Soil stabilisation by microbial induced calcium carbonate precipitation: investigation of some important physical and environmental aspects
Cheng, L., Shahin, M.A., Cord-Ruwisch, R., Addis, M., Haranto, T. and Elms, C. (2014) Soil stabilisation by microbial induced calcium carbonate precipitation: investigation of some important physical and environmental aspects. In: 7th International Congress on Environmental Geotechnics, 10 - 14 November, Melbourne, Australia
This work investigates an emerging and promising soil stabilisation method known as bio-cementation using microbial-induced calcite precipitation (MICP). MICP utilises bacteria to hydrolyse urea to give carbonate ions which react with a calcium-rich solution (i.e. calcium chloride) to produce calcium carbonate (calcite) that binds the soil particles together leading to increased soil strength and stiffness. In this paper, the effectiveness of bio-cementation of silica sand under different environmental and physical conditions was investigated including the initial soil density, temperature and pH of soil. A set of laboratory tests were conducted including soil permeability, unconfined compression strength and determination of calcium carbonate content. The results indicate that bio-cementation is more effective for sand of high initial density. The results also demonstrate that although the calcium carbonate production was facilitated at an elevated temperature of 50oC, the build-up of strength was less efficient than at room temperature. Also alkaline (pH 9.5) or acidic (pH 3.5) conditions were adverse to strength development. Sufficient permeability was retained by all bio-cemented samples, which indicates good drainage ability that allows rapid dissipation of the excess pore water pressure upon loading.
A new promising and innovative modification of MICP treatment was also evaluated using the seawater as a replacement for one of the reactants in production of calcium carbonate. This new process provides a high potential for using bio-cementation in maritime environment for applications such as coastal erosion prevention. Treatment using the seawater to replace the calcium chloride has resulted in stabilised soils that exhibit reasonable strength and efficient crystal formation, which confirms the viability of the proposed seawater process for bio-cementation.
|Publication Type:||Conference Paper|
|Murdoch Affiliation:||School of Engineering and Information Technology|
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