Bio-Grout Materials: A Review

Bio-mediated and bio-inspired improvement of granular soils via microbially induced CaCO₃ precipitation (MICP), enzyme induced CaCO₃ precipitation (EICP), and microbially induced desaturation and precipitation (MIDP), techniques sometimes referred to bio-grouting, have attracted an increasing amount of attention in the past decade. MICP and EICP are techniques which rely upon the hydrolysis of urea as catalyzed by the enzyme urease. MIDP is a technique that relies upon dissimilatory reduction of nitrate and also desaturates the soil via biogas generation. MICP and MIDP are bio-mediated process, as they rely on living organisms. EICP may be considered a bio-inspired technique as, while it employs biologically generated free urease, no living organisms are involved in the precipitation reaction. Bio-grouting has the potential to serve as a sustainable technique for a variety of soil improvement applications. While bio-grouting has not been commercialized, promising results have been obtained in the laboratory and limited field trials.