Self-repairing foam concrete and preparation method thereof

Abstract

The invention provides self-repairing foam concrete and a preparation method thereof, and belongs to the technical field of concrete. The preparation method comprises the following steps: carrying out hydroxylation treatment on stone powder to obtain hydroxyl stone powder, modifying sodium alginate by using a silane coupling agent to obtain a grafted copolymer, compounding the hydroxyl stone powder, the grafted copolymer and nano silicon dioxide to obtain a composite carrier, and inoculating bacillus pasteurii onto the composite carrier; 300-400 parts by mass of cement, 100-150 parts by mass of the composite carrier inoculated with the bacillus pasteurii, 1 part by mass of a composite foaming agent and 10 parts by mass of urea are mixed according to the water-binder ratio of 0.35-0.45, and the self-repairing foam concrete is obtained. The self-repairing foam concrete is prepared by a one-step method through an innovative microbial carrier design and a composite repairing mechanism, and the problem that microbial inoculation and self-repairing foaming in composite concrete in the prior art need to be carried out step by step 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 lightweight 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. The process is relatively complex.

[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. Bacillus pasteurii is inoculated on the composite carrier. The self-repairing foam concrete is prepared by an innovative microbial carrier design and a composite repair mechanism in one step. The problem that the microbial inoculation and the self-repairing foaming need to be carried out in steps in the composite concrete in the prior art is solved. Therefore, 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: A preparation method of a self-repairing foam concrete, comprising the following steps: Step S2, hydroxyl stone powder is obtained by hydroxylating stone powder. Silane coupling agent is used to modify sodium alginate to obtain grafted copolymer. Bacillus pasteurii is inoculated on the composite carrier by compounding hydroxyl stone powder, grafted copolymer and nano-silicon dioxide as a composite carrier. 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.

[0008] As a preferred improvement, 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% nano-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.

[0009] 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.

[0010] As a preferred improvement, 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, and pre-hydrolysis is carried out at 60℃ for 30min; sodium alginate is dissolved in a pH=5, 3wt% acetic acid-sodium acetate buffer solution, and pre-heating is carried out at 60℃ 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℃ for 2h, to finally form the graft copolymer.

[0011] As a preferred improvement, the inoculation process of Bacillus pasteurii specifically comprises the following steps: 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-0.095MPa for 30min; then, 2wt% sterile CaCl2 solution is sprayed, and standing is carried out for 20min, 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.

[0012] As a preferred improvement, step S3 specifically comprises the following process: According to the mass fraction, 300-400 parts of 350 kg / m 3 ordinary Portland cement is mixed with 100-150 parts of 120 kg / m 3 compound carrier inoculated with Bacillus pasteurii by double-shaft forced mixer for 3 minutes; according to the water-binder ratio of 0.35-0.45, a water solution containing 0.1 wt% retarder is added, and the slurry is continuously stirred for 3 minutes until it is uniform, 1 part of a compound foaming agent and 10 parts of urea are added, foaming is carried out according to the dilution ratio of 1:30 and the 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 , and the planetary stirring is adopted with the mixing time controlled within 1 minute, the layer pouring and the inserted 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.

[0013] As a preferred improvement, 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, and the temperature is controlled below 40℃.

[0014] As a preferred improvement, the step S2 further includes the following steps before the step S2: Step S1, preparing a liquid culture medium, and cultivating Bacillus pasteurii in the liquid culture medium.

[0015] As a preferred improvement, the preparation process of the liquid culture medium includes the following steps: Step S111, adding proteose peptone, sodium chloride and soybean peptone into 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, adding 0.1 mol / L sodium hydroxide solution drop by drop into the mixed solution by using a rubber bulb dropper to adjust the pH value of the mixed solution to 7.3; Step S113, placing the mixed solution into an autoclave, adjusting the temperature of the autoclave to 121℃ and the pressure to 0.105 MPa, and sterilizing for 30 minutes to ensure that the mixed solution is in a sterile state, and then cooling the mixed solution to 45℃; Step S114, injecting a 20% mass fraction urea solution into the mixed solution by using a syringe with a microporous filter head in a sterile manner to obtain the liquid culture medium; The cultivation process of Bacillus pasteurii includes the following steps: Step S121, providing an inoculation loop and a slant medium inoculated with Paenibacillus polymyxa; Step S122, in a sterile operation table, first sterilize the inoculation loop with an alcohol lamp, then gently scrape the surface of the slant medium with the inoculation loop, insert the inoculation loop into the liquid medium and stir uniformly, sterilize the inoculation loop again with an alcohol lamp after inoculation to avoid bacterial contamination of the operation table; Step S123, place the inoculated solid medium in a constant temperature biochemical incubator at 30 DEG C for culture until clear colony formation is visible in the solid medium, then store the solid medium in a refrigerator at 4 DEG C for preservation.

[0016] A self-repairing foam concrete prepared by the above-mentioned method.

[0017] The present application has the following advantages: (1) Hydroxyl stone powder, graft copolymer and nano silicon dioxide are compounded as a composite carrier, Paenibacillus polymyxa is inoculated on the composite carrier, and through innovative microbial carrier design and composite repair mechanism, a self-repairing foam concrete is prepared by one-step method, solving the problem that microbial inoculation and self-repairing foaming need to be carried out in steps in the prior art composite concrete; (2) Significantly improve microbial activity and long-term survival rate, the 28-day survival rate of the microbial population in the high-alkali environment (pH>12) of the concrete is improved from <30% of the traditional carrier to ≥70%, the Si-O-Ca covalent bond on the surface of the composite carrier provides stable anchoring to avoid loss of the microbial population, and the hydrophobic modification reduces the erosion of alkaline pore solution, thereby ensuring long-term repair capability; (3) High-efficiency self-repairing capability: the final repairable crack is ≤0.25mm, and the repair effect is shown in Figure 4 , the prior art is usually ≤0.2mm, and larger cracks can be repaired; (4) Overall improvement of mechanical properties and durability: the 28-day compressive strength reaches 2.00MPa, while the ordinary foam concrete is 1.52MPa, and the fracture toughness is improved by 40%; (5) Industrialization and environmental protection advantages: the cost of the stone powder carrier is 40% lower than that of the synthetic microbial carrier (such as sodium alginate-fly ash microspheres); low-carbon normal temperature curing saves energy consumption (compared with high-temperature steam curing of foam concrete); and has the function of microbial carbon sequestration, and the carbon sequestration capacity is 3-5kgCO2 / m 3 ; (6) Convenient construction: compatible with existing concrete production lines, slump 160±20mm, no blockage during pumping, and convenient for construction. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings. Figure 1 A micrograph of the sample in M5 group in Example 1 is shown; Figure 2 A micrograph of the sample in M6 group in Example 1 is shown; Figure 3 A micrograph of the sample in M7 group in Example 1 is shown; Figure 4 A repair effect diagram of the self-repairing foam concrete provided by the present application on a 0.25mm crack is shown; Figure 5 A repair effect diagram of the self-repairing foam concrete provided by the present application on a 0.48mm crack is shown. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort fall within the scope of protection of the present application.

[0020] The present embodiment provides a preparation method of self-repairing foam concrete, comprising the following steps: Step S1, preparing a liquid culture medium, and cultivating Bacillus pasteurii on the liquid culture medium.

[0021] The preparation process of the liquid culture medium comprises the following steps: Step S111, adding proteose peptone, sodium chloride and soybean peptone into 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; Step S112, adding 0.1 mol / L sodium hydroxide solution drop by drop into the mixed solution by using a rubber bulb dropper to adjust the pH value of the mixed solution to 7.3; Step S113, placing the mixed solution into an autoclave, adjusting the temperature of the autoclave to 121℃ and the pressure to 0.105 MPa, and continuously sterilizing for 30 minutes to ensure that the mixed solution is in a sterile state, and then cooling the mixed solution to 45℃; Step S114, a syringe equipped with a microporous filter head is used to inject the 20% mass fraction urea solution into the mixed solution in a sterilized manner, to obtain a liquid culture medium.

[0022] The cultivation process of the Bacillus pasteurii includes the following steps: Step S121, a looplifter and a slant culture medium inoculated with the Bacillus pasteurii are provided; Step S122, the looplifter is first sterilized with an alcohol lamp in a sterile operation table, then the surface of the slant culture medium is scraped with the looplifter, the looplifter is inserted into the liquid culture medium and stirred uniformly, and after inoculation, the looplifter is sterilized again with an alcohol lamp to avoid bacterial contamination of the operation table. Step S123, the inoculated solid culture medium is placed in a constant temperature biochemical incubator at 30°C for cultivation, until clear colony formation is visible in the solid culture medium, and then the solid culture medium is stored in a refrigerator at 4°C for standby.

[0023] Step S2, the stone powder is subjected to hydroxylation treatment to obtain hydroxyl stone powder, the sodium alginate is modified with a silane coupling agent to obtain a graft copolymer, and the Bacillus pasteurii is inoculated on the composite carrier composed of the hydroxyl stone powder, the graft copolymer, and nano-silicon dioxide.

[0024] The preparation process of the hydroxyl stone powder includes the following steps: Step S211, the stone powder is ultrasonically treated (power 300 W, frequency 40 kHz) in 0.1 mol / L hydrochloric acid for 15 minutes, and then washed with deionized water until neutral.

[0025] In this embodiment, the stone powder is taken from the argillaceous siltstone powder of a certain section of the Zero-Dao Expressway project in Shuangpai County, Yongzhou City, and the main components are quartz and calcareous and magnesian carbonate minerals, of which the mass content of quartz is 60-70%, and the balance is calcite and dolomite.

[0026] The pickling process can remove organic contaminants, grease, dust, etc. that may exist on the surface of the stone powder, and also slightly etch the surface of the stone powder, increase its roughness and specific surface area, and expose more active sites, thereby improving the subsequent adhesion capacity of the nanoparticles. The surface of the hydrochloric acid-activated stone powder forms two types of active sites: the quartz component exposes ≡Si-OH (silicon hydroxyl), and the carbonate component produces a cleavage plane of ≡Ca-OH / ≡Mg-OH.

[0027] Step S212, the hydrochloric acid-activated stone powder of step S211 is immersed in a solution containing 5 wt% nano-hydroxyapatite (Ca 10The nanoparticles were uniformly dispersed by ultrasonic treatment (40 kHz, 30 min) in an ethanol suspension of 1 wt% KH-550 and 1 wt% n-HA (Ca5(PO4)3(OH), particle size 20-50 nm). Then the suspension was reacted at 60°C for 90 min, and finally dried at 60°C to constant weight to obtain the hydroxyl stone powder.

[0028] The following reactions mainly occur in the composite system of stone powder, nano-hydroxyapatite (nHA-OH) and KH-550: (1) Phosphate-carbonate bond The phosphate groups (-PO4) on the surface of the nano-hydroxyapatite 3- react with the Ca 2+ / Mg 2+ on the surface of the carbonate in the stone powder to form a coordination bond: ≡Ca-CO3+PO4 3- →≡Ca-O-PO4 2- +CO3 2- ; (2) Calcium ion bridging The silanol groups on the surface of the quartz in the stone powder form a coordination bond with the Ca 2+ on the surface of the carbonate in the stone powder: ≡Si-OH+Ca 2+ →≡Si-O-Ca - ; (3) Bridging of hydrolyzed KH-550 The hydrolyzed KH-550 can simultaneously react with the stone powder and the nano-hydroxyapatite to form a bridging structure through coordination: nHA-OH+HO-Si-(CH2)3NH2→nHA-O-Si-(CH2)3NH2; ≡Si-OH+HO-Si-(CH2)3NH2→≡Si-O-Si-(CH2)3NH2+H2O.

[0029] Through the above reactions, the nano-hydroxyapatite is firmly coated on the surface of the stone powder particles under the coupling action of KH550, forming a "core-shell" structure composite powder with stone powder as the core and n-HA as the shell, i.e. the hydroxyl stone powder. This composite powder not only retains the low-cost characteristics of the stone powder, but also has the biological activity and surface properties of n-HA.

[0030] The preparation process of the graft copolymer includes the following steps: KH-550 is dissolved in acetic acid-sodium acetate buffer solution (concentration 5wt%) with pH=5, and pre-hydrolyzed at 60℃ for 30min; sodium alginate is dissolved in acetic acid-sodium acetate buffer solution (concentration 3wt%) with pH=5, and pre-heated to reduce viscosity at 60℃; the hydrolyzed KH-550 solution is added dropwise into the sodium alginate solution at a mass ratio of 1:3, and stirred at 60℃ for 2h to form the graft copolymer finally.

[0031] The hydrolysis product of KH-550 (γ-aminopropyl triethoxysilane) is mainly γ-aminopropyl trisilanol, which includes silanol groups and amino groups. After being added to the sodium alginate solution, the amino groups react with the carboxyl groups of sodium alginate to form an amide, thereby forming the graft copolymer.

[0032] To confirm that the silane coupling agent KH-550 has been successfully grafted onto the molecular chain of sodium alginate, the solubility and gelation behavior of the synthesized product are compared and verified. Solubility test: a small amount of pure sodium alginate (SA) sample and the graft copolymer sample prepared by the present application are added into deionized water, respectively. The pure sodium alginate can be quickly dissolved to form a uniform viscous solution; while the graft copolymer only swells in water to form white gel particles that are insoluble in water. This phenomenon indicates that the grafting of KH-550 introduces hydrophobic organic long chains and cross-linking structures, which significantly change the hydrophilicity of sodium alginate, proving the occurrence of grafting reaction and the formation of a new graft copolymer.

[0033] In the composite carrier, the gap of the hydroxyl stone powder is 10-50μm, which can be used as a carrier for Bacillus pasteurii. Bacillus pasteurii can be distributed in the pores of the hydroxyl stone powder, providing physical protection for Bacillus pasteurii, thereby improving the survival rate of the bacterial population. On the other hand, the hydroxyl stone powder can also be used as a foaming stabilizer. The surface hydroxyl groups of the stone powder form a hydrogen bond network with the polar groups of the foaming agent, which can effectively reduce the drainage rate of the bubble membrane and prolong the half-life of the foam to more than 120min. At the same time, the stone powder particles adsorb on the gas-liquid interface to form a physical barrier, preventing the coalescence of bubbles.

[0034] The graft copolymer is used as a gel material to encapsulate Bacillus pasteurii, isolating Bacillus pasteurii from the high alkaline environment inside the concrete and improving the survival rate of the bacterial population. At the same time, the graft copolymer can effectively resist the high alkaline environment, prolonging the failure time of the gel material and preventing the premature release of the bacterial population.

[0035] The addition of nano-silicon dioxide is used for hydrophobic modification of the composite carrier. The silanol groups on the surface of the nano-silicon dioxide react with the silanol groups of the hydrolysis product of KH-550 to form Si-O-Si bonds, constructing a micro-nano hierarchical rough structure and producing a synergistic hydrophobic effect with the long-chain alkyl groups of the graft copolymer, thereby reducing the foam collapse rate and optimizing the foam structure. The condensation reaction process is represented as: Si-OH + HO-Si→Si-O-Si + H2O.

[0036] The inoculation process of Bacillus pasteurii specifically includes the following steps: 10 8 The Bacillus pasteurii bacterial solution with a CFU / mL of 10 is mixed with the grafted 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 under a vacuum degree of -0.095 MPa for 30 min; then 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 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 the CaCl2 solution is 5% of the mass of the hydroxyl stone powder.

[0037] In step S3, 300-400 parts of cement, 100-150 parts of the Bacillus pasteurii-inoculated composite carrier, 1 part of the composite 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.

[0038] Step S3 specifically includes the following process: 300-400 parts of 350 kg / m3 ordinary Portland cement are mixed with 100-150 parts of 120 kg / m 3 of the Bacillus pasteurii-inoculated composite carrier by a double-shaft forced mixer (rotation speed 45 rpm) for 3 min of dry mixing; a water solution containing 0.1 wt% of a retarder is added at a water-binder ratio of 0.35-0.45, 1 part of the composite 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 machine is uniformly injected into the concrete initial mixing material at a rate of 50 L / m 3 The self-repairing foam concrete is obtained by adopting planetary stirring (revolution 30 rpm + rotation 60 rpm), controlling the mixing time within 1 min, layering pouring, inserting type vibrating, and covering the surface with a polyethylene film to prevent water evaporation.

[0039] The silane coupling agent KH-550 is used to covalently graft sodium alginate to the surface of the stone powder, forming a double chemical bonding network of Si-O-Ca bonds (binding energy > 200 kJ / mol) and amide bonds (-CO-NH-). This network gives the concrete multiple performance advantages: the rigid Si-O-Ca bonds significantly improve the stone powder-cement matrix interface strength, and the flexible amide bond network not only protects the bacteria through pH response characteristics (28-day survival rate > 85%), but also intelligently releases the repair bacteria at the crack site (the final repair rate for 0.45 mm cracks is ≥ 90%, see Figure 5);Meanwhile, the interface structure of rigidity and flexibility makes the material have excellent resistance to chloride ion erosion and water regulation function, realizing the synergistic improvement of self-repairing function and durability. The addition of urea is used to provide a continuous carbon and nitrogen source for bacteria and adjust the pH value of the pore solution.

[0040] The composite foaming agent is configured by 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 the HF-60 type composite polymer cement foaming agent SDS produced by Yantai Green Forest Heavy Industry Co., Ltd., and includes sodium fatty alcohol polyoxyethylene ether sulfate, ninal and water. The composite polymer cement foaming agent SDS in the composite foaming agent mainly plays a foaming role, and the L-cysteine hydrochloride provides a stable foaming effect, and the released sulfhydryl (-SH) and the Ca 2+ / Mg 2+ Forming a coordination structure is the key to realizing the synergistic effect of double-mode foaming.

[0041] The present application constructs a unique double-mode foaming system on the surface of quartz-carbonate composite stone powder (quartz content 60-70%, calcite / dolomite 30-40%) through the synergistic effect of the composite foaming agent and bacillus pasteurii. In the chemical foaming process, the -SH group released by the L-cysteine hydrochloride in the composite foaming agent preferentially reacts with the Ca 2+ / Mg 2+ Forming a [M-S-Ca / Mg] coordination structure, and bonding on the surface of quartz through Si-O-S under pressure to generate stable macrofoam of 100-300 μm. When bacillus pasteurii (urease activity ≥ 15 U / mg) metabolizes urea, the secreted β-1, 3-glucan and Ca 2+ / Mg 2+ (ICP-MS determination [Ca 2+ ] reaches 150 mg / L) form organic-inorganic composite microfoam (10-50 μm), and the calcite (104) crystal face is directionally combined with the carboxyl group of EPS. This interface modification based on the difference of mineral components increases the compressive strength of the material, and the preferential dissolution-redeposition characteristics of the carbonate region enable 0.48 mm cracks to be self-repaired by 90%.

[0042] The prepared 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℃.

[0043] A contrast test is set up to compare the performance of the self-repairing foam concrete prepared in the application with that of ordinary foam concrete, and the contrast test includes: (1) Compressive strength test: Compared with ordinary foam concrete, the compressive strength of the self-repairing foam concrete provided in the application is increased by 47%; (2) Bending strength test: Compared with ordinary foam concrete, the bending strength of the self-repairing foam concrete provided in the application is increased by 28%; (3) Crack repair test: A crack with a width of 0.25 mm is prefabricated, and curing is carried out under the conditions of 20℃ / 95%RH (moisture trigger) and 5%CO2 (pH trigger) respectively, the self-repairing foam concrete provided in the application successfully completes the repair of the crack, and the repair result is shown in Figure 4 ; (4) Bacterial survival rate test: SYTO9 / PI + confocal microscope is used to observe the distribution and survival state of the bacterial population in the carrier. The survival rate is as high as 72% higher than the initial value.

[0044] The embodiment also provides a self-repairing foam concrete prepared by using the preparation method of the self-repairing foam concrete.

[0045] Example 1 In this embodiment, a cross experiment is set up, and Bacillus pasteurii and silane coupling agent KH-550 are respectively compounded with stone powder to prepare carriers, and then the influence of different components of the carriers on the performance of the self-repairing foam concrete is verified. The experiment is carried out according to the preparation method described in the application. In the cross experiment, a total of 10 groups of samples are designed, and the only difference between the groups of samples is whether Bacillus pasteurii is added and different carriers are used to load Bacillus pasteurii. The total amount of cement and stone powder is fixed at 300 parts, so as to determine the absolute proportion of each component. In addition, the addition amount of the composite foaming agent is fixed at 1 part, the addition amount of urea is fixed at 10 parts, and the water-binder ratio is fixed at 0.35. The specific data of each sample are shown in Table 1.

[0046] Table 1 Cross experiment data table

[0047] The above 10 groups of samples are cured under the same curing conditions, and the performance of the 10 groups of samples is tested. The performance indicators include slump, compressive strength, splitting tensile strength and closure rate.

[0048] (1) Slump Slump is an important indicator for measuring the workability of concrete, specifically including the water retention, fluidity and cohesiveness of concrete, and good slump can ensure that the concrete is easy to operate and uniformly compacted during the construction process, thereby ensuring the construction quality. The slump data of each group of samples are shown in Table 2: Table 2 Slump data table

[0049] As can be seen from Table 2, all samples show ideal slump, controlled in the range of 100-180 mm, meeting the pumping requirements of JG / T 266-2011.

[0050] M1 has the highest slump (187 mm), and the slump shows a downward trend with the increase of stone powder content (M10 group decreases 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 makes the slump loss of M4 / M7 / M10 group reduce by 5-15 mm compared with the corresponding unmodified group (M3 / M6 / M9), proving that it can improve the lubricity of particles.

[0051] (2) Compressive strength The compressive strength of each group of samples after 28 days of curing is shown in Table 3:

[0052] As can be seen from Table 3, M7 group (15% stone powder + bacteria + silane) reaches 2.00 MPa, which is 33% higher than M1, and the strength growth is mainly due to the silane-stone powder bonding network and the microbial mineralization product filling microcracks. The strength of 30% stone powder group (M8-M10) is significantly reduced, and the 30% stone powder content makes the strength decay by 40-53%, confirming that the dilution effect of stone powder dominates.

[0053] (3) Splitting tensile strength The splitting tensile strength of each group of samples after 28 days of curing is shown in Table 4: Table 4 Splitting tensile strength

[0054] As can be seen from Table 4, M1 has a strength of 0.25±0.03 MPa, and the fracture surface shows typical brittle failure characteristics; the silane coupling agent modified group (M4 / M7 / M10) shows an increase in toughness: the strength of M7 group reaches 0.35 MPa (40% higher than M1); it is speculated that the microbial mineralization product forms a CaCO3-Si composite phase at the crack, delaying the crack propagation.

[0055] At the same time, the stone powder content also has a significant impact, and 5-15% stone powder can improve the tensile strength, which in turn improves the interfacial bonding, but more than 15% causes the strength to decrease due to the agglomeration effect (M10 is 37% lower than M7).

[0056] (4) Closure rate A standard cube test specimen (100x100x100mm) at 28 days of age was placed in a three-point bending device, loaded at a rate of 0.1mm / min to produce a 0.25mm wide through crack (crack width calibrated by a crack microscope), and the initial crack morphology was recorded immediately. At the 28th day of repair, crack width monitoring was performed, and the closure rate was (1-current crack width / initial crack width) x 100%, and was recorded as follows.

[0057] Table 5 Closure rate data table

[0058] The micrographs of M5, M6 and M7 groups are shown in Figures 1-3 It can be seen from Figure 1 that the macro-bubbles in the M5 group are mainly chemical foaming, the chemical foaming pores have high connectivity, the stone powder and the cement matrix have poor combination, which leads to weak interface; the Bacillus pasteurii metabolite optimizes the pore structure and improves the interface combination in the M6 group, but does not completely solve the problem of pore connectivity; the silane coupling agent enhances the interface combination between the stone powder and the cement, reduces the unreacted particles, improves the matrix density, and the overall structure is relatively dense in the M7 group.

[0059] The embodiments of the present application are described above in combination with the drawings, but the present application is not limited to the above specific embodiments, and the above specific embodiments are only illustrative, but not restrictive, and those skilled in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, which all belong to the protection of the present application.

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 the hydroxyl group treatment and obtain the hydroxyl stone powder, take the silane coupling agent to modify the sodium alginate and obtain the graft copolymer, take the hydroxyl stone powder, the graft copolymer and the nanometer silicon dioxide as a compound carrier, and inoculate the bacillus pasteurii on the compound carrier; 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 to obtain the self-repairing foam concrete, wherein the water-binder ratio is 0.35-0.45, the compound foaming agent is configured by the compound high molecular cement foaming agent SDS and L-cysteine hydrochloride according to the mass ratio of 5:1, and the compound high molecular cement foaming agent SDS comprises sodium fatty alcohol polyoxyethylene ether sulfate, ninal and water.

2. The method for preparing self-repairing foamed concrete according to claim 1, characterized in that: The preparation process of the hydroxyl stone powder comprises the following steps: Step S211, the stone powder is ultrasonically treated 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 5 wt% nanometer hydroxyapatite and 1 wt% KH-550, and ultrasonically treated to uniformly disperse the nanoparticles; Then, under the condition of 60 DEG C, it is reacted for 90 min, and finally dried at 60 DEG C to constant weight to obtain the hydroxyl stone powder.

3. The method for preparing self-repairing foamed concrete according to claim 1, characterized in that: 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, and pre-hydrolyzed at 60 DEG C for 30 min; sodium alginate is dissolved in a pH=5, 3wt% acetic acid-sodium acetate buffer solution, and pre-heated to reduce viscosity at 60 DEG C; the hydrolyzed KH-550 solution is added to the sodium alginate solution according to a mass ratio of 1:3, and stirred and reacted at 60 DEG C for 2 h 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, the foaming agent, and the water-reducing agent. The inoculation process of the 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.

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. 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.

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. The obtained self-repairing foam concrete is cured according to the following conditions: Stage I: 0-24 h, temperature 20±1 DEG C, relative humidity RH≥95%; Stage II: 24-72 h, temperature 25±2 DEG C, relative humidity RH≥90%; Stage III: after 72 h, natural curing, and the temperature is controlled below 40 DEG C.

8. 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 the bacillus pasteurii on the liquid culture medium.

9. The method of claim 8, 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 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; 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.

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

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