Augmenting Pozzolanic Stabilization Using Novel Microbial Carbonate Precipitation in a Soft Soil

Abstract

To reduce carbon dioxide (CO2) emissions from the use of cement and lime in civil engineering applications, microbially induced calcite precipitation (MICP) is one of the sustainable technologies being explored. MICP utilizes the metabolic activities of bacterial species to produce chemical environments that are conducive for calcite formation, which either plugs the pore spaces and/or bonds the soil particles together to reduce permeability and increase the strength and stiffness of soils. This study examined the reduction in use of chemical stabilizers by employing microbially induced carbonate cementation (MICC) along with magnesium oxide (MgO) stabilization. A soft soil [unconfined compressive strength (UCS) = 20 kPa] was prepared in the laboratory by mixing equal-weight proportions of kaolinite (50%) and sand (50%) at a high (21%) water content. Simultaneous pozzolanic and microbial activity was induced in the soft soil by the addition of MgO and cattle manure (CM). Degradation of the CM by native microbes produced CO2, which dissolved in the water to form bicarbonate ions