An Environmentally Friendly Soil Improvement Technology with Microorganism

Abstract

Cement or lime is generally used to improve the strength of soil. However, bacteria were utilized to produce cementa-tion of loose soils in this study. The microo rganism called Bacillus, and CaCl 2 was introduced into loose sand and soft silt and CaCO 3 in the voids of soil particles were produced, leading to cementation of soil particles. In this study, loose sand and soft silt typically encountered in Korea were bio-treated with 3 types of bacteria concentration. The cementa-tion (or calcite precipitation) in the soil particles induced by the high concentration bacteria treatment was investigated at 7 days after curing. Based on the results of Scanning Electron Microscope (SEM) tests and EDX analyses, high concen-tration bacteria treatment for loose sand was observed to produce noticeable amount of CaCO 3 , implying a significant cementation of soil particles. It was observed that higher calcium carbonate depositions were observed in poorly graded distribution as compared to well graded distribution. In addition, effectiveness of biogrouting has also been found to be feasible by bio-treatment without any cementing agent.