2025, Vol. 6, Issue 1, Part A

Cracks in concrete not only affect structural integrity but also allow ingress of harmful agents, accelerating degradation and reducing the lifespan of civil structures. In this study, we explore the efficacy of self-healing concrete using Bacillus subtilis and Bacillus pasteurii bacteria capable of precipitating calcium carbonate to seal micro cracks autonomously. Concrete specimens were prepared with bacterial spores and a nutrient source (calcium lactate) encapsulated in lightweight aggregates. Upon crack formation, water ingress triggered bacterial germination, leading to CaCO? precipitation. The mechanical properties, crack width closure, water permeability, and microscopy analyses (SEM/EDX) were used to assess healing performance. Results revealed that specimens incorporating bacterial agents exhibited up to 80-90% healing in crack widths ? 0.5 mm within 28 days, with minimal impact on compressive strength. This experimental study validates bacterial concrete as a sustainable and intelligent material capable of autonomously repairing structural damage, thus significantly enhancing durability and reducing maintenance costs in infrastructure.