Effect of curing method on unconfined compressive strength of silty sand treated with Bacillus Megaterium

Abstract

Laboratory tests were carried out to evaluate the effect of curing method on the unconfined compressive strength (UCS) of silty sand treated with Bacillus megaterium. (B. megaterium) using the Microbial Induced Calcite Precipitation (MICP) technique. Compaction test was conducted using the British Standard light (BSL) energy. UCS tests were performed on two sets of specimens treated with varying B. megaterium suspension densities and cementation reagent using trial mix ratio of 50% B. megaterium (B) and 50 % cementation reagent (C) (i.e., 50B-50C) for the treated specimen and 100 % cementation reagent (C) (i.e., 100C) for the control specimen. One set of specimens extruded from compaction mould was air-cured at room temperature for 24 hours, while the second set of specimens were placed in sealed polythene bags immediately after extrusion from the moulds. The results obtained show that the peak UCS values of the air-cured specimens and the sealed specimens are 448.8 kN/m2 and 19.8 kN/m2, respectively, for treatment with B. megaterium suspension density of 6.0 x 108 cells/ml. The study shows that the UCS of silty sand treated with B. megaterium is sensitive to curing method.