PERMEABILITY OF CLAY-MODIFIED FLY-ASH UNDER THERMAL-GRADIENTS

Mixtures of geomaterials and by-products have potential as barriers fo r containing contaminants. In this investigation, the permeability of fly ash to distilled water was found to decrease due to the addition o f pure bentonite. On subjection of the compacted bentonite-modified fl y ash to cycles of freeze-thaw action, using a specially designed free ze-thaw permeameter, the permeability of the composite material decrea sed to a constant value after one cycle. It is postulated here that th e observed permeability decrease stems from the dispersion of floccula ted clay material that occupies the intergranular regions among the fl y-ash particles. The specific results of this study are fitted into a general framework for describing textural changes and deterioration of composite materials under cyclic thermal gradients. In this framework , a comparison of the response of clay-modified fly ash and ash-modifi ed clay to the stresses induced by freeze-thaw action is made. Both cl ass-C and class-F fly ash are examined.