Contaminant Barrier Material Textural Response to Interaction with Aqueous Polymers

An experimental investigation of the use of polymers dissolved in aqueous solutions to enhance the resistance of clay-based barrier materials to freeze-thaw action and desiccation was performed. The polymers considered included a nonionic polysaccharide (guar gum) and a cationic polyacrylamide (PAM). Concentrations ranging from 0.25 to 8.00 g/L were used and mixed with three barrier materials, namely, 100% Na-montmorillonite clay, a mixture of 70% sand, 30% clay, and a mixture of 90% sand, 10% clay (by weight). Freeze-thaw and desiccation tests were used to investigate material durability. The effects of freeze-thaw action on the materials were assessed in terms of crack measurements, while the drying rates as well as crack measurements were used to assess the influence of desiccation. The extent to which crack formation was mitigated by polymer amendment varied according to polymer type, mode of crack initiation, and clay fraction. In particular, unmodified mixtures of 70% sand and 30% clay exposed to desiccation stress resulted in crack area density values as high as 11.9% while modification with guar or PAM reduced this to 2.7 and 3.4%, respectively, as revealed by analysis of the computed tomography-generated images. Increases or reductions in performance are attributed to polymer–clay interactions and relative hydration between clay and polymer phases.