Abstract
The study presented herein adopts a new vision of the processes involved in carbonate mineralization induced by MICP from an electrochemical and crystal growth perspective. More precisely a specific line of focus refers to the species involved in the bio-chemical reactions and especially their net particle charge. By altering electro-chemical conditions via the application of direct electric currents, we observe distinctive trends related to: (i) overall reaction efficiency; (ii) carbonate mineralization/dissolution and (iii) spatial distribution of precipitates. The study introduces the concept of EA-MICP which stands for Electrically Assisted MICP as a means of improving the efficiency of soil bio-consolidation and overcoming various challenges which were previously reported in conventional MICP-based works. Results reveal both the detrimental and highly beneficial role that electric currents can hold in the complex, reactive and transport processes involved. An interesting finding is the “doped” morphology of calcite crystals, precipitated under electric fields, validated by microstructural observations.
Highlights
The present study aims to shed light on the critical role applied Electrokinetics (EKs) can hold in MICP
Other findings relate to the injection of calcium ions at the anode and carbonate ions originating from microbially hydrolysed urea at the cathode which results into a good rate of calcification throughout soft clay by means of EKs transport of the reactive species (Keykha et al 2014)
ΔEC measurements are correlated to the ionic chromatography (IC) analyses which validate the depletion of NH4+ with relevant concentrations reaching almost zero after 6 days in the applied field cases
Summary
The present study aims to shed light on the critical role applied Electrokinetics (EKs) can hold in MICP. Applied EKs enhance electrical motion forces that are effective in distributing either dissolved ions, charged particles or even organic ones. The most efficient electrically induced motion force is electromigration of dissolved ions where the electrical force F=qE, with q being the charge of the considered species and E the electric field across the specimen, distributes the ions according to the electric potential distribution. Other findings relate to the injection of calcium ions at the anode and carbonate ions originating from microbially hydrolysed urea at the cathode which results into a good rate of calcification throughout soft clay (kaolinite) by means of EKs transport (electromigration and electroosmosis) of the reactive species (Keykha et al 2014). The present study focuses on the potentially detrimental and beneficial effects of applied EKs to suggest an efficient EA-MICP approach
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