Self-Healing Concrete

Abstract

Crack formation is very common phenomenon in concrete structure which allows the water and different type of chemical into the concrete through the cracks and decreases their durability, strength and which also affect the reinforcement when it comes in contact with water, CO2 and other chemicals. Cracks in concrete structures can significantly decrease their lifespan by exposing reinforcement to outside environment, leading to concrete degradation. To address this issue, self-healing techniques have been developed, including Biomineralization-based-self healing, where bacteria are employed to initiate Microbially Induced Calcium Precipitate (MICP), promoting the healing of cracks. Moreover, there exists a direct correlation between bacterial cell concentration and alterations in the mechanical properties of concrete. The incorporation of bacteria in concrete leads to increment in strength properties, with strength enhancement of up to 42.8 %. The selection of the bacteria was according to their survival in the alkaline environment such as Bacillus subtilis and B. lichenformis which are mainly used for the experiments by different researchers for their study. Cement and concrete matrices reinforced with randomly oriented short fibers are finding increasing applications in both precast and in situ concrete construction. In this process, fibers are incorporated to regulate crack width, ensuring an optimal environment for bacterial activity. By limiting crack expansion, the effectiveness of bacteria in the self-healing mechanism is enhanced, leading to improved durability and performance of the material.

Introduction

In modern urban construction, concrete durability is challenged by cracks from thermal effects, shrinkage, corrosion, and environmental stress. While these cracks often don't affect structural integrity initially, they can allow water and chemicals to corrode embedded steel, eventually leading to structural failure. Traditional repair methods using resins or epoxies are costly, environmentally harmful, short-lived, and ineffective against microcracks.

To address these issues, bacteria-based self-healing concrete is emerging as a sustainable and cost-effective solution. It uses specific bacterial strains (e.g., Bacillus subtilis, Bacillus licheniformis) that remain dormant in the concrete and activate upon crack formation and moisture exposure. These bacteria precipitate calcium carbonate (CaCO?) through Microbial Induced Calcium Carbonate Precipitation (MICP), sealing the cracks and extending the life of the structure.

Technical Details:

Types of Self-Healing:

1. Autogenous Healing (natural, limited to small cracks ≤ 100 µm):

   • Utilizes unhydrated cement particles.

   • Influenced by age, water availability, and composition.

2. Autonomous Healing (engineered):

   • Chemical: Uses admixtures like crystalline agents and synthetic fibers to block water and enhance crack sealing.

   • Biological: Incorporates bacteria that precipitate CaCO? to fill cracks up to 1 mm.

Bacterial Mechanism (MICP):

• Bacteria use urease to decompose urea into ammonium and carbonate ions.

• These react with calcium (from additives like calcium lactate) to form calcium carbonate, which fills cracks.

• Bacteria return to dormancy after healing, ready for reactivation when new cracks form.

Experimental Setup:

• Four reinforced concrete beam specimens (100×100×500 mm) were cast.

  • Specimens 1 & 2 used B. subtilis and B. licheniformis without encapsulation.

  • Specimens 3 & 4 used the same strains but were encapsulated in sodium alginate to protect bacteria in harsh alkaline environments.

• Mix included nylon fibers and 5% calcium lactate for structural support and as a nutrient source.

Procedure:

1. Layered addition of concrete, fibers, calcium lactate, and bacterial solution.

2. Controlled crack induction via flexural loading.

3. Monitoring healing over 7, 14, and 28 days via strength tests and visual inspection.

Results:

• A lag phase was observed initially due to bacteria transitioning from dormancy.

• Over time, calcium carbonate precipitated, visibly sealing cracks and improving strength.

• Nylon fibers controlled crack width and supported bacterial activity.

• Encapsulated bacteria showed better survival and healing efficiency.

Conclusion

The development and evaluation of self-healing concrete using bacterial strains such as Bacillus subtilis and Bacillus licheniformis demonstrate a promising shift in the construction industry toward smarter and more sustainable materials. Through the process of Microbial Induced Calcium Carbonate Precipitation (MICP), cracks in the concrete matrix can be autonomously sealed, thereby improving the material’s durability, strength, and service life. The use of calcium lactate as a nutrient and sodium alginate for encapsulation proved effective in enhancing bacterial viability and healing performance, especially under the high pH conditions of concrete. The experimental results confirmed that crack healing efficiency increased significantly between the 3rd and 7th day after bacterial activation. The integration of nylon fibers further supported this healing mechanism by controlling crack width and giving bacteria sufficient time to act. Overall, this study reinforces the potential of bacterial self-healing concrete as a sustainable and cost-effective solution for reducing long-term maintenance and increasing the lifespan of concrete structures. Continued research and optimization can further pave the way for its practical implementation in infrastructure projects worldwide.

References

[1] Yasmeena Javeed, Yingxin Goh, Kim Hung Mo, Soon Poh Yap, and Bey Fen Leo, “Microbial Self-Healing in Concrete: A Comprehensive Exploration of Bacterial Viability, Implementation Techniques, and Mechanical Properties,” Department of Civil and Mechanical Engineering, Universiti Malaya, Kuala Lumpur, Malaysia, 2023. [2] Xiaohong He, Muhammad Nasir Amin, Kaffayatullah Khan, Waqas Ahmad, Fadi Althoey, and Nikolai Ivanovich Vatin, “Self-Healing Concrete: A Scientometric Analysis-Based Review of the Research Development and Scientific Mapping,” College of Civil Engineering and Architecture, Changchun Sci-Tech University, China; King Faisal University, Saudi Arabia; COMSATS University, Pakistan; Najran University, Saudi Arabia; Peter the Great St. Petersburg Polytechnic University, Russia, 2023. [3] Salmabanu Luhar and Suthar Gourav, “A Review Paper on Self Healing Concrete,” Malaviya National Institute of Technology, Jaipur, India. [4] V. S. Parameswaran, T. S. Krishnamoorthy, and K. Balasubramanian, “Current Research and Applications of Fiber Reinforced Concrete Composites in India,” Journal of Structural Engineering (India), 2022.

Copyright

Copyright © 2025 Atharv Raut, Kartik Bansode, Lakshay Jain, Ishan Marwa, Atif Naik, Anushri Isal. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.