ABSTRACT
The geotechnical applications of microorganisms, using biocementation, bioclogging, and biodesaturation, are aiming at improving the mechanical properties of soil so that it will be more suitable for construction or environmental engineering purposes. Bioclogging is the production of pore-filling materials through microbial means, so that the porosity and hydraulic conductivity of soil can be reduced. Biocementation is the generation of particle-binding materials through microbial or enzymatic processes in situ, so that the shear strength of soil can be increased. Bioaggregation of soil particles can be used for dust control, soil erosion control, and decontamination of chemical, biological, and radiological pollutants of land and demolished infrastructure. The most suitable microorganisms for soil bioclogging or biocementation are facultative anaerobic and microaerophilic bacteria, although anaerobic fermenting bacteria, anaerobic respiring bacteria, and obligate aerobic bacteria may also be suitable to be used in geotechnical engineering. Major biogeochemical reactions for geotechnical engineering are biomediated precipitations of calcium carbonate, calcium phosphate, and ferric hydrate. Due to complexity, the applications of microbial geotechnology would require an integration of microbiology, ecology, geochemistry, and geotechnical engineering knowledge. Microbial polysaccharides are used as admixtures improving some properties of concrete. Use of biodegradable microbial plastics in construction reduces the land for disposal of construction wastes after demolition and diminishes cost of the construction works because the biodegradable plastic foams, sheets, liners, and fences can be left in the soil without their excavation and disposal. A tutorial with solutions and a quiz bank are added to this chapter.
