Sectional repair material based on halophilic mucoid-forming bacteria

Abstract

Disclosed is a new eco-salt tolerant repair material for repairing concrete structures that have been exposed to a chemically degrading environment caused by salt damage (Cl ‑ ) in a marine environment, wherein the repair material does not include existing organic materials. The invention provides a material for repairing a concrete section in a salt-damaged environment, the concrete section repair material comprising a mixture of a salt-tolerant repair material and a carrier, wherein the salt-tolerant repair material comprises a binder including conventional Type I Portland cement and EVA-based polymer, polyethylene fibers, and fine aggregate, and the carrier has a porous structure on which bacteria for decomposing chloride ions and halophilic slime-forming bacteria are immobilized.

Description

[0001] Citations of relevant applications

[0002] This application claims priority to Korean Patent Application No. 10-2020-0150193, filed on November 11, 2020, the entire contents of which are incorporated herein by reference. Background Technology

[0003] This invention relates to materials for repairing concrete sections, and more specifically, to bacteria-based section repair materials.

[0004] This invention originates from research conducted through a research grant supported by the Building Technology Research Project of the Ministry of Land, Infrastructure and Transport.

[0005] [Project No.: 20SCIP-C158976-01, Research Project Title: Development of salt-damage-resistant ecological coating material for concrete based on halophilic bacteria slime]

[0006] The durability of concrete structures exposed to saline environments can be significantly reduced due to concrete deterioration and rebar corrosion. Specifically, materials that require rapid construction and quick healing are needed for the repair and reinforcement of structures responding to saline damage, such as those used in shipyards, breakwaters, and marine vegetation.

[0007] Organic materials (coatings) used to repair offshore structures deteriorated due to salt damage, such as those based on epoxides, vinyl esters, and acrylic rubbers, exhibit excellent bond strength to the initial concrete structure. However, they differ from concrete in terms of their coefficient of thermal expansion or deformation characteristics due to drying and shrinkage. Therefore, from a long-term perspective, organic materials have the disadvantage of the elastic film detaching at the concrete interface, and thus, salt resistance cannot be expected. Furthermore, when the surface treatment of the concrete substrate surface to be repaired is not fully performed, the bond strength to the concrete is significantly reduced, and the bond strength is shown to be significantly altered even by the moisture state of the underlying concrete.

[0008] Specifically, in the case of nearshore structures requiring repair, it is practically impossible to completely remove all fouling inevitably caused by pollutants and marine life present in seawater. Therefore, when constructing organic coatings, phenomena such as partial lifting and poor filling can easily lead to peeling and detachment. Furthermore, using organic materials in paint form, and applying coatings in three stages—outer coat, intermediate coat, and primer—with coatings of varying properties, makes the construction of organic materials difficult. Defects in any stage of the coating process severely impact overall performance, which is extremely detrimental to ensuring long-term durability. Additionally, organic coatings contain significant amounts of environmental pollutants and harmful substances, leading to strict regulations worldwide regarding the raw materials and production processes used. Therefore, environmentally friendly coating materials free of heavy metals and volatile organic compounds (VOCs) are being developed; however, this is due to the increased material and construction costs resulting from the use of advanced technologies.

[0009] Unlike organic materials, inorganic materials offer advantages in ensuring the integrity of offshore concrete structures being repaired when used for repair. However, without the addition of chemical additives such as desalination agents and concrete strengtheners, the repaired surface remains inevitably exposed to the deteriorating environment caused by salt damage. Furthermore, the use of inorganic materials to impart improved resistance to degradation within existing inorganic materials used for salt damage repair is somewhat limited, leading to increased economic losses due to common reconstruction efforts.

[0010] [Prior technology patent documents]

[0011] - Korean Patent No. 1779935 (September 13, 2017)

[0012] - Korean Patent Registration No. 1355392 (January 20, 2014) Summary of the Invention

[0013] This invention will provide an eco-friendly salt-tolerant remediation material that does not include existing organic materials as a means of remediating exposure to salt damage (Cl) in marine environments. - A new concept of materials for concrete structures in chemically degraded environments caused by chemical degradation.

[0014] To address the aforementioned problems, this invention provides a concrete cross-section repair material for saline environments, obtained by mixing the following: a salt-resistant repair material comprising a binder containing type I ordinary silicate cement (Portland cement) and an EVA-based polymer, polyethylene fibers, and sand; and a carrier having a porous structure on which chloride-decomposing bacteria and halophilic slime-forming bacteria are immobilized.

[0015] In addition, a concrete section repair material for saline environments is provided, wherein the saline-resistant repair material may comprise 90-95 wt% of Portland cement, 5-10 wt% of an EVA-based polymer, and 0.1-0.3 wt% of polyethylene fiber relative to 100 wt% of the repair material. The sand may be silica sand with an average particle size of 0.25-0.7 mm, and may have a sand-to-binder ratio (S / B) of 1.8-2.2 by weight, and a water-to-binder ratio (W / B) of 28-35 wt%.

[0016] In addition, a concrete section repair material for saline environments is provided, wherein the carrier may be expanded vermiculite, and chloride-decomposing bacteria and halophilic slime-forming bacteria can be immobilized under negative pressure conditions.

[0017] In addition, a concrete section repair material for saline environments is provided, wherein the chloride-decomposing bacteria is *Halomonas venusta*, and the halophilic slime-forming bacteria is *Sulfitobacter mediterraneus*.

[0018] According to the present invention, it is possible to provide an eco-friendly salt-tolerant remediation material for remediating exposure to chloride ions in chloride compounds, based on halophilic bacterial strains that decompose chloride ions in chloride compounds and a slime that protects concrete against salt damage in marine environments. - Materials that control the deterioration of concrete structures caused by the chemical degradation environment of salt damage to concrete.

[0019] Therefore, it improves the repair and durability of near-shore concrete and reinforced concrete structures, enhances the efficiency of structural maintenance and management through the ecological salt damage protection effect of halophilic slime-forming bacteria, and has the potential to reduce construction costs and shorten construction cycles by eliminating the need for moisture absorption inhibitors and repair processes such as primer application. Detailed Implementation

[0020] Preferred embodiments of the invention will be described in detail below with reference to the accompanying drawings. In describing the invention, detailed descriptions of well-known features will not be provided unless it is intended to obscure the subject matter. In the drawings, for clarity, parts not relevant to the description are omitted; similar reference numerals denote similar parts throughout the specification, and detailed configurations of the invention will be described based on the drawings. Furthermore, throughout the specification, when a part is described as "comprising" some components, it does not mean that other components are excluded, but rather that other elements may be further included unless specifically stated otherwise.

[0021] This invention discloses a concrete cross-section repair material in a salt-damaged environment for repairing concrete structures exposed to chemical degradation caused by salt damage and for controlling degradation caused by salt damage to concrete. The material comprises a salt-resistant repair material and a carrier having a porous structure on which bacteria are immobilized.

[0022] The salt-resistant repair material (referred to as "Herb-con C") is a mixture developed with consideration of bacterial growth, adhesive strength, etc., and includes a binder containing Portland cement and a polymer based on ethylene-vinyl acetate copolymer (EVA), polyethylene fibers, and sand.

[0023] The binder is preferably composed of 90-95 wt% of Type I ordinary Portland cement and 5-10 wt% of EVA-based polymer, and in this case, it is confirmed that the function of controlling the deterioration caused by salt damage to concrete is optimal.

[0024] Furthermore, the polyethylene fiber is a component added to give the salt-resistant repair material enhanced strength and rigidity, and polyethylene fiber materials with an average diameter of 50-200 μm, and preferably 100-50 μm, can be used.

[0025] The content of the polyethylene fiber is preferably 0.1-0.3 parts by volume relative to 100 parts by volume of the repair material, and in this case, it is confirmed that the function of enhancing the strength and rigidity of the repair material is most excellent in the state of improving the control of deterioration caused by salt damage to concrete.

[0026] As the sand, quartz sand with an average particle size of 0.25-0.7 mm is preferably used, and considering the implementation of the function of controlling the deterioration caused by salt damage to concrete, the sand content is preferably determined such that the sand-to-binder ratio (S / B) is 1.8-2.2 by weight. In this document, the water-to-binder ratio (W / B) is preferably 28-35 wt%.

[0027] In this invention, bacteria that can effectively protect concrete from salt damage in marine environments by being mixed with repair materials are selected as halophilic strains capable of decomposing chloride ions in chlorides.

[0028] The mechanism of salt damage to concrete lies in the penetration and diffusion of chloride ions into the concrete. - Chloride ions in concrete bond to Ca(OH)₂, a cement hydrate formed when concrete is exposed to seawater, to form CaCl₂. CaCl₂ is a soluble porous compound that dissolves in seawater, increasing the porosity of the concrete and thus reducing its durability (chlorination corrosion). The CaCl₂ compounds formed from chloride ions in seawater then react with monosulfates to form Friedel's salt and hydrated ferric chloride. When the pH decreases along with the carbonation of the concrete, Friedel's salt decomposes, increasing chloride ions in the concrete pores, which again accelerates the formation of CaCl₂ compounds, creating a severe salt corrosion mechanism. Furthermore, as chloride ions increase in the concrete pores, the reinforcing steel bonds to chlorides to produce FeCl₂, which reacts with water to create a corrosion-activated environment. The corrosion of the reinforcing steel leads to volume expansion, causing cracks and spalling in the concrete, thus drastically reducing its durability.

[0029] In this invention, for the various halophilic strains (marine microorganisms) shown in Table 1 below, it was examined whether the function of controlling the deterioration caused by salt damage could be effectively implemented, and thus it was confirmed that, for Halomonas venusta (an anaerobic halophilic bacterium with the ability to decompose chloride ions), the function of consuming Cl compounds (CaCl2 and FeCl2), which are factors leading to the deterioration and reduced durability of concrete caused by salt damage, by growing in a marine environment and releasing yeast capable of decomposing chloride ions.

[0030] [Table 1]

[0031]

[0032] The isolation process of the strain is as follows:

[0033] (1) Sample collection

[0034] Seawater and mussels were collected from the port of Wando, Gunnae-ri, Wando-eup, Wando-gun, and Jeollanam-do, and the collected samples were stored and transported in ice boxes.

[0035] (2) Conditions for microbial isolation and culture

[0036] The collected mussel shells and flesh were vortexed to desorb microorganisms. After collecting the microorganisms desorbed from the seawater and mussels onto filter paper through filtration, vortexing was performed to desorb the microorganisms from the filter paper, and then the microorganisms were sequentially diluted to 10 with a 3.5% NaCl solution. -4 The microorganisms were smeared onto a culture medium (50% seawater + 50% R2A agar (3.5% NaCl), pH 7.6) and incubated aerobically at 30°C for one week. Colonies appearing after incubation were purified and cultured according to their characteristic types. Each cultured microorganism was isolated and identified by 16S rDNA sequencing, thus confirming that the cultured microorganisms were those well-known in Table 1.

[0037] In addition, in this invention, bacteria capable of effectively forming halophilic slime on concrete surfaces are selected.

[0038] In this invention, for the various halophilic strains shown in Table 1, it was examined whether the formation of halophilic slime could be effectively carried out under conditions similar to marine environments. Thus, it was confirmed that, in the case of *Sulfitobacter mediterraneus*, a halophilic bacterium capable of growing in seawater with a salt concentration of about 3-5 wt%, the superior function of forming a viscous slime film on the concrete surface to act as a barrier against the penetration and diffusion of chloride ions in the concrete structure is achieved through growth and proliferation in the aforementioned environment.

[0039] The mucus film formed by bacteria creates a barrier film on the concrete surface that blocks the penetration and diffusion of chloride ions, thereby inhibiting the production of CaCl2 and FeCl2 compounds that affect the increase of porosity and the reduction of durability in concrete.

[0040] In this invention, chloride-decomposing bacteria and halophilic slime-forming bacteria are immobilized on a porous carrier (referred to as "healing bacteria"). + C”) on.

[0041] The chloride-decomposing bacteria and halophilic slime-forming bacterial substrate carrier includes bacteria discovered for the repair and durability improvement of concrete deteriorated by salt damage, and a culture solution for the growth and proliferation of said bacteria. This solution involves inoculation in a culture medium containing yeast extract, ferric citrate, etc., and then... 8 -10 10 A culture solution of halophilic bacteria and slime-forming bacteria capable of decomposing chlorine, cultured in an incubator at a concentration of 1 cell / mL at 5-50°C and preferably 30-40°C, is immobilized on a carrier with a porous structure having numerous pores. In this invention, considering the function of protecting concrete against salt damage in marine environments, expanded vermiculite has been identified as the most suitable material for this purpose.

[0042] In this study, an effective culture medium composition (based on up to 1 L of distilled water) for the growth and proliferation of *Halomonas venusta*, a chloride-decomposing bacterium, and *Sulfitobacter mediterraneus*, a halophilic slime-forming bacterium, can contain 3-7 g peptone, 0.5-1.5 g yeast extract, 0.05-0.2 g ferric citrate, 17-23 g sodium chloride, 3-9 g magnesium chloride, 2-5 g magnesium sulfate, 1-3 g calcium chloride, 0.3-1 g potassium chloride, 0.1-0.5 g sodium bicarbonate, 0.05-0.15 g potassium bromide, 20-50 mg strontium chloride, 15-30 mg boric acid, 2-6 mg sodium silicate, 1-5 mg sodium fluoride, 1-5 mg ammonium nitrate, and 5-15 mg disodium hydrogen phosphate.

[0043] The bacteria and their culture medium in expanded vermiculite, used for protection against salt damage, self-grow and proliferate on the surface of concrete structures exposed to salt-damaged environments (marine environments), acting as a protector against concrete degradation and erosion. The bacterial culture solution can be immobilized on the immobilization material by adsorption in a sterile negative pressure container under conditions of 10-30 Torr and 10-60 minutes. After immobilization, the expanded vermiculite contains not only bacterial cells but also a large amount of water and culture medium nutrients.

[0044] Depending on the amount of bacterial substrate carrier added, the mixture of the above-mentioned salt-resistant remediation material and the above-mentioned carrier with a porous structure and immobilized bacteria can exist in various ways, and in this case, the amount of added bacterial substrate carrier is preferably 10-35% relative to the aggregate volume in the remediation material. Table 2 below exemplarily shows the thickness when constructing a 1m... 2 When developing ecological salt-resistant concrete cross-section repair materials, the required quantities of salt-resistant repair materials and bacterial substrate carriers are specified.

[0045] [Table 2]

[0046]

[0047] Table 2, disregarding the construction method described below, shows the required amounts of salt-resistant remediation material and halophilic bacterial substrate carrier for constructing eco-friendly salt-resistant concrete cross-section remediation materials, indicated by thickness. The construction thickness (T) can range from 10 to 50 mm, and the amount of salt-resistant remediation material can be 10 to 65 kg / m² depending on the mixing ratio of the bacterial substrate carrier. 2 Furthermore, the amount of halophilic bacteria substrate carrier can be 0.4-7.0 kg / m³. 2 .

[0048] Eco-friendly salt-resistant concrete section repair materials can be constructed using machine spray placing, as exemplified below. When mixing the material, use a mixer, manual mixer, or similar method to mix for 3-5 minutes to ensure uniform mixing. In the first stage of spraying, to remove voids and improve adhesion to the substrate surface, a spray build-up is performed to achieve a thickness of up to 5 mm. A second stage of spraying is then performed to achieve a thickness within 90% of the designed thickness, including the thickness from the first stage. When leveling the surface after spray building, care must be taken when connecting build-up components, connecting parts with substrate surfaces, etc.

[0049] Specific embodiments of the invention will be described below.

[0050] Example

[0051] A binder comprising 92 wt% Portland cement and 8 wt% EVA-based polymer was prepared. Polyethylene fibers (average diameter 120 μm) were prepared at 0.2 parts by volume relative to 100 parts by volume of the total repair material. Quartz sand (average particle size 0.25-0.7 mm) was used as sand, resulting in a sand-to-binder ratio (S / B) of 2. The components were blended to achieve a water-to-binder ratio (W / B) of 28-35 wt% to produce a salt-resistant repair material.

[0052] In addition, *Halomonas venusta*, a chloride-decomposing bacterium, and *Sulfitobacter mediterraneus*, a halophilic slime-forming bacterium, were inoculated at the same concentration into a culture medium with the composition shown in Table 3 below, and then cultured in an incubator (30-40℃) for 7 days to achieve a concentration of 10. 9 Cells / mL. Subsequently, the bacterial culture solution was placed in an internally stirred sterile negative pressure container, and 10 parts by weight of expanded vermiculite relative to 100 parts by weight of the bacterial culture solution were immersed in the bacterial culture solution. The door was then closed, and the valve was adjusted to create a negative pressure environment of 10-30 Torr, and adsorption was performed for 30 minutes. The expanded vermiculite with immobilized bacteria was then collected.

[0053] Subsequently, relative to the aggregate volume of the resulting salt-resistant repair material, expanded vermiculite with immobilized bacteria was mixed in a mixer at a mixing ratio of 20% to produce the final concrete section repair material.

[0054] [Table 3]

[0055]

[0056] Test Implementation Examples

[0057] The performance of the concrete section repair materials produced above was evaluated according to various testing standards, and the results are shown in Table 4 below.

[0058] [Table 4]

[0059]

[0060]

[0061] Referring to Table 4, the performance of the eco-friendly salt-resistant concrete section repair material according to the present invention is 2.1 times or more higher than the required bond strength (1.0 MPa or above) and compressive strength (20 MPa) performance present in KS F 4042 (polymer cement mortar). Furthermore, with a neutralization depth of 0 mm and a length change rate of 0.04%, it meets the performance requirements of KS F 4042. Additionally, in the evaluation results of chloride diffusion coefficient according to NT BUILD 492, the evaluation result of the eco-friendly salt-resistant concrete section repair material according to the present invention is 90% lower than that of general repair materials, and according to KS F2711, the total current passing through the eco-friendly salt-resistant concrete section repair material is 88% lower than that of general repair materials. Therefore, the eco-friendly salt-resistant concrete section repair material shows significantly superior results in all evaluation items.

[0062] The preferred embodiments of the present invention described above have been disclosed to solve the technical problems. Those skilled in the art can make various modifications, changes, additions, etc., within the spirit and scope of the present invention, and such modifications and changes should be considered to fall within the scope of the appended claims.

Claims

1. A concrete section repair material in a salt damage environment, wherein the concrete section repair material is obtained by mixing: a salt damage resistant repair material including a binder containing a type I ordinary Portland cement and an EVA-based polymer, a polyethylene fiber, and sand; and a carrier having a porous structure and on which a chloride ion decomposing bacterium and a halophilic slime-forming bacterium are fixed, wherein the chloride ion decomposing bacterium is Halomonas aestuarii ( Halomonas venusta ), and the halophilic slime-forming bacterium is Sulfitobacter mediterranei ( Sulfitobacter mediterraneus ), the carrier being in an amount of 10-35% with respect to a volume of aggregates in the salt damage resistant repair material.​​​​ 2. The concrete section repair material for saline environments according to claim 1, wherein the saline-resistant repair material comprises 90-95 wt% of the Type I ordinary Portland cement, 5-10 wt% of the EVA-based polymer, and 0.1-0.3 wt% of the polyethylene fiber relative to 100 parts by volume of the repair material. The sand is quartz sand with an average particle size of 0.25-0.7 mm, and has a sand-to-binder ratio (S / B) of 1.8-2.2 by weight. The water to binder ratio (W / B) is 28-35 wt%.

3. The concrete section repair material in a saline environment according to claim 1, wherein the carrier is expanded vermiculite, and the chloride-decomposing bacteria and the halophilic slime-forming bacteria are immobilized under negative pressure conditions.

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