Self-healing mortar: a bacterial-based solution

Abstract

The invention described herein pertains to a novel biological healing agent specifically formulated for use in mortar, aiming to enhance the longevity and durability of construction materials. Tradicional mortar and concrete structures are susceptible to cracking and degradation over time. This inventions seeks to address these problems by integrating a bacterial-based solution comprising Proteus mirabilis and an organic calcium source that promotes self-healing when cracks occur.

Description

[0001] Self-Healing Mortar: A Bacterial-Based Solution

[0002] Field of the Invention

[0003] The present invention relates to the field of construction materials, specifically focusing on a bacterial-based self-healing solution designed for mortar applications. It addresses the need for enhanced durability and longevity in mortar structures by utilizing biological agents capable of autonomously repairing cracks and degradation. This innovative approach leverages the properties of specific bacterial strains, such as Proteous mirabilis, combined with organic compounds to create a healing agent that is effective in tropical environments. The invention aims to improve the performance of mortar in various construction settings, ultimately contributing to more sustainable and resilient building practices.

[0004] Prior Art

[0005] The field of self-healing materials has garnered considerable attention in recent years, leading to various innovative approaches aimed at enhancing the durability of construction materials such as concrete and mortar. Several patents have been filed in this domain, showcasing diverse methodologies for incorporating healing agents.

[0006] WO 2009 / 093898 A1 - This patent discusses the utilization of healing agents in cement-based materials, specifically highlighting the use of organic compounds and bacteria-loaded porous particles. The emphasis is on nano-scale loading particles, which, while effective, can be challenging to source and apply in practical settings. The patent suggests that this solution is particularly beneficial in scenarios where cracks are visible and problematic.

[0007] US 2016 / 0226704 A1 - This invention focuses on a self-healing concrete that employs encapsulated healing agents, including bacteria and nutrient solutions, which are released upon crack formation. While the encapsulation method is effective, it may not address the specific needs of mortar applications, especially in tropical climates where moisture and temperature variations can affect performance. US 2017 / 0115477 A1 - This patent presents a self-healing concrete composition that includes microcapsules containing healing agents, such as calcium carbonate, which precipitate to fill cracks. While similar in concept to the current invention, it relies on microencapsulation, which can complicate the production process and may not be as effective in high-pH environments typical of mortar applications.

[0008] EP 3053515 A1 - This patent describes a method for producing self-healing concrete using specific bacterial strains that produce calcite upon metabolic activity. While this approach is promising, it primarily focuses on concrete and does not specifically address the unique requirements and formulations necessary for mortar.

[0009] US 2019 / 0230562 A1 - This invention involves a healing agent that utilizes various microorganisms to promote the healing of cracks in concrete and mortar. The focus is on the metabolic processes of these microorganisms; however, the specificity of bacterial strains and their adaptability to different environmental conditions, particularly in tropical regions, is not thoroughly explored.

[0010] The invention distinguishes itself by utilizing indigenous strains of Proteous mirabilis, specifically adapted for tropical environments, combined with a direct mixing method that simplifies application and enhances efficiency in mortar settings (Breugel, 2007). This focus on local strains and functional formulations seeks to overcome the limitations found in existing patents, offering a more sustainable and effective solution for the self-healing of mortar in construction applications (Zhong and Yao, 2008).

[0011] Description

[0012] The invention described herein pertains to a novel biological healing agent specifically formulated for use in mortar, aiming to enhance the longevity and durability of construction materials. Traditional mortar and concrete structures are susceptible to cracking and degradation over time, leading to significant maintenance challenges and structural integrity issues. This invention seeks to address these problems by integrating a bacterial-based solution that actively promotes self-healing when cracks occur. The healing agent comprises a water-based organic compound, which serves as a mixing solution, into which Proteous mirabilis bacteria are incorporated. These bacteria were isolated from samples collected from tropical river environments and subjected to rigorous laboratory procedures to ensure their efficacy and purity. The use of these indigenous strains is particularly advantageous, as they are adapted to thrive in tropical climates, making the solution highly applicable for construction in such regions (Balazs, 2007).

[0013] In addition to the bacterial component, the healing agent includes a chemical biomineral precursor compound, specifically calcium formatted, which facilitates mineral formation during the healing process. The mixture is designed to function optimally within a mortar composition having a cement-to-water ratio of 4:1 , and it operates effectively in a pH range of 11 to 13, withstanding temperatures up to 60°C.

[0014] The invention provides several key advantages over existing solutions. Unlike traditional synthetic healing agents, this biological approach utilizes naturally occurring microorganisms, minimizing environmental impact while enhancing the structural resilience of mortar. This technology not only promotes self-repair mechanisms within the material but also extends the lifespan of mortar applications, reducing the need for frequent repairs and maintenance. Ultimately, this self-healing mortar presents an innovative solution to the challenges faced in the construction industry, fostering more sustainable building practices and improving overall structural performance (Ghosh et al., 2009).

[0015] The present invention introduces a novel biological healing agent specifically designed for mortar applications, aiming to enhance the durability and self-repair capabilities of construction materials. This solution addresses the prevalent issue of cracking and degradation in mortar structures, particularly in tropical environments where climate conditions can exacerbate such problems (Shariati et al., 2023; Shariati et al., 2024).

[0016] The biological healing agent comprises two primary components: a water-based organic compound and Proteous mirabilis bacteria. The organic compound serves as a mixing solution, facilitating the integration of the bacteria into the mortar matrix. Proteous mirabilis was selected due to its indigenous nature, having been isolated from soil samples collected in the vicinity of tropical rivers. This strain is specifically adapted to thrive in the high temperatures and moisture levels characteristic of tropical climates, making it particularly suitable for local construction practices.

[0017] Upon the formation of cracks in the mortar, the encapsulated bacteria become activated, utilizing available nutrients and moisture to metabolize and produce urease enzymes. This enzymatic activity results in the precipitation of calcium carbonate, which effectively fills the cracks and restores the structural integrity of the mortar. The organic compound, specifically calcium formatted, acts as a biomineral precursor, enhancing the healing process by providing the necessary ions for mineral formation.

[0018] The formulation is designed to function optimally within a mortar mixture with a cement-to-water ratio of 4:1 , and it operates effectively in a pH range of 11 to 13, which is typical for alkaline environments found in cementitious materials. Moreover, the mortar can withstand temperatures up to 60°C, ensuring that the healing process remains effective even under high thermal conditions.

[0019] This invention presents several advantages over existing self-healing technologies. Unlike conventional approaches that rely on synthetic healing agents or microencapsulated solutions, the current invention utilizes a straightforward mixing method that directly incorporates the bacteria into the mortar. This not only simplifies the production process but also enhances the immediate efficacy of the healing agent upon crack formation. Additionally, the use of local bacterial strains minimizes environmental impact and fosters sustainability in construction practices.

[0020] In summary, the invention provides an innovative, cost-effective, and environmentally friendly solution for enhancing the longevity and performance of mortar structures, ultimately contributing to the development of more resilient building materials.

[0021] The preparation of the biological healing agent involves the following steps:

[0022] 1. Isolation of Bacterial Strain: Soil samples are collected from the vicinity of tropical rivers and transported to the laboratory under controlled conditions (4°C) to prevent degradation. The samples are suspended in sterile physiological serum and mixed to isolate the bacteria. 2. Culturing: The isolated bacteria are cultured in a suitable medium (e.g., MC) and incubated at 28°C with continuous shaking to promote growth. Following incubation, colonies are purified through a series of transfers onto fresh plates until pure cultures are obtained.

[0023] 3. Testing for Urease Production: The purified bacteria are tested for urease enzyme production. Only those strains that demonstrate urease positivity are selected for incorporation into the biological healing agent.

[0024] 4. Mixing with Organic Compound: The selected strain of Proteous mirabilis is mixed into the water-based organic compound to create the healing agent. The mixture is designed to be incorporated directly into the mortar during the mixing process.

[0025] Application in Mortar

[0026] The biological healing agent is designed to be used in a mortar mixture with a cement- to-water ratio of 4:1. The application process involves the following:

[0027] 1. Mixing: The healing agent is added to the mortar mix during the preparation phase, ensuring a uniform distribution of the bacteria throughout the mixture.

[0028] 2. Curing: Once applied, the mortar is allowed to cure under standard conditions. The curing process creates an environment that supports the activation of the bacteria within the matrix.

[0029] Mechanism of Action

[0030] Upon the formation of cracks in the cured mortar, the following sequence of events occurs:

[0031] 1. Crack Formation: As stress is applied to the mortar, cracks develop, creating pathways for moisture ingress.

[0032] 2. Bacterial Activation: The presence of moisture and nutrients triggers the activation of the Proteous mirabilis bacteria, which metabolizes and produces urease enzymes. 3. Calcium Carbonate Precipitation: The urease enzymes catalyze the hydrolysis of urea, leading to the formation of ammonia and carbonic acid. This process increases the pH of the environment, resulting in the precipitation of calcium carbonate from the calcium ions provided by the calcium formate in the organic compound.

[0033] 4. Crack Filling: The precipitated calcium carbonate fills the cracks, effectively sealing them and restoring the structural integrity of the mortar.

[0034] Performance and Advantages

[0035] The biological healing agent exhibits several key advantages:

[0036] 1. Environmental Adaptability: The use of indigenous Proteous mirabilis strains ensures that the healing agent remains effective under the specific environmental conditions found in tropical regions.

[0037] 2. Simplicity of Application: The direct mixing method simplifies the incorporation of the healing agent into the mortar, enhancing its usability in construction practices.

[0038] 3. Sustainability: By utilizing natural biological processes, the invention minimizes environmental impact compared to synthetic healing agents or microencapsulated solutions.

[0039] Regarding analyses four samples were taken from 5-cm-deep soil in the normal soil surface of land scape area, all these samples were taken from the surrounding area of tropical river and samples were transferred to the laboratory in a cool box (4°C) then all samples were separately suspended into sterile physiological serum (9 g NaCI in one liter of water) and were completely mixed by a shaker with 160 rpm for 30 min and after that one ml of each sample was transferred into 250-ml Erlenmeyer flasks containing 100 ml of MC then the Erlenmeyer flasks were incubated for 48 h by a shaker incubator with 160 rpm at 28°C. After 48 h, by a laboratory loop, 0.1 ml of each Erlenmeyer was transferred onto plates containing solidified MC, after that the plates were incubated for 24 h at 28°C, then 24 h, many colonies of micro-organisms with different morphologies and colors grew on the solidified MC and Liner culture method was applied for the purification of micro-organisms then using liner culture, colonies with same color and morphology were transferred onto fresh plates containing solidified MC and they were incubated at 28°C for 24 h and this process was frequently repeated until the colonies in each plate had same color and morphology then finally plates containing pure micro-organisms were kept in a refrigerator maintained at a temperature of 4°C and all micro-organisms were tested for production of urease enzymes, then only the micro-organisms that were urease positive were selected for identification and further experiments in this study.

[0040] Overview of the Drawings

[0041] The accompanying drawings illustrate various aspects of the biological healing agent for mortar as described in the invention. Each figure provides a visual representation of the components, processes, and applications of the proposed solution.

[0042] Figure 1 : Composition of the Biological Healing Agent

[0043] This figure depicts the two main components of the healing agent: the water-based organic compound and the Proteous mirabilis bacteria. The diagram illustrates how these components are mixed to create a homogenous solution suitable for incorporation into the mortar matrix.

[0044] Figure 2: Process of Bacterial Activation

[0045] This figure outlines the steps involved in the activation of Proteous mirabilis upon crack formation in the mortar. It shows the conditions necessary for bacterial metabolism, including moisture and nutrient availability, leading to the production of urease enzymes and subsequent calcium carbonate precipitation.

[0046] Figure 3: Mechanism of Self-Healing

[0047] This figure illustrates the self-healing process within the mortar. It highlights the formation of cracks, the activation of the healing agent, and the filling of cracks with calcium carbonate, thereby restoring the structural integrity of the mortar. Figure 4: Application of the Healing Agent in Mortar

[0048] This figure showcases the practical application of the biological healing agent in a mortar mixture. It demonstrates how the agent is integrated into the mortar during the mixing process and the resulting properties of the mortar post-curing.

[0049] References:

[0050] 1. S. K. Ghosh (Ed.), (2009) Self-Healing Materials: Fundamentals, Design Strategies, and Applications, Wiley WCH, GmbH.

[0051] 2. K. van Breugel (2007) Is There a market for self-healing cement-based materials. In: Proceedings of the first international conference on self-healing materials, Noordwijkaan zee, the Netherlands.

[0052] 3. W. Zhong, W. Yao, (2008) Influence of damage degree on Self-healing of Concrete. Construction and Building Materials, 22: 1137-1142.

[0053] 4. A. C. Balazs, (2007) Modeling self-healing materials, Mater. Today 10: 18- 23.

[0054] 5. Shariati, M., Kamyab, H., Habibi, M., Ahmadi, S., Naghipour, M., Gorjinezhad, F., Aminian, A. (2023). Sulfuric acid resistance of concrete containing coal waste as a partial substitute for fine and coarse aggregates. Fuel, 348, 128311.

[0055] 6. Shariati, M., Raeispour, M., Naghipour, M., Kamyab, H., Memarzadeh, A., Nematzadeh, M., Toghroli, A. (2024). Flexural behavior analysis of double honeycomb steel composite encased concrete beams: An integrated experimental and finite element study. Case Studies in Construction Materials, 20, e03299.

Claims

Claims1. A biological healing agent for mortar comprising:• Water based organic compound as mixing solution; and• Proteous Mirabilis bacteria directly mixed into said water based compound2. The biological healing agent according to claims 1 , characterized in that the bacterial spores or species belong to the genera Proteous.

3. The biological healing agent according to claim 2, characterized in that the bacteria is Proteous mirabilis.

4. The biological healing agent according to claim 1 , characterized in that the organic compound is a chemical biomineral precursor compound.

5. The biological healing agent according to claim 4, characterized in that the organic compound is calcium formatted.

6. The biological healing agent according to claim 1 , characterized in that mortar mixture C:W 4:1 (cement to water ratio) applied.

7. The biological healing agent according to claim 1 , characterized in that Proteous mirabilis mixed directly.

8. The biological healing agent according to claim 1 , characterized in that pH range from 11 to 13 of the mortar.

9. The biological healing agent according to claim 1 , characterized in that based on Temperature up to 60 C of mortar.

10. A method according to claim 1 , comprising• Crack Formation: As stress is applied to the mortar, cracks develop, creating pathways for moisture ingress.• Bacterial Activation: The presence of moisture and nutrients triggers the activation of the Proteous mirabilis bacteria, which metabolizes and produces urease enzymes.• Calcium Carbonate Precipitation: The urease enzymes catalyze the hydrolysis of urea, leading to the formation of ammonia and carbonic acid. This process increases the pH of the environment, resulting in the precipitation of calcium carbonate from the calcium ions provided by the calcium formatted in the organic compound.• Crack Filling: The precipitated calcium carbonate fills the cracks, effectively sealing them and restoring the structural integrity of the mortar.

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