, sodium chloride 0.005 g / mL, and soybean peptone 0.005 g / mL;

[0029] Step S112, using a rubber dropper to add 0.1 mol / L sodium hydroxide solution drop by drop to the mixed solution, and adjusting the pH value of the mixed solution to 7.3;

[0030] Step S113, the mixed solution is placed in a high-temperature and high-pressure sterilization pot, the temperature of the high-temperature and high-pressure sterilization pot is adjusted to 121 DEG C, the pressure is 0.105 MPa, and sterilization is continued for 30 minutes, so that the mixed solution is in a sterile state, and then the mixed solution is cooled to 45 DEG C;

[0031] Step S114, a syringe provided with a microporous filter head is used to inject a 20% mass fraction urea solution into the mixed solution in a sterilized manner, so as to obtain a liquid culture medium;

[0032] The cultivation process of the bacillus pasteurii includes the following steps:

[0033] Step S121, a loop and a slant culture medium inoculated with the bacillus pasteurii are provided;

[0034] Step S122, the loop is sterilized by using an alcohol lamp in a sterile operation table, then the surface of the slant culture medium is scraped by using the loop, the loop is inserted into the liquid culture medium and stirred uniformly, and the loop is sterilized again by using the alcohol lamp after inoculation, so as to avoid bacterial contamination of the operation table;

[0035] Step S123, the inoculated solid culture medium is placed in a constant-temperature biochemical incubator at 30 DEG C for cultivation, until clear colonies are formed in the solid culture medium, and then the solid culture medium is stored in a refrigerator at 4 DEG C for standby use.

[0036] A self-repairing foam concrete is prepared by using the preparation method of the self-repairing foam concrete.

[0037] The self-repairing foam concrete has the following beneficial effects:

[0038] (1) The bacillus pasteurii is inoculated on the composite carrier by using the hydroxyl stone powder, the graft copolymer and the nano silicon dioxide as the composite carrier, the self-repairing foam concrete is prepared by using the innovative microbial carrier design and the composite repair mechanism in one step, and the problem that the microbial inoculation and the self-repairing foaming need to be performed in steps in the prior art is solved;

[0039] (2) The microbial activity and the long-term survival rate are significantly improved, the 28-day survival rate of the microbial population in the high-alkali environment (pH>12) of the concrete is increased from <30% of the traditional carrier to >=70%, the Si-O-Ca covalent bond on the surface of the composite carrier provides stable anchoring and avoids the loss of the microbial population, and the hydrophobic modification reduces the erosion of the alkaline pore solution, so that the long-term repair capability is ensured;

[0040] (3) High-efficiency self-repairing capability: the cracks with a size of <=0.25 mm can be finally repaired, and the repair effect is shown in Figure 4 The cracks with a size of <=0.2 mm can be repaired in the prior art, and larger cracks can be repaired;

[0041] (4) Improved mechanical properties and durability: The 28-day compressive strength reaches 2.00 MPa, while that of ordinary foamed concrete is 1.52 MPa, and the fracture toughness is increased by 40%;

[0042] (5) Industrialization and environmental protection advantages: Cost reduction: Stone powder carrier is 40% cheaper than synthetic microbial carrier (such as sodium alginate-fly ash microspheres); low-carbon room temperature curing saves energy (compared to high-temperature steam-cured foamed concrete); and it has microbial carbon fixation function with a carbon fixation capacity of 3-5 kg ​​CO2 / m³. 3 ;

[0043] (6) Convenient construction: It is compatible with existing concrete production lines, with a slump of 160±20mm, and pumping is unblocked, making construction convenient. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0045] Figure 1 This shows a microscopic image of the M5 group of samples in Example 1;

[0046] Figure 2 This shows a microscopic image of the M6 ​​group of samples in Example 1;

[0047] Figure 3 This shows a microscopic image of the M7 group of samples in Example 1;

[0048] Figure 4 The diagram shows the repair effect of the self-healing foamed concrete provided by this invention on a 0.25mm crack;

[0049] Figure 5 The image shows the repair effect of the self-healing foamed concrete provided by this invention on a 0.48mm crack. Detailed Implementation

[0050] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] This embodiment provides a method for preparing self-healing foamed concrete, including the following steps:

[0052] Step S1: Prepare a liquid culture medium and culture Pasteurella multocida on the liquid culture medium.

[0053] The preparation process of liquid culture medium includes the following steps:

[0054] Step S111: Add peptone, sodium chloride and soybean peptone to ultrapure water to obtain a mixture. The concentrations of each component in the mixture are: peptone 0.015 g / mL, sodium chloride 0.005 g / mL and soybean peptone 0.005 g / mL.

[0055] Step S112: Add 0.1 mol / L sodium hydroxide solution dropwise to the mixture using a dropper to adjust the pH of the mixture to 7.3;

[0056] Step S113: Place the mixture into a high-temperature and high-pressure sterilizer, adjust the temperature of the high-temperature and high-pressure sterilizer to 121°C and the pressure to 0.105 MPa, and continue sterilization for 30 minutes to ensure that the mixture is in a sterile state. Then cool the mixture to 45°C.

[0057] In step S114, a 20% urea solution is injected into the mixture using a syringe equipped with a microporous filter head for filtration sterilization to obtain a liquid culture medium.

[0058] The cultivation process of Bacillus pasteurellis includes the following steps:

[0059] Step S121: Provide an inoculation loop and a slant culture medium inoculated with Bacillus pasteurellii;

[0060] Step S122: First, disinfect the inoculation loop with an alcohol lamp in a sterile operating table. Then, gently scrape the surface of the slant culture medium with the inoculation loop, insert the inoculation loop into the liquid culture medium and stir evenly. After completing the inoculation, disinfect the inoculation loop again with an alcohol lamp to avoid bacterial contamination of the operating table.

[0061] Step S123: Place the inoculated solid culture medium in a constant temperature biochemical incubator at 30°C and incubate until clear colonies are visible in the solid culture medium. Then, store the solid culture medium in a refrigerator at 4°C for later use.

[0062] Step S2: Hydroxyl stone powder is obtained by hydroxylation treatment of stone powder, and sodium alginate is modified with silane coupling agent to obtain graft copolymer. Hydroxyl stone powder, graft copolymer and nano silica are used as composite carrier and Bacillus pasteurellis is inoculated onto the composite carrier.

[0063] The preparation process of hydroxyl powder includes the following steps:

[0064] Step S211: Place the stone powder in 0.1 mol / L hydrochloric acid and sonicate it (power 300W, frequency 40kHz) for 15 minutes, then wash it with deionized water until neutral.

[0065] In this embodiment, the stone powder is taken from a section of the Lingdao Expressway project in Shuangpai County, Yongzhou City. The main components are quartz and calcareous and magnesium carbonate minerals, of which the mass content of quartz is 60-70%, and the remainder is calcite and dolomite.

[0066] The acid pickling process can remove organic contaminants, grease, dust, and other substances that may be present on the surface of the stone powder. It can also slightly etch the surface of the stone powder, increasing its roughness and specific surface area, exposing more active sites, thereby improving the adhesion of subsequent nanoparticles. The surface of the stone powder activated by hydrochloric acid forms two types of active sites: quartz components expose ≡Si-OH (silanol groups), and carbonate components decompose cleavage surfaces to produce ≡Ca-OH / ≡Mg-OH.

[0067] Step S212: Immerse the stone powder activated with hydrochloric acid in step S211 into a solution containing 5 wt% nano-hydroxyapatite (Ca). 10 The nanoparticles were uniformly dispersed by ultrasonic treatment (40 kHz, 30 min) in an ethanol suspension containing (PO4)6(OH)2 (particle size 20-50 nm) and 1 wt% KH-550; then reacted at 60 °C for 90 min; and finally dried at 60 °C to constant weight to obtain hydroxyl stone powder.

[0068] The composite system of stone powder, nano-hydroxyapatite (nHA-OH), and KH-550 mainly undergoes the following reactions:

[0069] (1) Phosphate-carbonate bond

[0070] Phosphate groups (-PO4) on the surface of nano-hydroxyapatite 3- ) and Ca on the surface of carbonates in stone powder 2+ / Mg 2+ Formation of coordinate bonds:

[0071] ≡Ca-CO3+PO4 3- →≡Ca-O-PO4 2- +CO3 2- ;

[0072] (2) Calcium ion bridging

[0073] The silanol groups on the surface of quartz in stone powder and the Ca groups on the surface of carbonate in stone powder 2+ Formation of coordinate bonds:

[0074] ≡Si-OH+Ca 2+ →≡Si-O-Ca - ;

[0075] (3) Bridging of KH-550 after hydrolysis

[0076] After hydrolysis, KH-550 can react simultaneously with stone powder and nano-hydroxyapatite, forming a bridging structure through coordination:

[0077] nHA-OH+HO-Si-(CH2)3NH2→nHA-O-Si-(CH2)3NH2;

[0078] ≡Si-OH+HO-Si-(CH2)3NH2→≡Si-O-Si-(CH2)3NH2+H2O.

[0079] Through the above reaction, under the coupling effect of KH550, nano-hydroxyapatite is firmly coated on the surface of stone powder particles, forming a "core-shell" structured composite powder with stone powder as the core and n-HA as the shell, which is hydroxyapatite powder. This composite powder retains the low-cost characteristics of stone powder while also possessing the bioactivity and surface properties of n-HA.

[0080] The preparation process of graft copolymers includes the following steps:

[0081] KH-550 was dissolved in an acetate-sodium acetate buffer solution (pH=5, concentration 5wt%) and pre-hydrolyzed at 60℃ for 30 min; sodium alginate was dissolved in an acetate-sodium acetate buffer solution (pH=5, concentration 3wt%) and preheated at 60℃ to reduce viscosity; the hydrolyzed KH-550 solution was added dropwise to the sodium alginate solution at a mass ratio of 1:3, and the mixture was stirred at 60℃ for 2 h to finally form a graft copolymer.

[0082] The hydrolysis product of KH-550 (γ-aminopropyltriethoxysilane) is mainly γ-aminopropyltrisilol, which includes silanol and amino groups. When added to sodium alginate solution, the amino group reacts with the carboxyl group of sodium alginate to form a graft copolymer.

[0083] To confirm the successful grafting of the silane coupling agent KH-550 onto the sodium alginate molecular chain, the solubility and gelation behavior of the synthesized product were compared and verified. Solubility test: Small amounts of pure sodium alginate (SA) and the graft copolymer sample prepared in this invention were added separately to deionized water. Pure sodium alginate dissolved rapidly, forming a homogeneous viscous solution; while the graft copolymer only swelled in water, forming water-insoluble white gel particles. This phenomenon indicates that the grafting of KH-550 introduced hydrophobic organic long chains and cross-linked structures, significantly altering the hydrophilicity of sodium alginate, proving the occurrence of the grafting reaction and the formation of a novel graft copolymer.

[0084] In the composite carrier, the gaps between hydroxyl powder particles are 10-50 μm, which can serve as a carrier for Bacillus pasteurellii. Bacillus pasteurellii can be distributed within the pores of the hydroxyl powder, providing physical protection for the Bacillus pasteurellii and thus improving the survival rate of the bacterial community. On the other hand, hydroxyl powder can also serve as a foaming stabilizer. Its surface hydroxyl groups form a hydrogen bond network with the polar groups of the foaming agent, which can effectively reduce the drainage rate of the bubble film and extend the foam half-life to more than 120 min. At the same time, the powder particles adsorb at the gas-liquid interface to form a physical barrier, preventing bubble coalescence.

[0085] Graft copolymers, used as gelling materials, are employed to encapsulate Bacillus pasteurellii, isolating the bacteria from the highly alkaline environment inside concrete and improving bacterial survival rates. Simultaneously, the graft copolymers effectively resist highly alkaline rings, extending the gelling material's lifespan and preventing premature release of the bacteria.

[0086] The addition of nano-silica is used to hydrophobically modify the composite carrier. The silanol groups on its surface undergo a condensation reaction with the silanol groups of the KH-550 hydrolysis products to form Si-O-Si bonds, constructing a micro-nano hierarchical rough structure. This, combined with the long-chain alkyl groups of the graft copolymer, generates a synergistic hydrophobic effect, reducing the foam breakage rate and optimizing the foam structure. The condensation reaction process is represented as: Si-OH + HO-Si → Si-O-Si + H2O.

[0087] The inoculation process of Bacillus pasteurellis includes the following steps:

[0088] 10 8 CFU / mL of Bacillus pasteurellium bacterial suspension and graft copolymer solution were mixed at a 1:1 volume ratio, and nano-silica was added to form a mixture. Then, the mixture was impregnated with hydroxyl powder under a vacuum of -0.095 MPa for 30 min. Subsequently, 2 wt% sterile CaCl2 solution was sprayed on and allowed to stand for 20 min to complete the microencapsulation and fixation of Bacillus pasteurellium. The amount of nano-silica was 1-3% of the mass of hydroxyl powder, and the amount of CaCl2 solution was 5% of the mass of hydroxyl powder.

[0089] Step S3: Mix 300-400 parts cement, 100-150 parts composite carrier inoculated with Bacillus pasteurellii, 1 part composite foaming agent, and 10 parts urea at a water-cement ratio of 0.35-0.45 according to the mass proportions to obtain self-healing foamed concrete.

[0090] Step S3 specifically includes the following process:

[0091] Mix 300-400 parts of 350kg / m³ ordinary Portland cement with 100-150 parts of 120kg / m³ ordinary Portland cement. 3The composite carrier inoculated with Bacillus pasteurellis was mixed and stirred for 3 minutes using a biaxial forced mixer (45 rpm) to obtain dry material. An aqueous solution containing 0.1 wt% retarder was added at a water-to-cement ratio of 0.35-0.45, along with 1 part composite foaming agent and 10 parts urea. Foaming was carried out at a dilution ratio of 1:30, a foaming machine pressure of 0.6 MPa, and a flow rate of 50 L / m³. 3 The agent is injected evenly into the initial concrete mix at a uniform rate, and planetary mixing (30 rpm revolution + 60 rpm rotation) is used, with the mixing time controlled within 1 minute. Layered pouring and immersion vibration are employed, and a polyethylene film is applied to the surface to prevent moisture evaporation, resulting in self-healing foamed concrete.

[0092] Sodium alginate was covalently grafted onto the surface of stone powder using the silane coupling agent KH-550, forming a dual chemical bonding network of Si-O-Ca bonds (binding energy >200kJ / mol) and amide bonds (-CO-NH-). This network endows concrete with multiple performance advantages: the rigid Si-O-Ca bonds significantly improve the interfacial strength of the stone powder-cement matrix, while the flexible amide bond network not only protects bacteria through pH-responsive characteristics (28-day survival rate >85%), but also intelligently releases repair bacteria at cracks (final repair rate ≥90% for 0.45mm cracks, see...). Figure 5 Simultaneously, this rigid-flexible interfacial structure endows the material with both excellent resistance to chloride ion corrosion and moisture regulation capabilities, achieving a synergistic improvement in self-healing function and durability. The addition of urea provides a continuous carbon and nitrogen source for bacteria and adjusts the pH of the pore fluid.

[0093] The composite foaming agent is prepared by mixing composite polymer cement foaming agent SDS and L-cysteine ​​hydrochloride at a mass ratio of 5:1. The composite polymer cement foaming agent SDS is selected from HF-60 type composite polymer cement foaming agent SDS produced by Yantai Lulin Heavy Industry Co., Ltd., and includes sodium fatty alcohol polyoxyethylene ether sulfate, Niñar, and water. In the composite foaming agent, the composite polymer cement foaming agent SDS mainly plays a foaming role, while L-cysteine ​​hydrochloride, in addition to providing foam stabilization, releases thiol groups (-SH) that react with the exposed CaO on the cleavage surfaces of carbonate minerals in the stone powder. 2+ / Mg 2+ Forming a coordination structure is key to achieving the synergistic effect of dual-mode foaming.

[0094] This invention utilizes the synergistic effect of a composite foaming agent and Bacillus pasteurization to construct a unique dual-mode foaming system on the surface of quartz-carbonate composite stone powder (quartz content 60-70%, calcite / dolomite 30-40%). During the chemical foaming process, the -SH groups released from L-cysteine ​​hydrochloride in the composite foaming agent preferentially react with the Ca2+ exposed on the cleavage surfaces of carbonate minerals in the stone powder. 2+ / Mg 2+A [MS-Ca / Mg] coordination structure is formed, and stable macrobubbles of 100-300 μm are generated on the quartz surface through Si-OS bonding. When *Bacillus pasteurellii* (urease activity ≥15 U / mg) metabolizes urea, its secreted β-1,3-glucan reacts with the Ca provided by the dissolution of carbonate minerals. 2+ / Mg 2+ (ICP-MS determination of [Ca)) 2+ Organic-inorganic composite microbubbles (10-50 μm) are formed by adding 150 mg / L of calcite (104) crystals to form oriented bonds with the carboxyl groups of EPS. This interface modification based on the differentiation of mineral components increases the compressive strength of the material, and the preferential dissolution-reprecipitation characteristics of the carbonate region enable 90% self-repair of 0.48 mm cracks.

[0095] The prepared self-healing foamed concrete was cured under the following conditions:

[0096] Phase I (0-24h): Temperature 20±1℃, relative humidity RH≥95%;

[0097] Phase II (24-72h): Temperature 25±2℃, relative humidity RH≥90%;

[0098] Phase III (after 72 hours): Natural curing, with the temperature controlled below 40℃.

[0099] A comparative experiment was set up to compare the performance of the self-healing foamed concrete prepared in this application with that of ordinary foamed concrete. The comparative experiment included:

[0100] (1) Compressive strength test: Compared with ordinary foamed concrete, the compressive strength of the self-healing foamed concrete provided in this application is increased by 47%;

[0101] (2) Flexural strength test: Compared with ordinary foamed concrete, the flexural strength of the self-healing foamed concrete provided in this application is increased by 28%;

[0102] (3) Crack repair test: A precast crack with a width of 0.25 mm was cured at 20℃ / 95%RH (moisture-triggered) and 5%CO2 (pH-triggered) conditions. The self-healing foamed concrete provided in this application successfully repaired the crack. The repair results are as follows: Figure 4 As shown;

[0103] (4) Bacterial survival test: The distribution and survival status of the bacterial community inside the vector were observed using a SYTO9 / PI confocal microscope. The survival rate was as high as 72% compared to the initial value.

[0104] This embodiment also provides a self-healing foamed concrete, which is prepared using the above-described method for preparing self-healing foamed concrete.

[0105] Example 1

[0106] This embodiment sets up a cross-conversion experiment, using *Bacillus pasteurellii* and silane coupling agent KH-550 mixed with stone powder to prepare carriers, and then verifying the effect of different carrier components on the performance of self-healing foamed concrete. The experiment was conducted according to the preparation method described in this invention. Ten groups of samples were designed for the cross-conversion experiment, the only difference between the groups being whether *Bacillus pasteurellii* was added and the different carriers used to load *Bacillus pasteurellii*. The total parts of cement and stone powder were fixed at 300 parts to clarify the absolute proportions of each component. In addition, the amount of composite foaming agent added was fixed at 1 part, the amount of urea added was fixed at 10 parts, and the water-cement ratio was fixed at 0.35. The specific proportions of each sample are shown in Table 1.

[0107] Table 1 Cross-experimental data

[0108]

[0109] The 10 groups of samples were cured under the same conditions, and their performance was tested. The performance indicators included slump, compressive strength, splitting tensile strength, and closure rate.

[0110] (1) Slump

[0111] Slump is an important indicator of concrete workability, specifically including water retention, fluidity, and cohesiveness. A good slump ensures that concrete is easy to handle and uniformly compacted during construction, thus guaranteeing construction quality. The slump data for each sample group are shown in Table 2.

[0112] Table 2 Slump Data Table

[0113]

[0114] As can be seen from Table 2, all samples exhibited ideal slump, controlled within the range of 100-180 mm, which meets the pumping requirements of JG / T 266-2011.

[0115] M1 had the highest slump (187 mm), and the slump decreased with increasing stone powder content (M10 group dropped to 158 mm), which is related to the high specific surface area of ​​stone powder adsorbing free water. The hydrophobic modification of silane coupling agent KH-550 reduced the slump loss of M4 / M7 / M10 groups by 5-15 mm compared with the corresponding unmodified groups (M3 / M6 / M9), proving that it can improve particle lubricity.

[0116] (2) Compressive strength

[0117] The compressive strength of each group of samples after 28 days of curing is shown in Table 3:

[0118]

[0119] As shown in Table 3, group M7 (15% stone powder + bacteria + silane) reached 2.00 MPa, a 33% increase compared to M1. This strength increase mainly stemmed from the silane-stone powder bonding network, with microbial mineralization products filling microcracks. In contrast, groups with 30% stone powder (M8-M10) showed a significant decrease in strength, with the 30% stone powder content causing a 40-53% strength reduction, confirming the dominant dilution effect of the stone powder.

[0120] (3) Splitting tensile strength

[0121] The splitting tensile strength of each group of samples after 28 days of curing is shown in Table 4:

[0122] Table 4 Splitting Tensile Strength

[0123]

[0124] As shown in Table 4, the strength of M1 is 0.25±0.03MPa, and the fracture surface exhibits typical brittle fracture characteristics; the silane coupling agent modified group (M4 / M7 / M10) shows improved toughness: the strength of the M7 group reaches 0.35MPa (40% higher than that of M1); it is speculated that its microbial mineralization products form a CaCO3-Si composite phase at the crack, which delays crack propagation.

[0125] Meanwhile, the amount of stone powder also has a significant impact. 5-15% stone powder can improve its tensile strength, thereby improving the interfacial bonding. However, after exceeding 15%, the strength decreases due to the agglomeration effect (M10 is 37% lower than M7).

[0126] (4) Closure rate

[0127] A standard cubic specimen (100×100×100mm) aged 28 days was placed in a three-point bending apparatus and loaded at a rate of 0.1mm / min until a 0.25mm wide through crack was generated (crack width was determined by a crack microscope); the initial crack morphology was recorded immediately. On day 28 of the repair process, the crack width was monitored, and the closure rate was (1 - current crack width / initial crack width) × 100%, as recorded below.

[0128] Table 5 Closure Rate Data Table

[0129]

[0130] The microscopic images of groups M5, M6, and M7 are as follows: Figures 1-3 As shown, from Figure 1It can be seen that in group M5, macrobubbles generated by chemical foaming are the main component. Chemical foaming has high pore connectivity, but the bonding between stone powder and cement matrix is ​​poor, resulting in a weak interface. In group M6, the metabolites of Bacillus pasteurellii optimize the pore structure and improve some interfacial bonding, but do not completely solve the problem of pore connectivity. In group M7, silane coupling agent enhances the bonding between stone powder and cement interface, reduces unreacted particles, increases matrix density, and the overall structure is relatively dense.

[0131] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. A method for producing a self-repairing foamed concrete, characterized by, It comprises the following steps: Step S2, take the stone powder to carry out hydroxylation treatment to obtain hydroxyl stone powder, take silane coupling agent to modify sodium alginate to obtain graft copolymer, take hydroxyl stone powder, graft copolymer and nanometer silicon dioxide as a composite carrier, and inoculate bacillus pasteurii on the composite carrier; Step S3, according to the mass fraction, 300-400 parts of cement, 100-150 parts of the composite carrier inoculated with bacillus pasteurii, 1 part of the composite foaming agent and 10 parts of urea are mixed to obtain self-repairing foam concrete, wherein the water-binder ratio is 0.35-0.45, the composite foaming agent is prepared by mixing composite high molecular cement foaming agent SDS and L-cysteine hydrochloride according to a mass ratio of 5:1, and the composite high molecular cement foaming agent SDS comprises sodium fatty alcohol polyoxyethylene ether sulfate, ninal and water; The inoculation process of bacillus pasteurii specifically comprises the following steps: 10 8 The Bacillus pasteurii bacterial solution with CFU / mL is mixed with the graft copolymer solution at a volume ratio of 1:1, and nano-silicon dioxide is added to form a mixed solution. Then, the mixed solution is immersed in hydroxyl stone powder under a vacuum degree of -0.095 MPa for 30 min. Subsequently, a 2 wt% sterile CaCl2 solution is sprayed, and the mixture is left to stand for 20 min, thereby completing the microencapsulation and fixation of the Bacillus pasteurii. The doping amount of nano-silicon dioxide is 1-3% of the mass of the hydroxyl stone powder, and the amount of the CaCl2 solution is 5% of the mass of the hydroxyl stone powder.

2. The method of claim 1, wherein the self-healing foam concrete is prepared by mixing the cement, the fly ash, the silica fume, the water, the superplasticizer, and the polymer solution. The preparation process of the hydroxyl stone powder comprises the following steps: Step S211, the stone powder is treated with ultrasonic in 0.1 mol / L hydrochloric acid for 15 minutes, and then washed with deionized water until neutral; Step S212, the stone powder activated by hydrochloric acid in step S211 is immersed in an ethanol suspension containing 5wt% nanometer hydroxyapatite and 1wt% KH-550, and ultrasonic treatment is performed to uniformly disperse the nanoparticles; Then, reaction is carried out at 60℃ for 90min, and finally, drying is carried out at 60℃ until the weight is constant, to obtain the hydroxyl stone powder.

3. The method of claim 1, wherein the self-healing foam concrete is prepared by mixing the cement, the fly ash, the silica fume, the water, the superplasticizer, and the polymer. The stone powder is argillaceous siltstone powder, and the mass content of quartz is 60-70%, and the balance is calcite and dolomite.

4. The method of claim 1, wherein the self-healing foam concrete is prepared by mixing the cement, the fly ash, the silica fume, the water, the superplasticizer, and the foaming agent. The preparation process of the graft copolymer comprises the following steps: KH-550 is dissolved in a pH=5, 5wt% acetic acid-sodium acetate buffer solution, pre-hydrolyzed at 60℃ for 30min; sodium alginate is dissolved in a pH=5, 3wt% acetic acid-sodium acetate buffer solution, pre-heated to reduce viscosity at 60℃; the hydrolyzed KH-550 solution is added to the sodium alginate solution according to a mass ratio of 1:3, and stirred to react at 60℃ for 2h, to finally form the graft copolymer.

5. The method of claim 1, wherein the self-healing foam concrete is prepared by mixing the cement, the fly ash, the silica fume, the water, the superplasticizer, and the foaming agent. Step S3 specifically comprises the following process: According to the quality parts, 300-400 parts of 350 kg / m 3 ordinary Portland cement and 100-150 parts of 120 kg / m 3 complex carrier inoculated with Bacillus pasteurii are mixed and stirred for 3 min with a double-shaft forced mixer; a water solution containing 0.1 wt% retarder is added at a water-binder ratio of 0.35-0.45, and stirring is continued for 3 min until the slurry is uniform; 1 part of a complex foaming agent and 10 parts of urea are added, foaming is performed at a dilution ratio of 1:30 and a foaming machine pressure of 0.6 MPa, and the foaming agent is injected into the concrete initial mixing material at a rate of 50 L / m 3 , planetary stirring is adopted, the mixing time is controlled within 1 min, layer pouring is adopted, a plug-in type vibrator is used, and a polyethylene film is used to cover the surface to prevent evaporation of moisture, to obtain self-repairing foam concrete.

6. The method of claim 1, wherein the self-healing foam concrete is prepared by mixing the cement, the fly ash, the silica fume, the water, the superplasticizer, the foaming agent, and the water-reducing agent. The obtained self-repairing foam concrete is cured according to the following conditions: Stage I: 0-24h, temperature 20±1℃, relative humidity RH≥95%; Stage II: 24-72h, temperature 25±2℃, relative humidity RH≥90%; Stage III: after 72h, natural curing, control the temperature below 40℃.

7. The method of claim 1, wherein the self-healing foam concrete is prepared by mixing the cement, the fly ash, the silica fume, the water, the superplasticizer, the foaming agent, and the water-reducing agent. Before step S2, the following steps are further included: Step S1, preparing a liquid culture medium, and cultivating bacillus pasteurii on the liquid culture medium.

8. The method of claim 7, wherein the self-healing foam concrete is prepared by mixing the cement, the fly ash, the silica fume, the water, the superplasticizer, the foaming agent, and the water-reducing agent. The preparation process of the liquid culture medium comprises the following steps: Step S111, adding proteose peptone, sodium chloride and soybean peptone to ultrapure water to obtain a mixed solution, and the concentrations of the components in the mixed solution are: proteose peptone 0.015 g / mL, sodium chloride 0.005 g / mL, and soybean peptone 0.005 g / mL; Step S112, using a rubber dropper to add 0.1 mol / L sodium hydroxide solution drop by drop to the mixed solution, and adjusting the pH value of the mixed solution to 7.3; Step S113, the mixed solution is put into the high-temperature and high-pressure sterilization pot, the temperature of the high-temperature and high-pressure sterilization pot is adjusted to 121℃, the pressure is 0.105 MPa, and the sterilization is continuously performed for 30 minutes, so that the mixed solution is in a sterile state, and then the mixed solution is cooled to 45℃; Step S114, a syringe provided with a microporous filter head is used to inject the 20% mass fraction urea solution into the mixed solution in a sterile filtration manner, so as to obtain the liquid culture medium; The cultivation process of the bacillus pasteurii includes the following steps: Step S121, a loop and a slant culture medium inoculated with the bacillus pasteurii are provided; Step S122, in the sterile operation table, the loop is first sterilized by using an alcohol lamp, then the surface of the slant culture medium is scraped by using the loop, the loop is inserted into the liquid culture medium and stirred uniformly, after the inoculation is completed, the loop is sterilized by using the alcohol lamp again, so as to avoid the bacterial contamination of the operation table; Step S123, the inoculated solid culture medium is placed in a constant-temperature biochemical incubator at 30℃ for cultivation, until clear colonies are formed in the solid culture medium, and then the solid culture medium is stored in a refrigerator at 4℃ for standby.

9. A self-healing foam concrete, characterized by The self-repairing foam concrete is prepared by using the preparation method of any one of claims 1-8. The self-repairing foam concrete is prepared by using the preparation method of any one of claims 1-8.

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