Effects of Different Calcium Sources and Cementation Environments on Microbially Induced Calcium Carbonate Precipitation

Microbially induced carbonate precipitation (MICP) is one of the techniques to improve ground. One critical part of this technique is the crystallization of calcium carbonate, where the calcium ions are commonly provided by calcium chloride (CaCl2). While, the threat of chloride ions raises serious concerns; consequently, calcium acetate [Ca(CH3COOH)2] acting as a promising alternative to offer calcium ions has received growing attention. However, the relevant observations reported by previous studies are not comprehensive. To fill this gap, this study selects Ca(CH3COOH)2 and CaCl2 as the calcium sources, then examines and compares their effects in two types of cementation environments including aqueous and silica sand environment, respectively. The micro characteristics via XRD analyses and SEM images indicate that the calcium source and cementation environment greatly affect the bio-cementation results, changing the crystal polymorph and morphology. Notably, the aragonite precipitated in the silica sand environment under the involvement of carboxyl groups can potentially contribute to the mechanical behaviors.