Effects of Micro-organisms on Concrete Properties – A Review

The integration of micro-organisms into concrete materials has emerged as a ground breaking approach to enhance durability, sustainability, and mechanical properties. This review consolidates findings from recent research exploring the effects of various bacteria, including Bacillus subtilis, Sporosarcina pasteurii, and others, on the performance of concrete. These micro-organisms, primarily employed through microbial- induced calcium carbonate precipitation (MICP), offer self-healing, strength improvement, and resistance to aggressive environments. The study highlights that bacterial incorporation generally enhances compressive, tensile, and flexural strength due to the biogenic formation of CaCO₃, which fills microcracks and voids. Workability, although sometimes negatively impacted due to altered particle interactions, can be optimized through proper mix design. Improvements in elastic modulus and chloride penetration resistance indicate enhanced durability and service life. The paper also reviews the nature of microbial additives, their survival under highly alkaline cementitious environments, and methods to ensure their sustained activity, including encapsulation techniques. Overall, bacterial concrete has proven effective, especially in structures exposed to frequent cracking and harsh environments, such as bridges and marine infrastructures. While promising, challenges persist in scalability, standardization, and long-term performance validation.