Volumetric Shrinkage of Compacted Lateritic Soil Treated with Bacillus pumilus

Abstract

Lateritic soil was treated with Bacillus pumilus in stepped concentration of 0/ml, 1.5 × 108/ml, 6.0 × 108/ml, 12 × 108/ml, 18 × 108/ml and 24 × 108/ml, respectively. Specimens were prepared at −2, 0, 2 and 4% relative to optimum moisture content (OMC) and compacted with British Standard light (BSL) (or standard Proctor) energy. The specimens extruded from the compaction moulds were air-dried in the laboratory to determine the volumetric shrinkage of the material when used to construct liners and covers for the containment of municipal solid waste (MSW). High volumetric shrinkage strain (VSS) values were recorded in the initial 5 days of air-drying but became relatively constant after 15 days. VSS values of specimens increased with higher Bacillus pumilus concentration and moulding water content in the range from the dry side (–2%) to wet side (+4%) relative to OMC. A compaction plane that satisfied the regulatory VSS value ≤ 4% was obtained at 24 × 108/ml Bacillus pumilus concentration recommended for the optimal treatment of lateritic soil to be used as liner or cover in engineered MSW landfill.