Strength related geotechnical testing of lateritic soil prior to the application of microbially induced calcite precipitation treatment

Microbially induced calcite precipitation (MICP) is an emerging solution to issues faced by geotechnical engineers that has yet to turn its attention to strengthening fine particle clays, including lateritic soil. The lateritic clays found in tropical regions have long been used as a low cost construction material for earth roads linking rural village clusters. However, earth roads are exposed to prolonged tropical wet seasons and become inundated with rainwater, deteriorating their ability to bear traffic. MICP soil strengthening may provide a low cost, sustainable solution that would allow earth roads to remain usable. This paper presents the first phase of geotechnical strength related tests undertaken on a lateritic soil, prior to any MICP treatment, including plasticity index, Proctor compaction, Californian bearing ratio (CBR) and unconfined compressive strength (UCS). They have been undertaken to provide the baseline data against which future MICP treated samples can be assessed. The results indicate that the lateritic sample was a low plasticity clay, which may be prone to turbulent shearing when past its semisolid/plastic limit of 12 %. When tested at 12.5 % moisture content, the values of CBR and UCS fell by 96.4 and 87.4 %, respectively, when compared to samples tested at 7.5 % moisture content.