The effect of isolated Bacillus ureolytic bacteria in improving the bio-healing of concrete cracks

Background Reinforcement corrosion and the concrete strength reduction are critical problems that resulted from crack creation in concrete. Very expensive and hazardous technologies based on chemical materials have been provided for repairing the cracks. Recently, crack repair using bio-catalysis precipitating bacteria has been developed as a viable and ecofriendly alternative technique. The main target of this study was to select and identify bacterial isolates with high urease activity to use in filling the cracks by the precipitation of CaCO3. Results Two endospore-forming and alkali-resistant ureolytic bacteria were combined with concrete to tolerate the mechanical stresses generated by mixing. The two isolates designated as (B1 and B2) were selected and identified as Bacillus wiedmannii strain FSL W8-0169 and Bacillus paramycoides strain MCCC 1A04098, respectively, using 16SrDNA gene sequencing. Both bacterial species completely heal cracks in fully destructed concrete and significant enhancement in compressive strength was illustrated. The calcite filling of cracks and CaCO3 crystals that were screened using a scanning electron microscope may explain the crack healing and the enhancement in concrete strength. Conclusions Bacillus wiedmannii strain FSL W8-0169 and Bacillus paramycoides strain MCCC 1A04098 can be inserted with the concrete to improve the compressive strength and the self-healing of cracks. The two ureolytic bacterial strains can be used to protect water buildings from exposure to frequent cracks.

Isolation and Screening for Ureolytic Bacteria from Bukilat Cave, Camotes Islands, Cebu

Microbial-induced calcite precipitation (MICP) is an eco-friendly technique used in creating better soil substrate often for engineering purposes. This is done through the application of the ureolytic pathway of certain bacteria. This study aims to discover whether any of these bacteria can be found in Bukilat Cave, Camotes Islands, Cebu. Samples from the pools of water, drip water, and swabs of the walls of the cave were collected, cultured, and then tested using Christensen’s agar for their ability to undergo the ureolytic pathway. The rate at which they undergo the ureolytic pathway was then measured and compared between different sources and to the positive control, Bacillus megaterium. The results showed that there was no significant difference between the rate at which bacteria from the different sources underwent ureolysis. There was also no significant difference between the rate at which the collected bacteria underwent ureolysis and the rate of the positive control (2.588 mM/min). Finally, the species with the fastest rate of ureolysis was identified to be Bacillus cereus NR 074540 with a rate of 3.033 mM/min. However, it is not ideal for MICP purposes because of its potential pathogenicity.