Effect of microbially induced calcite precipitation on the strength of cemented sand

Microbially induced calcite precipitation (MICP) using Sporosarcinapasteurii was employed to enhance the strength of weakly cemented soil and fill its voids. Weakly cemented sand with a cement ratio of 3% was prepared and cured for 3 days. The cemented sand was treated up to ten times with the Sporosarcinapasteurii microbe over a 20-day period. The resulting sand was then tested to evaluate its unconfined compressive strength (UCS) and the amount of calcite precipitation within the cemented sand particles. The level of calcite precipitation increased slightly with increasing number of microbe treatments. The UCS of the specimen treated once with the microbes showed a 5% increase compared to the untreated specimen. On the other hand, for the specimens treated more than twice, their strength decreased gradually by up to 50% compared to the untreated specimen. The precipitation of calcites within the cemented sand can adversely weaken the existing cementation caused by cement hydration.