New isolation of hydrocarbonoclastic bacteria from local limestone mining as promising concrete strength enhancer

A small group of bacteria which are able to precipitates calcium carbonates (CaCO₃ ) are known as hydrocarbonoclastic bacteria. Since CaCO₃ is a main raw material for cement production, hydrocarbonoclastic bacteria are reliable to be applied as concrete additive for strengthen concrete structures. The objectives of present study were to isolate hydrocarbonoclastic bacteria strains that are able to precipitate CaCO₃ and examine its potential as concrete reinforcement materials. Isolates identification through phenotypic methods was conducted following Bergey’s Manual of Determinative Bacteriology protocols. Meanwhile, concrete was prepared following SNI 7656:2012 with bacteria cell introduction. Concrete compressive strength test was conducted using compression testing method. Although 15 isolates were able to precipitate CaCO₃, only 8 isolates give positive result for urease test. One of the isolates identified as Bacillus JB2 has the highest ability to precipitates CaCO₃ with amount of 3.28 mg/mL. This strain could successfully increase concrete maximum load up to 26,673.48 kg and compressive strength up to 33.30 Mpa compared to control concrete. Our result suggest that Bacillus JB2 is suitable to be applied as concrete additives to strengthen concrete structures.