Concrete rapid repair material based on microbial mineralization and preparation method and application thereof

Abstract

The present invention discloses a rapid concrete repair material based on microbial mineralization, as well as its preparation method and application. The method utilizes hydrophobically modified porous particles as carriers, and microbial bacteria with mineralization behavior, nutrients, and a calcium source are impregnated into the pores of the porous particles through vacuum impregnation. The particle pores are appropriately sealed with water-based epoxy, and then encapsulated with metakaolin and sodium silicate. Finally, the material is composited with fiber composite mortar to form a rapid concrete repair material. The rapid concrete repair material of the present invention has the advantages of strong interface bonding, environmental friendliness, light weight, excellent surface density enhancement effect, and crack self-repair, and can be applied to repair defective concrete surfaces.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete repair materials, and relates to a quick concrete repair material based on microbial mineralization, and a preparation method and application thereof. Background Art

[0002] Deterioration and damage of concrete materials are extremely common, which poses a huge safety hazard to structural engineering. Therefore, fast and high-performance repairs are of great significance to extending their service life. At present, crack repair materials and defect repair materials based on microorganisms generally have the following deficiencies: (1) The microorganisms are not active enough in the high alkaline environment of concrete, resulting in low mineralization repair efficiency ([1] Zhu Fuhao. Experimental study on the acclimation of Bacillus pasteurianus and the solidification of aeolian sand in a high pH environment of steel slag [D]. Xinjiang Agricultural University, 2023. DOI: 10.27431 / d.cnki.gxnyu.2023.000127; [2] Cheng Wenfeng. Research on the performance of microcapsule-embedded microorganisms in the self-repair of concrete cracks [D]. Shenzhen University, 2016; [3] Lai Xiaoying. Research on the effect of coral reef-immobilized microorganisms in the self-repair of concrete cracks [D]. Zhejiang Ocean University, 2022. DOI: 10.27747 / d.cnki.gzjhy.2022.000267.); (2) Although the porous particle immobilization method is used, Although it can effectively guarantee the activity of microorganisms, it also causes the mineralization products to accumulate inside the porous particles and cannot diffuse to play the role of mineralization repair ([4] Wei Shuangni, Wang Yinghui, Lai Junxiang, et al. Research progress of microbial self-repairing concrete [J]. Bulletin of the Chinese Ceramic Society, 2024, 43(08): 2737-2747+2757. DOI: 10.16552 / j.cnki.issn1001-1625.2024.08.001; [5] Hou Fuxing, Bai Yiming, Shen Di, et al. Research progress of carrier materials for microbial self-repairing concrete [J]. Materials Review, 2024, 38(13): 84-98; [6] Zhou Mengjun, Zhang Jiaguang, Li Zhu, et al. Experimental study on the compressive strength of crack self-repairing concrete based on microbial mineralization deposition [J]. Concrete, 2018, (03): 35-39; [7] Wiktor, V. and Jonkers, HM, 2011. Quantification of crack-healing in novel bacteria-based self-healing concrete. Cement and concretecomposites, 33(7), pp.763-770.). Summary of the Invention

[0003] The present invention aims to provide a microbial mineralization-based rapid concrete repair material, its preparation method, and its application. This material offers advantages such as strong interfacial bonding, environmental friendliness, lightweight, excellent surface densification, and crack self-repair. It is in powder form and converts into a viscous fluid upon addition of water, which can be applied to repair concrete defects.

[0004] The technical solutions for achieving the purpose of the present invention are as follows:

[0005] A rapid concrete repair material based on microbial mineralization comprises porous particles encapsulating and immobilizing microorganisms and a fiber composite mortar; the porous particles encapsulating and immobilizing microorganisms are prepared by the following steps:

[0006] (1) Hydrophobic modification of porous particles: ultrafine porous particles are added to water and mixed and stirred, and a mixed solution containing a hydrophobic modifier and sodium hydroxide is added under heating conditions, and the particles are modified under stirring. After the modification is completed, the particles are filtered, washed, and dried to obtain hydrophobically modified porous particles;

[0007] (2) Preparation of microbial solution: After the microorganisms are expanded and cultured, the bacterial sludge is obtained by centrifugation. The bacterial sludge is diluted to an OD600 value of 0.8, and then a water-based epoxy emulsion and a curing agent are added to obtain a microbial solution;

[0008] (3) Immobilizing microorganisms: adding hydrophobically modified porous particles to a microbial solution, evacuating the solution, and performing vacuum impregnation to allow the microbial solution to penetrate into the pores of the porous particles. After complete impregnation, filtering and drying are performed to obtain porous particles immobilizing microorganisms;

[0009] (4) Impregnation of nutrients and calcium sources: adding the porous particles carrying microorganisms to the nutrient solution containing the calcium source, evacuating the solution, and performing vacuum impregnation. After the impregnation is complete, filtering and drying are performed to obtain the porous particles carrying microorganisms impregnated with nutrients and calcium sources;

[0010] (5) Encapsulation: After mixing metakaolin and sodium silicate in a mass ratio of 1:1, add an equal mass of water and stir evenly to form a slurry. Then, place the porous particles immobilized with microorganisms after being impregnated with nutrients and calcium sources in the slurry for complete adsorption. After natural curing, dry to a constant weight to obtain porous particles encapsulating the immobilized microorganisms.

[0011] Furthermore, in step (1), the ultrafine porous particles are selected from coral reef sand, ceramsite, expanded perlite, etc., with a fineness of 0.5 μm to 200 μm, and the fineness is normally distributed; the hydrophobic modifier is selected from fatty acids, stearic acid, oleic acid, etc.

[0012] Furthermore, in step (1), in the mixed solution containing the hydrophobic modifier and sodium hydroxide, the concentration of the hydrophobic modifier is 2.5% to 8%, and the concentration of the sodium hydroxide is 2% to 10%.

[0013] Furthermore, in step (1), the heating temperature is 60-80° C., and the modification time is more than 0.5 h.

[0014] Furthermore, in step (2), the microorganism is a microbial bacterium with mineralization behavior, and is selected from two or more of Bacillus pasteurianus, Bacillus cohnii and Bacillus subtilis.

[0015] Furthermore, in step (3) or (4), the pressure is evacuated to -0.07 MPa.

[0016] Furthermore, in step (4), the nutrients in the nutrient solution are yeast extract and glucose, and the calcium source is selected from calcium lactate, calcium chloride, etc.

[0017] Furthermore, in step (5), the adsorption time is 2 hours, the natural curing time is 24 hours, and the drying temperature is 45°C.

[0018] Furthermore, the fiber composite mortar is composed of cementitious material, fine aggregate, water reducer, fiber, water-based epoxy and water, wherein the water-cement ratio is 0.35, the mortar-sand ratio is 1:0.7, the mass ratio of cementitious material and porous particles encapsulating and immobilizing microorganisms is 1:1.3, the dosage of water reducer is 1.8%, the dosage of fiber is 0.4%, and the dosage of water-based epoxy is 4%.

[0019] The fine aggregate described in the present invention is the fine aggregate conventionally used in mortar. Further, the fine aggregate is standard sand.

[0020] The cementitious material of the present invention is a cementitious material commonly used in mortar. Further, the cementitious material is a low-alkalinity, fast-hardening cement such as magnesium phosphate cement or sulphoaluminate cement.

[0021] The fiber of the present invention is a fiber commonly used in fiber composite mortar. Further, the fiber is selected from polypropylene fiber, polyethylene fiber, glass fiber or polyvinyl alcohol (PVA) fiber.

[0022] The water reducing agent of the present invention is a water reducing agent commonly used in mortar. Further, the water reducing agent is selected from polycarboxylate water reducing agent.

[0023] The method for preparing the above-mentioned rapid concrete repair material based on microbial mineralization comprises the following steps:

[0024] Cementitious materials, fine aggregate, water reducing agent, fiber, water-based epoxy and porous particles encapsulating immobilized microorganisms are stirred until uniformly mixed, the hydrophobic layer on the surface of the porous particles is ground off, and then water is added and stirred until uniformly mixed to prepare a concrete rapid repair material.

[0025] The present invention also provides application of the above-mentioned concrete rapid repair material in rapid repair of buildings.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] The present invention utilizes porous particles immobilized with microorganisms and fiber composite mortar to form a concrete rapid repair material, wherein the porous particles immobilized with microorganisms are subjected to hydrophobic treatment, which has the following effects: (1) in actual application, since the porous particles are hydrophobic inside, the microbial mineralization products tend to diffuse to the hydrophilic environment outside the particles, and the particle immobilization will not restrict the mineralization repair and densification effect; (2) the stability of the particle immobilization environment is increased, the activity of microorganisms is enhanced, the pores at the interface of new and old concrete are compacted, and a long-term crack self-healing effect is achieved; (3) the hydrophobicity of the concrete surface is increased to a certain extent, thereby improving its erosion resistance. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is described in detail below through the preferred embodiments of the present invention, but the following embodiments do not limit the scope of protection of the present invention.

[0029] The present invention uses hydrophobically modified porous particles as carriers, and impregnates microbial bacteria with mineralization behavior, nutrients and calcium sources into the pores of the porous particles through vacuum impregnation. The particle pores are properly sealed with water-based epoxy, and the adhesion between the particles and the cement matrix is ​​increased. The particles are then encapsulated with metakaolin and sodium silicate, and finally compounded with fiber composite mortar to form a concrete rapid repair material.

[0030] Example 1

[0031] (1) 30 g of coral reef sand powder and 120 mL of water (mass-to-volume ratio of 1:4) were mixed and stirred, and the temperature was kept constant at 80 °C in a water bath. A mixture of 0.5 g / mL stearic acid and 30 g / mL sodium hydroxide was added, and the mixture was stirred for half an hour. The mixture was filtered and washed three times, and dried to obtain hydrophobically treated coral reef sand powder.

[0032] (2) 3.0 g beef extract, 10.0 g peptone, 20 g urea, 5.0 g sodium chloride, and 1 L water were mixed and stirred uniformly, and the pH was adjusted to 7 with 1 mol / L sodium hydroxide solution. The mixture was sterilized by high-pressure steam sterilization to obtain a sterile culture solution. Bacillus pasteurianus and Bacillus cohnii were inoculated into the cooled culture solution for expansion culture. The cultured bacteria were encapsulated in a centrifugal test tube and centrifuged to obtain a bacterial slurry. The bacterial slurry was diluted with water to an OD600 value of 0.8, and then a water-based epoxy emulsion and 10% curing agent were added at a mass ratio of 1:1 to obtain a microbial solution.

[0033] (3) Pour the hydrophobically treated coral reef sand powder into the above-mentioned microbial solution, evacuate under a -0.07 MPa environment, and vacuum impregnate for 5 hours to allow it to penetrate into the pores of the coral reef sand. After filtering, place it in an environment at 35°C and dry it to constant weight.

[0034] (4) 40 g yeast extract, 40 g calcium lactate, 80 g glucose and 1 L water were mixed and stirred to prepare a nutrient solution. The coral reef sand powder dried in (3) was immersed in the nutrient solution under a vacuum environment of -0.07 MPa for 5 h, taken out and placed in an environment of 40°C to dry to constant weight.

[0035] (5) Mix metakaolin and sodium silicate in a mass ratio of 1:1, add an equal mass of water, stir evenly to form a slurry, place the dried coral reef sand powder in (4) in the slurry for adsorption for 2 hours, and then naturally cure for 24 hours and dry in an environment of 45°C to constant weight.

[0036] (6) The cementitious material, fine aggregate, water reducer, fiber, water-based epoxy and the dried coral reef sand powder in (5) were stirred for 30 minutes, the hydrophobic layer on the surface of the coral reef sand powder was ground off, and then water was added and stirred until the mixture was uniform to prepare a concrete quick repair material. The cementitious material was sulfoaluminate cement, the fine aggregate was standard sand, the water reducer was a standard polycarboxylate water reducer, and the fiber was polyvinyl alcohol fiber. The water-cement ratio was 0.35, the cement-sand ratio was 1:0.7, the mass ratio of the cementitious material to the dried coral reef sand powder in (5) was 1:1.3, the water reducer and fiber content were 1.8% and 0.4% respectively, and the water-based epoxy content was 4%.

[0037] Comparative Example 1

[0038] This comparative example is substantially the same as Example 1, except that the mass ratio of the cementitious material to the dried coral reef sand powder in (5) is 1:1, and the cementitious material to sand ratio is 1:1.

[0039] Comparative Example 2

[0040] This comparative example is substantially the same as Example 1, except that the coral reef sand is not subjected to hydrophobic treatment.

[0041] Comparative Example 3

[0042] Pure sulphoaluminate cement fiber composite mortar was used as a blank control group, and the water-binder ratio, mortar-sand ratio, water-reducing agent and fiber content, and waterborne epoxy content were the same as those in Example 1.

[0043] The concrete repair materials prepared in the examples and comparative examples were tested for their effectiveness through strength tests, pore structure tests, and new-to-old concrete bonding strength tests. The results are shown in Table 1.

[0044] Table 1

[0045] 3-point bending strength / MPa Porosity / % Bond strength of new and old concrete / MPa Example 1 9.2 11.0 7.1 Comparative Example 1 7.6 13.9 5.8 Comparative Example 2 7.5 16.6 5.2 Comparative Example 3 8.1 14.1 6.1

[0046] By comparing Example 1 and Comparative Example 1, it was found that reducing the amount of coral reef sand that immobilizes microorganisms will reduce the overall mechanical properties of the repair material, including the bending strength of the repair material itself and the bonding strength between new and old concrete, as well as the porosity. This shows that the addition of coral reef sand that immobilizes microorganisms plays an important role in compacting pores and improving mechanical properties.

[0047] By comparing Example 1 and Comparative Example 3, it was found that if the coral reef sand was not hydrophobically treated, the porosity, flexural strength and bonding strength of the new and old concrete of the repair material would decrease. This was attributed to the fact that the mineralized products of microorganisms immobilized in the coral reef sand were difficult to diffuse to the outside, resulting in almost no effect.

[0048] Comparison of Example 1 and Comparative Example 4 revealed that the addition of the microorganism-loaded coral reef sand increased the inherent strength and repair performance of the repair material, indicating that the microbial mineralization-based rapid concrete repair material of the present invention has application potential in the field of rapid building repair.

Claims

1. A rapid concrete repair material based on microbial mineralization, characterized in that: The method comprises porous particles encapsulating and immobilizing microorganisms and a fiber composite mortar; the porous particles encapsulating and immobilizing microorganisms are prepared by the following steps: (1) Hydrophobic modification of porous particles: ultrafine porous particles are added to water and mixed and stirred, and a mixed solution containing a hydrophobic modifier and sodium hydroxide is added under heating conditions, and the particles are modified under stirring. After the modification is completed, the particles are filtered, washed, and dried to obtain hydrophobically modified porous particles. (2) Preparation of microbial solution: After the microorganisms are expanded and cultured, the bacterial sludge is obtained by centrifugation. The bacterial sludge is diluted to an OD600 value of 0.8, and then a water-based epoxy resin emulsion and a curing agent are added to obtain a microbial solution; (3) Immobilizing microorganisms: Add hydrophobically modified porous particles to the microbial solution, evacuate, and perform vacuum impregnation to allow the microbial solution to penetrate into the pores of the porous particles. After complete impregnation, filter and dry to obtain porous particles that immobilize microorganisms. (4) Impregnation of nutrients and calcium sources: Add the porous particles carrying microorganisms to the nutrient solution with calcium source added, evacuate, and perform vacuum impregnation. After the impregnation is complete, filter, and dry to obtain the porous particles carrying microorganisms impregnated with nutrients and calcium source. (5) Encapsulation: Mix kaolin and sodium silicate in a mass ratio of 1:1, add an equal mass of water, stir evenly to form a slurry, place the porous particles of immobilized microorganisms after impregnation of nutrients and calcium sources in the slurry for complete adsorption, dry to constant weight after natural curing, and obtain porous particles encapsulating immobilized microorganisms.

2. The concrete rapid repair material according to claim 1, characterized in that: In step (1), the ultrafine porous particles are selected from one or more of coral reef sand, ceramsite and expanded perlite, with a fineness of 0.5 μm to 200 μm and a normal distribution; the hydrophobic modifier is selected from fatty acid, stearic acid or oleic acid; in the mixed solution containing the hydrophobic modifier and sodium hydroxide, the concentration of the hydrophobic modifier is 2.5% to 8%, and the concentration of the sodium hydroxide is 2% to 10%; the heating temperature is 60 to 80°C, and the modification time is more than 0.5 h.

3. The concrete rapid repair material according to claim 1, characterized in that: In step (2), the microorganisms are selected from two or more of Bacillus pasteurianus, Bacillus cohnii and Bacillus subtilis.

4. The concrete rapid repair material according to claim 1, characterized in that: In step (3) or (4), the pressure is evacuated to -0.07 MPa.

5. The concrete rapid repair material according to claim 1, characterized in that: In step (4), the nutrients in the nutrient solution are yeast extract and glucose, and the calcium source is selected from calcium lactate or calcium chloride.

6. The concrete rapid repair material according to claim 1, characterized in that: In step (5), the adsorption time is 2 h, the natural curing time is 24 h, and the drying temperature is 45 °C.

7. The concrete rapid repair material according to claim 1, characterized in that: The fiber composite mortar is composed of cementitious material, fine aggregate, water reducer, fiber, water-based epoxy resin and water, wherein the water-cement ratio is 0.35, the mortar-sand ratio is 1:0.7, the mass ratio of cementitious material and porous particles encapsulating and immobilizing microorganisms is 1:1.3, the dosage of water reducer is 1.8%, the dosage of fiber is 0.4%, and the dosage of water-based epoxy resin is 4%.

8. The concrete rapid repair material according to claim 7, characterized in that: The fine aggregate is standard sand, the cementitious material is magnesium phosphate cement or sulphoaluminate cement, the fiber is selected from polypropylene fiber, polyethylene fiber, glass fiber or polyvinyl alcohol fiber, and the water reducer is selected from polycarboxylate water reducer.

9. The method for preparing a rapid concrete repair material according to claim 7, characterized in that: The following steps are involved: Cementitious materials, fine aggregate, water reducing agent, fiber, water-based epoxy resin and porous particles encapsulating immobilized microorganisms are stirred until uniformly mixed, the hydrophobic layer on the surface of the porous particles is ground off, and then water is added and stirred until uniformly mixed to prepare a concrete rapid repair material.

10. Use of the concrete rapid repair material according to claim 1 in rapid repair of buildings.