Original Investigation of Biocementation for Ground Improvement of Tropical Lateritic Soils in North Central Nigeria

Biocementation using microbially induced calcite precipitation (MICP) is an emerging ground improvement technique with significant potential for strengthening weak granular soils without the energy intensity and CO2 emissions of conventional cementitious stabilisation. Its application to tropical lateritic soils in North Central Nigeria, which have distinctive mineralogy, iron-oxide coatings, and pH environments, has not been scientifically investigated. This study conducts an original experimental investigation of MICP biocementation for improving lateritic soils from Plateau, Niger, and Kogi States. Native urease-producing bacteria were isolated from the three laterite sources and characterised. The influence of treatment variables including bacterial concentration, cementing solution concentration (calcium chloride and urea), number of treatment cycles, and curing temperature on carbonate precipitation yield and mechanical improvement was investigated through a full factorial experimental design. Treated specimens were characterised by scanning electron microscopy, X-ray diffraction, X-ray fluorescence, and geotechnical tests (UCS, CBR, and permeability). Results indicate that UCS improvements of 2.8 to 4.6 MPa are achievable for lateritic soils with iron oxide coatings between 5 and 12 percent Fe2O3. Treatment efficacy is strongly influenced by iron oxide coating, which inhibits calcite nucleation on grain surfaces, requiring adapted bacterial consortium selection. CBR improves from 8 to 42 percent with optimised treatment. The study provides an original characterisation of MICP biocementation behaviour in tropical lateritic environments, advancing sustainable ground improvement science.

Keywords: biocementation, MICP, lateritic soils, ground improvement, North Central Nigeria