Evaluation of the consistency and microstructural properties of lateritic soil treated using microbial induced calcite precipitation technique

The consistency of lateritic soil amended using Bacilus thuringiensis (Bt) via microbial-induced calcite precipitation (MICP) technique was evaluated. Three mix ratios of Bacilus thuringiensis suspension and cementation reagent (Cs) (i.e., 25% Bt : 75 % Cs, 50% Bt : 50 % Cs and 75% Bt : 25% Cs) were prepared on the basis of the natural soil liquid limit. Bacilus thuringiensis density in solution of 0, 1.5 × 108, 6.0 × 108, 12 × 108, 18 × 108 and 24 × 108 cells/mL were treated with four (4) varying cementation reagent levels of 0.25, 0.5, 0.75 and 1 M, correspondingly. Specimens were subjected to consistency limits, calcium carbonate content (CCC) and scanning electron microscopy (SEM) tests. The consistency limit findings indicated that lateritic soil treated using a 50:50 Bt–Cs mix ratio recorded the best improvement with the lowest plasticity index value of 14.3% for 6 × 108 cells/ml at 0.5 M compared to the 18.9% plasticity index for the natural soil. SEM results depicted calcites formation and microstructure modification of the treated lateritic soil. It is therefore suggested that lateritic soil amended with 50% Bt (6 ×108 cells/ml): 50% Cs (0.25 M) and 50% Bt (24 ×108 cells/ml): 50% Cs (0.5 M) with PI values of 16.9% and 15.7% respectively could be used to enhancee the consistency and other microstructural characteristics of lateritic soil for use as fill or embankment material.