<p>This pivotal study reveals the presence of <i>Bacillus subtilis</i> in waste coconut shell aggregate (CSA) light-weight concrete (LWC) at different bacterial concentrations.&#xa0;The control mix (CM) was prepared with 100% CSA and 0% bacteria. The B6, B7, and B8 mixes are prepared by incorporating the bacteria at 10⁶, 10⁷, and 10⁸ colony-forming units/ml (CFU/ml) in CSA LWC. Therefore, the cube compressive strength and splitting tensile strength of the B7 mix are 11.26% and 4.14% stronger than CM at 28 days, respectively. The binder chemistry achieved by microbiologically induced calcite precipitation (MICP) and gehlenite phase refines the meso-capillary pores and accelerates the mechanical properties of LWC. The B7 mix’s transport and deterioration mechanism of longevity properties (water absorption, rapid chloride penetration test (RCPT), acid and sulphate attack) are synergistic when compared to other mixes due to bio-cementation. The imaging technique with thermogravimetric&#xa0;(TG/DTG) unlocks the crack sealing mechanism and delve into a detailed investigation of the schematic bio-precipitation (CaCO₃) on <i>Bacillus subtilis</i>.</p> Graphical abstract <p></p>