WO2022236998A1

WO2022236998A1 - Microbial self-repair agent having viscous product and application thereof

Info

Publication number: WO2022236998A1
Application number: PCT/CN2021/113377
Authority: WO
Inventors: 钱春香; 苏依林; 郑天文; 张旋
Original assignee: 东南大学
Priority date: 2021-05-08
Filing date: 2021-08-19
Publication date: 2022-11-17
Also published as: CN113149499A

Abstract

A microbial self-repair agent having a viscous product and an application thereof. The method can improve the viscosity of a repair product, thereby improving a repair effect. The microbial self-repair agent comprises a microbial preparation for producing flocculation substances and a sugar-containing substance. The application method comprises: adding a microbial self-repair agent into concrete, the added amount of the microbial self-repair agent for each cubic meter of the concrete being 3-20 kilograms. Compared with common microbial self-repair agents, the repair product induced by said method can be tightly packed to form a repair product having better cohesion and a larger size, thus improving the stability of repair product, reducing the loss of repair product, and improving the durability of concrete.

Description

A kind of microbial self-healing agent with sticky product and its application

technical field

The invention relates to the field of concrete materials, in particular to a microbial self-repairing material and its application.

Background technique

Concrete is an important building material with a wide range of applications. Due to the brittleness of concrete itself and the complex service environment, cracking of concrete is inevitable. If the cracks in concrete are not repaired in time, oxygen, moisture and corrosive media will gradually infiltrate from the surface defects of the material, causing more serious salt crystal expansion and steel corrosion expansion, and finally accelerating the deterioration of concrete. Traditional concrete repair methods, such as grouting and surface filling, need to consume a lot of manpower and material resources, and there are problems that cracks are not found in time and repairs are delayed.

At present, self-healing concrete technology has become one of the most concerned technologies for improving the durability of concrete in recent years. The use of microbial mineralization technology to repair cement-based materials has attracted much attention because of its environmental friendliness, non-toxicity and harmlessness. However, the repair products in the prior art are powdery and are easily washed away; and the germination and proliferation of microorganisms in the self-repairing concrete materials need a certain amount of time, and the dissolution of calcium and magnesium ions always exists during this process, and the dissolved Calcium and magnesium ions cannot be used to form repair products, and the repair effect is difficult to guarantee.

Contents of the invention

Purpose of the invention: one of the purposes of the present invention is to provide a sticky microbial self-healing agent, which has excellent repair effect and good stability; the second purpose of the present invention is to provide an application method of the microbial self-healing agent.

Technical solution: a sticky microbial self-healing agent according to the invention, including microbial bacterial agents that produce flocculation substances, sugar-containing substances, nitrogen sources and other additives.

Preferably, the mass ratio of the flocculation-producing microbial agent to the sugar-containing substance is 1:1-200. Excessively high sugar substances will easily affect the osmotic pressure of the microorganisms, causing the microorganisms to dehydrate and lose their vitality.

In the present invention, microorganisms that produce flocculation substances are used to form a more cohesive mineralization through the adsorption and bridging of the bacteria itself and secretions and the ability of flocculation and agglomeration under the condition of rich sugar (including monosaccharides, disaccharides and polysaccharides). Products; Microbial secretion products refer to biological macromolecules such as exopolysaccharides and polypeptides produced by fungi or bacteria in the process of growth and proliferation. These molecules contain active groups such as carboxyl groups, hydroxyl groups, and amino groups. The action of force, ionic bond and electrostatic attraction traps the positively charged ions in the repair process and quickly forms three-dimensional deposits.

Among them, the microorganisms producing flocculation substances are at least one of Bacillus colloidus, Bacillus subtilis and alkali-resistant yeast; sugar-containing substances can be at least one of monosaccharides, disaccharides and polysaccharides, and some agricultural products containing sugar It can also be used as a sugar-containing substance in self-healing agent components, such as corn flour, wheat flour, etc., to promote the production of microbial secretions.

Preferably, the self-healing agent also includes a nitrogen source, the mass ratio of the microbial agent to the nitrogen source is 1:0.1-0.5, and the nitrogen source is at least one of yeast extract, peptone and beef extract; excessive nitrogen source The ratio is not conducive to the granulation of the inner core, and it is difficult to add.

Preferably, the self-healing agent also includes an admixture, the mass ratio of the microbial agent to the admixture is 1:0.05-0.5, and the admixture is a calcium source composition and an oxygen supplement for providing calcium ions and dissolved oxygen. Wherein, the calcium source composition contains 20%-70% calcium peroxide, 30%-80% calcium nitrate and calcium carbonate.

Among them, adding nitrogen source and admixture to the microbial self-healing agent can promote the growth of microorganisms, increase the concentration of bacteria in the crack area, and increase the production of microbial flocculation substances.

That is: the formation of a large amount of microbial secretions requires carbon and nitrogen sources and a suitable ratio of carbon and nitrogen sources. The carbon source can be one or more mixtures of monosaccharides, disaccharides or polysaccharides such as glucose, starch, and fructose. The source can be one or more of yeast extract, peptone, and beef extract; some agricultural by-products or agricultural waste can also be used to promote the production of microbial secretions, such as corn flour, wheat flour, etc.

The present invention also provides the application mode of the microbial self-healing agent in concrete. The microbial self-healing agent is added to the concrete for self-healing of cracks, and the amount of the microbial self-healing agent added to each cubic meter of concrete is 3-20 kg.

Preferably, in order to avoid the impact of sugar-containing substances on concrete hydration and setting time, the microbial self-healing agent is prepared into a protective core-shell structure, and then added into the concrete, the microbial self-healing agent (microbial agent, containing Sugar substance, nitrogen source and additive) are prepared into an inner core by extrusion granulation, and then the inner core is wrapped with low-alkali cement or organic polymer coating.

Specific steps are as follows:

(1) The microbial self-healing agent is prepared into an inner core by extrusion granulation; the diameter of the inner core is 1-3mm, and the moisture content of the inner core is 10-30wt%;

(2) Use low-alkali cement or organic polymer coating to wrap the inner core to form microbial self-repairing particles with a core-shell structure; wherein, the mass ratio of the coating layer in the microbial self-repairing particles is ≤50wt%, this limitation is to limit The amount of low-alkali cement used as the outer protective shell, too much low-alkali cement will easily cause too little active ingredient (inner core) of the repair agent.

(3) Add the prepared microbial self-healing particles into concrete to perform self-healing of cracks.

Among them, the microbial strains used should be added in the form of spores or stem cells before adding to preserve activity.

Among them, the concrete added with microbial self-repairing particles is cured in a natural precipitation environment, a dry-wet cycle or a water-saturated environment, so the present invention greatly alleviates the water dependence of common microbial self-repairing agents in the repair process. Concrete repair can be achieved immediately under immersion water environment or wet-dry cycle environment is better.

Among them, the temperature in the process of repairing concrete cracks is preferably in the range of 15-40°C.

The process of microbial self-healing is to pre-mix carbonate-precipitating bacteria, nutrients and precipitation precursors into concrete; after cracks appear, the bacteria around the cracks are activated by moisture and oxygen, and precipitate biocalcite to heal the cracks. The significance of this repair agent is that the extracellular polymer secreted by microorganisms in the process of growth and germination can significantly absorb calcium and magnesium ions, so that the cations in the crack area will not be lost, and the repair effect will be improved; in addition, the organic matter secreted by microorganisms is beneficial With a large number of active groups, these molecular groups can make repair products more dense.

The principle of the invention: the present invention utilizes the adsorption bridging effect and flocculation and agglomeration ability of the microbial cells themselves and the secretions to form a mineralized product with more cohesive ability. The synergistic effect of microorganisms is manifested in the low-concentration stage of microorganisms, the secretions adsorb positively charged ions, and reduce the movement of cations out of the crack interval; tightly packed. Microbial secretion products are biomacromolecular substances such as exopolysaccharides and polypeptides produced by fungi or bacteria during the growth and proliferation process. These molecules contain active groups such as carboxyl, hydroxyl, and amino groups. The role of ionic bonds and electrostatic attraction captures positively charged ions during the repair process, quickly forming three-dimensional deposits, which can effectively reduce the dissolution of ions and the loss of repair products. The technical difficulty of the present invention is: since the adsorption and bridging ability and flocculation and aggregation of microbial secretion products are caused by soluble and insoluble extracellular polymers secreted by microorganisms, more extracellular polymers can still be secreted in an alkaline environment. The microorganism of the object is the core of the method, including at least one of Bacillus colloidus, Bacillus subtilis and alkali-resistant yeast.

Beneficial effect:

(1) The present invention can significantly improve the viscosity of microbial self-repairing concrete repair products, and then improve the repair effect; the present invention utilizes the adsorption bridging effect and flocculation and agglomeration ability of the microbial cells themselves and secretion products, and continuously absorbs calcium during the repair process ions, reduce the dissolution of calcium ions, and increase repair products. Compared with ordinary microbial self-repairing concrete, the repair products induced by this method can be closely packed to form repair products with better cohesiveness and larger size; the stability of the repair products is improved, the loss of repair products is reduced, and the durability of concrete is improved sex.

(2) Unlike previous microbial self-repairing concrete products, the microbial self-repairing concrete product provided by the present invention can form three-dimensional agglomerated repair products, which are organic-inorganic composite products, and the size of the agglomerated products can be greater than or equal to 1 mm.

(3) Unlike previous microbial self-repairing concrete products, the microbial self-repairing concrete products provided by the present invention have stronger cohesion, mainly by means of hydrogen bonds, van der Waals forces, ionic bonds and static electricity between biological macromolecules attraction.

(4) Different from the previous microbial self-repairing concrete, the microbial repairing agent provided by the present invention has the ability of microbial secretion to retain water, which greatly alleviates the water dependence problem of ordinary microbial self-repairing agents in the repairing process. That is, concrete repair can be realized.

Description of drawings

Fig. 1 is an optical microscope picture of the repair product with larger size and better viscosity induced by the method in Example 1.

Fig. 2 is the SEM picture of the repair product of embodiment 2 and comparative example 2; Wherein, figure (a), (b) is the picture of the repair product under different magnifications in embodiment 2, and figure (c) is in comparative example 2 Repair products formed by other microbial self-healing agents on the surface of concrete cracks.

Fig. 3 is an infrared analysis diagram of the repair product induced in Example 3, and the marked peaks are characteristic peaks of proteins and polysaccharides produced by microorganisms.

Fig. 4 is an X-ray tomographic analysis diagram of the repaired self-repairing concrete prepared by the present invention.

Figure 5 is a photo of microbial self-healing particles with a core-shell structure, using an organic protective outer layer.

Figure 6 shows the results of changes in ultrasonic propagation velocity and water penetration resistance of self-healing concrete after repair; Figure (a) shows the results of changes in ultrasonic propagation speed, and figure (b) shows the results of changes in water penetration resistance.

Detailed ways

The present invention will be further described in detail below in conjunction with the examples.

The microorganisms in the present invention are at least one of Bacillus colloidus, Bacillus subtilis and alkali-resistant yeast; the carbon source can be monosaccharides such as glucose, starch, fructose, one or more mixtures of disaccharides, polysaccharides and agricultural products ; The nitrogen source can be one or more of yeast extract and peptone. In order to prevent the sugar from affecting the concrete, the microbial self-healing agent is added in the form of a carrier. Specifically, the self-healing components (microbial agents, sugar-containing substances, nitrogen sources, and admixtures) are used to prepare internal granules by extrusion and granulation. The inner core has a water content of 10% to 30% by weight, and then wraps the inner core with low-alkali cement or organic polymer coating. In order to ensure the technical effect of this method, microorganisms should be added in the form of spores or dried cells. In the method, the mass ratio of microbial cells to nutrients is preferably between 1:1 and 200.

Example 1:

The microbial self-healing agent in this example contains 2 g of complex flora of yeast and Bacillus colloidus, and 20 g of glucose.

The microbial self-healing agent was continuously mineralized in a saturated calcium hydroxide solution for 3 days, and the microbial mineralization product was obtained by filtration, as shown in Figure 1, which is a picture of the repair product with a larger size and better viscosity induced by this embodiment , it can be seen that the repair products are closely agglomerated, the diameter of the product is greater than 1 mm, and the product presents a stable sheet, which is mainly due to the organic network formed by the complex flora of yeast and Bacillus colloidus and their secretions to absorb ions, The crystals formed by subsequent ion nucleation are also attracted by the organic network to form three-dimensional deposition.

The microbial remediation agent in this example has a strong mineralization ability. Compared with other microbial self-repair agents (see Comparative Example 2 for specific proportions), as shown in Figure 2(c), the repair product of Comparative Example 2 is mainly 50- Calcium carbonate particles with a size of 100 microns cannot form continuous and compact repair products.

Example 2:

The microbial self-healing agent in this embodiment contains 3 g of mixed flora of yeast and bacillus colloidus, 5 g of glucose and 1.5 g of yeast extract, and the microbial self-healing agent is added to the mortar in the form of carrier protection.

In this embodiment, 450g of cement, 1350g of sand, and 225g of tap water are used. During the stirring process, this repair agent is added, and the test piece is obtained by stirring and molding.

The specific steps are: firstly, the microbial self-healing agent is prepared into an inner core with a diameter of 2 mm by extrusion granulation, and the water content of the inner core is 20 wt %; then, the inner core is wrapped with low-alkali sulfoaluminate cement to form a Microbial self-healing granules with a shell structure; wherein, the mass proportion of the coating layer in the microbial self-healing granules is 50wt%; finally, the prepared microbial self-healing granules (carrier protection) are added to the mortar for self-healing of cracks.

Cracks were created after 7 days of standard curing, and the specimen was placed in an ambient temperature of 25°C for immersion and ventilation curing. The SEM pictures of the repaired products are shown in Figure 2(a) and Figure 2(b). SEM observation shows that in the concrete crack repair products formed by this repair agent, microorganisms act as nucleation sites, absorbing ions to nucleate, and yeast cells firmly consolidate the repair products together, and the formed products are tightly packed.

Example 3:

In this embodiment, 2 kg of mixed flora of yeast and Bacillus colloidus, 5 kg of sucrose and 1 kg of yeast extract are introduced into each cubic meter of C35P8 concrete in the form of carrier protection.

The specific steps are as follows: first, the microbial self-healing agent is prepared into an inner core with a diameter of 2 mm by extrusion granulation, and the water content of the inner core is 30 wt %; then, the inner core is wrapped with low-alkali sulfoaluminate cement to form a Microbial self-healing granules with a shell structure; wherein, the coating layer in the microbial self-healing granules is 8kg; finally, the prepared microbial self-healing granules (carrier protection) are added to the mortar for self-healing of cracks.

Add the self-healing agent with a dosage of 16kg into 1 cubic meter of concrete by loading, and add it when mixing the concrete. After cracking, carry out maintenance in natural state for 28 days (wherein the number of rainy days is 9 days), the infrared analysis of the repair product at the crack place is as shown in Figure 3, and the marked peaks are the characteristic peaks of protein and polysaccharide produced by microorganisms. There are obvious biological macromolecules secreted by microorganisms in the product, and the infrared absorption peak at 1650 cm ^-1 corresponds to the polypeptide (carbonyl) in the microorganism secretion.

Example 4:

The microbial self-healing agent of this embodiment is suitable for normal temperature environments, specifically, 3kg of mixed flora of yeast and Bacillus colloidus, 4kg of corn flour and 1.5kg of yeast extract are added to each cubic meter of concrete, and the admixture is 0.5kg .

The specific steps are: firstly, the microbial self-healing agent is prepared into an inner core with a diameter of 3 mm by extrusion granulation, and the water content of the inner core is 25 wt %; then, the inner core is wrapped with low-alkali sulfoaluminate cement to form a Microbial self-healing particles with a shell structure; wherein, particles with core-shell protection are prepared, and low-alkali cement is used to make the outer coating layer (47.06% by mass).

Add 17kg of self-healing agent to 1 cubic meter of C35P8 concrete while stirring, and replace the sand with equal mass. The specific ratio is shown in Table 1 below.

Table 1, C35P8 concrete mix ratio

Concrete was prepared at room temperature, and 0.5 mm wide cracks were introduced on the surface. The specimen was placed at room temperature for dry-wet cycle curing. After 28 days of curing, X-ray tomography was used to observe the repair of the cracks. Attached Figure 4 is the selected area The three-dimensional analysis diagram shows the distribution of repair products in the fracture interval. It can be seen that the maximum repair depth has reached 2.5 cm. This method helps to retain the repair products in the fracture interval and improve the repair effect.

Example 5:

The microbial self-healing agent of this embodiment is suitable for normal temperature environment. Specifically, in each cubic meter of concrete, 4 kg of mixed flora of yeast and colloidal bacillus, 5 kg of corn flour, 2 kg of yeast extract, and 1 kg of admixture are added.

The specific steps are as follows: first, the microbial self-healing agent is prepared into an inner core with a diameter of 3mm by extrusion granulation, and the inner core has a moisture content of 25wt%; then, resin is used to wrap the inner core to form a microbial self-healing agent with a core-shell structure Particles; wherein, prepared as particles with core-shell protection, low-alkali cement is used to make the outer cladding layer (the mass proportion of the cladding layer is 7.7%). The particles prepared with core-shell protection are shown in Figure 5.

Add 13kg of the prepared self-healing agent into 1 cubic meter of C35P8 concrete while stirring, and replace the sand with equal mass.

Comparative example 1:

This comparative example is an ordinary concrete component, that is, the same concrete proportion as that of Example 5 is used, but no microbial restoration agent is introduced.

Comparative example 2:

In this comparative example, other microbial self-repairing agents were used, 3 kg of alkalophilic bacillus powder and 5 kg of calcium lactate were added to the concrete member of the conventional repairing agent.

The specific proportions of the above-mentioned embodiment 5 and comparative examples 1 and 2 can be seen in the following table 2.

The concrete mix proportion of table 2, embodiment 5 and comparative examples 1,2

Prepare contrast concrete at the same time, compare Example 5 with Comparative Examples 1 and 2, prepare concrete at 25 ° C, introduce 0.5 mm wide cracks on the surface, and place the test piece at an ambient temperature of 25 ° C for water immersion and ventilation Curing, after 28 days of curing, the ultrasonic sound velocity and permeability coefficient of the specimen with cracks were measured, and the results are shown in Figure 6.

It can be seen that the supersonic sound velocity of the ordinary concrete in Comparative Example 1 basically did not increase, indicating that the compactness of the crack interval did not increase significantly; at the same time, the ultrasonic sound velocity of the microbial self-repairing agent in Comparative Example 2 was only about 2.2km/s. Combined with the water seepage test, Show that the microbial self-healing agent of comparative example 2 is limited to the repair of crack; And after mixing the self-healing agent provided by the present invention, the supersonic sound velocity in the crack area returns to more than 3.0km/s; The water penetration pressure in the crack area reaches 0.02MPa, the method Cracked areas are better filled.

Therefore, the present invention provides a microbial self-repairing agent with sticky products. When the method is applied to concrete, the stickiness of the repaired product can be significantly improved, thereby improving the repairing effect. The method utilizes the adsorption bridging effect and flocculation and agglomeration ability of the microbial cell itself and the secreted product, continuously adsorbs calcium ions during the repair process, reduces the dissolution of calcium ions, and increases repair products. The secreted products of microorganisms refer to biological macromolecules such as exopolysaccharides and polypeptides produced by fungi or bacteria during the growth and proliferation process; , ionic bonds and electrostatic attraction, capture the positively charged ions in the repair process, and quickly form three-dimensional agglomerated deposits. Compared with ordinary microbial self-healing agents, the repair products induced by this method can be tightly packed to form repair products with better cohesiveness and larger size; the stability of the repair products is improved, the loss of repair products is reduced, and the durability of concrete is improved sex.

Claims

A microbial self-healing agent with viscous products is characterized in that the self-healing agent includes a microbial agent that produces flocculation substances and sugar-containing substances.
The microbial self-healing agent according to claim 1, characterized in that the mass ratio of the microorganisms producing flocculation substances to the sugar-containing substances is 1:1-200.
The microbial self-healing agent according to claim 1, characterized in that: the microorganisms producing flocculation substances are at least one of Bacillus colloidus, Bacillus subtilis and alkali-resistant yeast; sugar-containing substances are monosaccharides, disaccharides and at least one of polysaccharides.
The microbial self-healing agent according to claim 1, characterized in that: the self-healing agent also includes a nitrogen source, the mass ratio of the microbial agent to the nitrogen source is 1:0.1-0.5, and the nitrogen source is yeast extract, peptone At least one of Wagyu beef paste.
The microbial self-healing agent according to claim 1, characterized in that: the self-healing agent also includes an admixture, the mass ratio of the microbial bacterium agent to the admixture is 1:0.05～0.5, and the admixture is a calcium source combination agent and Oxygen Supplement.
An application of the microbial self-healing agent described in any one of claims 1 to 5 in concrete.
The application according to claim 6, characterized in that: the microbial self-healing agent is added to the concrete for self-repairing of cracks, and the amount of the microbial self-healing agent in each cubic meter of concrete is 3-20 kg.
The application according to claim 6, characterized in that it comprises the following steps:

(1) The microbial self-healing agent is prepared into an inner core by extrusion granulation;

(2) Use low-alkali cement or organic polymer coating to wrap the inner core to form microbial self-repairing particles with core-shell structure;

(3) Add the prepared microbial self-healing particles into concrete, and perform self-healing of cracks after cracks appear in the concrete.
The application according to claim 6, characterized in that: the diameter of the inner core is 1-3mm, and the water content of the inner core is 10-30wt%; in the microbial self-repairing particles, the mass proportion of the cladding layer is ≤50wt%.
The application according to claim 8, characterized in that in step (3), the restoration process is maintained in a natural precipitation environment, a dry-wet cycle or a water-saturated environment.