Effects of environmental temperature on the effectiveness of microbially
induced carbonate precipitation
Abstract
Microbial-induced calcium carbonate precipitation (MICP) is an
innovative technique used for soil improvement, for controlled reduction
of permeability in porous media or immobilization of soil contaminants.
The application of MICP in the field is influenced by the environmental
factors. In the present study, the main purpose is to explore the
effectiveness of MICP in treating porous media at different
environmental temperatures and reveal the underlying mechanisms. The
microstructure characteristics were investigated via SEM imaging, EDS
and XRD analyses and consolidated drained triaxial compression tests
were performed to examine the performance of MICP-treated samples.
Results indicate that the shear strength depends heavily on the
treatment temperature, which was mainly due to the different content,
size and distribution of CaCO3 in samples at different
conditions. The observations of pore-scale characteristics revealed that
low temperature (4℃) and high temperature (50℃) produced less
CaCO3 precipitation, resulted in smaller carbonate
crystals precipitation and thus lower strength. In contrast, samples
treated at room temperature and 35 ℃ show more CaCO3
precipitation and greater strength. The crystal forms, though, were not
influenced by the temperature. The climate conditions are a very
important parameter that needs to be tuned specifically for the purposes
of each MICP application (whether controlled alteration of permeability
or for soil stabilization). However, in most MICP field applications,
temperature is nearly impossible to control, and in such conditions
where bacterial activity is reduced, the alteration of the MICP recipe
is required, and specifically the number of bacterial solution
injections are worth to be considered.