Iron-Based Bio-Grout For Soil Improvement and Land Reclamation V. Ivanov, J. Chu, V. Stabnikov, J. He, and M. Naeimi School of Civil and Environmental Engineering, Nanyang Technological University, Singapore <cvivanov@ntu.edu.sg> ABSTRACT Chemical grouts have often been used in geotechnical applications. However, they are expen- sive, usually toxic, and may be harmful to the environment. A new type of grout, biogrout, which is based on ferrous/ferric salts, has been developed using microbial technology. The time for the biogrout to take effect and the extent that biogrouts penetrate the soil depend on the concentration and activity of specific bacteria in the biogrout. The reaction time varies from several minutes to several days. Testing results show that ferrous/ferric-based biogrouts are applicable for construction of reservoirs, ponds, dams, and land reclamation. The biogrout also increases the strength and decreases the permeability of the soil. Geotechnical applications of the biogrout could be; 1) formation of grout curtains; 2) diminishing piping of earth dams and dikes; 3) construction of reservoirs and ponds; 4) seepage control; 5) fixation of the leakages of ground water in underground constructions; 6) reduction of pipeline corrosion; 7) land reclama- tion; 8) sealing of tunnel seepage; 9) the reduction of soil liquefaction. INTRODUCTION Chemical grouting is a common technique adopted in geotechnical engineering to improve the mechanical properties of soil (Karol, 2003). In adopting this method, grout is injected into the voids of soil to increase the strength or reduce the permeability of soil. However, chemical grouting can be expensive and toxic for environment. An alternative approach is to use biogrout (Ianov and Chu, 2008; Mitchell and Santamarina, 2005). Biogrouting is to fill the voids, channels or fissions in soil or rock through microbial activity or by the microbial products. Due to small size of bacterial cells, 1-3 μm, biogrouts can be applied to soils with permeability below 10 -6 m/s. It can decrease the permeability to 10 -10 m/s. This effect is similar to the effect of chemical grouts (Sarsby, 2000; Indraratna and Chu, 2005). However, cement grout is applicable for soils with permeability below 10 -4 m/s and can decrease permeability up to 10 -6 m/s (Sarsby, 2000). Coventry University and The University of Wisconsin Milwaukee Centre for Byproducts Utilization, Second International Conference on Sustainable Construction Materials and Technologies June 28  June 30, 2010, Università Politecnica delle Marche, Ancona, Italy. Special Technical Proceedings ed. P Claisse, E Ganjian, F Canpolat and T Naik ISBN 9781450714884 http://www.claisse.info/Proceedings.htm