Summary: Biocalcification of Sand through Ureolysis
; Eric A. Seagren, A.M.ASCE2
; Ahmet H. Aydilek, M.ASCE3
; and Michael Lai4
Abstract: Biological processes may provide great and previously unexplored opportunities for cost-effective, in situ improvement of the
engineering properties of soil. A laboratory study was conducted to evaluate the changes in geomechanical properties of sand attributable to
the formation of calcium precipitates induced through ureolysis catalyzed by Sporosarcina pasteurii (S. pasteurii). Specifically, direct shear
and California Bearing Ratio (CBR) tests were conducted on sand specimens subjected to treatment by growing, resting, and dead S. pasteurii
cells in completely stirred tank reactors and completely mixed biofilm reactors, respectively. Scanning electron microscopy analyses were
also conducted to evaluate microbially induced precipitation. The results of the study show that the bacterial cells effectively improved the
geomechanical properties of the sand. Growing cells improved the sand properties owing to microbially induced precipitation and related
pore volume changes, whereas dead and resting cells generally caused smaller increases in friction angle and bearing strength. Analysis of
the sand from CBR specimens treated with growing cells demonstrated that the microbial and chemical processes both contributed to the
clogging of the porous medium. DOI: 10.1061/(ASCE)GT.1943-5606.0000532. © 2011 American Society of Civil Engineers.
CE Database subject headings: Soil properties; Bacteria; Calcium carbonate; Soil strength; Sand (soil type).
Author keywords: Soil properties; Bacteria; Calcium carbonate; Strength.
Microbial activities are ubiquitous in surface and subsurface soils
and have a tremendous effect on the composition, properties, and