Experimental study of microbial induced carbonate precipitation (MICP) in the presence of CaCO3 seeds

Microbial-induced calcium carbonate precipitation (MICP) is a biological process inducing bio-mineralization of CaCO3, which can be used to form a solid, concrete-like material. To be able to use MICP successfully for engineering purposes, it is important to understand the formation of the material at the micro-scale to control CaCO3 crystallization. In this contribution we present a systematic study investigating the influence of calcite seeds on the CaCO3 crystallization in MICP. The pH changes during the crystallization process have been monitored in real time with absorption spectroscopy in small volumes, and the optical density (OD) signal was used to analyze the precipitation process. Furthermore, microscopy was used to visualize the precipitation processes in the sample and connect them to changes in pH and OD. We show that there is a significant difference in the pH evolution between samples with and without calcite seeds present and that the shape of the pH evolution and the changes in OD can give valuable information about the precipitation process.