Microbially induced carbonate precipitations to improve residual soil at various temperatures

Abstract

Microbial induced carbonate precipitation (MICP) has emerged recently as a new approach of green and sustainable soil improvement technique. The main aim of this study was to determine the most suitable temperature for MICP to improve tropical residual soil. The physical and engineering properties of residual soil used in the study were determined through several laboratory experiments. A urease active strain of Sporosarcinapasteurii obtained from American Type Culture Collection (ATCC) was used to trigger the carbonate precipitation. Experimental parameters such as curing temperature, treatment duration and bacteria to cementation reagents ratios were evaluated. The results show that the optimum temperature for MICP treatment of residual soil is 55°C. It was also found that at this optimum temperature, specimens treated with bacteria and cementation reagents in proportion of 2:1 produces the highest strength improvement ratio of 1.27 relative to untreated sample and calcite content of 1.09% after 7-day curing. The shear strength of the treated soil also increases with the increase in treatment durations as the 7 days curing produces higher strength improvement for all the experimental conditions. The specimens cured under the atmospheric temperature recorded the lowest calcite content and hence the lower shear strength improvement ratio. Moreover, the experimental results obtained from this study also can be used as a guide in the future bio-geotechnology researches and lead to further scope in geotechnical applications.