Water retention properties and microstructure of compacted expanded perlite

A double porosity structure is recognized in compacted expanded perlite, a granular material made from crushed perlite rock subjected to heating treatment. Due to its generation process, each grain has a micro-scale porosity network and a series of closed pores (isolated holes), while particle size distribution is highly uniform. An experimental investigation combining water retention tests and mercury intrusion porosimetry is presented. The results allowed for a detailed description of the double porosity system and retention properties and may represent a basis for a future contribution on hydraulic and mechanical aspects of the behaviour of double porosity materials.