Authors:
Kefas Natsa Victor
Joel Margret
Loveth Sanda
Affiliations:
- Department of Biology, Kaduna State College of Education, Gidan Waya
- Department of Chemistry, Faculty of Sciences, Kaduna State University, Kaduna, Nigeria
Abstract
Concrete is one of the most widely used construction materials but is highly susceptible to cracking, which reduces its durability and increases maintenance costs. Conventional crack-repair techniques involving chemicals and polymers pose environmental and health risks and often offer only short-term solutions. Microbial self-healing concrete, also known as bioconcrete, provides a sustainable alternative by utilizing bacteria to precipitate calcium carbonate and seal cracks naturally. This review examines biological processes involved in self-healing concrete, highlighting microbial-induced calcite precipitation as an eco-friendly and long-lasting solution for improving concrete durability.
Keywords: Bioconcrete, Microbial Induced Calcite Precipitation, Biomineralization, Autogenous Healing, Calcium Carbonate
Introduction
Concrete remains the preferred construction material due to its strength, durability, and affordability. However, cracks often develop during its service life due to factors such as shrinkage, temperature variations, and external loads. These cracks allow water and corrosive agents to penetrate, leading to reinforcement corrosion and reduced structural integrity.
Traditional crack-repair methods, including epoxy resins and polymer-based fillers, are costly, environmentally hazardous, and often incompatible with concrete’s thermal properties. In response, biotechnology has introduced bioconcrete, a sustainable approach that employs microorganisms to repair cracks through biological mineralization.
Self-Healing Concrete Concept
Self-healing concrete mimics natural biological processes such as bone regeneration. When bacteria embedded in concrete become active in the presence of water and nutrients, they produce calcium carbonate, which fills and seals cracks. This process improves concrete durability while reducing maintenance costs and environmental impact.
Natural Self-Healing (Autogenous Healing)
Autogenous healing occurs naturally when calcium hydroxide reacts with carbon dioxide and water to form calcium carbonate. This process can seal small cracks (up to 0.18 mm) without external intervention. However, autogenous healing is limited and ineffective for larger cracks.
Autonomous Self-Healing Concrete
Autonomous self-healing involves the deliberate incorporation of bacteria, nutrients, or encapsulated healing agents into concrete. When cracks occur, these agents activate biological or chemical reactions that promote healing. Microbial-based healing has proven more durable and environmentally friendly than chemical alternatives.
Biomineralization Technique
Biomineralization is the process by which living organisms produce minerals. In concrete, bacteria induce the precipitation of calcium carbonate through metabolic activities, sealing cracks effectively.
There are two main biomineralization mechanisms:
1. Biologically Controlled Mineralization
In this process, mineral formation is genetically regulated by organisms. The minerals produced are uniform in size and structure and form under tightly controlled biological conditions.
2. Biologically Induced Mineralization
This occurs as a by-product of microbial metabolism interacting with the environment. The most common example is Microbially Induced Carbonate Precipitation (MICP), where bacteria produce calcium carbonate that seals concrete cracks.
Microbial Processes in Calcium Carbonate Formation
Microorganisms contribute to calcium carbonate precipitation through several metabolic pathways, including:
- Photosynthesis (cyanobacteria and algae)
- Sulfate reduction
- Nitrogen cycle reactions
- Urea hydrolysis (ureolytic bacteria)
Among these, urease-producing bacteria are most widely used due to their efficiency in increasing pH and carbonate concentration, leading to calcium carbonate precipitation.
Benefits of Bioconcrete
- Enhances concrete durability and lifespan
- Reduces maintenance and repair costs
- Environmentally friendly and sustainable
- Minimizes carbon dioxide emissions
- Improves resistance to water penetration and corrosion
Environmental and Economic Implications
Concrete production contributes significantly to global carbon dioxide emissions. Self-healing bioconcrete reduces the need for frequent repairs and reconstruction, thereby lowering emissions associated with cement production, transportation, and raw material extraction.
Conclusion
Bioconcrete represents a promising innovation in sustainable construction. By integrating bacteria into concrete, cracks can heal naturally through calcium carbonate precipitation, improving structural longevity and reducing environmental impact. Widespread adoption of self-healing bioconcrete could significantly reduce carbon emissions and enhance infrastructure sustainability.
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