Influence of bacterial suspension type on the strength of biocemented sand

Soil properties, the chemical composition of cementation solution, injection technique, and environmental conditions have all been extensively studied as variables influencing microbially induced carbonate precipitation performance. However, de-spite the fact that different researchers have used different bacterial suspensions, the influence of bacterial suspension type, more specifically some organic matters in bacterial suspensions, which can play a key role in the morphology and mechanical properties of CaCO₃, has often been overlooked. In this study, the harvested bacterial solutions were centrifuged to separate bacterial cells and supernatant. The precipitated cells were then diluted with three distinct solutions: supernatant (RB), fresh culture medium (FB), and 0.9% NaCl solution (NB), which were subsequently utilized to stabilize the sand. The results indicated that the bacterial suspension type could greatly impact the strength of biocemented sand, particularly coarse and medium sand. Differences in unconfined compressive strength can be related to differences in precipitated CaCO₃ microstructures, morphologies, and compositions, which were examined using scanning electron microscopy, X-ray diffraction analysis, and Fourier transform infrared spectroscopy.