Bio-mediated soil improvement: An introspection into processes, materials, characterization and applications

For a long time in the practice of geotechnical engineering, soil has been viewed as an inert material, comprising only inorganic phases. However, microorganisms including bacteria, archaea and eukaryotes are ubiquitous in soil and have the capacity and capability to alter bio-geochemical processes in the local soil environment. The cumulative changes could consequently modify the physical, mechanical, conductive and chemical properties of the bulk soil matrix. In recent years, the topic of bio-mediated geotechnics has gained momentum in the scientific literature. It involves the manipulation of various bio-geochemical soil processes to improve soil engineering performance. In particular, the process of microbial-induced calcium carbonate precipitation (MICP) has received the most attention for its superior performance for soil improvement. The present work aims to shape a comprehensive understanding of recent developments in bio-mediated geotechnics, with a focus on MICP. Referring to around one hundred studies published over the past five years, this review focuses on popular and alternative MICP processes, innovative raw materials and additives for MICP, emerging tools and testing methodologies for characterizing MICP at multi-scale, and applications in emerging and/or unconventional geotechnical fields.

Automated summary

Soil is not just made up of inorganic phases, as microorganisms such as bacteria, archaea, and eukaryotes have the ability to alter the properties of soil in geotechnical engineering practices. Among these, microbial-induced calcium carbonate precipitation (MICP) has gained significant attention for improving soil engineering performance. Recent developments in bio-mediated geotechnics focus on popular and alternative MICP processes, innovative raw materials and additives, testing methodologies for characterizing MICP at multi-scale, and applications in emerging and unconventional geotechnical fields.