Development of tools to investigate biocementation - microscale analysis for studying bacterial solutions

CERIS/ Instituto Superior Técnico, Civil Engineering Department, Lisbon, Portugal

^* corresponding author: mariana.mateus.pinto@gmail.com

Abstract

Biocementation consists on the use of microorganisms (bacteria) to promote the precipitation of calcium carbonate (biocement). When this technique is applied in soils or fractured rocks, the biocement which is precipitated can fill voids and discontinuities, being easy to apply, not very intrusive and requiring low energy consumption. There are several aspects that must be investigated when using living microorganisms for such purpose, mainly related with ensuring the environmental conditions for their survival and the maximization of production of biocement. The age of the bacteria and the increment of biocement production after increasing the number of inoculations were investigated in the work presented in this paper. A microfluidic device was developed to visualize the production of biocement after multiple injections of bacteria and feeding solution. These devices allow for an easy and straight forward visualization of small-scale physical, chemical and biological processes. The results of injection cycles in microfluidics channel were examined with imaging techniques. In parallel, experimental tests were carried out on samples of uniform sand soil, with the objective of evaluating the penetration resistance and the calcium carbonate content that was formed, according to the number of injections. There was also a verification of the electrical conductivity of the bacterial solutions in use, to guarantee its viability. As expected, the production of biocement increased after three injections of bacteria, which is consistent with the results found in both microfluidic devices and soil samples.