Healing concrete crack by using bacteria

This paper presents the use of bacteria for improving the mechanical properties of concrete and healing of crack in concrete structures. Two different types of bacteria namely Bacillus subtilis and Sporosarcina pasteurii were cultured using different media and three different mixes of concrete which were prepared by replacing 1%, 3% and 5% of water with bacteria solutions. The concrete specimens were then tested to evaluate the ability of the bacteria to heal cracks, which were evaluated by measuring the compression and flexural strength of concrete at different curing period. Two different mechanisms were used to check whether the concrete has healed i.e., by visualization of the cracked specimen and by re-loading the cracked specimen. Re-loading mechanism was performed by applying a flexural load on beam specimens to form micro-cracks in the concrete. The experimental test results indicated that the compressive strength and flexural strength of bacteria concrete increases compared to normal concrete at different ages of curing period. Both species of bacteria showed a positive influence in healing of concrete cracks. Out of the two types of bacteria and different nutrients used in this study, it was concluded that B. subtilis cultured with nutrient broth media has a better healing capability in concrete.