Microbial Induced Calcite Precipitate Improvement of Aeolian Soil for Use as a Construction Material

An environmentally friendly and successful technique of soil improvement known as Microbial Induced Calcite Precipitation (MICP) has attracted the attention of geotechnical engineers. This study was conducted to modify the engineering behaviour of an aeolian soil bio-treated with Bacillus brevis (B. brevis) to evaluate its suitability for use in construction works. Stepped B. brevis suspension density (i.e., 0.5, 2.0, 4.0, 6.0 and 8.0 McFarland standards equivalent to 0, 1.50 × 108, 6.0 × 108, 1.20 × 109, 1.80 × 109 and 2.40 × 109 cells/ml, respectively) and cementation reagent (i.e., 0.25, 0.5, 0.75 and 1.0 M), respectively, were utilized to activate the MICP process. Compaction was conducted using British Standard light (BSL) (or standard Proctor) energy. Tests results indicate that the engineering behaviour of the bio-treated non-plastic aeolian silt soil improved. The maximum dry density (MDD) and the angle of internal friction values marginally increased, while cohesion and optimum moisture content (OMC) decreased with higher B. brevis suspension density and cementation reagent concentration. Peak angle of internal friction and minimum cohesion were recorded at 1.5 x 108 cells/ml. Highest unconfined compressive strength (UCS) value of 215.58 kN/m2 was obtained for specimen treated with 25 % B. brevis (6.0 × 109 cells/ml): 75 % cementation reagent (0.75 M) mix ratio. The results recorded show that the improved aeolian soil could be used in engineering works.