MEASUREMENT OF EFFECTIVE DIFFUSIVITIES IN SOLIDIFIED WASTES

An electrical conductivity method has been developed to determine the effective diffusivity of contaminants through porous solids, such as hazardous waste solidified with cementitious binders. The electrical conductivity method calculates the MacMullin number, which is the ratio of the effective diffusivity of a compound in a porous solid to the molecular diffusivity of that compound. The effects of water-to-cement ratio, curing time, and sample thickness on the MacMullin number were determined. The validity of this method was established through comparison with effective diffusivities measured by conventional techniques. These values were measured during the study with a two-chamber diffusion device; other values were obtained from the literature. Correlations of the MacMullin number with porosity and bulk density were developed. The electrical conductivity method was found to be a rapid and reliable method for measuring effective diffusivities of contaminants in porous solids such as solidified hazardous wastes and offers the advantages of much more rapid analysis than conventional methods.