Evaluation of Mechanical and Self-Healing Performance of Bacterial Concrete Using BACTAHEAL-PR and Fly Ash: A Sustainable Approach

Concrete, the backbone of modern infrastructure, suffers from a critical limitation: cracking. These micro- and macro-cracks compromise its integrity, accelerate degradation, and lead to high maintenance costs. Inspired by biomimetic systems and ancient Roman concrete, this study investigates the incorporation of a commercial bacterial healing agent, BACTAHEAL-PR, into M25 grade concrete. This agent comprises Bacillus spores, nutrients, and enzymatic activators that catalyze calcium carbonate (CaCO3) precipitation upon activation by moisture ingress through cracks. Concrete specimens were prepared by partially replacing cement with 1%, 2.5%, and 5% BACTAHEAL-PR. Additionally, 2% fly ash was introduced in select batches to assess its synergistic effects. The research involved a systematic investigation including workability analysis (slump, flow table, and compaction factor), compressive strength testing at 28 days, and visual evaluation of autonomous crack healing over an additional 28-day period. Results revealed that 1% BACTAHEAL-PR with 2% fly ash significantly improved compressive strength (25.63 N/mm²) and enabled full crack closure. In contrast, higher bacterial dosages negatively affected strength due to potential interference with cement hydration. This study demonstrates that optimized bacterial concrete can extend service life, reduce carbon footprint, and support the transition toward sustainable civil engineering materials. Keywords: Bacterial concrete, self-healing concrete, BACTAHEAL-PR, M25 concrete, compressive strength, calcium carbonate precipitation, fly ash, Bacillus subtilis, sustainable construction.