Investigating the Growth of Microbial Colonies in Cement Paste to Aid in Concrete Repair

Synthetic polymers generally used for repair of concrete are harmful to the environment. Hence, the use of alternative repair techniques for concrete is being investigated. Calcium carbonate-precipitating bacteria can be used to plug the pores and impart a self-healing capacity to the concrete. However, these bacteria require specific conditions to survive. The environment inside concrete has a pH of 10.2–13.3 and an internal temperature that can go up to as high as 45 °C due to the exothermic nature of the hydration reactions. This study investigates the microbial growth as colony formation inside the hydrated cement paste to check the survival characteristics in these severe conditions. A direct technique of streaking to grow microorganism in a cement paste plate is used to check that, the cement paste has enough nutrients to support this growth. In this study, different species from same genus Bacillus, Bacillus cereus, Bacillus licheniformis bacteria are taken for comparative study along with Bacillus subtilis. From the current study, it was found that bacterial growth is clearly visible with 1% yeast extract. Also, from the SEM-EDS analysis calcium carbonate precipitation is evident. Further study can be performed to investigate the cell viability in cement paste as an extension of this work.