Textural characterization of media composed of compacted pieces of cardboard and polyethylene using a gas tracer method

Abstract

The aim of this work is the experimental determination of effective transport properties of porous media consisting of compacted pieces of cardboard and polyethylene (PE). The proposed method itself is more general and can be applied to many different materials and contexts. Three major transport properties were determined: porosity, tortuosity factor and permeability. Three parameters characterizing the media were varied over a wide range: the bulk density, the size of the elements entering the mix, and the proportion of cardboard and PE in the mix. The properties were measured by means of a specially designed experimental device based on miscible gas tracing. The porosity and tortuosity factor were simultaneously determined by parametric identification, based on the experimental sample output response to an inlet gas concentration step change compared to the results of a direct numerical model. Permeability was calculated in the standard way from the measurement of the pressure drop across the sample. The reproducibility of the measurements was very good. It was found that changing the material density of the medium significantly affects all three structural properties. When the bulk density is varied between 300 and 900 kg m(-3), the tortuosity factor varies in a range as large as 18-8 and the permeability decreases by a ratio of 2-3. The tortuosity factor shows unusual variation, characterized by a decrease when density is increased above 500 kg m(-3). The size of the elements does not significantly affect the structural properties of the medium in the range of parameters studied.