EXPERIMENTAL INVESTIGATION OF SELF-HEALING CONCRETE USING BACTERIA-BASED CRACK-REPAIR MECHANISMS

Abstract

Concrete is one of the most extensively used construction materials, but its inherent tensile weakness and susceptibility to shrinkage, thermal effects, mechanical loading, and environmental exposure make crack formation difficult to avoid. Even relatively small cracks can increase permeability and provide pathways for water, chlorides, carbon dioxide, and other aggressive agents, accelerating reinforcement corrosion and reducing structural durability. Bacteria-based self-healing concrete provides an autonomous crack-repair approach in which selected microorganisms precipitate calcium carbonate within cracks when moisture and suitable nutrients become available. This study presents an experimental investigation of bacterial self-healing concrete incorporating Bacillus subtilis as a biological healing agent. A conventional concrete mixture is considered as the control, while bacterial concrete mixtures are prepared using different bacterial dosages to investigate their influence on compressive strength, crack closure, and durability-related performance. Specimens are cured under controlled conditions and deliberately pre-cracked before being exposed to a healing environment. Crack widths are monitored at predetermined healing ages, and the crack-healing efficiency is evaluated from the reduction in visible crack width. The experimental framework also considers water absorption and compressive-strength recovery as indicators of the effectiveness of the bacterial repair mechanism. However, the results also emphasize that crack closure should not automatically be interpreted as complete structural recovery and that long-term bacterial viability, field exposure, mixture compatibility, environmental effects, and economic scalability require additional investigation before widespread structural implementation. The study therefore establishes an experimental framework for evaluating bacterial concrete and highlights microbial-induced calcium carbonate precipitation as a promising pathway toward more durable and maintenance-efficient concrete infrastructure.