Abstract:
Microbial induced carbonate precipitation (MICP) is a promising bio-cementation
method that involves ureolytic bacteria to improve the geotechnical properties of soil. The
laboratory-scale studies carried out in the recent past showed that the MICP can be a potential
alternative for slope surface preservation. However, the use of analytical-grade chemicals makes
this method too expensive, limiting the applicability of the method especially when implicated at
field-scale. The purpose of this research work was to assess the effectiveness of using
inexpensive low-grade chemicals for the in-situ stabilization of slope surface. Two test plots
were established at the project site (Hokkaido expressway slope, Japan) and subjected to MICP
treatment via surficial spraying. One was treated using the cementation media formulated by
low-grade chemicals (inclusive of fertilizer urea, snow-melting agent and beer-yeast), while the
typical analytical-grade media was used to treat the other plot. After 20 days of treatment, the
treated slope surfaces were evaluated by surface strength, CaCO3 content, scanning electron
microscopy, energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses. The
outcomes indicated that the surface was significantly improved by low-grade chemicals; a stiff
surface layer was desirably formed to the depth of 5 – 10 cm with the surface strength and
CaCO3 content in the ranges of 0.14 – 1.02 MPa and 0.56 – 3.7%, respectively. The results are
compared and discussed, and the challenges in the use of low-grade chemicals are pointed out for
the way forward. Cost analysis disclosed that the material cost of the cementation media was
reduced by around thirty-seven-fold (by 97%) compared to the analytical-grade media. While
demonstrating the potential use of low-grade chemicals, the field-scale experiment could
contribute to narrow down the gap between the present-state and real-scale deployment of MICP
technology.
