Experimental Study on Self-Healing of Micro-Cracks in Concrete with Combination of Environmentally Friendly Bacteria

Abstract

Micro-cracks in constructions are unavoidable due to freezing, thawing, and shrinkage in concrete, as well as when concrete is exposed to the seafloor, on offshore platforms, or in tunnels and sewage pipes. This exposure also has an impact on the durability and service life of concrete. Standard healing materials are not long-lasting and are difficult to mend fine cracks with. According to new research, bacterial concrete is an effective approach for repairing concrete and boosting its longevity. The problem has been reduced using calcite-producing microorganisms that do not pollute the environment and are sustainable to produce. In the presence of carbonate ions, bacteria release calcium precipitate, a process known as bio-calcification. This study includes four blends as (1) normal concrete, (2) Bacillus cereus with normal concrete, (3) Bacillus subtilis with normal concrete, and (4) combined cereus and subtilis with normal concrete. Blend 4 provided the lowest slump value of 70 mm, the highest splitting tensile strength of 2.83 MPa, and the highest flexural strength of 4.37 MPa. This combination was more sustainable and cost-effective because it used less water and cement. Blend 4’s self-healing ability was remarkable, as the microcracks were cured after 7 days. Similarly, Blend 3 had a higher compressive strength of 33 MPa.