Influence of bacteria Bacillus subtilis and its effects on flexural strength of concrete

Abstract

Concrete is a robust and mouldable construction material which comprise of sand, cement and aggregates blended with water or with any admixtures. Concrete structures are prone to develop cracks due to environmental conditions or by load. These cracks compromise the integrity of structure by weathering the reinforcement caused by moisture entering through these cracks. Many advanced investigations are being done to control the cracks in the concrete structures, one such investigation is by incorporating microorganisms that are capable of precipitating Calcium carbonate (CaCO3) which can self-heal the cracks. This study explores multiple avenues using mineralizing bacteria to increase the structural strength of concrete. We have shown the effect on the flexural strength of concrete by adding laboratory cultured Bacillus subtilis (ATCC 9372). The bacteria were grown in the nutrients like soya bean digestive media, substituted with calcium acetate (Ca(C2H3O2)2, L-alanine (C2H7NO2), manganous sulfate (MnSO4) and nutrient agar. Cultured Bacillus subtilis was added into regular water for M20 grade of concrete mix. In this research flexural strength of concrete was quantified by casting rectangular beams of dimension 500 mm*100 mm*100 mm test is performed as per Is 415:1949 & amp 456:200. The flexural strength of bacterial concrete is increased when compared with normal concrete. The Bacillus Subtilis used in our research was also found to be able to grow in the presence of plasticizer, which makes it a viable candidate for implementing concrete with self-healing property and increase flexural properties.