Experimental determination of representative elementary volume of sands using X-ray computed tomography

Abstract

The concept of a representative elementary volume (REV) provides an effective means of developing macroscopic measures in the description of granular materials. However, due to the difficulties associated with the measurement and characterization of granular microstructure the existence and size of an REV has remained largely conjectural. This study presents a systematic method to examine the characteristics of the REV using X-ray computed tomography images. The 3-D images of Silica sand, and Ottawa sand have been characterized using advanced image processing techniques. The porosity variation of Silica sand and Ottawa sand showed three characteristic regions: an initial fluctuation region due to microscopic variations, a constant plateau region, and a region with a monotonic increase/decrease due to heterogeneity. The results show that for Silica sand composed mainly of elongated particles the REV is between 5 to 11 times of D50 and for Ottawa sand composed mainly of subrounded particles is between 9 to 16 times of D50.