Assessment of the mechanical and durability characteristics of bio-mineralized Bacillus subtilis self-healing concrete blended with hydrated lime and brick powder

Cement is the main constituent of the concrete structure. Using rejected brick as pozzolana in replacement of cement reduced the utilization of natural resources, conserved the environment, and controlled waste disposal. Hydrated lime has been utilized as a chemical additive to improve the pozzolanic reaction of finely ground waste brick particles. This research investigates the process of biomineralization to enhance the strength and durability characteristics of bacterial concrete incorporating hydrated lime and brick powder (HBr). In this context, cement was partially replaced with HBr in different proportions 10%, 20%, and 30% by weight. Furthermore, the HBr mixtures were meticulously prepared with and without the incorporation of Bacillus subtilis. Tests for strength and durability were performed at the age of 28 and 56 days of concrete. The self-healing proficiency of the bacterial concrete was evaluated through compressive strength, water permeability, and chloride penetration, while the microstructure analysis was conducted using field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). The results show that at the age of 56 days, CaCO₃ precipitation caused by Bacillus subtilis increases the compressive strength of BHBr10 by 19.07%. The durability properties in terms of chloride ion penetrability and water permeability exhibited substantial improvements of 40.03% and 61.9% respectively. Additionally, the FESEM micrographs along with the EDS analysis corroborated the presence of CaCO₃ precipitation crystals.