Formation of Biomineralized Calcium Carbonate Precipitation and Its Potential to Strengthen Loose Sandy Soils
Microbially induced calcium carbonate precipitation (MICP) is considered as a sustainable and environmentally friendly technique for the strengthening of loose sandy soils. MICP is triggered as a result of a biomineralized reaction product of bacteria and a cementation reagent in soils. In the present study laboratory experiments were performed on sand columns to investigate the MICP potential to consolidate and strengthen the loose and collapsible sand specimens using the ureolytic bacteria Sporosarcina pasteurii. The sand columns were treated initially using bacterial cell solution and followed by percolating a cementation reagent solution that consists of urea and calcium chloride. In the MICP process, urease enzymes released by the bacteria plays a major role in urea hydrolysis. The results showed that MICP could effectively strengthen the sand columns through calcium carbonate precipitation as calcite to bind the sand grains. The improvements, however, varied with treatment conditions, soil types and other environmental factors such as pH and temperature of the local environment. The results from Scanning Electron Microscope (SEM) analysis confirmed the precipitation of calcite by bridging the sand grains. This study suggests that calcite precipitation through biomineralization as a metabolic product of ureolytic bacteria are highly effective and may provide as a green construction material as a sealing agent for filling the gaps, cracks and fissures for civil engineering structures. Further, another effective technique of MICP is for sequestration of CO2 present both in the atmosphere and in the soil.
KeywordsBiomineralization Calcite CO2 sequestration MICP Urease Urea hydrolysis
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