Effect of biogrouting in improving soil properties-a review

Soil stabilization implies modifying the properties of soil and making it into a strong and durable mass. Soil needs to be densified to improve its shear strength and bearing capacity. It can be achieved through various means like mechanical compaction, addition of chemicals or additives like lime, cement, bitumen and resin. Grouting technique incorporates injecting fluid or suspension called grout into the pores of soil. Chemical grouts and cement grouting are expensive and harmful ways which affect the ecosystem adversely. Hence alternative methods have to be proposed. Biogrouting is an emerging, environmental friendly and economical technique for stabilizing sandy soils where nontoxic micro-organisms are used as grouting material. Bio-chemical reaction happening due to the injected bacteria produces calcium carbonate precipitates. This technique which incorporates microbes for calcite precipitation is termed as Microbial Induced Calcite Precipitation (MICP). The precipitated calcium carbonate seals the cracks and voids within soil mass. Urea hydrolysis is the most preferred CaCO3 precipitation method. It has highest rate of calcite precipitation and CaCO3 yield than other existing methods. This paper presents a review on effect and feasibility of biogrouting for improving properties of soil using variety of bacterial concentration. The influence of MICP on the properties of soil such as shear strength, compressibility and permeability reported by researchers are evaluated.