Stress-Strain Characteristics of a Cement-Bentonite Mix for a Barrier System The Implication of Time and Curing

Abstract

For containment and water exclusion purposes, cement-bentonite (CB) barrier walls are usually built, with certain design criteria specified for the wall to fulfill intended purposes. While permeability is believed to be the most important criterion, it can be impacted by the stress-strain properties of the wall, which define the strength and stiffness. This study investigates the influence of curing time, confinement, rate of axial deformation, and quantity of cement (mix of Portland cement (PC) and ground granulated blast furnace slag (GGBS)) on the stress-strain properties of CB slurry walls. An unconfined compressive test supported by (i.e. UCT) undrained triaxial (UUT) tests were carried out on specimens prepared from two mix-designs (differentiated by the proportion of GGBS in the cement component) and cured 7, 14, 28, 60, and 90 days. Two rates of deformation (1.0mm/min and 1.2mm/min) were examined, using a range of confining pressure (i.e., 50 - 200 kPa) in the UUT. The results reveal that varying rates of deformation and the range of confining pressures have no clear influence on the mechanical properties (e.g., deviator stress, shear strength, and stiffness) of the CB mix-designs. However, increased curing time, and the proportion of GGBS significantly improved these properties. An increased proportion of GGBS enhances early strength. Thus, further work needs to be done to establish a balance between adequate strength and adequate flexibility of CB walls in order to not compromise permeability.