Reduction of the Wetting Collapse of Sandy Gypseous Soil by Using Microbial-Induced Calcite Precipitation

Abstract

Microbial-induced carbonate precipitation (MICP) is a promising technology for cementing sandy soils, improving ground, repairing concrete cracks, and remediating contaminated land. The aim of this research is to implement this technology in mitigating wetting collapse of Ramadi sandy gypseous soil which has a gypsum content of about 35%. To achieve this aim, the urease-producing bacterial strain Bacillus Megaterium SI was used and treated soil specimens were prepared. The preliminary results showed a well-defined bacterium activity with a precipitated calcite of 13-16.5% by the end of the first week. The results of the collapsibility test showed that increasing cementation solution molarity from 0.25M to 1M lowered the wetting strain and total strain caused by both loading to 100 kPa and wetting by about 75%. Therefore, the MICP demonstrates the potential to mitigate the wetting collapse of the sandy gypseous soil despite its high gypsum content.