Assessing multi-parameter performance and acceptability zones of biocemented lateritic soil for sustainable waste containment

• This study evaluates the effect of compacted bio-treated lateritic soil on key performance parameters ((hydraulic conductivity (k), desiccation induced volumetric shrinkage strain (VSS) and unconfined compressive strength (UCS)) under the influence of compaction energy, moisture content range, and bacterial suspension density. • A 0.5 M bio-cementation solution (urea–CaCl₂) was applied under gravity onto the bio-treated, compacted soil to activate calcite precipitation, thereby enhancing soil bonding. • The results show that increasing bacterial cell concentration in MICP improves soil properties by reducing permeability, enhancing strength, and mitigating shrinkage. SEM images, XRD and FTIR of the bio-treated samples show the bonding network carbonate crystals and minerals. • The overall acceptable zone (OAZ) reached a more optimized level under the combined effects of bio-treatment, compaction energy, and moulding water content. Recent advancements in biogeotechnics have harnessed the potential of ubiquitous soil microorganisms to address diverse geotechnical challenges. One promising, eco-friendly approach is microbially induced carbonate precipitation (MICP), which improves soil properties by promoting calcite precipitation through natural microbial processes. Although MICP has been widely applied in various engineering and scientific fields, its use in sustainable waste containment systems remains limited. This study evaluates the effect of compacted bio-treated lateritic soil on key performance parameters ((hydraulic conductivity (k), desiccation induced volumetric shrinkage strain (VSS) and unconfined compressive strength (UCS)) under the influence of compaction energy, moisture content range, and bacterial suspension density. A 0.5 M bio-cementation solution (urea–CaCl₂) was applied under gravity onto the bio-treated, compacted soil to activate calcite precipitation, thereby enhancing soil bonding. The results show that increasing bacterial cell concentration in MICP improves soil properties by reducing permeability, enhancing strength, and mitigating shrinkage. While the numerical measurement of these parameters are important, insight into the internal structures of the samples at micro-nano level cannot be measured. SEM images, XRD and FT-IR of the bio-treated samples show the bonding network carbonate crystals and minerals. The overall acceptable zone (OAZ) reached a more optimized level under the combined effects of bio-treatment, compaction energy, and moulding water content. This was achieved using a bacterial suspension density of 2.4 × 10⁹ cells/ml of Bacillus megaterium in a 0.5 M cementation solution. Under BSL, WAS, and BSH compaction energies, the moulding water content ranges were 14.4 % - 16.4 %, 13.2 % - 15.2 %, and 11.8 % - 13.8 %, respectively.