The Influence of Environmental Pollution on Cyclic Swell and Shrink Behavior of Na-Bentonite Clay

Most civil engineering structures built on expansive soil are subject to damage due to seasonal changes and different environmental conditions. The possibility of damage to such structures due to the swelling and shrinking of clay cause severe problems in design and construction. The environmental pollution effects of saline water, kerosene and sanitary leachate of cyclic wetting and drying on the swelling and shrinkage behaviour of compacted Na-bentonite clay were studied. While the distilled water-added Na-bentonite had the highest free swelling, saline water-added Na-bentonite had the lowest free swelling among them. The experimental results showed that, after each cycle, the swelling and shrinkage behaviour of compacted Na-bentonite clay decreased. A honeycomb structure and a random and a more open flocculated structure dominated by large interdomain macrovoids and cavities were evident in salt water-added Na-bentonite. Some domains and orientation were seen in distilled water-added Na-bentonite micrographs. An aggregated and agglomerated structure was evident in kerosene-added Na-bentonite micrographs. 5 refs.