Bio-remediation of cracks – a novel technique to self-heal cracks in the concrete

A novel technique of self-healing cracks by bacterial species through microbial-induced calcite precipitation (MICP) was developed to counteract the effect of the cracks in concrete structures. This article investigates the influence of two bacterial species, <i>Bacillus subtilis</i>, and <i>Escherichia coli</i>, on the mechanical, durability, and self-healing properties of concrete. The bacterial solutions were cultured in <i>Luria bertani</i> medium to different cell concentrations of 10¹, 10³ and 10⁵ cells/ml. Tests were performed to evaluate the workability, hardened properties such as compressive strength, split tensile strength, flexural strength and durability properties, such as water absorption, acid attack and marine water attack at respective ages. The study concluded that concrete containing bacterial species improves mechanical and durability properties compared to control concrete, and the concrete mixtures with <i>B. subtilis</i> performed better than <i>Escherichia coli</i>. A maximum of 12.8% increase in the strength of the concrete and a 62.1% decrease in water absorption was observed with <i>B. subtilis</i> at 10⁵ cells/ml concentration. SEM analysis performed shows the precipitation of calcite that deposits on the micro-pores and improves the properties of the concrete. Self-healing studies show the deposition of calcite that seals the cracks on the surface of the concrete specimens.