Self-repairing microbial concrete and crack repairing method thereof

Abstract

The invention relates to the field of concrete materials, and particularly discloses self-repairing microbial concrete and a crack repairing method thereof. Comprising the following components in parts by weight: 100 parts of Portland cement, 150-300 parts of aggregate of which the particle size is 0.1-5mm, mixing water of which the water-cement ratio is 0.3-0.5, 0.5-5 parts of bacillus pasteurii spores of which the concentration is greater than or equal to 107 CFU / g, 3-10 parts of calcium lactate, 2-8 parts of histidine-urea composite substrate and 10-30 parts of carrier material, through collaborative design of the histidine-urea composite substrate and the pH response type slow-release carrier, a microbial metabolism microenvironment regulation and control system is creatively constructed, histidine is used as a metabolism buffer medium, a pH window needed by microbial enzyme activity is effectively stabilized, and cytotoxicity caused by local pH sudden change of a traditional urea substrate is avoided; the dynamic balance of urea hydrolysis and histidine chelation significantly prolongs the duration period of calcium carbonate production by microorganisms, and realizes gradient repair of cracks from outside to inside.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of concrete materials, in particular, a self-repairing microbial concrete and a crack repairing method thereof. BACKGROUND

[0002] Due to the advantages of high compressive strength, good durability, easy availability of raw materials and low price, concrete is still the most demanded material in the field of construction. However, due to the high brittleness, low tensile strength and early shrinkage deformation of concrete material, many micro-cracks and defects are prone to occur in the interior or surface of concrete during use.

[0003] These cracks not only affect the durability of the structure, but also accelerate the corrosion of steel bars, freeze-thaw damage and chemical corrosion, ultimately leading to degradation or even failure of the structural performance.

[0004] The existing crack surface repairing method can only deal with shallow cracks and cannot repair deep or dynamically expanding cracks. Meanwhile, when the grouting method is used, the compatibility of the grouting material with the concrete matrix is poor, which is prone to secondary interfacial peeling. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a self-repairing microbial concrete to solve the problem that the crack surface repairing method in the prior art can only deal with shallow cracks and cannot repair deep or dynamically expanding cracks, and the compatibility of the grouting material with the concrete matrix is poor when the grouting method is used, which is prone to secondary interfacial peeling.

[0006] A self-repairing microbial concrete, comprising the following components by weight fraction:

[0007] 100 parts of Portland cement, 150-300 parts of aggregate with a particle size of 0.1-5 mm, mixing water with a water-cement ratio of 0.3-0.5, 0.5-5 parts of Bacillus pasteurii spores with a concentration of ≥10 7 CFU / g, 3-10 parts of calcium lactate, 2-8 parts of histidine-urea composite substrate and 10-30 parts of carrier material;

[0008] The carrier material is porous zeolite particles coated with a pH-responsive polyacrylic acid slow-release layer on the surface, the porous zeolite particles are modified by silane coupling agent KH-550 and loaded with ferroferric oxide nanoparticles, and the pores are encapsulated with the Bacillus pasteurii spores, calcium lactate and histidine-urea composite substrate by vacuum impregnation method.

[0009] Preferably, the pore size of the porous zeolite particles is 10-50 μm, and the porosity is 70%-90%.

[0010] Preferably, the mass ratio of histidine to urea in the histidine-urea composite substrate is 1:1-1:3.

[0011] Preferably, the thickness of the polyacrylic acid slow-release layer is 20-30 μm.

[0012] A preparation method of self-repairing microbial concrete comprises the following steps:

[0013] S1, loading ferroferric oxide nanoparticles on porous zeolite particles after surface treatment by silane coupling agent KH-550;

[0014] S2, filling the pores of the modified porous zeolite particles by vacuum impregnation by dissolving Bacillus pasteurii spores, calcium lactate and histidine-urea compound substrate in a phosphate buffer solution with pH 7.4;

[0015] S3, forming a polyacrylic acid slow-release layer with a thickness of 10-50 μm on the surface of the carrier loaded with the microbial system;

[0016] S4, mixing the carrier obtained in S3 with silicate cement and aggregate, adding water with a water-cement ratio of 0.3-0.5, stirring, pouring and curing.

[0017] Preferably, the pressure of vacuum impregnation in S2 is 0.08-0.1 MPa, and the impregnation time is 2-4 h.

[0018] A crack self-repairing method based on microbial concrete comprises the following steps:

[0019] (1) when the crack width of the concrete reaches 0.05-1 mm, environmental moisture penetrates into the carrier and dissolves the polyacrylic acid slow-release layer to release microbial spores;

[0020] (2) applying an alternating magnetic field with a frequency of 50-100 kHz to the concrete for 10-30 minutes to heat the inside of the carrier to 35±2℃ and activate spore germination;

[0021] (3) microbial metabolism produces carbonate ions to generate calcium carbonate precipitates with calcium ions at the crack, and hydrophobic biological membranes are secreted to fill the cracks;

[0022] (4) using the ASTMC597 standard to detect the ultrasonic propagation speed, when the recovery rate is ≥95% and the crack water seepage height is ≤0.5 mm, it is determined that the repair is completed.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] By the synergistic design of histidine-urea complex substrate and pH-responsive slow-release carrier, a microbial metabolic microenvironment regulation system is constructed: histidine as a metabolic buffer medium effectively stabilizes the pH window required for microbial enzyme activity, avoiding the cell toxicity caused by the sudden change of local pH due to the traditional urea substrate; the dynamic balance of urea hydrolysis and histidine chelation significantly prolongs the continuous period of microbial calcium carbonate production, realizing the gradient repair of cracks from the surface to the inside.

[0025] The magnetic-thermal energy conversion system based on ferroferric oxide nanoparticles breaks through the environmental limitations: the targeted temperature rising characteristics induced by the alternating magnetic field enable the spore germination process to break away from the environmental temperature constraints, and still enable the repair program to be quickly started under low temperature or large temperature difference working conditions; the local thermal field formed in the carrier promotes the substrate diffusion efficiency, solving the problem of nutrient transmission lag in traditional microbial concrete. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a preparation process schematic diagram of the self-repairing microbial concrete of the present application. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the 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 creative labor fall within the scope of protection of the present application.

[0028] As shown in Figure 1

[0029] Embodiment 1

[0030] Components: Portland cement: 100 parts, aggregate (particle size 0.1 mm): 150 parts, water-cement ratio: 0.3, Bacillus pasteurii spores (1×10 7 CFU / g): 0.5 parts, calcium lactate: 3 parts, histidine-urea complex substrate (mass ratio 1:1): 2 parts, carrier material: 10 parts, porous zeolite particles (pore size 10 μm, porosity 70%), polyacrylic acid slow-release layer thickness: 20 μm

[0031] Preparation method:

[0032] Carrier treatment: zeolite particles are modified by KH-550 silane coupling agent, and loaded with Fe3O4 nanoparticles (particle size 20 nm).

[0033] Vacuum impregnation (0.08 MPa, 2 h) perfuses the mixed solution of spores, calcium lactate and substrate (pH 7.4 PBS buffer).

[0034] ​Electrostatic spraying method to form 20 μm polyacrylic acid release layer.

[0035] Concrete casting: dry cement, aggregate and carrier, then add water and stir (water-cement ratio 0.3), standard curing for 28 days.

[0036] Repair effect: when the crack width is 0.05 mm, the ultrasonic propagation velocity recovery rate is 96% after magnetic field activation (50 kHz, 10 minutes), and the water penetration height is 0.3 mm.

[0037] SEM shows that dense calcium carbonate crystals (particle size 1-3 μm) are generated in the crack.

[0038] Example 2

[0039] Components: Portland cement: 100 parts, aggregate (particle size 2.5 mm): 225 parts, water-cement ratio: 0.4, Bacillus pasteurii spores (5 x 10 7 CFU / g): 2.5 parts, calcium lactate: 6.5 parts, histidine-urea complex substrate (mass ratio 1:2): 5 parts, carrier material: 20 parts, porous zeolite particles (pore size 30 μm, porosity 80%), polyacrylic acid release layer thickness: 25 μm

[0040] Preparation method:

[0041] Carrier optimization: Fe3O4 loading increased to 15 wt%, vacuum impregnation (0.09 MPa, 3 h) improved encapsulation efficiency.

[0042] The polyacrylic acid layer controls the thickness by microfluidic spraying.

[0043] Construction process: add 0.1% water reducing agent to improve workability, then steam curing (60°C, 6h) after vibration compaction.

[0044] Repair effect: when the crack width is 0.5 mm, the magnetic field activation (75 kHz, 20 minutes):

[0045] After repair, the compressive strength is restored to 98% of the initial value, and the contact angle is increased to 120° (hydrophobic film effect).

[0046] Example 3

[0047] Components: Portland cement: 100 parts, aggregate (particle size 5 mm): 300 parts, water-cement ratio: 0.5, Bacillus pasteurii spores (1 x 10 8 CFU / g): 5 parts, calcium lactate: 10 parts, histidine-urea complex substrate (mass ratio 1:3): 8 parts, carrier material: 30 parts, porous zeolite particles (pore size 50 μm, porosity 90%), polyacrylic acid release layer thickness: 30 μm

[0048] Preparation method:

[0049] High loading support: zeolite particles pre-holed, Fe3O4 loading up to 20wt%.

[0050] High pressure impregnation (0.1 MPa, 4h) ensures homogeneous substrate distribution.

[0051] Large volume construction: layered casting to avoid support sedimentation, curing humidity > 95%.

[0052] Repair efficiency: crack width 1 mm, magnetic field activation (100 kHz, 30 min):

[0053] Calcium carbonate deposition up to 1.2 kg / m 3 Crack volume, permeability coefficient of chloride ions after repair reduced by 90%.

[0054] Example 1:

[0055] 1. Experimental group design

[0056]

[0057] 2. Experimental procedure

[0058] Test piece preparation:

[0059] Concrete test pieces (size 100 x 100 x 100 mm) were prepared according to the method of Example 2, pre-cracked to a crack width of 0.5 mm.

[0060] Comparative Examples 1-3 were adjusted according to the table for substrate or magnetic field conditions, the remaining components being identical to the reference group.

[0061] Repair process:

[0062] Reference group / Comparative Example 1: application of an alternating magnetic field of 75 kHz for 20 minutes (35 ± 2°C).

[0063] Comparative Examples 2 / 3: placed in a constant humidity environment (RH > 90%) at 25°C.

[0064] Crack width variation (microscopic measurement every hour), calcium carbonate deposition (EDX analysis) were monitored.

[0065] Spore germination rate detection:

[0066] After 24 hours of repair, the support particles were ultrasonically broken down, diluted and spread on LB plates, which were incubated at 37°C for 48 h to count the colonies (CFU / g).

[0067] Experimental data table

[0068] Table 1: Repair efficiency vs. spore activity (24 hours data)

[0069]

[0070] Table 2: Repair speed comparison of key time nodes

[0071] Group Time for 50% crack closure (h) Time for complete closure (h) Reference group 4.2±0.5 18.6±1.2 Comparative Example 1 8.7±0.9 > 48 (not complete) Comparative Example 2 12.4±1.3 > 72 (not complete) Comparative Example 3 > 72 (not reach 50%) -

[0072] Experimental result analysis

[0073] 1. The improvement of repair speed by composite substrate

[0074] Data support: The crack closure rate of the reference group is 35.1% higher than that of Example 1, and the calcium carbonate deposition amount is increased by 71.7%.

[0075] Mechanism of action:

[0076] Histidine acts as a pH buffer to maintain the metabolic environment of microorganisms (pH 8-9) and avoid ammonia toxicity caused by rapid hydrolysis of urea.

[0077] Histidine-urea synergistically promotes urease gene expression, increasing the calcium carbonate generation rate from 0.38 mg / (cm 2 ·h) in Comparative Example 1 to 0.66 mg / (cm 2 ·h).

[0078] 2. Effect of magnetic field activation on spore germination rate

[0079] Data support: The spore germination rate of the reference group (88.7%) is significantly higher than that of Comparative Example 2 (32.6%).

[0080] Mechanism of action:

[0081] Fe3O4 nanoparticles generate heat under alternating magnetic field, and the 35℃ environment shortens the spore germination time to 2-3 hours (8-10 hours in Comparative Example 2).

[0082] The local thermal effect induced by the magnetic field simultaneously enhances the substrate diffusion efficiency in the carrier, accelerating the start of metabolism.

[0083] 3. Comprehensive repair performance

[0084] Advantages of the reference group: ultrasonic recovery rate ≥ 95% and repair time shortened by more than 60%, proving the synergistic effect of composite substrate and magnetic field activation.

[0085] Economic analysis: Although the cost of composite substrate increases by about 15%, the reduction in repair cycle can reduce engineering maintenance costs by 30%-40%.

[0086] Conclusion

[0087] Necessity of composite substrate: The histidine-urea composite substrate optimizes the metabolic environment of microorganisms, increasing the repair speed to 1.5 times that of the pure urea system.

[0088] Magnetic field activation criticality: Alternating magnetic field increases spore germination rate from <35% under natural conditions to >85%, and avoids the energy consumption problem of traditional heating.

[0089] Engineering applicability: This technology is particularly suitable for underground engineering that needs to be repaired quickly or concrete structures in low-temperature environments (<15℃).

[0090] Experimental Example 2:

[0091] 1. Experimental design purposes

[0092] Verify the repair performance stability and long-term durability (multiple repair capacity and carrier life) of the self-repairing microbial concrete of the application in extreme environments (low temperature, high salt, dry-wet cycle).

[0093] 2. Experimental grouping and variable control

[0094]

[0095] 3. Experimental methods

[0096] Preparation of test pieces: Prepare concrete test pieces (pre-crack width 0.5mm) according to the formulation of Example 2, 3 parallel samples per group.

[0097] Repair process:

[0098] Experimental group A: maintenance in a 5℃ constant temperature box, and continuous application of alternating magnetic field during repair.

[0099] Experimental group B: immersed in NaCl solution, and monitor the diffusion of chloride ions at the crack.

[0100] Experimental group C: daily cycle of drying (60℃, 4h) and wetting (spraying water), and trigger the magnetic field once per cycle.

[0101] Detection method:

[0102] Spore survival rate: carrier crushing culture counting (CFU / g) after repair.

[0103] Calcium carbonate purity: XRD quantitative analysis of calcite content.

[0104] Biofilm hydrophobicity: contact angle measurement.

[0105] 4. Experimental results and data analysis

[0106] Table 1: Repair effect in extreme environment (28-day data)

[0107]

[0108] Key findings:

[0109] Low temperature adaptability (experimental group A):

[0110] The magnetic field activation increased the spore germination rate at low temperature to 76.3% (control group without magnetic field <20%), which proved the effectiveness of the magnetic heat conversion of Fe3O4 nanoparticles.

[0111] The repair speed was only 7.3% slower than the standard condition, which met the needs of cold region engineering.

[0112] Salt corrosion resistance (experimental group B):

[0113] In a high-salt environment, the hydrophobicity of the biofilm (contact angle 118°) blocked the penetration of chloride ions, reducing the diffusion coefficient by 74.4%.

[0114] XRD showed that the purity of calcium carbonate was >95%, and there was no chloride impurity phase (such as CaCl2), indicating that the metabolism of microorganisms was not inhibited by salt.

[0115] Dry-wet cycle durability (experimental group C):

[0116] After 10 cycles, the carrier sustained-release layer did not fall off (verified by SEM), and the biofilm was still intact and covered the cracks.

[0117] The compressive strength retention rate was >97%, which proved that the combination of the repair body and the matrix was stable.

[0118] 5. Long-term multiple repair ability verification

[0119] Method: The same test piece was repeatedly pre-cracked (0.3-0.5mm) and triggered repair, and the repair efficiency of each time was recorded.

[0120] Results:

[0121] Repair times Crack closure rate (%) Spore survival rate (%) Ultrasonic recovery rate (%) 1st time 92.5±3.2 88.7±4.1 97.3±1.8 3rd time 89.4±3.8 75.2±4.6 94.1±2.2 5th time 82.6±4.3 58.3±5.1 88.7±3.0

[0122] Conclusion:

[0123] The carrier can sustainably release spores for at least 5 times, and the repair efficiency of the 5th time still reaches 82.6% of the initial value.

[0124] The limiting factor is the depletion of nutrient substrate (EDX detects that the residual amount of urea in the carrier after the 5th repair is <5%).

[0125] 6. Engineering economic analysis

[0126] Cost comparison:

[0127] Item Traditional grouting repair Invention (counted as 5 times repair) Single repair cost (yuan / m 2 )]]> 320-400 150-180 (all) Construction time 2-3 days Automatic triggering (no need for intervention)

[0128] Advantages: The whole life cycle cost of the invention is reduced by more than 50%, which is especially suitable for unattended infrastructure (such as submarine tunnels).

[0129] 7. Experimental conclusion

[0130] The microbial concrete has significant advantages in adaptability to extreme environment and long-term durability:

[0131] The magnetic field activation system breaks through the low temperature limit (efficiency > 85% at 5℃);

[0132] The biological membrane-calcium carbonate synergistic repair can resist salt corrosion and dry-wet cycle;

[0133] The carrier design supports ≥5 times of effective repair, and the economy is better than that of the traditional method.

[0134] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" and the like means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction.

[0135] In the drawings of the embodiments disclosed in the present application, only the structures related to the embodiments of the present disclosure are involved, and other structures can be referred to the general design. In the case of no conflict, the same embodiment and different embodiments of the present application can be combined with each other.

[0136] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A self-repairing microbial concrete, characterized in that: It comprises the following components in parts by weight: 100 parts of Portland cement, 150-300 parts of aggregate with a particle size of 0.1-5mm, mixing water with a water-cement ratio of 0.3-0.5, and a concentration of ≥10 7 0.5-5 parts of Bacillus pasteurianus spores (CFU / g), 3-10 parts of calcium lactate, 2-8 parts of histidine-urea composite substrate, and 10-30 parts of a carrier material; The carrier material is porous zeolite particles coated with a pH-responsive polyacrylic acid sustained-release layer. The porous zeolite particles are modified with a silane coupling agent KH-550 and loaded with ferrosoferric oxide nanoparticles. The Bacillus pasteurianus spores, calcium lactate, and histidine-urea composite substrate are encapsulated in the pores of the porous zeolite particles by a vacuum impregnation method.

2. The self-repairing microbial concrete according to claim 1, characterized in that: The porous zeolite particles have a pore size of 10-50 μm and a porosity of 70%-90%.

3. The self-repairing microbial concrete according to claim 1, characterized in that: The mass ratio of histidine to urea in the histidine-urea composite substrate is 1:1-1:

3.

4. The self-repairing microbial concrete according to claim 1, characterized in that: The thickness of the polyacrylic acid sustained-release layer is 20-30 μm.

5. A method for preparing the self-repairing microbial concrete according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, treating the porous zeolite particles with a silane coupling agent KH-550 and then loading ferrosoferric oxide nanoparticles; S2, dissolving Bacillus pasteurianus spores, calcium lactate and histidine-urea composite substrate in a phosphate buffer solution at pH 7.4, and pouring them into the pores of the modified porous zeolite particles by vacuum impregnation; S3, forming a polyacrylic acid sustained-release layer with a thickness of 10-50 μm on the surface of the carrier loaded with the microorganism system; S4. Mix the carrier obtained in S3 with Portland cement and aggregate, add water according to a water-cement ratio of 0.3-0.5, stir, pour and cure.

6. The preparation method according to claim 5, characterized in that: The vacuum impregnation pressure in S2 is 0.08-0.1 MPa, and the impregnation time is 2-4 hours.

7. A crack self-repairing method based on the microbial concrete according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) When the width of the concrete crack reaches 0.05-1 mm, the ambient moisture penetrates into the carrier and dissolves the polyacrylic acid slow-release layer, releasing microbial spores; (2) applying an alternating magnetic field with a frequency of 50-100 kHz to the concrete for 10-30 minutes to raise the temperature inside the carrier to 35±2°C and activate spore germination; (3) Microbial metabolism produces carbonate ions, which react with calcium ions in the cracks to form calcium carbonate precipitation, and at the same time secrete a hydrophobic biofilm to fill the cracks; (4) The ultrasonic propagation velocity was tested using the ASTM C597 standard. The repair was considered complete when the recovery rate was ≥95% and the crack water seepage height was ≤0.5 mm.

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