Factors Affecting Improvement of Engineering Properties of MICP-Treated Soil Catalyzed by Bacteria and Urease

Microbial induced calcite precipitation (MICP) is one of the potential methods for improvement of engineering properties of soil. A laboratory study was conducted to investigate the influence of various factors on engineering properties of MICP-treated soil catalyzed by bacteria and ureases. Some of these factors include bacteria concentration, urease concentration, cementation media concentration, reaction time, type of sand, and curing conditions. The experiments of MICP catalyzed by Sporosarcina pasteurii and urease were conducted in similar conditions. The soil samples were prepared with full contact flexible molds (FCFMs). The results of unconfined compression test show that the experimental factors (bacteria/urease concentration, cementation media concentration, reaction time, and type of sand) have a significant impact on the MICP process and engineering properties of sand treated by both bacteria and urease, whereas the curing conditions has a small effect. The unconfined compression strength (approximately 1.76–2.04 MPa) of bacteria treated samples is almost 5× (approximately 0.33–0.43 MPa) that of urease treated samples under similar urease activity. The MICP process catalyzed by bacteria is much more effective than the process catalyzed by urease in terms of engineering soil properties improvement.