Influence of electrochemical treatment on a typical laterite

The results of the undrained shear strength (Su) and stiffness (Vs) of electrochemically stabilised residual tropical laterite soil (RTLS) are presented. Calcium (Ca2+) and phosphate (PO43-) ions from calcium chloride and phosphoric acid, respectively, were injected individually and together into remoulded RTLS by applying 1 and 2 V/cm direct current electrical gradient for 5 d to facilitate cementation within the treated soil. Three different systems were employed using 1.0 M calcium chloride or 0.01 M sodium chloride as the anolyte and 1 M phosphoric acid or 0.01 M sodium chloride as the catholyte. Polarity reversal was also employed in some tests. The efficacy of the treatment was based on the soil Su and stiffness. The injection of Ca2+ led to a reduction in both the Su (90%) and stiffness (8%) of the treated RTLS. The injection of PO43- resulted in improvement in both the soil Su (151%) and stiffness (20%) of the treated RTLS. The study concluded that in stabilising the RTLS, injection of PO43- is effective whereas the injection of Ca2+ is not.