Advancing sustainable concrete with bacterial self-healing technology and Kuhn-Tucker condition

This research investigates the self-healing potential of Bacillus subtilis in concrete due to its high capacity for calcium carbonate precipitation. Mathematical modelling and machine learning methods, i.e., Random Forest Method (RFM) and Kuhn-Tucker (KT) Condition, were used to maximize healing efficiency. Bacteria-free and bacteria-containing concrete samples were subjected to control cracking, and results indicated complete healing of cracks in 21 days under optimal curing conditions. Comparative study of river sand (RS) and manufactured sand (MS) in bacterial concrete indicated improved mechanical strength in MS-based bacterial concrete with 9.27% improvement in compressive strength and 12.78% and 6.36% improvement in split tensile and flexural strengths, respectively. Load removal and subsequent re-loading tests indicated effective healing of cracks up to 1 mm, especially in 14 day cured samples. Besides, reinforced concrete beams (M20, M25 and M30) were subjected to flexural stress and load removal and subsequent re-loading. 14 and 28-day cured beams exhibited complete closure of cracks within 21 days, indicating the dependability of bacterial self-healing mechanisms. This research identifies Bacillus subtilis-based self-healing concrete as a cost-effective, sustainable, and durable material for infrastructure durability. Future studies should aim at field application, large-scale production, and optimization of bacterial survival rates for global application.