SELF-HEALING CONCRETE:

Concrete, once considered a prominent building material, is now recognized as one of the major contributors to greenhouse gas emissions (CO2), directly affecting environmental degradation. Additionally, the maintenance expenses for concrete construction are substantial. Another concern is the formation of cracks of varying sizes in concrete structures, necessitating frequent sealing and ultimately reducing their lifespan. However, self-healing concrete (SHC) emerges as a versatile construction material that offers solutions to these challenges, making it a promising innovation for the near future.

Definition of Self-healing

Self-healing materials are characterized by their ability to repair and return to their original state. The concept of self-healing concrete (SHC) has been observed in numerous older structures, which can endure for extended periods if adequately protected. This observation revealed that cracks in these structures are mitigated when moisture reacts with water-resistant cement during an explosion. However, the employment of modern construction techniques has led to a decrease in the use of such resilient cement in contemporary construction. Consequently, the quantity of this specialized cement is limited, resulting in a reduction of the natural healing effect.

How does bio concrete work?

Self-healing concrete is a revolutionary product designed to generate limestone, which aids in repairing cracks on the surface of concrete structures. This innovative material incorporates carefully selected bacteria from the genus Bacillus, along with calcium-rich components like calcium lactate, nitrogen, and phosphorus, into the concrete mixture. These self-healing agents remain dormant within the concrete for remarkably extended periods, up to 200 years.

In the event of damage to the concrete structure and the infiltration of water seeking out cracks, the dormant bacterial particles become active upon contact with water and nutrients. These bacteria start to consume calcium lactate as their food source. During this consumption, the bacteria absorb oxygen, leading to the conversion of soluble calcium lactate into invisible limestone. This limestone then solidifies within the damaged area, effectively sealing the crack.

Another noteworthy benefit of this process is the consumption of oxygen during the conversion of calcium lactate to limestone. This depletion of oxygen is advantageous, as it reduces the potential for metal corrosion. Consequently, the activity of these bacteria enhances the overall strength of the reinforced concrete structure.

Some disadvantages

The widespread adoption of self-healing concrete as a replacement for traditional concrete structures in the next decade faces two significant challenges.
The first obstacle pertains to the clay pellets infused with the self-healing agent, which only contain 20% solids. Within this 20%, hardened materials like gravel are present on average. Unfortunately, the strength of this clay-based mixture is considerably weaker than that of conventional concrete, leading to a 25% reduction in overall structural integrity. As a consequence, its applicability may not pose significant issues in most ordinary buildings. However, in specialized cases that demand high-pressure resistance, such as constructing very tall buildings, it may not be a viable solution.