Abstract

Unconfined compressive strength (UCS) of soil is usually affected by curing time (in days) and compactive effort. In order to determine the effect of curing days and compactive effort on microbial induced calcite precipitate (MICP) treated lateritic soil, the UCS of Bacillus pumilus (B. pumilus) microbial induced calcite precipitate treated lateritic soil were carried out at different curing days and different compactive effort. Lateritic soil was treated with stepped densities of Bacillus pumilus suspensions densities of 0 /mL (for natural soil), 1.5x108 /mL, 6.0x108 /mL, 12x108 /mL, 18x108 /mL and 24 x108 /mL, respectively and compacted with three compaction energies namely; British Standard Light (BSL), West African Standard (WAS) and British Standard Heavy (BSH). The treated soil samples were cured for 7, 28 and 56 days. The result shows an increase in UCS value with increase in B. pumilus suspension density and also with increase in compactive energy. The UCS values obtained showed an increase with curing days from 7 to 28 days curing but beyond 28 days curing period UCS value obtained were constant which indicates that MICP process has sustainability strength values even after long time curing which is an indication of a very good construction material. The peak UCS values were obtained at 1.8 × 109 cells/mL of B. pumilus suspension density for all compactive effort considered.