Effect of Inorganic Salt Solutions on Physical and Mechanical Properties of Bentonite Based Liner

Abstract

The influence of inorganic salt solutions on the physical and mechanical properties of bentonite based liner materials is highlighted. Compacted pond ash-bentonite (PAB) and sand-bentonite (SB) liners, prepared at their respective maximum dry unit weight (MDD) and optimum moisture content (OMC) are permeated with NaCl, CaCl2, and FeCl3 solutions of concentrations from 0.1 to 1 M. The physical and mechanical properties are determined after permeations of 7, 14, and 21 days. The consistency limits, free swell indices, and volumetric shrinkage strain are found to reduce and the hydraulic conductivity increased as the concentration of salt solutions and their permeation time increased. Permeation of lower concentration salt solutions increases the unconfined compressive strength (UCS) value and this reduces substantially as the concentration increases. Salt solutions of polyvalent cations have more impact than those of monovalent cations. PAB specimens are less vulnerable to these changes compared with those of SB specimens. The concentration of permeating cations increases substantially in the liner materials with an increase in salt concentration and permeation time, and the concentration of inherently adsorbed elements decreases.